Other Stuff Flashcards
Describe a synovial joint:
3 Defining features
Accessory structures
Types
Protective capsule, surrounding joint
Synovial membrane secreting Synovial fluid
Articular surfaces covered with hyaline cartilage
Ligaments (intrinsic/extrinsic)
Menisci
Fibrous capsule / muscle (strengthen joint)
Plane (gliding/sliding) (e.g. Acromioclavicular joint)
Hinge (flexion/extension) (e.g. Elbow)
Saddle (concave & convex: fwd/bkwd, side-side) (e.g. 1st CPMJ)
Ball & socket (several axis) (e.g. Shoulder, hip)
Condyloid (flex/ext, add/abd, circumduction) (e.g. MCPJ i.e. Knuckles)
Pivot (rotation) (e.g. Proximal radioulnar joint)
Classification of joints (according to tissue that lies between them)
Synovial
Cartilaginous
Fibrous
Describe a cartilaginous joint:
2 broad categories For each describe: Another name Connecting medium Where it is found
Primary cartilaginous:
Synchondrosis
Hyaline
Mostly in growth, except btw 1st rib & sternum
Secondary cartilaginous:
Symphysis
Fibrocartilage
Throughout body e.g. Intervertebral disc, pubic symphysis
Describe a fibrous joint:
Type of connective tissue
Where it is found
Fibrous CT
E.g. Btw plates of skull (sutures),
gomphosis (peg-like bones of teeth into socket),
syndesmosis (flattened sheet of CT connecting ulna & radius)
Concerning functional classification of joints:
Define the following & state which type of joint each is involved in:
Diarthrosis
Amphiarthrosis
Synarthrosis
Diarthrosis:
Allow greatest ROM
Synovial joints
Amphiarthrosis:
allows for slight mobility
cartilaginous joints
Synarthrosis:
Fixed/immovable
Fibrous joints
Describe the 7 types of arrangement of skeletal muscle
Give an example of each
Circular (e.g. Orbicularis oris) Convergent (e.g. Pec major) Parallel (e.g. Sartorius) Unipennate (e.g. Extensor digitorum longus) Multipennate (e.g. Deltoid) Bipennate (e.g. Rectus femoris) Fusiform (e.g. Biceps brachii)
Describe the 3 classes of levers in the body
First class lever:
Like a seesaw
Most efficient
E.g. Neck/skull
Second class lever:
Like a whelbarrow
Less efficient
E.g. Toes/foot
Third class lever:
Like a fishing rod
Least efficient
Most muscles in body
Name the 4 muscle groups
Agonists: prime mover
Antagonists: oppose prime mover
Synergists: assist prime mover
Fixators: stabilise prime mover
Name the 4 types of muscle fibres
I Slow twitch
IIa Fast twitch (oxidative)
IIb Fast twitch (glucolytic)
Proprioceptors
Can cartilage be converted into bone? Explain.
No.
Cartilage can be replaced by bone. Cartilage
(cartilage matrix) can become calcified thus restricting
nutrient and gaseous supply to chondrocytes;
chondrocytes thus die. Osseous tissue can be laid on the
surface of the calcified matrix, eventually replacing all
cartilage by bone.
What are the factors that restrict movement at synovial joints?
Tension exerted by ligaments of the articular cartilage (e.g. iliofemoral ligament of
hip).
Muscle tension (thigh difficult to raise when knee is straight – stretched hamstrings)
Interference by other structures. Stability at joints is also related to the depth of bony
articulations.
State the mechanical functions of bones
Provide the rigid framework that supports the body.
Protect vulnerable internal organs (e.g. brain, heart, lungs,
etc.).
Make body movements possible by providing anchoring
points for muscles and by acting as levers at the joints.
What factors are responsible for the appearance of
tuberosities, tubercles, ridges and grooves on a
typical long bone?
Tuberosities, tubercles and ridges – mechanical forces
resulting from attachment of muscles, tendons and
ligaments to bone.
Grooves – pressures from adjacent structures e.g. nerves
and blood vessels
What is the basic difference between intramembranous and endochondral ossification?
Intramembranous – develops directly from mesenchymal tissue
Endochondral – develops by replacing hyaline cartilage model.
What are the 3 types of bone cells & their function?
Osteoblasts are bone-forming cells (secrete collagen to form a matrix which is
calcified)
Osteocytes are former osteoblast cells that become encased in the bone
matrix, forming tight junctions with each other across the matrix.
Osteoclasts are bone-breaking cells (resorb bone).
why is hypocalcaemia or hypercalcaemia dangerous?
(To maintain homeostasis, bones help to regulate the amount and consistency of
extracellular fluid by adding calcium to it or taking calcium out of it.) Small decreases
of calcium in plasma and extracellular fluid (hypocalcaemia) can cause the nervous
system to become more excitable because of increased neuronal membrane
permeability with resultant muscular spasm. Too much calcium (hypercalcaemia) in
body fluids depresses the nervous system and causes muscles to become sluggish
and weak because the effects of calcium on muscles’ plasma membranes. Bones
represent a calcium store for homeostasis.
What is the action of PTH & Calcitonin on bone?
What stimulates their release?
Parathyroid hormone (PTH) and calcitonin (CT) have direct effects on bones. PTH
released from the parathyroid glands in response to low calcium levels in the blood
stimulates the uptake of calcium from bone, kidneys and the intestinal tract to return
calcium levels to normal. PTH increases the number and activity of osteoclasts in
bone to increase calcium (and phosphate) resorption from bone and stimulate
release of the minerals into blood.
C
T is released from specific thyroid cells (parafollicular cells) in response to elevated
calcium levels in the blood. CT causes calcium levels to be lowered by inhibiting
osteoclastic activity in bone; it also favours calcium uptake by bone, promoting bone
formation and decreasing blood calcium levels.
PTH increases blood calcium, while CT lowers it.
(Human growth hormone, thyroid hormones, sex hormones, adrenal cortical
hormones and vitamins A,C and D are also important in bone function.
How does nutritional deficiency in the following affect bone:
Calcium/phosphorous
Vitamin A
Vitamin C
State how nutritional deficiency of the following compounds may affect bone.
i) Calcium / phosphorous (2 X ½ marks)
Proper nutrition (calcium and phosphorus constitute almost half the content of bone)
is essential for normal bone development and maintenance; thus their deficiency
causes bones to become brittle.
ii) Vitamin A (2 X ½ marks)
Deficiency in vitamin A may cause an imbalance in the ratio of osteoblasts and osteoclasts, thereby slowing the growth rate.
iii) Vitamin C (2 X ½ marks)
Low levels of vitamin C inhibit growth by causing an insufficient production of
collagen and bone matrix, a condition that delays the healing of broken bones.
Explain the cause of Oesteomalacia in adults/rickets in children
If the diet is too low in vitamin D, the normal ossification process at the epiphyseal
growth plate is affected and the bones may easily become deformed. Osteomalacia
and rickets are defects skeletal resulting from vitamin D deficiency. This leads to
widening of the epiphyseal plates, increased number of cartilage cells, wide osteoid
seams and decrease in linear growth. Rickets is a childhood disease caused by
insufficient mineralisation.
In children with highly pigmented skin and others whose body surfaces are not
exposed to sunlight, absorption of ultra-violet rays is markedly affected; ultra-violet
rays are involved in vitamin D formation; skeletal deformities such as bowed legs,
knock-knees, etc. are common. Osteomalacia leads to demineralisation, an
excessive loss of calcium and phosphorus; this condition can be reversed with large
doses of vitamin D.
How do bisphosphonates & calcitonin help those with oesteoporosis?
Both inhibit osteoclast activity. Calcitonin can also stimulate osteoblast activity and
favours calcium uptake into bone.
What process, within the muscle fibre, causes skeletal muscle relaxation?
The active transport of calcium ions back into the sarcoplasmic reticulum.
halothane (general anaesthetic) can cause an abnormal rise in cytoplasmic calcium within skeletal muscle fibres. Suggest two ways by which this could occur. (Hint, consider the role of sarcoplasmic reticulum on how
changes could cause a rise in cytoplasmic calcium).
i. Entry of calcium from the extracellular fluid
ii. Blocking the re-uptake of calcium back into the sarcoplasmic reticulum
after its release
iii. Increasing the release of calcium from the sarcoplasmic reticulum
The latter is the actual mechanism and is caused by a faulty calcium
channel in the sarcoplasmic reticulum through which the calcium is released.
Dantrolene is a directly acting skeletal muscle relaxant that blocks the release
of calcium from intracellular stores.
How does an increase in intracellular calcium produce
symptoms of muscle rigidity?
An increase in intracellular calcium activates the crossbridge cycle promoting
contraction. The sustained release of calcium counteracts the process of re-
uptake of calcium back into intracellular stores necessary for relaxation.
List clinical signs of a large increase in body metabolism.
Rise in body temp, Fall in blood oxygen, rise in blood carbon dioxide, fall in blood pH,
tachycardia, increased ventilation, etc. Blood vessel compression due
to muscular rigidity impairs blood flow and contributes to the changes
in blood gas levels.
Name the structures are contained within the axillary sheath in the axilla
Axillary artery, axillary vein and cords & branches of the brachial plexus.
In a female patient, explain why would you be concerned about enlargement
of lymph nodes in the axilla?
The axillary lymph nodes receive lymph from the breast; in cancer of the breast,
cancerous cells may enter the lymph vessels and pass to the axilla lymph and may
produce enlargement of axillary lymph nodes.
Name the nerves that supply flexor muscles of the arm and the forearm.
Musculocutaneous, radial, median and ulnar
The lateral, medial and posterior cords of the brachial plexus are named with
respect to an important blood vessel. Name this vessel.
Axillary artery
Which important blood vein lies immediately posterior
to the sternoclavicular joint?
Brachiocepalic vein
Explain what would happen to the position of the arm and clavicular
fragments in the event of a fracture of the clavicle?
The clavicle acts as a strut (rigid support) from which the scapula and the upper limb
are suspended and keeps them away from the thorax (allowing the arm to have
maximum freedom of motion).
W
hen the clavicle fractures, the sternocleiodomastoid muscle elevates the medial
segment; because the trapezius muscle is unable to hold the lateral segment up and
because of the weight of the upper limb, the shoulder drops and the arm is pulled
medially by the adductor muscles of the arm.
Define the following terms:
Amelia
Meromelia
polydactyly
Amelia: A complete absence of a limb or limbs
Meromelia: Partial absence of a limb or limbs
polydactyly:
Supernumery (extra) fingers or toes; often an extra digit is incompletely formed and lacks proper muscle fixation. In the hand, the extra digit is either on the ulnar or radial side rather than central; in the foot it on the fibular side.
Explain syndactyly?
What is the structural difference between “cutaneous syndactyly” and
“osseous syndactyly”?
Fusion of fingers or toes; more frequent in the foot than in the hand. results from a lack of differentiation between two or more digits. Normally the mesenchyme in the periphery of the hand and foot plates condenses to form the primordial of the fingers and toes and the thinner tissue between them breaks down. In some cases, there is also fusion of the bones.
most frequently observed between the third and fourth fingers and second and third toes.
Cutaneous syndactyly:- Webbing of the skin between the fingers and toes results from failure of this tissue breakdown to occur.
Osseous syndactyly: fusion of the bones.
What is the structural defect underlying congenital dislocation of the hip (CHD)?
CHD is associated with breech presentation (i.e. buttocks rather than head delivered first). Speculate on why this might be so?
Underdevelopment of acetabulum and head of femur.
Breech presentation may place undue pressure on the developing hip joint: fails to complete normal development.
What is the function of the apical ectodermal ridge (AER)?
Explain what happens if the AER is disrupted and give one mechanism
causing its disruption.
Stimulates outgrowth of limb and maintains undifferentiated state in mesenchyme immediately underlying it.
No limb growth/ shortened limbs; interference affecting blood vessels of AER
Where does the brachial artery lie in relation to the median nerve in the upper arm and in the cubital fossa?
In the upper arm, it lies medial to the median nerve
in the cubital fossa, it lies lateral to it
Which structure lies immediately anterior to the brachial artery and the median nerve in the cubital fossa?
What is its function?
Bicipital aponeurosis:
comprises collagen fibres radiating from the distal part of the biceps tendon passes obliquely across the cubital fossa and merges with the fascia covering the flexor muscles in the medial
side of the forearm.
provides some protection to the brachial artery & the median nerve.
Where in the elbow region can you normally palpate the ulnar nerve against the humerus?
The ulnar nerve at the elbow passes behind the medial epicondyle of the humerus. It lies in close proximity to the bone surface (& grooving it). It enters the forearm passing through a structure called the “cubital tunnel” formed by the tendinous arch joining the humeral and ulnar heads of the attachment of flexor carpi ulnaris.
Here the nerve could get compressed to produce symptoms/signs of the “cubital tunnel syndrome”.
What is subcutaneous olecranon bursitis and how does it occur.
The bursa lying between the skin and the olecranon process of the ulna becomes inflamed and produces a swelling due to excessive friction. (also known as “student’s elbow, miner’s elbow).
The bursa may become infected and the skin area superficial to it may become inflamed.
State three specific factors contribute to the stability of the shoulder joint?
The tone of the rotator cuff muscles:’coracobrachialis, short head of
biceps and long head of triceps assist the deltoid in resisting downward dislocation of the joint.
Capsular and extracapsular ligaments.
Glenoid labrum helps to deepen the glenoid fossa (cavity).
Why does the humeral head dislocate so easily?
What is the usual direction of dislocation and why?
The glenoid fossa (cavity) is relatively shallow; it accepts a little more than a third of the humeral head.
Although the joint is strengthened on its superior, anterior and posterior aspects, it is weak on its inferior aspect. Hence, the head of the humerus usually dislocates inferiorly, but ends up as an anterior (subcoracoid location) due to the pull of muscles , i.e. anterior-inferior dislocation.
What is the “coraco-acromial arch” and what is its role at the shoulder when falling down on an outstretched hand?
an extrinsic, protective osseoligamentous structure formed by the smooth inferior aspect of the acromion and the coracoid process of the scapula with the coracoacromial ligament spanning between them. It forms a protective arch that overlies the head of the humerus, preventing its superior displacement from the glenoid cavity of the scapula.
Which nerve and blood vessels are at risk during the inferior displacement of the humeral head from the glenoid cavity (as in anterior-inferior dislocation of the shoulder?)
Axillary (circumflex) nerve and circumflex humeral arteries
How would you determine the integrity of the above nerve in a patient with a dislocated shoulder? What would you not do and why?
Test for sensation in the “regimental badge area” on the upper lateral part of the arm (area supplied by the cutaneous branch of the axillary nerve).
Do not test motor function, as this would lead to more damage.
In injuries of the shoulder joint, the humerus may fracture at its “surgical neck”. Where is the “anatomical neck” of the humerus and give one anatomical significance of it?
The anatomical neck is formed by the groove circumscribing and separating the head from the greater and lesser tubercles.
Significance:
• The articular capsule of the joint is attached nearby.
• The anatomical neck also marks the region of the epiphyseal growth plate during the growth in length of the humerus.
Describe two effects of a torn supraspinatus tendon as shown in clinical examination of the shoulder joint?
Failure of initiation of abduction in first 15 degrees
When the person is asked to lower the fully abducted arm slowly and smoothly, from approximately 90 °, the limb suddenly drops to the side in an uncontrolled manner.
This is mainly due to the torn supraspinatus tendon (the tendon tears due to degenerative tendonitis because it is relatively avascular).
What is the significance of the subacromial bursa? Describe the condition of painful arc syndrome.
The tendon of supraspinatus is separated from the coracoacromial ligament, acromion and deltoid by the subacromial bursa.
When the bursa is inflamed (subacromial bursitis), abduction of the arm is extremely painful during the arc of 50° to 90° (“painful arc syndrome”).
The pain may radiate as far distally as the hand.
Acute pain is also felt lateral to the acromion.
Define dermatome
the area of skin supplied by a single spinal
nerve
(e.g., C5. If you trace all the cutaneous nerves in the C5
spinal nerve to the skin, it would be the area of the lateral arm to
just below the elbow)
Define myotome
the group of muscles innervated by a single nerve root
Define cutaneous distribution of a peripheral nerve
an area of skin this peripheral nerve innervates.
When nerve fibres leave the spinal cord, they travel through
their spinal root and then often get redistributed via the nerve
plexus (e.g., brachial or lumbosacral plexus) and become peripheral nerves.
often has nerve fibres from several spinal roots.
It is not a dermatome
(E.g. axillary nerve innervates lateral shoulder and arm; regimental badge area).
Cervical nerves 5, 6 and 7 emerge above the corresponding numbered
vertebra, while cervical nerve 8 emerges below vertebra C7. Explain why this is so.
There are 7 cervical vertebrae & 8 cervical nerves.
The first cervical nerve emerges from the spinal cord and passes between the base of the skull and the 1st cervical vertebra; thus the 8th nerve emerges below C7.
From T1 down, the spinal nerves exit below their corresponding vertebra.
Which nerve is likely to be injured in mid-shaft humeral fracture and why?
Radial nerve; the nerve runs in the radial (or spiral) groove on the posterior surface of the shaft of humerus.
It is closely associated with the bone and is likely to be injured
in mid-shaft humeral fracture.
What would be the effect of mid shaft humeral fracture on movement at the elbow?
No effect or weakened extension of the elbow.
Flexion is fine.
Most of the nerve supply to the triceps the three heads of the triceps branches prior to the radial nerve entering the spinal groove or just in the proximal part of the groove.
As they most likely branch before the nerve lesion there will be no or little compromise of extension.
Anconeus is paralysed but this has only a minor role in elbow extension.
Explain why mid shaft humeral fracture causes poor wrist and finger extension?
Injury to the radial nerve in the radial groove would result in paralysis of
brachioradialis and all extensor muscles of the wrist and fingers. results in “wrist drop” (i.e. inability to extend the wrist and fingers at the metacarpophalangeal joints (MCP joints)
wrist is flexed because of unopposed flexor muscles & gravity
Precisely, where in the injured arm in a mid shaft humeral fracture would the surgeon feel for arterial pulses?
In the cubital fossa (brachial pulse)
at the wrist (radial pulse between flexor carpi radialis & brachioradialis & ulnar pulse above the flexor retinaculum)
If the brachial artery was injured in a mid shaft humeral fracture, describe and explain the pattern of colour change you would expect and the level of its upper limit in the arm.
Bruising of the cubital fossa & ischemia & pallor of the forearm.
The distal limb would be pale below site of the lesion.
Some colour may remain in the limb if superior ulnar
collateral arteries arise superior to vessel damage.
The deep brachial artery anastomoses with the recurrent radial artery, also providing some blood flow to forearm.
Concerning the elbow joint, joints of the forearm and the wrist joint:
Where is the axis of rotation in the movements of pronation and supination?
The axis passes longitudinally along the head of the radius (proximally) and through the distal radio-ulnar joint at the wrist.
During pronation and supination the radius rotates over the ulna; movements take place at the proximal and distal radio-ulnar
joints.
What is ‘pulled elbow’ & why does it happen more often in children?
partial (subluxation) or complete separation (dislocation) of the
articulating surfaces of the bones forming the proximal radio-ulnar joint.
The injury results when a person is lifted by the upper limb with the forearm in a pronated position.
The pulling of the upper limb tears the distal attachment of the annular
ligament (surrounding the radial head) where it is loosely attached to the neck of the radius. The radial head moves down (distally) and out of the torn ligament.
The injury is more common in children because the radial head and the annular ligament has not fully formed.
Why is supination a more more powerful movement than pronation?
because of the strength of the biceps brachii is greater than the muscles of pronation (pronator teres and pronator quadratus; consider cross-sectional area of the muscles).
What group of muscles arise (originate) from the lateral epicondyle?
The extensor-supinator muscles arise by a common extensor tendon from the lateral epicondyle of the humerus.
What bony structures can be palpated around the elbow?
Lateral & medial epicondyle of the humerus, olecranon process of the ulna, & head of radius
