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GEM > Module 4 Limbs and Back > Flashcards

Module 4 Limbs and Back Flashcards

1
Q

Describe the generic structure of a synovial joint and the function of each of its features​

A

Articular Cartilage (hyaline) on bone surfaces

Articular Capsule
Inner synovial membrane
Outer fibrous membrane

Synovial fluid-filled Joint Cavity

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2
Q

What are Bursae?

A

Bursae - Synovial membrane-lined ‘sacs’ or ‘cushions’ which are normally ‘collapsed’

Vary in size depending on the individual and the location in the body, usually really thin

Located at points of friction between bone and surrounding soft tissue, such as skin, muscles, ligaments and tendons

Some bursae are just beneath the skin’s surface while others are deep below muscles and other soft tissue

adventitious bursae may develop as a result of repeated stress

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3
Q

tendon sheath

A

This is a delicate synovial structure (like the finest ‘silk’) called tenosynovium (also known as a tendon sheath), which can be found lining some tendons in specific parts of the body.

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4
Q

Tenosynovitis

A

Inflammation of the tendon sheath

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5
Q

Articular discs & menisci

A

Fibrocartilage (type I collagen fibres)
Between poorly congruent articular surfaces
If crescent shaped: ‘menisci’ (sing. meniscus)
If complete: ‘articular discs’

Improvement of fit between articulating surfaces
Deployment of weight over larger surface areas
Shock absorption
Limitation and facilitation of automatic movements
Protection of articular margins

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6
Q

Structural Classification of Joints

A

SOLID JOINTS
(Joints without a joint cavity)

Fibrous (synarthrotic) joints: bones held together by dense fibrous connective tissue. Very little or no movement.

Cartilaginous (amphiarthrotic) joints: bones are held together by either fibrocartilage (symphysis joints) or hyaline cartilage (synchondrosis joints). Moderate but limited movement.

SYNOVIAL (DIARTHROTIC) JOINTS

Bones are connected by a joint capsule composed of two layers (fibrous+synovial) enclosing a joint cavity. Freely moveable.

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7
Q

Examples of fibrous joints

A

Sutures between flat bones e.g. skull
Gomphosis - peridontal ligament e.g. teeth
Syndesmosis - interosseous membrane

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8
Q

Examples of cartilaginous joints

A

Synchrondrosis - cartialge betwwen head and shaft of long bone
Symphysis - intervertebral discs and pubic symphysis

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9
Q

Hinge joint

A

Uniaxial
Flexion/extension
Elbow Joint

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10
Q

Pivot joint

A

Uniaxial
Rotation
Atlantoaxial joint - first and second cervical vertebrae

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11
Q

Plane/gliding joint

A

Gliding in multiple directions
Slide/glide
Intertarsal; intercarpal joints

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12
Q

Condyloid (ellipsoid)

A

Biaxial
Flexion/extension, adduction/abduction
The atlantooccipital joint - synovial articulation between the occipital bone and the first cervical vertebra (atlas).

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13
Q

Ball and socket

A

tri-axial
Flexion/extension, adduction/abduction, rotation/ circumduction
Pelvic and Pectoral girdle

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14
Q

Saddle

A

Biaxial
Flexion/extension, adduction/abduction
Carpometacarpal of the thumb

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15
Q

Three major factors that determine the balance of mobility and stability of a joint:

A

The shape of the bones of the joint

The musculature of the joint

The ligament/joint capsule complex of the joint

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16
Q

Ligaments (in the MSK system):

A

Bone to bone

Dense fibrous connective tissue

Different proportion of collagen/elastin fibres

contain great amount of collagen fibres -> strength to withstand pulling forces

poorly vascularised -> do not heal quickly after injury

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17
Q

Tendons:

A

Muscle to bone

Dense fibrous connective tissue

Few elastin fibres

contain great amount of collagen fibres -> strength to withstand pulling forces

poorly vascularised -> do not heal quickly after injury

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18
Q

Arthritides symptoms

A

Joint pain, tenderness and stiffness

Joint Inflammation

Warm, red skin over affected joint(s)

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19
Q

Osteoarthritis

A

Disease involving inflammation of the bone and joint cartilage

Not life threatening, but it can cause severe pain and loss of mobility and independence.

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20
Q

Typical radiographic changes in osteoarthiritis: LOSS

A

Loss of cartilage
Osteophytes
Sclerosis and eburnation of the subchondral bone
Subchondral cysts (geodes)

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21
Q

osteoarthritic joint changes

A

Inflammation of the joint cartilage and bone
loss of articular cartilage - usually maintained by chondrocytes
Bone hypertrophy - Subchondral sclerosis and osteophyte formation
Narrowing of the joint space
Synovial membrane hyperplasia

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22
Q

Two types of cell within the synovium

A

Type A synovocytes - macrophages
Type B synovocytes - Fibroblasts; produce fluid

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23
Q

Gout characteristics

A

Hyperuricaemia (abnormally high level of uric acid in the blood)

Deposition of urate crystals within synovial joints causing attacks of acute inflammatory arthritis

Tophi (deposits of uric acid crystals) in soft tissues after 10+ years

Possible joint destruction

Renal disease and uric acid urolithiasis

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24
Q

Gout: Pathophysiology

A

Humans unable to degrade uric acid to a more soluble compound due to lack of the enzyme uricase

Within the joint, urate crystals interact with undifferentiated phagocytes which results in the release of TNF-alpha and interleukin (IL)-8, and other chemokines
An acute inflammatory responseis triggered

Cardinal signs of inflammation
(Usually) spontaneous resolution of an acute gout attack as urate crystals are gradually cleared

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25
Q

Gout: Signs and symptoms

A

A painful, red, hot, swollen joint, usually at the big toe metatarsophalangeal joint (MTPJ) in the first attack (‘Podagra’) is the typical presentation - but it can affect any joint.

Additional signs and symptoms:
Tophi
Firm, white, translucent nodules
NB: it usually takes at least 10years after the first attack of acute gout for tophi to develop

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26
Q

Most common cause of acute monoarthritis in the elderly

A

Pseudogout

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27
Q

Pseudogout

A

Most common cause of acute monoarthritis in the elderly

Most cases idiopathic

Caused by deposition of calcium pyrophosphate crystals

Also known as Calcium pyrophosphate dihydrate deposition (CPPD) disease

Most commonly involves the knee and the upper limb.

Knee most affected joint but shoulders, wrists and metacarpophalangeal joints can be too

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28
Q

Pseudogout S + S

A

Severe pain, stiffness, swelling, overlying erythema.
Tenderness over the joint
Fever

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29
Q

Psuedogout vs gout differentiation

A

Pseudogout: Calcium pyrophosphate dihydrate crystals extracted from the synovial fluid of a patient with pseudogout viewed under polarised light – crystals are rhomboid-shaped

Gout: Monosodium urate monohydrate crystals from a gouty tophus viewed under polarised light – crystals are needle-shaped

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30
Q

Septic Arthritis

A

Destructive arthropathy caused by an intra-articular infection.
Infection caused by micro-organisms via either direct inoculation or haematogenous spread
Large joints with abundant blood supply (i.e. shoulder, hip, knee).
Can lead to permanent joint damage and even death.
Requires prompt treatment.

Fever
Purulent synovial fluid
Hot, swollen, acutely painful joint with restriction of movement

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31
Q

How should this presentation be treated until proven otherwise?
Fever
Purulent synovial fluid
Hot, swollen, acutely painful joint with restriction of movement

A

Septic Arthritis

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32
Q

A hot, swollen, acutely painful, stiff joint is a …. until proven otherwise!

A

Septic arthiritis

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33
Q

Diagnosing septic arthritis

A

Arthrocentesis of affected joint for white blood cell (WBC) count, Gram stain and culture.

Cloudy, yellowish appearance of synovial fluid
Raised WBC count, but not 100% sensitive or specific and can be raised in other arthropathies
Identification of causative bacterium via culture (but negative culture does not exclude diagnosis)

Blood samples for cultures:

Full blood count: WBC count raised in 50% of cases (not 100% sensitive or specific)
Blood culture: should always be taken (but negative result does not exclude diagnosis)

Arthrocentesis and blood samples before starting antibiotic therapyunless more urgent treatment is indicated.

Imaging: Usually adjunct to arthrocentesis

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34
Q

Anatomy of muscle compartments: upper limb

A

Arm
Anterior compartment: arm flexion; forearm flexion and supination
Posterior compartment: forearm extension

Forearm
Anterior compartment: hand, thumb and digits flexion; forearm pronation
Posterior compartment: hand, thumb and digits extension; forearm supination

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35
Q

Anatomy of muscle compartments: lower limb

A

Thigh:
Anterior compartment: leg extension
Medial compartment: thigh adduction
Posterior compartment: thigh extension and leg flexion

Leg:
Anterior compartment: foot dorsiflexion and digits extension
Lateral compartment: predominantly foot eversion
Posterior compartment: foot plantarflexion and digits flexion

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36
Q

What define the muscular compartments?

A

Deep fascia: tough and inelastic

Inward projections called intermuscular septa

Septa define muscular compartments in limbs

Compartments contain muscles sharing neurovascular supply and fulfilling similar functions

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37
Q

compartment syndrome

A

Swelling/bleeding in a muscular compartment
Increased compartmental pressure
Ischaemia of muscles and nerves
Tissue necrosis

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38
Q

How is compartment syndrome relieved?

A

Urgent fasciotomy required to relieve the compartmental pressures and ‘save’ the muscle and nerve tissue

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39
Q

Fibroblast:
Chondrocyte:
Osteoblast:
Myofibroblast:
Adipocyte:

A

Fibroblast: secretes ECM for most tissues: collagen and elastin
Chondrocyte: secretes ECM for cartilage: collagen II
Osteoblast: secretes ECM of bone: collagen I
Myofibroblast: secrete ECM and have contractile function
Adipocyte: storage and metabolism of fat

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40
Q

Connective tissue makeup

A

Characterised by abundance of extracellular matrix (ECM, 95%) with few cells (5%) when mature
Cells depend on function/location
ECM is composed of fibres (collagen and elastin) and ground substance

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41
Q

Cartilage cells and matrix

A

Specialised connective tissue with a support function (often the shock absorbers of the body, can be tough or flexible depending on composition of matrix)

Cells: chondrocytes
Matrix: Type II collagen and proteoglycans + others depending on type of cartilage

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42
Q

Cartilage cells

A

Embryonic mesenchymal cells (spindle) become clusters of chondroblasts (rounded)
Surrounded by a layer of perichondrium (mesenchyme derived fibroblastic cells and collagen)
Growth of cartilage is by interstitial (limited division of chondroblasts in ECM) and appositional growth (new chondroblasts from perichondrium).
After matrix deposition cells become less active and become maintaining cells (chondrocytes)

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43
Q

Cartilage ECM

A

ECM = 70% water + Collagen II + ground substance
Proteoglycan - numerous glycosaminoglycans (GAGs) attached to a core protein (bottle-brush structure- negatively charged chains)
Hyaluronic acid – also a GAG
Aggrecan – cartilage specific proteoglycan arrangement

Hydrophilic - provides compressive strength: flexible cushioned surface

Woven with collagen to form an elastic and compressible structure

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44
Q

Hyaline cartilage at joints

A

Resist compression: elasticity and stiffness of proteoglycans
Tensile strength: collagen and hydrogel ground substance
Limited repair and regeneration capacity
Most is avascular: nutrition is by diffusion-limits thickness
Articular surfaces of joints has no perichondrium-no source of new chondroblasts
Cartilage atrophy is reversible after immobilisation – no impact exercise - gradual

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45
Q

Bone matrix

A

Organic: osteoid
Collagen I (90% of organic matrix)
Non-collagenous proteins
Osteocalcin: binds calcium ( local conc.)
Osteonectin: binds calcium to collagen

Inorganic: calcium salt-hydroxyapatite:
66% of dry weight of bone
Calcium phosphate (with some carbonate and fluoride)
Deposited in collagen hole zones

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46
Q

Bone organisation

A

Periosteum
Fibrous CT layer limiting bone
Carries blood supply and osteoprogenitor cells
Not present at the joint ends of long bones

Endosteum
Lines the interior of bones

Dense outer shell: compact bone arranged in osteons (parallel to long axis)

Inner cancellous bone arranged in interconnecting trabeculae with spaces for bone marrow

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47
Q

2 Types of bone structure

A

Woven Bone: immature, haphazard fibre arrangement, mechanically weak – foetal development/fracture repair (rapid osteoid formation)
Lamellar Bone: remodelled woven bone –regular parallel collagen, strong: all adult bone

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48
Q

Bone cells

A

Derived from mesenchymal stem cells
Differentiate into osteoprogenitor cells or chondroblasts
Osteoprogenitor cells differentiate into osteoblasts (periosteum)
Specialises to become osteoblast (ECM & collagen I secretion)
Osteoblasts becomes osteocyte when surrounded by mineralised bone
Osteoclasts from monocyte-macrophage lineage

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49
Q

Osteoblasts

A

Bone building cell – lines bone surfaces
Cuboidal cell with numerous RER and Golgi

Secretes organic bone matrix - osteoid (collagen and non-collagenous proteins)
Mediates mineralisation of osteoid (deposition of inorganic salts into the osteoid)

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50
Q

Mineralisation of bone tissue

A

Osteoblasts secrete collagen and matrix vesicles
Matrix vesicles contain calcium phosphatase.
Calcium released from osteocalcin, which enters the vessel to produce hydroxyapatite crystals.

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51
Q

Canals connecting osteon channels

A

Haversian canal - middle of osteon channel
Volkmanns channel - connect haversian channels

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52
Q

Osteocytes

A

Mature osteoblasts - surrounded by mineralised matrix
Long cytoplasmic processes connecting to each other and osteoblasts (gap junctions)
In lacunae surrounded by extracellular bone fluid that allows nutrient diffusion through the bony channels (canaliculi)

Maintain matrix -no osteocytes: matrix is resorbed
Stress information: respond to tiny currents generated when bone is deformed
Mediates short term release of calcium from bone

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53
Q

Osteoclasts

A

Bone resorbing cell
Phagocytic cell from monocyte-macrophage cell line
Multinucleate mobile cell which attaches to bone surface and resorbs bone leaving a pit behind (Howships lacuna)
Work with osteoblast to regulate bone turnover and remodelling

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54
Q

Osteoclasts action

A

Actin clear zone and ruffled border
Mineral is dissolved by acids
lysosomal enzymes resorb organic matrix

Number and function affected by parathyroid hormone (PTH) and calcitonin
Oestrogen also reduces activity - menopause

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55
Q

Wolff’s Law

A

Bone is constantly remodelled through the coordinated actions of bone cells, to adjust to stresses and strains.
Affects density, orientation and responds to micro fractures and wear & tear

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56
Q

In adults bone turnover is slower than in children, but can increase due to:

A

Change in function (onset of walking)
New demands (running, tennis, jumping)
Repair of fractures
Disease (e.g. Paget’s disease)

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57
Q

Bone growth

A

In long bones: bone grows in length via the epiphyseal growth plate
This fuses in adulthood
Other bones grow by coordinated appositional growth at periosteum and resorption at inner surface (long bones gain in circumference by this method also)

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58
Q

Intramembranous bone development

A

Sheets of mesenchymal cells
Differentiation to osteoblasts in centres of ossification- these merge to form trabecular bone that is remodelled (bone template)
Remaining mesenchyme makes bone marrow and periosteum
Flat bones of skull, maxilla and mandible
In the adult to increase the width of long bones

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59
Q

Endochondral bone development

A

Cartilage template
Blood supply to shaft of bone causes osteoblast differentiation: primary centre of ossification
At birth blood supply to the epiphyses instigate secondary centres of ossification
Cartilage growth plate remains to allow the bone to lengthen
Long bones

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60
Q

Growth plate of bone development

A

Epiphyseal end: Proliferation
Diaphyseal end: chondrocytes mature and die and are replaced by bone

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61
Q

What is autoimmunity?

A

Loss of self-tolerance and the production of antibodies (typically) against self proteins within cells or tissues which results in a hypersensitivity reaction or autoimmune disease.

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62
Q

How does self tolerance come about?

A

During lymphocyte maturation, clonal selection/de-selection prevents production of cells that recognise self-proteins and these are eliminated via apoptosis.
Remaining circulatory pool of mature B and T cells are non-responsive, that is tolerant to the normal components of the body.
But deselection not 100% effective, everyone has potentially autoreactive cells.

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63
Q

Peripheral tolerance

A

Can encounter antigens that are not exposed to lymphocytes or are present at such low amounts that they do not activate lymphocytes.

Peripheral tolerance can arise from lack of co-stimulatory signals to autoreactive cells.

Peripheral tolerance can arise from inhibition of autoreactive T-cells by Treg cells.

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64
Q

Autoimmune classifactions

A

antibodies to specific proteins (autoantibodies) (Type II).
formation of soluble immune complexes (Type III).
activation of T-cells (Type IV).

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65
Q

Organ specific autoimmune diseases and antigens examples

A

Graves disease - thyroid stimulating hormone receptor
Type I diabetes - islet cells

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66
Q

systemic autoimmune diseases and antigens examples

A

RA - IgG
Lupus - ds DNA

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67
Q

Examples of Type II autoimmune diseases

A

haemolytic anaemia - Rh blood antigen
pempigus vulgaris - epidermal cadherin

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68
Q

Examples of Type III autoimmune diseases

A

RA - Rh factor IgG complexes
Lupus - DNA

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69
Q

Examples of Type IV autoimmune diseases

A

RA
Type I diabetes

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70
Q

Autoimmune susceptibility: genetic influences

A

Human leukocyte antigen (HLA) houses a super locus with contains many genes that reside together on chromosome 6.
Allelic variation within these genes is linked to risk of autoimmune disease.

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71
Q

Rheumatoid Arthritis pathophysiology

A

abnormally produced antibody generally of IgM class specific for the Fc region of IgG. IgM RF can indicate poor prognosis if at high titre.
Termed rheumatoid factor present in ~85% of RA patients so reasonably sensitive marker but also detected in other autoimmune diseases such as SLE.

Anti-citrullinated protein antigen (ACPA) antibodies present in ~85% of RA patients so quite sensitive for RA and not often observed in other diseases.

Citrulline formed from de-imination of arginine residues in proteins
Citrullinted proteins detected in synovial membranes of affected joints in RA.
ACPA prognostic for more aggressive version of RA.
Presence of ACPA in undifferentiated arthritis indicates probably progression to RA.

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72
Q

Risk factors for RA

A

Shared HLA epitopes - favours autoantigenic presentation
PTPN22 - less clonal deletion
Smoking - induces citrullination of lung proteins

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73
Q

Other information that can differentiate between inflammatory (RA) andnon-inflammatory (osteo)arthritis ?

A

Extra-articular features

Synovialfluid examination

ESR, CRP

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74
Q

Inflammatory joint features of RA

A

Morning stiffness (longer than 30 minutes)

Joint swelling

Symmetry

No DIP joints involvement

Deformed joints (if untreated,long-standing disease)

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75
Q

Visual signs of rheumatoid arthritis

A

Metacarpophalangeal joint, proximal interphalangeal joint inflammation
symmetrical
30 minutes of pain in the morning but gets better as day goes on
Boutonniere deformity of the thumb (bent upwards)
Ulnar deviation at MCP
Swan necking of the fingers
Hammer toe

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76
Q

What can form within a joint after a period of RA

A

Pannus - a type of extra growth in your joints that can cause pain, swelling, and damage to your bones, cartilage, and other tissue.

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77
Q

Investigations of RA

A

Regular blood tests: FBC, U&E, LFT, ESR, CRP
Immunological : RF, Anti CCP
Blood tests to exclude other diseases

Radiology

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78
Q

Radiographic features of RA

A

Peri-articular osteopenia
Bony erosions
Joint space narrowing
Joint subluxations

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79
Q

Features of RA associated with poor prognosis

A

Presence of (and titre) of rheumatoid factor
Presence of (and titre) of anti-CCP antibodies
Presence of erosive disease at presentation
Disease activity at presentation
Number of swollen joints
Levels of acute phase reactants (CRP/ESR)
Presence of extra-articular features
nodules
vasculitis

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80
Q

Treatment of RA

A

NSAIDsNonsteroidal anti-inflammatory drugs (NSAIDs) can relieve pain and reduce inflammation. Over-the-counterNSAIDsinclude ibuprofenand naproxen

SteroidsCorticosteroid medications, such as prednisone, depomedrone

ConventionalDMARDs (Disease modifying anti rheumatic drugs) These drugs can slow the progression of rheumatoid arthritis and save the joints and other tissues from permanent damage. CommonDMARDsinclude methotrexate leflunomide, hydroxychloroquine and sulfasalazine

Biologic DMARDs (biology therapy)Various classes

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81
Q

Timeline of RA treatment

A

Early initiation of DMARD and escalation of treatment reduces risk of disease progression and co-morbidities

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82
Q

UK, WHO, UK EQUALITY ACT 2010 definition of long-term illness

A

Long-term conditions or chronic diseases are conditions for which there is currently no cure, and which are managed with drugs and other treatment, for example: diabetes, chronic obstructive pulmonary disease, arthritis and hypertension.

Disabilities is an umbrella term, covering impairments, activity limitations, and participation restrictions. An impairment is a problem in body function or structure; an activity limitation is a difficulty encountered by an individual in executing a task or action; while a participation restriction is a problem experienced by an individual in involvement in life situations

a physical or mental impairment that has a ‘substantial’ and ‘long-term’ negative effect on your ability to do normal daily activities.

Substantial = impacts daily tasks

Long-term = 12 months or more

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83
Q

International Classification of Functioning, Disability & Health

A

Principles:
universality – applicable to all irrespective of health condition or physical, social and cultural context
parity and aetiological neutrality – focuses on functioning, does not distinguish between ‘mental’ and ‘physical
neutrality – captures positive & negative aspects of disability
recognises environmental influence (e.g. climate, building design, attitudes, laws) as ‘an essential aspect of the scientific understanding of functioning and disability’

Dimensions:
(i) body functions and structures e.g. mobility at purely bodily level – can’t raise arm above head
(ii) activities (individual level) e.g. mobility at home – needs stairlift to access bedroom
(iii) participation (social level) e.g. mobility in performing social role – unable to walk unaided to work a mile away
(iv) environmental factors (whether as facilitators or barriers) e.g. mobility in wider social context – bus route to work exists but this bus doesn’t have wheelchair access

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84
Q

QALYs and DALYs

A

QALYs are years of healthy life lived; DALYs are years of healthy life lost

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85
Q

Kubler-Ross’s five stages of grief

A

Denial

Anger

Bargaining

Depression

Acceptance

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86
Q

Shontz adjustment theory

A

Shock
Realisation
Defensive retreat
Acknowledgment
Adjustment

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87
Q

Transactional model of stress & coping (Lazarus & Folkman)

A

Primary appraisal – benign or stressful
Secondary appraisal – challenge or threat
Coping – emotion based vs. problem based

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88
Q

Moo’ and Schafer’s crisis model

A

Desire of psychological homeostasis
Seven challenges
Coping shaped by: event-related factors, environmental factors, personal factors, and cognitive & coping styles

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89
Q

Frank’s 3 types of illness narratives

A

Restitution narrative

Chaos narrative

Quest Narrative

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90
Q

Social model of disability

A

Social model of disability

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91
Q

Impairment vs disability

A

Impairment = physical and/or cognitive limitation a person has
e.g. the inability to walk because of a spinal cord injury

Disability = the barriers to living a full life a person with an impairment experiences b/c of the way society is organised
e.g. Cannot eat out because restaurants are not wheelchair accessible

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92
Q

Vertebral Column levels

A

7 cervical vertebrae

12 thoracic vertebrae

5 lumbar vertebrae

5 fused sacral vertebrae

3-4 fused coccygeal vertebrae

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93
Q

A Typical Vertebra

A

Body

Pedicles

Vertebral (neural) Arch
Transverse processes
Laminae
Spinous process
Superior and inferior articular facets
Intervertebral notch*

Spinal canal

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94
Q

Typical Cervical Vertebrae

A

Saddle-shaped body

Uncinate process

Transverse foramina

Triangular spinal canal

Bifid spinous process

Parallel articular facets (cup-shaped or planar)

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95
Q

Atypical Cervical Vertebrae: C1

A

No vertebral body or spinous process
Kidney shaped articular facets
Anterior and posterior arch and tubercues

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96
Q

Atypical Cervical Vertebrae: C2

A

Dens/Odontoid process
Facies articularis posterior - attaches transverse ligament
Facies articularis anterior - articulates with C1

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97
Q

Atypical Cervical Vertebrae: C7

A

Long spinous process - vertebral prominens
attaches ligmentum nuchae

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98
Q

Typical Thoracic Vertebrae

A

Heart-shaped body

Demifacets for ribs

Round spinal canal

Long spinous process

Articulating facets on transverse processes

Planar articular facets
Superior: face posteriorly
Inferior: face anteriorly

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99
Q

Atypical Thoracic Vertebrae: T1, T10 - T12

A

T1 - complete superior costal facet
T10 - complete superior costal facet
T11 - No transverse articular facet
T12- Lumbar like pattern of inferior facet

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100
Q

Lumbar Vertebrae

A

Large vertebral body

Very small arch

Blunt, hatchet-shaped spinous process

Comparatively small transverse processes

Articular facets
Superior: face posteromedially, have mammillary bodies
Inferior: face anterolaterally

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101
Q

Lumbosacral transitional vertebrae

A

Lumbarisation of S1
Sacralisation of L5

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102
Q

Vertebral Column: Curvatures

A

Cervical Lordosis

Thoracic Kyphosis

Lumbar Lordosis

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103
Q

What is between adjacent vertebral bodies

A

Intervertebral (IV) discs

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104
Q

IV Disk

A

Inner nucleus polposus
Outer annulus fibrosis

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105
Q

IV discs degeneration with age

A

The nucleus pulposus gradually becomes less hydrated and increasingly fibrous with age

The discs become stiffer and more liable to injury

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106
Q

Joints of the vertebral bodies: Ligaments

A

Anterior Longitudinal Ligament

Posterior longitudinal Ligament

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107
Q

In which direction to slipped discs protrude

A

Lateral to posterior longitudinal ligament
Towards rami

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108
Q

Joints between inferior and superior articular facets

A

Zygapophyseal joints

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109
Q

Joints of the vertebral arches: Accessory ligaments

A

Ligamentum Flavum - connects adjacent lamina

Interspinous Ligament - between spinous processes

Supraspinous Ligament - connects tips of the spinous processes

Intertransverse Ligament - connects transverse processes

Ligamentum Nuchae - occipital to cervical

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110
Q

Atlanto-occipital joint

A

superior facet of the atlas - condyloid joint - condoyle of occiput

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111
Q

Atlanto-axial joint

A

1 median joint - pivot - anterior arch of the atlas and the Dens
2 lateral joints - plane/gliding - Z joint

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112
Q

Ligaments of the occipito-atlantoaxial region

A

Nuchal ligament

Posterior atlanto-occipital membrane - continuation of the flavum

Cruciate ligament of the dens - body of axis -> clivus

Alar ligaments of the dens - oblique direction dens -> clivus

Apical odontoid ligament - dens -> clivus

Tectorial membrane - continuation of the posterior longitudinal ligament

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113
Q

Muscles of the Back

A

(Extrinisic -> intrinsic)
Trapezius
Latissimus dorsi
Levator scapulae
Rhomboid minor
Rhomboid major

Serratus posterior superior
Serratus posterior inferior

Splenius capitis
Splenius cervicis

Erector Spinae group - Iliocostalis, longissimus, spinalis

Transversospinalis group - rotatores, semispinalis, multifidus.

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114
Q

Postural muscles

A

Psoas major – attaches to all the lumbar vertebrae and discs
It is a primary hip flexor but also helps to stabilize the spine

Quadratus lumborum – attaches to the lumbar vertebrae and pelvis and helps to maintain posture

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115
Q

The muscles of the back consist of:

A

Extrinsic back muscles – superficial and intermediate muscles, innervated by anterior rami of spinal nerves

Intrinsic (‘true’) back muscles – deep muscles, innervated by posterior rami of spinal nerves

Extrinsic muscles are responsible for producing movements of the ribs and upper limbs

Intrinsic muscles maintain posture and move the vertebral column (and head)

Gross spinal movements are a result of the sum of many small movements occurring at each vertebral level

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116
Q

Spinal cord origin and terminus

A

Spinal cord continuous cranially with the medulla oblongata and terminates caudally as the conus medullaris around L1/L2 vertebral level

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117
Q

Spinal nerve rootlets and roots

A

Ventral (anterior) rootlets and ventral root contain axons of somatic motor neurons and sympathetic neurons (for T1 – L1/L2 spinal nerves)

Dorsal (posterior) rootlets and dorsal root contain the central processes of pseudo-unipolar somatic sensory neurons and visceral afferent (sensory) neurons
Neuronal cell bodies in dorsal root ganglion

Ventral and dorsal roots join to form a spinal nerve

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118
Q

diseases that can affect the intervertebral foramen

A

Some disease processes that can affect this opening and compress the spinal nerve:

Osteoarthritis
Injury affecting the facet joints or the pedicles
Intervertebral disc herniation
Vertebral body fracture/dislocation
Injury to spinal ligaments

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119
Q

Ventral and dorsal rami

A

Ventral rami
Larger, supply the limbs and the anterolateral aspects of the trunk
Unite to form major nerve plexuses, e.g. the brachial plexus

Dorsal rami
Smaller and supply intrinsic back muscles, facet joints and a narrow strip of skin on the back

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120
Q

Cauda equina

A

Made up of spinal nerve rootlets from L3 – Co segments of the spinal cord
Innervate lower limbs + pelvic region

Rootlets of the sacral spinal nerves (S1-5) exit the spinal cord at vertebral level T12/L1 – the sacral spinal cord

These rootlets then run all the way down in the vertebral canal to exit the IV foramina of the sacrum

The actual spinal nerves for these rootlets are formed just prior to entering the intervertebral foramen

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121
Q

Cauda equina syndrome (spinal stenosis)

A

Sciatica
Loss of bladder and bowel control
Flaccid paralysis of the lower limbs
‘Saddle area’ (perineal) sensory loss

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122
Q

Spinal cord meninges - coverings

A

Dura mater
Extends from the foramen magnum to the coccyx
Continuous with cranial dura (around the brain)
Merges with epineurium of spinal nerves

Arachnoid mater
Surrounds the brain and extends down to S2 vertebral level
Has fine strands of connective tissue crossing subarachnoid space - trabeculae

Pia mater
Firmly adhered to the brain and spinal cord
Forms flat denticulate ligaments
Continuous with filum terminale

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123
Q

Spinal cord meninges - spaces

A

Epidural space (extradural space)
Between the dura mater and the vertebral column
Contains fat (adipose) and internal vertebral venous plexus
Local anaesthetics can be injected into this space

Subdural space
Potential space between dura and arachnoid mater
Only obvious when it fills with blood, CSF or pus

Subarachnoid space
Between arachnoid and pia mater
Extends further (S2) than the spinal cord (L1/2)
Contains cerebrospinal fluid (CSF) and vessels
Local anaesthetics can be injected into this space

CSF can be drawn from this space: lumbar puncture

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124
Q

Lumbar puncture (spinal tap) procedure

A

Needle inserted in adults between L3/L4 vertebrae or L4/L5 vertebrae
Avoids spinal cord (L1/L2 vertebral level)

Different in children: between L4/L5 recommended as spinal cord may extend more inferiorly e.g. L3 vertebral level

Contraindications
Raised intracranial pressure, local skin infections, coagulopathy

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125
Q

What happens to the spinal meninges when spinal nerves merge off

A

The dura mater of the spinal cord covers the rootlets and merges with the epineurium.
The arachnoid mater and pia mater merge with the perineurium of the spinal nerve, sealing the subarachnoid space

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126
Q

The spinal cord and its roots and nerves are supplied with blood via:

A

Longitudinal branches from the vertebral arteries
One anterior spinal artery
Two posterior spinal arteries

Segmental arteries – help to provide additional blood to supplement the anterior + posterior spinal arteries

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127
Q

Segmental arteries

A

Vertebral and deep cervical arteries (cervical region)
Intercostal arteries (thoracic region)
Lumbar arteries (lumbar region)

The largest segmental artery is the great radicular artery (artery of Adamkiewicz): reinforces blood supply to lower spinal cord

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128
Q

How do segmental arteries join the longitudinal arteries?

A

Segmental arteries enter the vertebral canal through the intervertebral foramina and anastomose with branches of the longitudinal spinal arteries to form a pial plexus

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129
Q

What supplies each section of the spinal cord

A

Anterior spinal artery = anterior 2/3rds of thespinal cord

Posterior spinal artery supplies the posterior 1/3rd of the spinal cord

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130
Q

Spinal cord: venous drainage

A

Veins from within the spinal cord drain into the venous plexus of the pia mater

The veins of the internal vertebral venous plexus (Batson’s plexus) lie in the epidural space

Veins draining the spinal cord and vertebral column eventually drain into the major veins of the body:
Azygos
Hemiazygos
Right highest intercostal veins
And eventually into the Superior vena cava (and back to the heart)

Internal vertebral plexus veins are valveless
Drainage flow dependent on posture and respiration

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131
Q

What about venous drainage of the spinal cord is problematic?

A

This venous plexus is continuous with the veins draining the prostate

prostate cancer may metastasise via the internal vertebral venous plexus to the CNS

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132
Q

Structure of a spinal nerve layers

A

epineurium: dense layer of fibrous tissue; external coat of nerve
perineurium: several layers of flattened cells separated by layers of collagen, surrounding a bundle (fascicle) of nerve fibres. Cells that form the inner surface are joined by tight junctions
endoneurium: thin layer of tissue surrounding individual axons and myelin sheath

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133
Q

Characteristics of muscle types

A

Skeletal muscle:
striated
capable of rapid, strong contractions
attached to the skeleton (hence its name), so it moves bones
under voluntary nervous control (usually)
multi-unit muscle (see later)

Cardiac muscle, confined to the heart:
striated
contracts rhythmically
involuntary, innervated by autonomic neurones
single-unit muscle (functional syncytium)

Non-striated or smooth muscle:
so-called because no striations visible
contracts in a slow and sustained manner
involuntary, innervated by autonomic neurones
can be single-unit OR multi-unit, depending on location or circumstances

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134
Q

Skeletal muscle organization

A

Myofibers (muscle cells) - formed from myofibrils
Elongate cells
Arranged parallel to one another and bundled by connective tissue into fascicles

Sarcolemma – cell membrane
Striated (banded)

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135
Q

myofibrils

A

Myofibrils: long bundles of protein
Made up of thick (myosin) and thin (actin) protein filaments

Myofilaments arranged in sarcomeres
Repeated units i.e. a polymer

From one Z-disc to the next, thick filaments are at center, thin filaments at either end attached to the Z-discs

I-band near either end – only thin myofilaments
A-band at midsection – thick filaments
H-zone at center – only thick filaments (no overlap with thin)

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136
Q

Two types of muscle fibre arrangments

A

Parellel-fibred muscles have longer fibres (more sarcomeres in series) than pennate-fibred muscles, thus they are capable of a greater shortening velocity

Pennate-fibres muscles have more fibres but of shorter length. Hence pennate muscles are stronger but slower contracting than parallel-fibred muscles

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137
Q

Motor units

A

an alpha motor neurone in the spinal cord and all of the muscle fibres it innervates

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138
Q

Muscles; HENNEMAN’S SIZE PRINCIPLE:

A

SMALLEST MOTOR UNITS RECRUITED FIRST

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139
Q

Types of Skeletal Muscle Fibres

A

Type I (slow twitch, red) fibers
Slow contraction speeds
Adapted for aerobic respiration
Large blood supply
High myoglobin content (O2 storing pigment)
High mitochondrial densities

Type II (fast twitch, white) fibers
Fast contraction speeds
Adapted for anaerobic respiration (fermentation)
Less blood, myoglobin, and mitochondria
High content of glycogen and glycolytic enzymes
- Two types
Fast glycolytic fibers (rely mainly on glycolysis)
Fast oxidative fibers (more capacity for aerobic respiration)

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140
Q

Nerve endings are referred to as sensory receptors. Functionally, there are 3 types of receptors:

A

Interoceptors. Occur in viscera and respond principally to mechanical and chemical stimuli

Exteroceptors. Lie superficially in the skin and respond to different sensory modalities i.e. painful, temperature and touch stimuli,

Proprioceptors. Occur in muscles, joints, and tendons and provide awareness of posture and movement (kinaesthesia)

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141
Q

Structurally, Sensory receptors may be:

A

Encapsulated – surrounded by a structural specialisation of non-neural tissue (often called a corpuscle)
Unencapsulated – terminal branch of sensory nerve fibre lying freely in the innervated tissue

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142
Q

Properties of cutaneous sensory receptors

A

Receptor type - Function - Threshold - Adaptation
Thermoreceptor (Free nerve ending) Temperature Varies Rapid

Nociceptor
(Free nerve ending) Pain High Slow

Mechanoreceptor (Meissner corpuscle) Touch (dynamic deformation) Low Rapid

Mechanoreceptor (Merkel cell/disks) Touch (indentation) Low Slow

Mechanoreceptor (Ruffini corpuscle) Touch (stretch) Low Slow

Mechanoreceptor (Pacinian corpuscle) Touch (vibration) Low Very rapid

143
Q

Properties of nerve fibres

A

Fibre type -Function - Diameter (µm) - Conduction velocity (m/s)

Aa (fast!) Motor 12-20 (big!) 70-90

Ab Touch, pressure 5-12 30-70

Ag Muscle spindle motor 3-6 15-30

Ad Pain, T, touch 2-5 12-30

B Preganglionic autonomic <3 3-15

C (slow!) Pain, reflex, postganglionic sympathetic 0.3-1.3 (small!) 0.5-2.3

144
Q

Muscle spindles detect changes in :

A

Muscle spindles (stretch receptors) detect changes in length of a muscle.

145
Q

Muscle spindle structure function

A

Small muscle fibres inside are known as intrafusal fibres
The main muscle fibres outside are known as extrafusal fibres

Type I(a) Annulospiral fibres sense muscle length and rate of change in length
Type II Flower-spray
fibres only really sense muscle length

146
Q

(Golgi) Tendon Organs sense:

A

(Golgi) Tendon Organs sense tension in muscle (or force of contraction)

147
Q

Golgi tendon structure function

A

Located at the junction of the muscle & the tendon

Active contraction of the muscle activates the Golgi tendon organ (it is compressed by collagen and fires action potentials)

Sensitive to increases in muscle tension caused by muscle contraction

It’s normal function is to regulate muscle tension within an optimal range (may also prevent muscle overload).

Golgi sensory neurone: 1b afferent fibre

148
Q

Stretch reflex (or myotatic reflex)

A

Anatomically, one of the simplest reflexes
Mediated by just two neurones – one afferent and one efferent
This is a monosynaptic reflex

Afferent neurones convey impulses from intrafusal muscle stretch receptors to the CNS
Motor neurones convey impulses back to the extrafusal muscle

Reciprocal innervation: The inhibitory input to the hamstrings involves inhibitory interneurones and is polysynaptic.

149
Q

Gamma motor neurones adjust:

A

Gamma motor neurones adjust the sensitivity of muscle spindles

150
Q

Gamma motor neurones structure function

A

Innervate intrafusal muscle at two ends of muscle spindle

They stretch muscle spindles & lower the threshold of stretch receptors to externally applied stretch (increases sensitivity of stretch reflex)

Increases likelihood of discharge of 1a afferents

This is a mechanism for maintaining sensitivity of the spindle over a wide range of muscle lengths

151
Q

AP Refractory period

A

When Na+ channels are closed and inactivated, no new action potential (AP) can be initiated – this is termed the absolute refractory period

When the membrane potential is returning to its resting level, some Na+ channels are in the resting state and a new AP can be initiated if the stimulus is strong enough – this is the relative refractory period

These mechanisms help to:
Limit the rate of firing of neurone
Prevent antidromic conduction

152
Q

ACh release at the NMJ AP

A

Release of a single vesicle of ACh (at rest) results in a so-called miniature end-plate potential, whereas release of several (when the motor neurone is activated) causes an end-plate potential or EPP

153
Q

Links to excitation-contraction coupling in skeletal muscle…

A

Action potential propagates down the sarcolemma
Transverse tubules conduct AP into the cell’s interior
Ca2+ release channels open in sarcoplasmic Reticulum

154
Q

What’s the relationship between T tubules and the SR?

A

The T tubules are deep invaginations of the muscle cell membrane and are placed at the junction of the A bands and the I bands
They provide a mechanism for changes in membrane potential to be communicated right to the inners of the muscle fibre
In striated muscle, each T tubule comes into close apposition with SR at several different levels
When the membrane on the T tubule is depolarised, this triggers release of calcium from the SR
Thus, the T tubules and SR allow calcium concentration in the sarcoplasm to rise in the area where they are needed

155
Q

Non-depolarising neuromuscular blocking drugs.

A

Competitive antagonists at nicotinic acetylcholine receptor on skeletal muscle
Derived from curare and tubocurarine (no longer used)
Tubocurarine – slow to recover, has adverse effects.
Superseded by…
Atracurium
Short-acting (15-30 min)
Can be given by infusion for longer term effects
Pancuronium
Longer duration (60-120 min)
Used for longer term action in intensive care
Rocuronium
Faster onset (within 2 min)
Intermediate duration (30-40min)

156
Q

Acetylcholinesterase inhibitors

A

Neostigmine, pyridostigmine
Increase concentration of acetylcholine in synapse
increased receptor activation – both nicotinic and muscarinic

=> depolarising block + PS effects

157
Q

Depolarising block drugs

A

Suxamethonium, fast onset and short duration
Nicotinic acetylcholine receptors are ligand-gated ion channels.
Activation of neuron
 influx of sodium ions through nicotinic receptor and sodium channels
 depolarisation (increase in membrane potential)
Muscle contraction
Continued activation  block

158
Q

Myasthenia Gravis + diagnosis + treatment

A

Most people with myasthenia gravis have weakness in the muscles of the eyes, eyelids and face.
Autoimmune – antibodies against nicotinic acetylcholine receptors  reduced muscle control

Diagnosis – use short-acting acetylcholinesterase inhibitor – edrophonium

Treatment – use medium-duration acetylcholinesterase inhibitor e.g. pyridostigmine

159
Q

Osteological landmarks of the clavicle:

A

Shaft(body)
Sternal end
Sternal facet
Acromial end
Acromial facet

160
Q

Osteological landmarks of the scapula:

A

Inferior angle
Medial border
Lateral border
Supraspinous fossa
Infraspinous fossa
Spineof the scapula
Acromion
Clavicular facet
Glenoid fossa
Supraglenoid and infraglenoid tubercles
Coracoid process
Subscapular fossa

161
Q

Osteological landmarks of the proximal humerus:

A

Head
Anatomical neck
Surgical neck
Lesser tubercle and crest
Greater tubercle and crest
Intertubercular (bicipital) groove(sulcus)
Deltoid tuberosity
Radial (spiral) groove

162
Q

Structures stabilising the sternoclavicular Joint:

A

Synovial saddle joint: elevation/depression; protraction/retraction

Anterior and posterior sternoclavicular joint ligaments
Interclavicular ligament
Costoclavicular ligament
Articular disc
Sternocleidomastoid, sternothyroid, sternohyoid, and subclavius muscles

163
Q

acromioclavicular joint

A

Between acromion and clavicle

Plane/gliding synovial joint: gliding movements in elevation/depression; protraction/retraction

Incomplete articular disc (when present)

Periarticular structures reinforcing joint

Dislocations common due to loose fibrous capsule

164
Q

Structures stabilising the acromioclavicular joint:

A

Acromioclavicular joint ligaments
Deltoid and upper trapezius
Coracoclavicular ligament
Articular disc (when present)

165
Q

scapulothoracic joint

A

The scapulothoracic ‘joint’ is a muscular articulation between the scapula and the rib cage.
Enables the scapula to slide and glide over the ribs

166
Q

glenohumeral joint

A

Between humeral head and glenoid fossa

Ball and socket joint, multiaxial

Very mobile, very unstable

Active and passive stabilisers

Dislocations more common antero-inferiorly

167
Q

Stabilisers of the GH joint:

A

Joint capsule and associated GH capsular ligaments
Coracohumeral ligament
Rotator cuff muscles
Tendon of long head of the biceps brachii& transverse humeral ligament
Glenoid labrum
Vacuum effect (negative intracapsular pressure)

168
Q

Condition affecting Glenohumeral joint capsule

A

adhesive capsulitis - frozen shoulder

169
Q

The subacromial space

A

Inferior to coraco-acromial arch

Subacromial bursa

Supraspinatus muscle & tendon

Inflammation of bursa or tendon  swelling and pain in flexion and abduction

170
Q

Osteological landmarks of the distal humerus

A

Trochlea
Coronoid fossa
Capitulum
Radial fossa
Medial and lateral epicondyles
Olecranon fossa
Groove for ulnar nerve

171
Q

Osteological landmarks of the proximal ulna

A

Olecranon process
Coronoid process
Trochlear notch
Radial notch
Ulnar tuberosity

172
Q

Osteological landmarks of the proximal radius

A

Articular facet head of the radius
Head of radius
Neck of radius
Radial tuberosity

173
Q

Radial head subluxation (‘Nursemaid’s elbow’)

A

Elbow dislocations: most common type in children

Bones and periarticular tissues still developing

Little force  ‘pulled elbow’

Reduction by gently moving bones back into position

Likelihood of recurrence

Prevention: educating parents and caregivers

174
Q

Muscles stabilising the pectoral girdle and nerve supply

A

Trapezius: supplied by a cranial nerve (Accessory CN XI)
Rhomboids: dorsal scapular nerve (C5)
Levator scapulae: dorsal scapular nerve (C5)

Serratus anterior: long thoracic nerve (C5-7)

175
Q

Rotation of the scapula in flexion and abduction

A

Trapezius and serratus anterior muscles laterally rotate the scapula during upper limb elevation

If the scapula can’t rotate, the humeral head ‘hits’ the acromion at about 90˚ of elevation  further flexion or abduction is impossible

176
Q

Anterior axio-appendicular muscles

A

Deltoid, pec major

177
Q

Pectoral girdle muscles origin and insertion

A

Rhomboids - spine => medial scapula
Levator scapulae - C vertebrae => superior angle of scapula
Serratus anterior - ribs => medial border of scapula
Pectoralis major - clavicle/sternum => greater tubercle of humerus
Deltoid - clavicle and scapula => deltoid tuberosity of humerus
Rotator cuff muscles - scapula => proximal humerus

178
Q

An unstable ‘winging’ scapula

A

Loss of the strength in stabilising muscles = loss of some stability of the whole of the upper limb

If you can’t place the hand where it needs to be for prehension (ie gripping activities), then major functional problems result

179
Q

The rotator cuff muscles

A

Originate from the scapula

Insert into proximal humerus

C5-6 nerve supply

Movement

Stability

180
Q

The rotator cuff muscles (SITS) - function

A

Supraspinatus - initiates abduction

Infraspinatus - external rotation

Teres minor - external rotation

Subscapularis - internal rotation

181
Q

Muscles controlling the elbow joint

A

Anterior:

Flexors (and supinator)
Musculocutaneous nerve
Biceps brachii reflex

Posterior:

Extensor
Radial nerve
Triceps reflex

182
Q

The axilla: contents

A

AXillary artery and vein
Infraclavicular part of brachial plexus
Lymph Nodes (5 groups)
Long thoracic nerve and intercostal nerves
Axillary fat tissue

183
Q

5 groups of axillary lymph nodes:

A

Apical: medial to axillary vein, superior to pectoralis minor

Central: near the floor, easiest to palpate

Pectoral (anterior): along lower border pectoralis minor

Subscapular (posterior): anterior to subscapularis

Humeral (lateral): behind axillary vein, drain the upper limb

184
Q

upper limb arterial and venous supply

A

Subclavian > axillary > Anterior and posterior humeral circumflex arteries – GHJ, humeral head, muscles
> Profunda brachii artery – posterior compartment of arm > radial and ulna

The cephalic vein usually forms over the anatomical snuff-box on the radial side of the wrist from the radial end of the dorsal venous plexus>

The basilic vein arises medially in the dorsal venous network of the hand

The median cubital vein runs medially to join the basilic vein

Deep veins accompany the radial and ulnar arteries

They unite near the elbow as paired, deep brachial veins

Brachial veins drain into Axillary vein

Axillary vein  Subclavian vein

Subclavian vein + internal jugular vein = brachiocephalic vein

L+R brachiocephalic veins drain into SVC

185
Q

Function of The arterial anastomoses around the scapula

A

anastomotic network provides alternative route for arterial blood in the event of occlusion

186
Q

Topography of brachial plexus

A

Emerges from the posterior triangle of theneck
Passes deep to the clavicle
Passes through the axilla

187
Q

posterior triangle of the neck

A

Boundaries of posterior triangle:

Middle third of the clavicle inferiorly
Trapezius muscle posteriorly
Posterior border of the sternocleidomastoid muscle anteriorly

Contents of posterior triangle:

Accessory nerve (CN XI)
Phrenic nerve
Lymph nodes
Subclavian artery
Roots of the brachial plexus

188
Q

Roots of the brachial plexus emerge from

A

Roots of the brachial plexus emerge between anterior scalene and middle scalene muscles

189
Q

Route of the Autonomic fibres of the brachial plexus

A

Exit the spinal cord segment of T1 travelling in anterior rootlets/root
Enter the spinal nerve
Exit via the white ramus communicans to enter the sympathetic chain
Use the sympathetic chain to travel up to join cervical spinal nerves (via grey ramus communicans)

190
Q

Which spinal nerves form the brachial plexus?

A

C5-8 and T1
Only part of T1 contributes to brachial plexus
There is some variation (as is usual in anatomy!!) – C4 and T2 may be involved

191
Q

Which rami of these spinal nerves form the brachial plexus?

A

Ventral (anterior) rami
Remember that this is the larger of the two rami that spinal nerves divide into (the smaller one is the dorsal or posterior ramus)

192
Q

What are the brachial plexus root short branches and their clinical relavance

A

Dorsal scapular n from C5
Long thoracic n. from C5,6,7

Nerve lesion: muscle paralysis and unstable scapula with ‘winging’

193
Q

What are the brachial plexus trunk short branches and their clinical relavance

A

Suprascapular n. from superior trunk

lesions > muscle wasting to supraspinatus muscle

194
Q

What are the brachial plexus cords short branches and their clinical relevance

A

Sup. subscapular n. from C5,6
Thoracodorsal n. from C6,7,8
Inf. subscapular n. from C5,6

All from the posterior cord

195
Q

Axillary Nerve

A

Axillary Nerve (C5-6)
Motor function:
Deltoid and teres minor

Sensory function:
Skin over upper lateral arm (Sergeant’s patch)

Clinical significance:
Numbness Sergeant’s patch & weak arm abduction (15-90°)

196
Q

Radial Nerve

A

Radial Nerve (C5-8; T1)

Motor function:
All muscles of posterior compartments of arm and forearm

Sensory function:
Skin posterior aspect of arm and forearm, lower lateral surface of the arm, dorsal lateral surface of the hand

Clinical significance:
Numbness rn distribution & weak extension @ elbow, wrist, fingers; ‘wrist drop’ deformity

197
Q

Musculocutaneous Nerve

A

Musculocutaneous Nerve (C5-7)

Motor function:
All muscles of anterior compartment of the arm

Sensory function:
Skin lateral aspect of forearm

Clinical significance:
Weak supination & flexion of the forearm

198
Q

Median Nerve

A

Median Nerve (C5; C6-T1)

Motor function:
All muscles anterior compartment forearm, except flexor carpi ulnaris and medial ½ of flexor digitorum profundus

Thenar muscles and 2 lateral lumbricals (hand)

Sensory function:
Palmar aspect of lateral 3 and ½ digits
Lateral side of palm
Middle of wrist

Clinical significance:
Carpal tunnel syndrome  wasting thenar muscles, numbness, weak grip

199
Q

Ulnar nerve

A

Ulnar Nerve (C7; C8-T1)

Motor function:
Flexor carpi ulnaris and medial ½ flexor digitorum profundus (forearm)

All intrinsic muscles hand, except thenar muscles and 2 lateral lumbricals

Sensory function:
Palmar aspect of medial 1 and ½ digits & associated palm and wrist

Dorsal aspect of medial 1 and ½ digits

Clinical significance:
wasting hypothenar muscles, numbness

200
Q

3 Types of nerve lesion

A

Avulsion: most severe, nerve root pulled out of the spinal cord

Stretch (neuropraxia): nerve fibres are stretched

Rupture: partial or full tear of the spinal nerve

201
Q

Brachial plexus Lesions usually affect either upper or lower brachial plexus, how?

A

Upper plexus (C5-C7):

Angle between the shoulder and the neck forcibly widens
Proximal musculature is involved

Lower plexus (C8-T1):

Angle between the shoulder and the trunk forcibly widens
Distal musculature is involved

202
Q

Upper brachial plexus lesions: causes

A

Motorcycle accidents: shoulder hits a fixed vertical structure (A) or the ground (B)

Large falling objects (C): result in brachial plexus injuries with shoulder fractures

Falls from a height (D): resulting in a side flexion stretch of the neck

Delivery: brachial plexus is stretched due to traction

203
Q

Upper brachial plexus lesions: clinical signs

A

‘Erb’s palsy’ or ‘waiter’s tip’ deformity:

Adducted and internally rotated gleno-humeral joint
Loss of deltoid muscle (C5/6)
Loss of supra- and infraspinatus muscles (C5/6)

Pronated forearm and extended elbow joint
Loss of elbow flexor muscles (C5-7)

Sensory changes:

lateral surface of arm & forearm; ‘sergeant’s patch’

Absent biceps reflex

204
Q

Lower brachial plexus lesions: causes

A

Upper extremity hyper – abduction

Traction injury in difficult childbirth

205
Q

Lower brachial plexus lesions: presentation

A

Klumpke’s palsy:

Claw hand:
Loss of intrinsic muscles of the hand (C8/T1)
Inability to grip
Loss of wrist and finger flexors (C6-T1)

Sensory changes:

Medial hand and forearm (C8/T1)

206
Q

Pancoast tumour pathophysiology

A

Tumour in the apex of the lung can result in compression of:

Inferior trunk (C8,T1) of the brachial plexus
Sympathetic chain

The patient will present with:

Klumpke’s palsy
Horner’s syndrome (due to damage to T1)
Ptosis (a drooping upper eyelid)
Miosis (constricted pupil)
Anhidrosis (loss of sweating of the face)

207
Q

Calcium Physiological Functions

A

Mechanical role in bone
Excitation – contraction coupling
↑ cytosolic Ca 2+ signals several cell processes
Cell shape change & motility (e.g. cilia action)
Secretion (e.g. exocytosis)
Mitosis
Second messenger system
Cofactor in the clotting cascade and the complement cascade

208
Q

Effect of pH on calcium levels

A

pH affects free ionized calcium
Acidosis increases proportion
Alkalosis decreases proportion

Example: Hyperventilation
Respiratory alkalosis (raised pH)
Increased calcium-albumin binding
Signs and symptoms of hypocalcaemia
Total calcium remains the same

209
Q

homeostasis of calcium level control - quick and slow

A

Long term regulation
Slow changes in intestinal absorption & renal excretion maintain total body Ca 2+

Short term regulation
Rapid, adjustments between bone & plasma maintains constant free Ca 2+

210
Q

Vitamin D metabolism

A

7-dehydrocholesterol -> D3 via UV-B in skin / via diet
then to liver to become calcifediol
Then to kidney to become calcitriol (active)

211
Q

Vitamin D (calcitriol)

A

Synthesis stimulated by PTH acting on kidney
Feedback loop - calcitriol increases calcium concentration & directly acts on parathyroid gland

Acts at kidneys to increase calcium reabsorption
Increases activity and production of calcium transport proteins

212
Q

(Hormone) Regulation of Calcium

A

Calcitonin from C cells in thyroid parafollicular cells:

Released in response to high plasma Ca2+
Inhibits osteoclast activity – slows release
Stimulates excretion from kidneys

PTH from parathyroid chief cells:

Released in response to low plasma Ca2+
Increases release from bone by affecting osteoblast and osteoclast activity – RANKL
Increases resorption from kidneys
Stimulates formation and secretion of calcitriol by kidneys

213
Q

Relationship between osteoblasts and osteoclasts and effect of PTH

A

Osteoclast precursors have RANK (Receptor Activator of Nuclear factor Kappa B) receptors on their cell membranes
Osteoblasts have the ligand for this receptor on their cell membranes: RANKL

Osteoblasts also produce osteoprotegrin which prevents resorption by binding to RANKL
The ratio of RANKL:osteoprotegrin determines bone resorption

PTH upregulates RANKL which binds to RANK and stimulates the differentiation of osteoclasts

214
Q

Other influential hormones on calcium levels

A

Oestrogen – increases osteoblast production and release of OPG

Corticosteroids – reduce gut absorption and increase renal excretion of Ca2+

Growth hormone – favours Ca2+ absorption

Also linked with serum phosphate levels (calcitriol, PTH, FGF23)

215
Q

Hyperalcaemia signs and symptoms

A

Decreased nerve & muscle excitability
- can give cardiac arrythmia

Signs and symptoms
Bone softening & fractures
Renal stones
Headaches
Decreased muscle tone

Polyuria, polydipsia, renal colic, lethargy, dyspepsia …..
Bones, Stones, Groans, Moans

216
Q

Hypocalcaemia signs and symptoms

A

Increased nerve & muscle excitability
- Low Ca 2+ increases Na+ permeability so threshold is reached quicker

Signs and symptoms
Neuromuscular irritability
Muscle twitching
Muscle spasm & cramp (asphyxia!)

Increased nerve excitability, psychosis, glottis spasm, convulsions…..

Tetany, Convulsions, Systolic arrest

217
Q

Tumour peptide PTH-related protein

A

Peptide that shares structural homology with PTH
Expressed in squamous cell carcinomas
lung, breast, kidney, lymphoid tumours
Not under feedback regulation by plasma calcium

Activates PTH receptor on osteoblasts (PTHR1) and mimics its biological effects (paraneoplastic)
Stimulates osteoclastic bone resorption

Malignancy associated hypercalcaemia

218
Q

Explain the process of fracture repair in bone

A

Periosteum is breached, haematoma, blood clot forms

Replaced by vascular collagenous tissue (granulation tissue)
New osteoprogenitor cells arise from mesenchymal cells
Neutrophils and macrophages phagocytose the heamatoma and necrotic debris

External callus – bridges fracture on the outside, uses cartilage
Internal callus – bridges fracture in the cavity, woven bone
Well established by 3rd week after fracture

Remodelling of callus takes many months
Osteoclasts remove woven bone and osteoblasts replace this with lamellar bone

Full replacement with lamellar bone

Orientation of trabecular bone determined by stresses applied when mobile

Some residual fibrosis, irregular cortical bone and muscle scarring

219
Q

Brittle Bone Disease

A

Osteogenesis Imperfecta, OI
Group of hereditary disorders
Defective synthesis of collagen I – quantity or quality (disrupts structure of triple helix)
Fragile skeleton – too little bone
Extra-skeletal manifestations: skin, joints, eyes: blue sclera

Many types with a range of clinical outcomes –
Type I increased childhood fractures (pre-puberty), normal stature
Type II fatal in utero or perinatal
Type III progressive and deforming, short stature
Type IV increased childhood fractures, short stature

220
Q

Achondroplasia

A

Most common form of dwarfism
Caused by mutation on the fibroblast growth factor receptor 3 resulting in activation (autosomal dominant and heterozygous)
FGFR3 activation inhibits chondrocyte proliferation: affects growth plates
Growth plates are disorganised and hypoplastic

All bones that develop by endochondral ossification are affected
Short stature with stunted extremities (esp. proximal), bowed legs, frontal bossing, pronounced lordosis/kyphosis

221
Q

Osteopetrosis

A

Rare group of inherited conditions
Characterised by high bone mass

Due to interference with osteoclast formation and differentiation & directly affecting their action
Leads to defective bone remodelling e.g. osteoclasts can not excrete H+ ions to dissolve bone mineral (needs H+ for the acidic environment)

Dense ‘stone bone’ but brittle and easily fractured
Deposited bone is not remodelled and remain as woven bone

Clinical effects: fractures, spinal nerve compression (excess bone) and recurrent infection (reduced bone marrow cavity). Hepatosplenomegaly due to haematopoiesis outside the bone

Bone marrow transplant to provide healthy osteoclast precursors can be effective

222
Q

Osteoporosis

A

Loss of bone mass - mineralisation of bone is normal
Trabeculae are thinned and eventually cortex is thinned also.
Affects areas with lots of trabecular bone (vertebrae, wrists, neck of femur)
Due to:
Old age
Post menopausal decrease in oestrogen
Disuse and reduced activity
Prolonged steroid use (especially in RA)
Some endocrine disease e.g. Cushings

Daiagnosis:Asymptomatic pre fracture, Serum ALP, Ca and Pi levels are unreliable, 30-40% reduction in bone mass needed to be seen radiologically. No marked numbers of osteoclasts on histology: Need sensitive DEXA
Clinical outcomes:
Pathological fractures due to falls in the elderly
Back pain and kyphosis due to compression fractures
Hip replacements-fractured neck of femur
Treatment: prevention (diet and exercise), Bisphosphonates, oestrogen receptor agonists, PTH

223
Q

Osteomalacia & Rickets

A

In mature bones: osteomalacia, growing bones: rickets
Vitamin D deficiency or abnormal metabolism
Dietary/sunlight/malabsorption (intestinal disease)/renal disease (conversion of vitamin D impaired in chronic renal failure)

Normal osteoid and architecture of bone but failure of correct mineralisation of osteoid leading to soft bones (cortical and trabecular)
Symptoms are bone pain (pelvis, back, legs), and if untreated structural abnormalities such as bowing of the legs
In children early signs can be swelling of the epiphyses of bones (wrist) and along the costochondral cartilage of ribs.
Diagnosis: X ray and labs show low serum vitamin D
Treatment is by supplementation and advice on prevention

224
Q

Hyperparathyroidism

A

Calcium metabolism:
Increased PTH secretion
Osteoclasts stimulated to resorb bone
Calcium is released into plasma
Feedback to reduce PTH secretion

Failure of this feedback is responsible for hyperparathyroidism: unchecked PTH secretion and osteoclast resorption
More susceptible to fractures, bone deformation & joint issues
Reduction PTH levels can reverse bone changes
Types:
Primary: Tumour - elevated serum calcium + focal osteolytic lesions
Secondary: low serum calcium caused by renal disease (excessive loss via abnormal kidneys) causes hyperplasia of parathyroid glands (kidney disease causes osteomalacia

225
Q

Paget’s disease

A

Affects up to 2.5% of population In Europe and US-mostly mild cases.
Excessive bone resorption by osteoclasts followed by haphazard bone formation; not related to stresses –poor architecturally
Net gain in bone mass, but it is structurally weak - immature woven bone – prone to fractures

Metabolic demand is high due to excessive bone turnover
Bone pain (80% in axial skeleton/proximal femur), consequences of nerve impingement (headaches, back pain)
Viral infection of osteoclasts (paramyxovirus) or hypersensitivity of osteoclasts?

226
Q

Osteomyelitis

A

Inflammation of the bone and marrow cavity
Most common in children under 12
Almost always due to infection
Staphylococcus aureus (>80%)
Mycobacterium tuberculosis
Escherichia Coli (particularly elderly & infants)
Salmonella (sickle cell disease)
Gains access by 3 main routes:
Open wound
Haematogenous spread
Extension from an adjacent site

Present with severe bone pain at sight of infection + fever & malaise
Acute inflammation causes cell death - organisms move throughout the Haversian system and reach the periosteum: abscess formation (subperiosteal and in adjacent soft tissues) and impaired blood supply
Can progress to chronic condition: limb deformity, fracture, increased cancer risk, spread of infection etc.
TB causes caseating granulomatous inflammation in joints and vertebral bodies (Pott’s disease)

227
Q

Osteonecrosis

A

Interruption of blood vascular supply leading to ischaemic necrosis and infarction due to:
Fractures
Steroid use
Alcohol use
Vessel disease (vasculitis)
Haematological diseases
Symptoms depend on size and location of injury
Sub-chondral infarcts – present with pain during physical activity that becomes more persistent with time. Often collapse and may lead to osteoarthritis
Medullary infarcts – stable and silent unless large

Dead bone with empty lacunae, interspersed with fat necrosis and insoluble calcium soaps
Rarely in cortical bone unaffected due to collateral supply
Overlying articular cartilage remains viable due to synovial fluid (subchondral)

Common locations:
Femoral neck
Scaphoid
Talus

228
Q

Primary benign bone tumours

A

bone forming (osteoma, osteoid osteoma, osteoblastoma, osteochondroma), osteolytic (Giant cell tumour) or fibrous tumours

Benign are more common than malignant, malignant are more common over age 40
Diagnosed by biopsy and histology
Evaluated by radiology
Location and age can give insights
May present as fracture
Associated with some genetic syndromes, Paget’s disease, infarction, osteomyelitis, radiation and metal orthopaedic implants though this is rare and usually the cause is unknown

229
Q

Primary malignant bone tumours

A

Osteosarcoma, Ewing sarcoma

High-grade bone-forming malignant tumour of osteoblasts
20% of primary bone cancers (2nd most common)
Men x1.6 compared to women
Affects 2 distinct age groups.

10-25 years old – majority of cases
Tumour usually arises near the end of a limb long bone (particularly around the knee)

Over 60 years old
50% associated with Paget’s disease. Long bones, pelvis and vertebrae most effected

Symptoms: gradually increasing bone pain as the tumour grows. Soft tissue mass if tumour extends beyond bony cortex and periosteum
Radiological features: Mass with indistinct, infiltrating margins. Mix of sclerotic and lytic activity
Histological features: poorly differentiated most common variety is medullary. Essential to see mineralised bone/osteoid production by malignant cells. Many mitoses
Prognosis: aggressive and metastatic (haematogenous to lungs). 5 year survival 60%

230
Q

Metastatic bone tumours

A

Most metastatic bone tumours are osteolytic – erosion of bone
Promotion of osteoclast activity e.g. PTH-rP
Prostatic carcinoma is osteosclerotic – new bone formation

Clinical features:
Bone pain
Pathological fracture
Leucoerythroblastic anaemia
Symptoms of hypercalcaemia

231
Q

Osteology: mid-distal ulna

A

Supinator fossa

Head of ulna:

Articular circumference of head of ulna

Articular facet of head of ulna

Ulnar styloid process

232
Q

Osteology: mid-distal radius

A

Radial styloid process

Ulnar notch

Dorsal radial tubercle

Scaphoid articular facet of radius

Lunate articular facet of radius

233
Q

Colles’ Fracture:

A

Dorsal displacement distal radius, ‘dinner-fork deformity’

Fall on outstretched hand (FOOSH)

234
Q

Smith’s Fracture:

A

Volar (= ventral) displacement distal radius

Fall on dorsum of hand with flexed wrist

235
Q

Monteggia fracture-dislocation.

A

Ulna fracture, radial head dislocation proximally

236
Q

Galeazzi fracture-dislocation

A

Radial fracture, distal radioulnar joint dislocation

237
Q

Essex-Lopresti type injury

A

interosseus membrane rupture

238
Q

Osteology of the wrist: carpal bones

A

L->M
Scaphoid, lunate, triquetrum, pisiform
M->L
Hamate, capitus, trapezoid, trapezium

239
Q

Radio-carpal (wrist) joint articulation and reinforcement

A

Articulation between:

Distal radius, scaphoid and lunate  Radiocarpal joint
Intervening articular disc between ulna and triquetrum
Synovial ellipsoid joint

Reinforced by:
Palmar and dorsal radiocarpal ligaments
Palmar and dorsal ulnocarpal ligaments
Lateral (radial) collateral ligament
Medial (ulnar) collateral ligament

240
Q

Intercarpal joints articulation and reinforcements

A

Synovial plane joints

Contribute towards wrist movements

Reinforced by:
Palmar and dorsal intercarpal ligaments
Ulnar and radial collateral ligaments

241
Q

carpometacarpal (CMC) joints articulation and reinforcement

A

CMC joints:

Between distal row of carpal bones and metacarpal bones

Synovial saddle joint for the thumb

Synovial plane joints for digits 2-5

Reinforced by:

articular capsules and by dorsal, palmar and interosseous ligaments

242
Q

metacarpo-phalangeal (MP) joints articulation and reinforcement

A

Articulation between:

metacarpal bones and proximal row of phalanges

Synovial ellipsoid joints

Allow flexion/extension; adduction/abduction

Reinforced by:

articular capsules and by palmar ligament and collateral ligaments

243
Q

inter-phalangeal (IP) joints

A

Synovial hinge joints  flexion/extension

Proximal and distal IP joints in digits 2-5

1 IP joint in the thumb

Reinforced by:

articular capsules and by dorsal, palmar and collateral ligaments

244
Q

Anterior forearm muscles

A

Superficial group (L->M): pronator teres, flexor carpi radialis, palmaris longus, flexor carpi ulnaris.

Intermediate: flexor digitorum superficialis

deep group: flexor digitorum profundus, flexor pollicis longus and pronator quadratus

245
Q

Posterior compartment of the forearm muscles

A

Superficial: Brachioradialis
Extensor carpi radialis longus
Extensor carpi radialis brevis
Extensor digitorum
Extensor digiti minimi
Extensor carpi ulnaris

Deep: Supinator
Abductor pollicus longus
Extensor pollicus longus
Extensor pollicus brevis
Extensor indicis

246
Q

Nerve supply of the forearm muscles

A

All except for two musclesof the flexor/anterior compartment are innervated by themedian nerve

Theflexor carpi ulnaris and ulnar half of flexor digitorum profundusare innervated by theulnar nerve

Theradial nervesuppliesall muscles of the extensor/posterior compartment

247
Q

medial and lateral epicondylitis

A

Golfers elbow - M
Tennis elbow - L

248
Q

Flexor Retinaculum

A

Thick ligament
Further reinforces carpal system
Prevents bowstringing of tendons across wrist joint
Roof of the carpal tunnel

Attachments:

(medial): pisiform+ hamate
(lateral): scaphoid and trapezium

249
Q

Extensor Retinaculum

A

Strong, obliquely oriented ligament
Prevents bowstringing of tendons across wrist joint
Gives off septa  6 extensor compartments

Attachments:
(medial): pisiform and triquetrum
(lateral): distal radius, near styloid process

250
Q

Palmar Aponeurosis

A

Anterior antebrachial fascia  palmar aponeurosis

Firmly attached to palmar skin
It forms fibrous digital sheaths for flexor muscles
It forms deep palmar spaces
Palmar aponeurosis + fascial projections  compartments of the hand

251
Q

Dupuytren’s contracture

A

Benign fibromatosis of unknown aetiology

Characterised by:
Finger flexion contractures
Contracture of palmar aponeurosis
Thickened bands of palmar/digital fascia
Formation of nodules
Pain, decreased range of motion (ROM)
Hand function compromised

Risk Factors:
Northern European origin
Family history of Dupuytren’s
Diabetes mellitus
Smoking
Alcoholism
Vascular disorders

252
Q

Muscles of the medial compartment of hand, nerve supply and movements

A

Palmaris brevis

Abductor digiti minimi
Flexor digiti minimi brevis
Opponens digiti minimi

Nerve supply: (branches of) ulnar nerve

Movements: act on 5th digit, except for palmaris brevis

253
Q

Muscles of the central compartment of hand, nerve supply and movements

A

Adductor pollicis
Origin: MCs & capitate
Insertion: PP and extensor expansion of thumb
Nerve supply: (deep branch of) ulnar nerve
Movements: Adducts thumb

Palmar and dorsal interossei
Origin: MCs
Insertion: PP and extensor expansion of digits
Nerve supply: (deep branch of) ulnar nerve
Movements: PAD and DAB
Palmar interossei ADduct
Dorsal interossei ABduct

Lumbricals
Origin: tendons of flexor digitorum profundus
Insertion: extensor expansion of digits 2-5
Nerve supply:
Lumbricals 1 and 2: median nerve
Lumbricals 3 and 4: (deep branch of) ulnar nerve

Movements:
Flex digits @ metacarpophalangeal joints
Extend digits @ interphalangeal joints

254
Q

Extensor expansions of hands

A

Triangular aponeuroses

Tendons of extensor digitorum flatten and wrap around metacarpals and proximal phalanges

Spread out distally:

Central band - attaching to middle phalanx
Lateral bands - attaching to distal phalanx

255
Q

Muscles of the lateral compartment of hand

A

Opponens pollicis
Flexor pollicis brevis
Abductor pollicis brevis

Nerve supply: (branches of) median nerve

Movements: act on the thumb

256
Q

The radial nerve pathway:

A

Passes anterior to the elbow joint

Both the motor and sensory branches wind round to the posterior forearm

257
Q

The median nerve pathway:

A

Passes under the bicipital aponeurosis at the cubital fossa

Travels down the anterior forearm

Passes under the flexor retinaculum and through the carpal tunnel to enter the hand

258
Q

The ulnar nerve pathway:

A

Passes posterior to the medial epicondyle in the cubital tunnel at the elbow

Re-enters the anterior compartment of the forearm

Travels down the medial border of the forearm

Enters the hand

259
Q

Cubital fossa boundaries and content

A

Triangular space anterior to the elbow

Boundaries:

Base: line drawn between epicondyles
Medial border: pronator teres
Lateral border: brachioradialis
Floor: brachialis & supinator
Roof: fascia + bicipital aponeurosis

Contents:

Median nerve
Brachial artery
Biceps Tendon

Superior to roof: venous drainage and cutaneous nerves

260
Q

Hand blood supply

A

radial artery -> thumb and 1/2 of digit 2
Ulnar -> rest of digits

Radial gives off deep palmar arch
Ulnar gives off superficial palamr arch

Both anastomose; tested by alans test

261
Q

Carpal tunnel

A

Boundaries:

Floor: carpal arch
Roof: flexor retinaculum

Contents:

Flexor digitorum profundus tendons
Flexor digitorum superficialis tendons
Flexor pollicis longus tendon

Median nerve

262
Q

carpal tunnel syndrome

A

Idiopathic in most cases

Associated with:

Repetitive strain or job-related mechanical overuse

Mass occupying lesions or as a result of trauma

Risk factors:

Diabetes
Obesity
female sex
Age
Pregnancy
Hypothyroidism
Rheumatologic & autoimmune disorders

263
Q

Anatomical Snuffbox

A

Boundaries:

Base: wrist
Medial border: tendon extensor pollicis longus
Lateral border: tendon extensor pollicis brevis
Floor: scaphoid & trapezium; tendons of extensor carpi radialis longus and brevis

Contains radial artery

Cephalic vein travels superior to it

Tenderness  scaphoid fracture

264
Q

What are the thick and thin filaments made of?

A

Thick filaments
Myosin
Head - interacts with the thin filaments
Tail - several of these come together in the centre of the sarcomere (arranged like two bunches of golf clubs, held together at the grip end) to form what we see as the M line

Thin filaments
Actin arranged like a twisted string of beads
Tropomyosin – filamentous protein that sits in the ‘groove’ of the actin polymer and can prevent the myosin head binding to the actin

Troponin complex composed of troponins C [calcium binding], T and I – regulate the position of the tropomyosin filament on the actin polymer

265
Q

muscle contraction at filament level

A

Action potentials induce the release of Ca2+ into the sarcoplasm
When Ca2+ binds to troponin on the thin filament, troponin changes
Shifts tropomyosin off myosin binding sites
Enables myosin to bind to actin

Myosin head binds to actin (ADP+Pi)

Globular head bends toward center of sarcomere (ADP)

thin filaments pulled toward center of sarcomere (nothing)

Cross bridge link broken and head ‘unbends’ (ATP)

Myosin binds to next actin molecule on the thin filament (ADP+Pi)

266
Q

Properties of slow and fast motor units

A

Slow motor units contain slow fibers:
Myosin with long cycle time and therefore uses ATP at a slow rate.
Many mitochondria, so large capacity to replenish ATP.
Economical maintenance of force during isometric contractions and efficient performance of repetitive slow isotonic contractions.

Fast motor units contain fast fibers:
Myosin with rapid cycling rates.
For higher power or when isometric force produced by slow motor units is insufficient.
Type 2A fibers are fast and adapted for producing sustained power.
Type 2X fibers are faster, but non-oxidative and fatigue rapidly.

267
Q

Visible fibre differences in muscle

A

Slow = red / high myoglobin content
Fast = white / low myoglobin content

268
Q

What determines the speed of contraction/relaxation and fatigue?

A

Activation
rate of Ca2+ release from SR

Cross-bridge kinetics
myosin ATPase, myosin HC isoform

Relaxation rate
Rate of removal of Ca2+ (rate of pumping back to SR)

Oxidative/ gycolytic potential
Mitochondrial density (capacity for O2 extraction/ use)
Glycolytic capacity (anaerobic enzymes)

269
Q

What can increase force in muscle contraction

A

The force generated by a contracting muscle can be increased by:
Recruiting additional MUs
Increasing the firing frequency of MUs

270
Q

How can muscle activity be assesed

A

EMG = muscle activity assessed by surface or needle electrodes

271
Q

Osteology of the pelvic girdle

A

A:
Obturator foramen
Pubic tubercles
Pubic symphysis
Superior and inferior pubic rami
Anterior superior iliac spine (ASIS)
Anterior inferior iliac spine (AIIS)
Iliac crest

P:
Posterior superior iliac spine
Posterior inferior iliac spine
Ischial spine
Ischial tuberosity
Sacrum & coccyx

272
Q

Sacro-iliac (SI) joints and ligaments

A

Synovial joints, become fibrous with age  ossify
Irregular, interlocking joint surfaces for very little movement
Weight bearing & transmission of forces

Ligaments of the SI Joint:

Anterior sacro-iliac ligament

Interosseous sacro-iliac ligament (the strongest!)

Posterior sacro-iliac ligament

273
Q

Other important ligaments of the pelvic girdle

A

Ligaments of the SI Joint:

Anterior sacro-iliac ligament

Interosseous sacro-iliac ligament (the strongest!)

Posterior sacro-iliac ligament

+

Iliolumbar ligament

Sacrospinous ligament  greater sciatic foramen

Sacrotuberous ligament  lesser sciatic foramen

274
Q

Pubic symphysis anatomy

A

Solid, fibrocartilaginous (symphysis)

Contains inter-pubic disc

Ligaments reinforcing the joint:

Superior pubic ligament
Inferior pubic ligament

275
Q

Pubic symphysis diastasis examples

A

Pregnancy & childbirth

Trauma

Osteogenesis imperfecta

Bladder exstrophy

Hypothyroidism

276
Q

Gateways to the lower limb

A

Anterior aspect:
Obturator canal: abdominopelvic region with the medial compartment of thigh.
Gap between the inguinal ligament and superior pubic ramus— abdominopelvic region with the anterior compartment of thigh.

Posterior aspect:
Greater sciatic foramen—between the pelvis and the gluteal region of the lower limb.

Lesser sciatic foramen— inferior to the greater sciatic foramen. Between gluteal region and perineum

277
Q

Osteology of the Femur

A

Head
Neck
Greater trochanter
Lesser trochanter
Shaft
Distal portion

Fovea capitis
Intertrochanteric line
Intertrochanteric crest
Gluteal tuberosity
Linea aspera

278
Q

The Acetabulo-femoral (hip) joint and stabilisers

A

Between femoral head and lunate surface of acetabulum
Ball and socket joint, multiaxial
Very stable, not quite mobile
Active and passive stabilisers
Very hard to dislocate

Stabilisers of the acetabulo-femoral joint:

(intracapsular) Ligament of the head of the femur
Transverse acetabular ligament
Acetabular labrum
Vacuum effect
Strong joint capsule & ligaments:
Iliofemoral
Pubofemoral
Ischiofemoral

279
Q

Fasciae of the Lower Limb

A

Superficial, subcutaneous fascia
In the thigh: continuous with abdominal fascia
In the gluteal region: continuous with fascia of the back

Deep fascia:
Fascia lata
Encloses tensor fasciae latae muscle
Iliotibial band (tract)

280
Q

Gluteal muscles and movements

A

Gluteus maximus:

Power extensor of the thigh
Assists in external rotation

Gluteus medius:

Abduction of the thigh
Medial rotation of the thigh
Assists in extension of the thigh

Gluteus minimus:

Abduction of the thigh
Medial rotation of the thigh

281
Q

Lateral rotators of the thigh

A

Piriformis:
External rotation of the thigh
Assists in abduction of the thigh
Supplied by S1-S2

Gemellus superior
Gemellus inferior
Obturator internus
Quadratus femoris

282
Q

Quadriceps femoris - muscles, nerve supply, attachment, movement

A

Muscles:
Rectus femoris
Vastus medialis
Vastus lateralis
Vastus intermedius (deep to rectus femoris)

Nerve supply: femoral nerve (L2, L3, L4)

Distal attachment: quadriceps femoris tendon

Movement: leg extension at the knee

283
Q

Sartorius movements

A

Flexion, abduction, external rotation of the thigh

Flexion of the leg

284
Q

Tensor fasciae latae movement

A

Abduction & flexion of thigh

285
Q

iliopsoas group

A

Power flexor of the thigh
Iliacus supplied by femoral nerve
Psoas supplied by L1-L3

They form a common tendon (iliopsoas muscle tendon) which inserts onto the lesser trochanter

286
Q

Medial compartment movements:
Gracilis
Pectineus
Obturator externus

A

Movements:
Adduction of the thigh: Gracilis, Pectineus

Lateral rotation the thigh: Obturator externus

Flexion of the leg: Gracilis

287
Q

Adductors group

A

Adductor longus
Adductor brevis
Adductor magnus

Movements:
Adduction of the thigh
Medial rotation of the thigh

288
Q

Hamstrings

A

Muscles:
Biceps femoris
Semitendinosus
Semimembranosus

Movements:
Extension of the thigh
Flexion of the leg

Medial rotation of the thigh & leg:
Semitendinosus
Semimembranosus

Lateral rotation of the thigh & leg:
Biceps femoris

289
Q

The femoral triangle

A

Boundaries:
Base: inguinal ligament
Medial border: adductor longus
Lateral border: sartorius
Floor: adductor longus, pectineus, iliopsoas
Apex: opens inferiorly to continue with the adductor canal which passes through the adductor hiatus

290
Q

Main blood supply to the tissues of the thigh

A

Profunda femoris - Main supply to the tissues of the thigh
(anterior and posterior compartments)

Gives off:

Medial and lateral circumflex arteries

Penetrating branches

291
Q

Blood supply to femoral head comes from…

A

Blood supply to femoral head comes from the medial and lateral circumflex arteries

They anastomose to form a ring around the neck of the femur.

 small arteries perfuse the femoral head

Negligible contribution from artery of the ligament of the head of the femur

Fractures of the neck of femur and dislocations of the hip joint can result in avascular necrosis (osteonecrosis) of the femoral head

292
Q

Femoral fractures types

A

Due to simple falls (older patients) or high impact trauma (young patients)

Fractures of the proximal femur can be intracapsular (hip fractures) or extracapsular

Intracapsular fractures threaten blood supply to femoral head

293
Q

How does a femoral fractures present?

A

externally rotated and shortened right leg

294
Q

The gluteal arteries

A

Direct or indirect branches of internal iliac artery

Anastomose with branches of profunda femoris around gluteal region

Anastomoses may provide collateral circulation is one of the vessels is interrupted

295
Q

The obturator artery

A

Branch of the internal iliac artery

Travels through the obturator canal

Enters medial compartment of thigh

296
Q

The femoral artery

A

Major artery of the lower limb

Continuation of the external iliac artery

Travels in the femoral triangle

297
Q

lumbo-sacral plexus

A

Anterior rami of lumbar spinal nerves (L1-L4) -> lumbar plexus

Anterior rami of sacral spinal nerves (L4-L5, S1-S4) -> sacral plexus

L4 shared -> lumbo-sacral trunk

298
Q

Important nerves of the lower limb:

A

Femoral nerve (L2-L4)

Obturator nerve (L2-L4)

Sciatic nerve (L4-S3)

Superior and inferior gluteal nerves

299
Q

The Femoral Nerve

A

The Femoral Nerve (L2-L4)
Pathway:
Passes through psoas major
Leaves the abdomen beneath inguinal ligament
Enters the femoral triangle

Branches:
Muscular: anterior compartment thigh (& pectineus)
Cutaneous: anteromedial thigh & leg

300
Q

The Obturator Nerve

A

The Obturator Nerve (L2-L4)
Pathway:
Emerges from medial aspect of psoas major
In the abdomen is deep to internal iliac vessels
Enters the obturator canal

Branches:
Muscular: medial compartment thigh
Cutaneous: medial thigh

301
Q

The Sciatic Nerve

A

The Sciatic Nerve (L4-S3)

Pathway:
Emerges from greater sciatic foramen
Exits the pelvis inferior to piriformis
Travels distally deep to the hamstrings
It splits into 2 divisions above the popliteal fossa

Branches:
Muscular: hamstrings & posterior portion adductor magnus; all muscles leg & foot
Cutaneous: posterior thigh, lateral leg and sole of foot

302
Q

The Gluteal Nerves

A

Superior Gluteal Nerve (L4-S1)

Leaves the pelvis via greater sciatic foramen superior to piriformis

Motor supply: gluteus medius and minimus, tensor fasciae latae

Inferior Gluteal Nerve (L5-S2)

Leaves the pelvis via greater sciatic foramen inferior to piriformis

Motor supply: gluteus maximus

303
Q

safe injection site in gluteal region

A

The upper lateral quadrant is the ‘safe zone’ for intramuscular gluteal injections – you’re unlikely to hit the sciatic and gluteal nerves up here!

304
Q

Primary Survey of a trauma patient

A

Primary Survey <C>ABCDE</C>

C Catastrophic Haemorrhage Control
A Airway and C-spine management
B Breathing
C Circulation and Haemorrhage Control
D Disability
E Exposure

305
Q

Classes of shock types

A

Hypovolaemic, Obstructive, cardiogenic, distributive

306
Q

Shock definition

A

Abnormality of the circulatory system that results in inadequate organ perfusion and tissue oxygenation

307
Q

Statistical tests for two groups of data

A

Unpaired (independent) t-test - Samples that are not related to each other (i.e. comparisons are made between values that are recorded from different individuals)

Paired t-test - Samples that are related to each other (i.e. comparisons are made between values recorded from the same individual)

The non-parametric version of an unpaired t-test is the Mann-Whitney U test
The non-parametric version of a paired t-test is the Wilcoxen signed-ranks test

308
Q

Statistical tests for more than one set of data

A

A one-way ANOVA tests the difference in means of two or more unmatched groups.

The non-parametric version of a one-way ANOVA is the Kruskal-Wallis test

Two-way ANOVAs are used when two experimental factors are being manipulated.

Repeated measures one-way ANOVA - The difference between an ordinary and repeated measures ANOVA is similar to the difference between unpaired and paired t-tests.
The term repeated measures means that you give treatments repeatedly to each subject.

309
Q

Femur osteological landmarks

A

Medial and lateral condyles
Articular surfaces of the condyles
Intercondylar fossa
Medial and lateral epicondyles
Adductor tubercle
Patellar surface

310
Q

Tibia osteological landmarks

A

Tibia:

Tibial plateau
Medial and lateral condyles
Intercondylar eminence
Tibial tuberosity
Articular facet for the fibula
Medial malleolus
Articular surface for the talus

311
Q

Fibula osteological landmarks

A

Head
Facet for articulation with the tibia
Neck
Shaft
Lateral malleolus
Articular surface for the talus

312
Q

Clinical applications of anatomy: Genu varum & genu valgum

A

Genu varum = knees spread apart
genu valgum = knock knee

313
Q

The knee joint: Intra- articular stabilisers

A

Medial & lateral menisci
Anterior & posterior cruciate ligaments
Transverse ligament
Coronary (menisco-tibial) ligament

314
Q

Meniscal pathology and s $ s

A

Acute tears can occur in young sports people
Degenerative tears occur in older people

Signs and symptoms:

Swelling, pain, tenderness, crepitus
Sensation of instability or buckling/’locking’ of the knee

Meniscectomy  secondary osteoarthritis

315
Q

Intra-articular structures of the knee: Cruciate ligaments

A

Resistance to displacement of the tibia relative to the femur:

Anterior cruciate ligament (ACL) – restraint to anterior displacement

Posterior cruciate ligament (PCL) – restraint to posterior displacement

Provide some mediolateral stability too

316
Q

How is ACL most commonly damaged?

A

Deceleration injuries are the most common mechanism of injury

317
Q

The knee joint: Extra-articular stabilisers

A

Joint capsule merging with tendinous expansions

Patellar ligament

Oblique and arcuate popliteal ligaments

Ilio-tibial band

Tibial (medial) and fibular (lateral) collateral ligaments

318
Q

The Knee joint: Collateral ligaments stability

A

The collateral ligaments of the knee provide passive stability to the joint especially to varus and valgus stresses

Collateral ligaments, cruciate ligaments & popliteal ligaments pulled taut in extension  knee is more stable in full extension (close packed position)

319
Q

Where is arthrocentesis performed for inflammatory arthirits

A

arthrocentesis of the suprapatellar bursa of the knee joint in a patient with inflammatory arthritis.

320
Q

Tibiofibular Joint types

A

Proximal tibio-fibular joint: Synovial plane

Interosseous membrane

Distal tibiofibular joint: Syndesmosis but slight rotation to accompany movements of the ankle

321
Q

tarsal bones

A

Proximal group: Talus & calcaneus
Intermediate bone: Navicular
Distal group (lateral to medial): Cuboid; lateral, intermediate & medial cuneiforms

322
Q

Ankle joint structure and stabilisers

A

Between distal tibia and fibula & talus

Synovial hinge joint with a ‘mortice & tenon’ or ‘nut & wrench’ configuration

Plantarflexion and dorsiflexion

Deltoid (or medial collateral):
Tibionavicular, tibiocalcaneal, and posterior tibiotalar
Anterior tibiotalar ligament

Lateral ligaments:
Anterior talofibular ligament
Posterior talofibular ligament
Calcaneofibular ligament

323
Q

The subtalar and transverse tarsal joints and related ligaments

A

Subtalar joint: Between talus and calcaneus
Synovial plane joint

Midtarsal joints:
Functional unit formed by: Talocalcaneonavicular joint,
Calcaneocuboid joint

Ligaments:
Plantar calcaneonavicular (spring)
Plantar and dorsal calcaneocuboid
Long plantar ligament
Bifurcate ligament

324
Q

Joints of the foot and type

A

Tarsometatarsal (TMT) joints: Synovial plane joints

Intermetatarsal joints: Synovial plane joints

Metatarsophalangeal (MTP) joints: Synovial condyloid joints

Interphalangeal (IP) joints: Synovial hinge joints

325
Q

Clinical applications of anatomy: Osteoarthritis of the hand and foot

A

Whereas the CMCJ of the thumb is a common site for osteoarthritis and deformity, the MTPJ of the great toe (hallux) is a common site for degenerative processes which result in a valgus deformity (hallux valgus or a ‘bunion’)

326
Q

Muscle compartments of the leg, main action and innervation

A

Anterior compartment:

Dorsiflexion of the foot
Extension of toes
Supplied by deep fibular (peroneal) nerve

Lateral compartment:

Eversion of foot
Supplied by superficial fibular (peroneal) nerve

Posterior compartment:

Superficial group:
Plantarflexion of foot

Deep group:
Plantarflexion & inversion of foot
Flexion of toes
Supplied by tibial nerve

327
Q

Anterior compartment of the leg - muscles, innervation, movements

A

Muscles:
Tibialis anterior
Extensor hallucis longus
Extensor digitorum longus
Fibularis (peroneus) tertius

Nerve supply: Deep fibular (peroneal) nerve

Movements:
All: Dorsiflexion of the foot

Extensor digitorum & hallucis longus:
extension toes & hallux

Tibialis anterior:
inversion of the foot & dynamic support arches of the foot

Fibularis tertius: eversion of the foot

328
Q

Lateral compartment of the leg - muscles, innervation, movements

A

Muscles:
Fibularis (peroneus) longus
Fibularis (peroneus) brevis

Nerve supply:
Superficial fibular (peroneal) nerve

Movements:
All: Eversion of the foot
Fibularis (peroneus) longus:
plantarflexion of foot & support for arches of foot

329
Q

Posterior compartment of the leg - muscles, innervation, movements

A

Muscles of the superficial layer:
Gastrocnemius
Plantaris
Soleus

All attach to calcaneus via calcaneal (Achille’s) tendon

Nerve supply: Tibial nerve

Movements:
All: Plantarflexion of the foot

Gastrocnemius & plantaris: Flexion of the leg @ the knee

Muscles of the deep layer:
Tibialis posterior
Flexor hallucis longus
Flexor digitorum longus
Popliteus

Nerve supply: Tibial nerve

All (except popliteus): Plantarflexion of the foot

Flexor digitorum & hallucis longus: Flexion toes & hallux

Tibialis posterior: Inversion of the foot & dynamic support medial arch

Popliteus: Acts on the knee joint

330
Q

Spinal segments innervating leg muscles

A

Anterior: All these muscles are supplied by the spinal segments L5-S1, except tibialis anterior (L4, L5)

Lateral: All these muscles are supplied by the spinal segments L5, S1, S2

Posterior superficial : All these muscles are supplied by the tibial nerve, spinal segments S1, S2

Posterior Deep: Flexor digitorum and hallucis longus supplied by S2,S3; tibialis posterior by L4, L5; popliteus by L4, L5, S1

331
Q

Locking/unlocking mechanism of the knee, by which muscle

A

Popliteus rotates femur over the tibia
Origin: lateral femoral condyle
Insertion: posterior surface proximal tibia

Functions:
Stabilises knee joint
Unlocks knee joint (laterally rotates femur on tibia)

332
Q

The arches of the foot

A

Longitudinal arches
Calcaneus -> head of metatarsals
Lateral and medial

Transverse arch
On the coronal plane; Highest proximally (near the talus)

Active support: Extrinsic and intrinsic muscles
Weakness of these muscle groups will result in pes planus (flat feet)

Passive support: Bones, joints and ligaments

333
Q

The popliteal fossa

A

Superomedial border: semitendinosus & semimembranosus
Superolateral border: biceps femoris
Inferomedial border: medial head gastrocnemius
Inferolateral border: lateral head gastrocnemius
Floor: knee joint capsule + popliteus inferiorly
Roof: deep fascia

Contents:
Common fibular nerve
Tibial nerve
Popliteal artery
Popliteal vein

334
Q

The tarsal tunnel

A

Formed by:
Depression found between: Medial malleolus
Posteromedial surfaces of the talus
Medial surface of calcaneus

Overlying flexor retinaculum

Contents (A->P):

Tibialis Posterior tendon
Flexor Digitorum longus tendon
Posterior tibial Artery
Tibial Vein
Tibial Nerve
Flexor Hallucis longus tendon

335
Q

Blood supply of leg

A

Femoral -> popliteal -> anterior tibial artery -> dorsal pedis -> posterior tibial artery
-> fibular artery

336
Q

Venous drainage of the lower limb

A

Deep veins follow the arteries

Superficial venous system:

Dorsal venous arch of the foot

Great saphenous vein (medial)  drains into femoral vein

Small saphenous vein (lateral)  drains into popliteal vein

Popliteal vein receives blood from tibial veins

Popliteal vein becomes femoral vein

Femoral vein  external iliac vein

External iliac vein  common iliac vein

Common iliac vein  IVC

337
Q

The sciatic nerve (L4-S3) and its branches

A

The sciatic nerve enters the posterior compartment of the thigh where it divides into the tibial (L4-S3) and common fibular (L4-S2) nerves

The tibial nerve enters the leg through the popliteal fossa and gives off a cutaneous branch (sural nerve) – the tibial nerve enters the sole of the foot through the tarsal tunnel (behind the medial malleolus)

The common fibular nerve enters the leg through the popliteal fossa and then winds round the neck of the fibula to enter the lateral compartment of the leg
It divides into the superficial and deep fibular branches

The superficial fibular nerve continues in the lateral compartment of the leg and supplies the muscles here

The deep fibular nerve enters the anterior compartment of the leg and supplies the muscles found here

338
Q

Clinical applications of anatomy: Sciatic, tibial, common fibular Nerve lesions & resultant muscle weakness

A

Sciatic nerve
May be damaged by posterior dislocations of the hip joint
Results in weakness of posterior thigh muscle group (hamstrings) and weakness of all leg and foot muscles

Tibial nerve
Vulnerable to compression in the tarsal tunnel
Results in weakness of foot muscles

Common fibular nerve
Is easily compressed at the neck of the fibula e.g. by plaster casts or sitting crossed legged
Results in foot drop/loss of dorsiflexion due to weakness of anterior and lateral leg muscles

339
Q

Embryology; Week 1: Fertilisation to Implantation

A

Fertilisation and Cleavage
The early rapid, multiple rounds of cell division which occur in the first few days after fertilization
Morula Development
Means ‘mulberry’ – when the fertilized cell has divided into a solid mass of cells (12-16 cells)
Occurs by the 3rd day following fertilization
Blastocyst Development and Implantation
The name for the hollow cellular mass that forms after the morula and about 4-5 days after fertilization
The process of attachment and invasion of the uterusendometrium by the blastocyst (conceptus)

340
Q

Embyology; Week 2 and 3: Bilaminar and Trilaminar Disc Development

A

Bilaminar Disc Formation
Cells of the inner cell mass or embryoblast differentiate into the hypoblast layer (yellow) and epiblast layer (blue)

Gastrulation (Trilaminar Disc Formation)
Gastrulation begins with formation of the primitive streakon the surface of the epiblast layer
Cells of the epiblast layer migrate toward the primitive streak and then slip underneath it (invaginate)
Once the cells have invaginated, some displace the hypoblast, creating the embryonic endoderm
Other cells come to lie between the epiblast and newly-created endoderm to form mesoderm
Cells that do not migrate through the streak but remain in the epiblast form ectoderm

341
Q

Embyology; Week 3: Notochord Formation

A

Notochordal Plate
The notochordal plate forms in the midline during the development of the trilaminar embryonic disc

Notochord
Thedefinitive notochord develops from cells of the notochordal plate, which proliferate and detach to form this solid cord of mesodermal cells
The notochord lies in the midline, under the neural tube
It is a signalling centre for inducing the axial skeleton – it will eventually disappear but does form the nucleus pulposus of the intervertebral discs

342
Q

Neurulation

A

Neural Plate Development
The appearance of the notochord induces the overlying ectoderm to thicken and form theneural plate (start of the 3rd week)
This begins the process of neurulation

Neurulation
Neurulation is the process whereby the neural plate forms the neural tube
The neural plate lengthens and as it does so its lateral edges elevate to formneural folds with the neural groove lying in the middle
Gradually, the neural folds approach each other in the midline, where they fuse together
This forms the neural tube

343
Q

Development of spinal nerves

A

A 25-day (3.5 week) embryo showing the structure of the neural tube wall and central lumen
The cells of the wall of the neural tube are called neuroepithelial cells and they form the neuroepithelium

The neuroepithelial cells give rise to neuroblast cells (primitive neurons)
Neuroblastcells form the mantle layer (yellow in images below)
The mantle layer goes on to form the alar plate and basal plate thickenings in the primitive spinal cord

alar plate forms the sensory dorsal horn of the spinal cord
The basal plate contains the cell bodies of motor nerve cells and forms the ventral motor horn

344
Q

How do motor neurons develop?

A

Motor axons from primitive nerve cells (neuroblasts) grow out from the basal plate (ventral horn) of the developing spinal cord
They will form the ventral (motor) rootlets of the spinal nerves

345
Q

How do sensory neurons develop?

A

Neural crest cells form spinal sensory ganglia: Neural crest cells, which are ectodermal in origin, (light blue in image A and B) will migrate from the edges of the neural folds to form (amongst other things) spinal sensory ganglia - eg the dorsal root ganglion

During further development, the neuroblasts (ie primitive neurons) in the sensory ganglia form two processes (remember that sensory neurons are pseudo-unipolar neurons)

The central process: the centrally growing processes grow towards to the neural tube and penetrate the dorsal portion of the neural tube and terminate in the dorsal horn (alar plate area) – these central processes form the dorsal (sensory) rootlets of the spinal nerve

The peripheral process: the peripherally growing processes join with fibres of the ventral motor roots to form the (mixed ie sensory and motor) spinal nerve – eventually these peripheral processes will grow outwards and terminate in the relevant sensory receptor organ (eg a temperature receptor in the index finger)

346
Q

How do sympathetic neurons develop?

A

The cell bodies of pre-ganglionic sympathetic neurons lie in the gray matter of the intermediate horn of the developing spinal cord – this area of the gray matter only exists at thoracic (T1–T12) and upper lumbar levels (L1 or L2) of the spinal cord!
Post-ganglionic sympathetic neurons and the associated sympathetic ganglia (eg in the sympathetic chain) develop from neural crest cells, which migrate to their relevant location in the body

347
Q

Embryology Week 3-8: Development of the Somites – review of mesoderm

A

By approximately the 17th day (image B), mesoderm cells of the trilaminar disc close to the midline proliferate and form a thickened plate of tissue known as paraxial mesoderm

By the start of week 3 the paraxial mesoderm has begun to organize itself into segments, called somites

By the end of week 5 there are 42-44 pairs of somites in the embryo

348
Q

Embrology; Week 4: Somite Differentiation

A

With further development, some of the cells of the somite will come to surround the neural tube to form the sclerotome (image C)
This collection of cells will differentiate into the vertebrae and ribs
Some of the cells of the somite form the myotome
These cells will form the muscles of the back, body wall and limbs
Some of the cells of the somite gather together to form the dermatome
These cells will form the dermis in the back, body wall and limbs

349
Q

Sclerotome

A

At the end of the fourth week, sclerotome cells (of the somite) form loosely organized tissue, called mesenchyme or embryonic connective tissue (blue structure in image above)

Mesenchymal cells can become fibroblasts, chondroblasts or osteoblasts and will go on to form
The vertebrae (eg the neural arch, vertebral canal, vertebral body and transverse and spinous processes)
The annulus fibrosus of the intervertebral disc
The ribs

350
Q

Embyrology; limb development

A

At the end of the 4th week of development, visible out-pocketings from the ventrolateral body wall can be seen (NB the upper limb develops before the lower limb)

At the end of the 5th week of development, limb buds become visible

In the 6th week the terminal portion of the limb buds become flattened to form thehandplatesandfootplates

Fingers and toes are then formed as a result of cell death (apoptosis)

In the 7th week, the limbs rotate in different directions

The upper limb rotates 90° laterally
The extensor muscles then lie on the lateral and posterior surface
The thumbs lie laterally

The lower limb rotates approximately 90° medially
The extensor muscles then lie on the anterior surface
The big toe lies medially

By the 10th week, the shafts of the limb bones are partly ossified (brown), although much of the skeleton and especially the distal bones (e.g. the carpal bones) remain cartilaginous (blue) at birth

351
Q

Carpal ossification

A

At birth, there is no calcification in the carpal bones

The capitate ossifies between 1-3 months after birth

The hamate ossifies between 2-4 months after birth

The whole carpus is not ossified until a child is 8-12 years of age!

352
Q

Limb and digital defects: Amelia, meromelia, Brachydactyly, Syndactyly (fused digits), Polydactyly, Cleft foot

A

Unilateral complete absence (amelia) of the an upper limb

meromelia (partial absence) calledphocomelia - the long bones are absent, and rudimentary hands and feet are attached to the trunk by small, irregularly shaped bones

A:Brachydactyly (short digits)

B:Syndactyly (fused digits)

C: Polydactyly (extra digits)

D: Cleft foot – an abnormal cleft between the 2nd and 4th MT/MC

353
Q

skeletal muscle development

A

Skeletal muscle is derived from paraxial mesoderm (which forms the somites) and lateral plate mesoderm
Cells of the paraxial mesoderm which stay close to the neural tube will form the epiaxial muscles (i.e. the muscles of the back)

Epiaxial muscles (from paraxial mesoderm) – form the muscles of the back (e.g. erector spinae)
They are supplied by the dorsal rami of spinal nerves

Some paraxial mesoderm cells will migrate to the lateral plate parietal layer of mesoderm to form the hypaxial muscles (i.e. the muscles of the body wall and limbs)

Hypaxial muscles (from lateral plate mesoderm) – form the muscles of the body wall and limbs

As muscle cells move into the limb, they split into dorsal (extensor) and ventral (flexor) muscle compartments
They are supplied by the ventral rami of spinal nerves

GEM (18 decks)

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