Musculoskeletal system Flashcards
Functions of the skeleton
support
protection
locomotion
mineral reserve
haematopoiesis
Describe Rickets
Vitamin D is required for calcium absorbtion and so with rickets the bones lack mineral content and are overly flexible.
Describe Osteogenesis Imperfecta
It is a congenital-genetic disorder that affects collagen production. This leads to the bones being brittle and fracturing easily
List the 5 shapes of bones
Long bones
Short bones
flat bones
irregular bones
sesamoid bones
Describe long bones
bones of the limbs
Longer than widem long diaphysis/shaft
describe short bones
bones of the wrist and ankle
Width is similar to length
Describe flat bones
Thin and flat
usually curved
found in the skull, sternum, scapula and ribs
Describe irregular bones
Bones that dont fit into other categories
vertebrae
sacrum and facial bones
describe sesamoid bones
Small round bones mebedded in tendons. Protect tendon and increase movement
ie patella
Describe the basic gross anatomy of bones
- Long tube like diaphysis - mostly compact bone, medullary caviity
- Two epitheses - articular surface for joints spongy bone but compact at surface
- Epitheseal growth plate - seperates D and E, site of growth, ossifies after growth = epitheseal line.
- Periosteum - connective tissue, covers outer surface, tendon attachment
- Endosteum - lines internal surfaces of cavities, similar structure to P
Describe how the basic gross anatomy of flat bones differs to others
No medullar cavity
two sheets of compact bone with spongy bone in the middle
When in the skullthe spongey bone is called diploë
Describe the 5 sections of the vertebral column
Cervical (7) - small, relatively mobile, susceptible to dislocation
Thoracic (12) - Articulate with ribs, long processes for muscle attachment
Lumbar (5) - Largest body, susceptible to herniated IVDs
Sacrum (5) - Vertebrae fused, articulates with hip bones
Coccyx (4 fused) - tailbone, fractures easily
Describe bone markings
Responses to other structures that cause markings - rough bridges, grooves or holes
Condyle/Epicondyle = femur and humerus rounded parts that form joints
Crest/line = ridge where muscle attaches
Facet = formed surface to help articulation
Foramen/Notch = holes for arteries and nerves to pass through
Fossa = Depth in bone, curved surface, muslce attachment
Process
protuberance
spine
trochanter
tubercule
tubersoity are all different terms for bumps on bones
3 structural classifications of joints
Fibrous - dense fibrous connective tissue
Cartilaginous
Synovial - not directly joined (allows movement)
3 functional classifications of joints
Synarthrosis - no movement (sutures, synchondrosis synostosis)
Amphiarthrosis - Little movement (distal tibiofibular, pubic symphysis)
Diarthrosis - Free movement (synovial joints)
Describe synovial joints
”"”true joints””
surrounded by joint capsule
membrane releases synovial fluid which acts as a lubricant to allow friction-less movement
bursae - pockets of fluid preventing friction
menisci - little parts of cartilage
labrum - surrounds the glenoid fassa of the scapula
describe the different shapes of synovial joints
pivot, hinge, plane - uniaxial
condyloid, saddle - biaxial
ball and socket - multiaxial
Describe skeletal muscle
Voluntary
connected to bones and facilitate body movement
striated
Describe cardiac muslce
involuntary
able to contract without external stimulation
forms walls of the heart
pacemaker cells that contract continuously
striated
describe smooth muscle
not striated
no conscious control
within walls or internal organs
contract continuously
describe the structure of skeletal muscle
Muscles consit of bundles of muscle fibres.
grouped into muscle fascicles - forming one or more heads or bellies
connected to other structures by a tendon (round) or aponeurosis (flat sheet)
range of movement depends on fibre length
strength depends on number of fibres
6 skeletal muscle classifications
flat muscles - parallel fibres often with an aponeurosis
pennate muslces - feather like
fusiform muscles - spindle shaped with round thick bellr and tapered ends
convergent muscles - arise from and borad are and converge to form a single tendon
quadrate muscles - four equal sides
circular or sphincteral muscles - surround a body opening or orifice
where do extrinsic muscles act
act structures outside of appendicular skeleton
innervated by anterior rami of spinal nerves
where do intrinsic muscles act
structures within the back
innervated by dorsal rami of spinal nerves
“Origins and inserstions of trapezius
”
Originates from the skull, nuchal ligament and the spinous processes of C7-T12.
inserts into clavicle, acromion and spine of scapula
“Actions of trapezius on shoulder girdle
descending: keeps shoulder girdle up (carrying bags) and tilts the scapula for arm elevation
ascending and horizontal: depress and pull scapula medially
“Actions of trapezius on head and neck
descending: with fixed shoulder, contralateral rotation or extension
“Actions of trapezius on vertebral column
flattens the thoracic kyphosis
“Actions of latissimus dorsi on arm
adduction, internal rotation, extension
“Actions of latissimus dorsi on the trunk
elevation (with arms fixed on a bar)
“Actions of latissimus dorsi on shoulder girdle
depression, pulls the scapula medially
“Actions of rhomboids on shoulder girdle
retract scapula, rotate glenoid inferiorly. fix scapula to the trunk
“Actions of levator scapulae on shoulder girdle
elevates scapula and rotates glenoid inferiorly
“Actions of levator scapulae on vertebral column
”
with fixed shoulder girdle it extends the neck
“Origins and insertions of the Latissimus Dorsi
”
origins:
1. spinous processes T7-T12
2. throaco-lumbar aponeurosis
3: dorsal surface of the sacrum
4. dorsal 1?3 of the iliac crest
5. 10th-12th ribs
6. inferior angle of the scapula
insertions:
humerus - floor of the intratubecular sulcus
“Origins and insertions of the major rhomboid
origin: spinous processes of T1-T4
insertion: below scapular spine
“Origins and insertions of the minor rhomboid
origin: spinous processes of C6-C7
insertion: root of scapular spine and medial margin of scapula
“attachments of the levator scapulae
- vertebrae C1-C4 transverse processes
- Scapular: superior angle
“Nerve supply of the trapezius
Cranial nerve XI accessory
“Nerve supply of the latissimus dorsi
thoraco-dorsal nerve from brachial plexus
“Nerve supply of the rhomboids
dorsal scapular nerve from brachial plexus
“Nerve supply of the levator scapulae
dorsal scapular nerve from brachial plexus
Bisphosphonates action
Inhibits osteoclasts
Denosumab action
Monoclonal antibody against receptor activator of RANK-Ligand (which binds to and activates osteoclasts in homeostasis)
Teriparatide action
N-terminal fragment of parathyroid hormone (which stimulates osteoblasts)
romosozumab action
monoclonal antibody which binds to and inhibits sclerostin (which inhibits bone formation is homeostasis)
HRT action
increaes oestrogen levels (regulates osteoclast lifecycle)
Strontium action
inhibits osteoclasts. (only used if no other treatments can be and only in cases where there is no cardiovascular disease)
Describe the thoracolumbar fascia
Covers the deep muscles of the back, critical to organisation and integrity of the region. Latissimus dorsi and trapezius are attached to it.
What muscles are on the superficial intrinsic layer
Splenius muscles
What muscles are on the intermediate intrinsic layer of the back
Erector spinae - 3 columns of muscle
Iliocostalis
Longissimus
Spinalis
What muscles are on the deep intrinsic layer of the back
Transversospinalis - semispinalis, multifidus, rotatores
others: levatores costradum, interspinales and intertransversarii
Origins and insertions of the splenius muscles
O: Spinous processes and bottom of nuchal ligament
I: base of skull, mastoid process (capitis) / transverse processes C1 - C3 (cervicis)
Actions of the splenius muscles
bilateral - extend neck
unilateral - rotate head to one side
What is the action of the eractor spinae muslces
Extensions of spine / vertebral column
What is the common origin of the eractor spinae muscles
Broad tendon attached to sacrumspinous processes of L and T vertebra, iliac crest
Insertion of iliocostalis (erector spinae)
angles of ribs and Cervical transverse processes
Insertions of longissimus (erector spinae)
inserts thoracic and cervical transverse processes and mastoid process.
Insertions of the spinalis (erector spinae)
inserts thoracic spinous processes and skull
Action of transversospinalis (deep layer of instrinsic back muscles)
Fills groove between transverse and spinous processes.
Extension and rotation of spine
Describe the anterior longitudinal ligament
From the base of the skull to the anterior surface of the sacrum.
Attached to anterior surface vertebral bodies and IVDs
Prevents hyperextension
Describe the posterior longitudinal ligament.
Attaches the C2 to the sacrum.
Attached to the posterior surface vertebral bodies and IVDs.
Links the anterior surface of the vertebral canal.
Weakly resits hyperflexion
Describe supraspinous ligaments
C7 to the sacrum
Connects the tips of spinous processes
Describe the nuchal ligament
Strong fibroelastic tissue
Base of skull to C7
supports the head on the neck
Provides attachment for muscle (eg trapezius)
Describe the ligamenta flava
Pass between laminae
Form part of the vertebral canal
Resits separation of verterbrae during flexion
Describe interspinous ligaments
Between spinous processes
Describe intertransverse ligaments
Between transverse processes
Describe the two different types of vertebral joints
Typical vertebrae form 6 joints
- 4 x zygapophyseal
- 2 x sympysis
zygapophyseal are facet joints - synovialplane
symphysis are intervertebral discs and are secondary cartilaginous
describe the annulus fibrosus of the IVD
high tensile strength
fibrous sheath on outer surface - collagen layers between rings
fibrocartilage inner zone
describe the nucleus pulposus of the IVDs
high resilience
gelatinous structure
80-85% water
what is a ‘slipped disc’
prolapse of an IVD (hernia)
tear in the annulus fibrosus - nucleus pulposus can protrude
can impinge on spinal cord or nerves
What are C1 and C2 otherwise called and their fucntions
C1 - Atlas: no body and involved in the nodding ‘yes’ movement through the atlanto-occipital joint
C2 - Axis: odontoid process (dens) and involved in the shaking head ‘no’ movement through the synovial pivot joint atlanto-axial
How do you measure the resting membrane potential
using a voltmeter - difference in electrical charge between two points. Measured with glass micropipettes filled with solutions that conduct charge. the micropipette is inserted through the membrane into the cell.
the resting membrane potential is between -40 to -90mV in nerve and muscle.
How do K ions contribute to the resting membrane potential
The membrane is more permeable to K+ ions. they leak out of the cell and down its concentration gradient. Excess -ve charge buildup inside the cell as Pr- cannot cross the membrane. An electrical gradient is then formed. The -ve charges attract K+ ions back into the cell down the electrical gradient.
What equation is used to measure equilibrium potential
The Nernst Equation - resting membrane conditions when the work required to move an ion across the membrane (up conc gradient) equals the electrical work required to move an ion againts a voltage gradient.
What does the Na/K ATPase pump move
3 Na ions out and 2 K ions in (both positive)
What does the Na/K/2CL symporter move
one +ve charge for every -ve charge
what does the HCo3/Cl antiport in red blood cells move
These ions in a one-for-one fashion
List the steps in muscle excitation
- Nerve impulse reaches neuromuscular junction
- Acetylcholine is released from the motor neuron
- Ach binds with receptors in the muscle membrane to allow sodium to enter
- Sodium influx will generate an action potential in the sarcolemma
- Action potential travels down T tubule
- Sarcoplasmic reticulum releases calcium
- Calcium binds to troponin to move the troponin-tropomyosin complex
- Binding sites in the actin filament are exposed
Motor unit ratios of back, finger and eye muscles
Back - 1:100 nerve to fibre innervation
Fingers - 1:10
Eye - 1:1
Define muscle tonus
tightness of a muscle
some fibres always contracted
Define tetany
sustained contraction of a muscle
result of a rapid succession of nerve impules
Define the refractory period
Brief period of time in which muscle cells will not respond to a stimulus.
much longer in cardiac muscle compared to skeletal
What does the light band of a muscle fibre consist of
Just actin - the light transmission is high
What does the darker band of a muscle fibre consist of
Actin and myosin overlapping - thicker and more proteins rsult in a darker band in light microscopy.
What holds myosin in place
Titan - held in the middle of the sarcomere
Describe the myosin heads
Action: Pulls actin towards the centre of the sarcomere
Actin heads are arranged hexagonally facing out in different directions. They can work independently from each other and compete to generate force.
Describe the role of calcium in muscle contraction
at low levels of calcium, circular protein troponin forms filaments.
(between the two helical filaments lies the myosin binding site)
For muscle activation the binding site must be exposed. It is inhibited by a protein called tropomyosin. This is disinhibited by the release of calcium within the cell.
calcium binds to the troponin complex and chnages the inhibitory site conformation.
what is the sarcoplasmic reticulum
an intracellular store that can compartmentalise calcium
how is myosin involved in death
stiffness of death is referred to as rigour mortis - when the myosin head is attached and cannot detach.
what does phosphate accumulation cause in muscles
fatigue.
List the steps in myosin action
- Myosin cross bridge attaches to the actin microfilament.
- working stroke - the myosin head pivots and bends as it pulls on the actin filamentsliding it towards the M line. ADP and P are released.
- As new ATP attaches to the myosin head the cross bridge detaches.
- As ATP is split into ADP and P, cocking of the mysoin head occurs
- REPEAT
two types of ECM
Interstitial connective tissue matrix and basement membrane
describe collagen in regards to ECM
major insoluble fibrous protein in the ECM.
structural features: 3 collagen polypeptides form a triple helixGly-X-Y repeat motif
Type 1 and 2 are fibrillar
Type 4 is a sheet/network-form
Location of Type 1 collagen
Dermis
tendons
ligaments
bones
fibrocartilage
Location of type 2 collagen
Hyaline cartilage
Location of type 3 collagen
Liver,
bone marrow
lymphoid organs; also in granulation tissue; aka reticulin
Location of type 4 collagen
Basement membranes
Location of type 5 collagen
Linker to Basement membranes
Cornea
Describe elastin
Structural protein arranged as fibres. Abundant in tissues that require stretch and recoil properties. Assembly into functional fibres requires the presence of a structural glycoprotein - fibrillin.
composition of lymphoid tissue
loose irregular connective tissue
composition of dermis tissue
dense irregular connective tissue
what is ground substance
amorphous, gel-like, non-fibrous substance surrounding cells.
consists of large molecules called glycosoaminoglycans which link together with a core protein to form even larger molecules called proteoglycans.
describe glycosaminoglycans
AKA mucopolysaccharides
chains of repeating disaccharide units
carbohydrate component of proteoglycans
attracts water
gel/cushioning and hydrating properties
where is hyaluronic acid found
synovial fluid
where is chondroitin sulphate found
cartilage
where is keratan sulphate found
cartilage
where is heparan sulphate found
basement membrane
describe proteoglycans
AKA mucoproteins
90-95% carbohydrate (GAG)
what GAG is perlecan composed of
heparan sulphate
what GAGs are aggrecan composed of
chondroitin sulphate and keratan sulphate
what GAGs is syndecan composed of
chondroitin sulphate and heparan sulphate
what GAGs is decorin composed of
chondroitin sulphate and dermatan sulphate
function of fibrillin
controls deposition and orientation of elastin
function of fibronectin
linker role in basement membrane; organises ECM and participates in cell attachment to BM
fucntion of laminin
primary organiser of basement membrane layer
post-translational modifications of collagen
glycosylation and hydroxylation
post translational modification of elastin
hydroxylation
Fucntions of MMPs
Matrix-metalloproteinases degrade the ECM and when there is excess activation it leads to tumour cell invasion.
describe cancer in relation to the basement membrane
epithelial tumours regarded as malignant once BM is breached
what causes diabetes mellitus
thickening of BM in glomurus changes permeability
what is epidermolysis bullosa
blistering condition where epidermis to dermis attchment id effected
what causes goodpastures syndrome
autoantibodies tp collagen IV destroy BM in glomerulus and lung
describe cartilage
synthesised by chondrocytes, type II collagen. Less rigid than bone due to abundant proteoglycans found in its ground substance.
3 types of cartilage
hyaline cartilage, elastic cartilage and fibrocartilage
describe hyaline cartilage
chondrocytes surrounded by matrix.
few visible collagen fibres
avascular
has perichondrium
found in nasal septum, larynx, tracheal rings
describe fibrocartilage
layers of collagen type 1 and hyalin-like cartilage with chondrocytes in rows between layers
abundant collagen fibres
avascular
no perichondrium
found in IV discs, pubic symphysis
describe elastic cartilage
enriched in elastin fibres
avascular
has perichondrium
found in external ear, auditory tube
what is osteoarthritis
over-degradation of ECM
what is fibrosis
over-production of ECM
Function of Osteoblasts
Bone formation - laying down of matrix and mineralisation
Function of Osteoclasts
Bone resorption (break down) with calcium release
Values for Hypercalcaemia
Above 2.6 mmol/L (2.5% of people)
Values for Hypocalcaemia
Below 2.20mmol/L (2.5% of people)
why is albumin measured
Calcium is so reactive and so is difficult to measure. To measure total calcium: free+bound+complexed
Bound calcium is bound to ALBUMIN
Where is the Calcium sensing receptor found
CaSR found on parathyroid cells - serves as a ‘calciostat’ for calcium homeostasis
Describe PTH
Parathyroid hormone is an 84 amino acid polypeptide produced by the parathyroid glands. Secretion is regulated by free/ionised calcium, sensed by the calcium sensing receptors
Measurement is done by immunoassay
Summarise Calcium homeostasis
In respinse to decrease in ionised CA, PTH stimulates calcium reabsorption in renal tubule, stimulates formation of 1,25 DHCC in kidney (enhances calcium absorbtion from gut and bone resorption)
promotes bone resorption
Define Osteoporosis
A syndrome associated with low bone mass and microarchitectural deterioration of bone tissue which leads to an increased risk of fractures
Risk factors for developing osteoporosis
Age
Gender (female)
Race (caucasian)
previous fracture
early untrested menopause
family history
Bone mineral density
alcohol
low BMI
smoking
physical inactivity
Osteoporosis screening methods
FRAX - includes BMD, but not several important variables
Q-Fracture - Includes more variables but not BMD
DXA scan - measurement of BMD at spine and hip. gives a T-score
(+1 to -1 = normal
-1 to -2.5 = osteopenia
-2.5 and below = osteoporosis)
Therapies for Osteoporosis
Bisphosphonates, Denosumab, teriparatide, Romosozumab, Hormone replacement, Strontium
Describe Bisphosphonates therapy
Inhibits Osteoclasts and has a high affinity for bone mineral
Describe Denosumab therapy
Monoclonal antibody against receptor activity of nuclear factor kappa B ligan (RANK L) which is required for osteoclast differentiation and function
Describe teriparatide therapy
1-34 N-terminal fragment of parathyroid hormone that has bone anabolic effects
Describe Romosozumab therapy
monoclonal antibody that binds to and inhibits sclerostin. Increases bone formation and decreases bone resorption
Describe hormone replacement therapy
Tibolone - partical oestrogen progesterone and androgen receptor agonist
Describe Strontium therapy
Inhibits Osteoclast activity by stimulating biochemical markers of bone formation. Can only be taken if other treatments cant be and if the patient doesnt have cardiovascular disease
What happens when the Elastin component of ECM goes wrong
Supravalvular Aortic Stenosis (section of aorta above the valve is narrowed)
What happens when the Fibrillin-1 component of ECM goes wrong
Marfan Syndrome
What happens when the Collagen 1 component of ECM goes wrong
Ehlers-Danlos Syndrome
What happens when the Collagen IV component of ECM goes wrong
Alport syndrome or Goodpasture’s disease
Describe Marfan syndrome
Affects connective tissue of skin, bone, blood vessels, and others
Mutations in fibrillin gene are autosomal dominant
Vision problems (lens dislocation)
heart/aortic defects
abnormally long and slender limbs, fingers and toes.
Describe Alport syndrome
Basement membrane in the glomerulus of kidney forms a part of the selectively permeable glomerular filtration barrier. Mutations in collagen IV genes
Describe Ehlers-Danlos syndrome
Affects connective tissues of skin, bone blood vessels and others
Structure, production and function of collagen
Mutations in collagen genes and others
Hypermobility - stretchy and fragile skin.
What is lamellae
Circular layers of bone within Osteons
What is trabeculae
Struts of cancellous bone which help to transfer weight through the bone. During life these spaces would be filled with bone marrow
What are osteoprogenitor cells
Cells that differentiate into osteblasts and osteoclasts
What are osteocytes
Mature Osteoblasts that have become trapped in the bone matrix in little caves called lacunae. They respond to mechanical strain and can send signals to initiate bone formation or resorption
What is appositional bone growth
Bone only laid down on the surface. Also occurs in cartilage growth
What is interstitial growth
cartilage cells divide and proliferate at the epiphysial plate
5 zones of the growth plate
Resting
Proliferation
Hypertrophy
calcification
Bone
describe the resting zone of the growth plate
Layer of resting or reserve cartilage cells (chondrocytes) that replicate slowly
describe the proliferation zone of the growth plate
cells divide more rapidly, lining up in rows along the long axis
describe the hypertrophy zone of the growth plate
The chondrocytes mature and expand in size
describe the calcification zone of the growth plate
Expanded cells become calcified and die via apoptosis. Calcified matrix provides structure for bone to be laid down.
describe the bone zone of the growth plate
Blood vessels and bone cells invade the calcified cartilage and begin to replace the structure with bone
What is endochondral ossification
Cartilage model is made first and then replaced
What is intramembranous ossification
Bone formed directly in mesenchyme
What are skeletal fontanelles
Soft spots - allow flexibility during birthing and rapid growth of brain during first 2 years of life
