Workbook questions session 3 & 4 Flashcards
Define Amelia
A complete absence of a limb or limbs
Define Meromelia
Partial absence of a limb or limbs
Explain polydactyly?
Supernumeracy (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?
Fusion of fingers or toes; more frequent in the foot than in the hand. Syndactyly
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. Syndactyly
is most frequently observed between the third and fourth fingers and second
and third toes.
What is the structural difference between “cutaneous syndactyly” and “osseous syndactyly”?
Cutaneous syndactyly:- Webbing of the skin between the fingers and toes results from failure of this tissue breakdown to occur.
Osseous syndactyly: In some cases, there is also fusion of the bones.
What is the structural defect underlying congenital dislocation of the hip (CHD)?
Underdevelopment of acetabulum and head of femur.
CHD is associated with breech presentation (i.e. buttocks rather than head delivered first). Speculate on why this might be so?
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)?
Stimulates outgrowth of limb and maintains undifferentiated state in mesenchyme immediately underlying it.
Explain what happens if the apical ectodermal ridge (AER) is disrupted and give one mechanism causing its disruption.
No limb growth/ shortened limbs; interference affecting blood vessels of AER
Name the muscles and their nerve supply that cause flexion at the elbow.
Brachialis – Musculocutaneous;
Biceps brachii – Musculocutaneous;
Brachioradialis – Radial nerve
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?
Bicipital aponeurosis; this structure which comprises of 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. It 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”.
Trauma of the ulnar nerve at the elbow results in numbness and tingling sensation and forearm and hand. What clinical term is used to describe this feeling?
Paraesthesia; anaesthesia means loss of feeling or sensation.
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. This condition which is known as subcutaneous olecranon bursitis (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; the coracobrachialis, the short head of biceps and the 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? (½ mark)
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?
The arch is 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
List all the movements of the scapula (six of them) and the principle muscles that produce them
Protraction – Serratus anterior
Retraction – (Middle fibres of) trapezius, rhomboids
Elevation – (Upper fibres of) trapezius, levator scapulae
Depression – (gravity) (relaxation of elevator muscles)
Lateral rotation/upward rotation – upper and lower fibres of trapezius
Medial rotation/downward rotation – Latissimus dorsi, levator scapulae, rhomboids (tilt glenoid cavity inferiorly)
NB In lateral/upward rotation of the scapula, the glenoid cavity moving superiorly (i.e. when upper limb is abducted). Converse is true for medial/downward rotation.
Which muscles are involved in the abduction of the arm from 0° to 90° and then 90° to 180°?
Supraspinatus (15 – 20°)
Deltoid (90°)
Upper and lower fibres of the trapezius (above 90°)
Serratus anterior
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).
