MSK - Semester 2 Flashcards
Which week in pregnancy do the limb buds appear?
week 4
Limb bud is a core of proliferating __________ cells with an _ _ _ _ derm covering
Limb bud is a core of proliferating MESENCHYME cells with an ECTODERM covering
Thickened ectoderm at apex of limb bud forms the ________ ___________ _______
Thickened ectoderm at apex of limb bud forms the APICAL ECTODERMAL RIDGE
Differentiate between:
1) apical ectodermal ridge
2) dorsal ectoderm, and
3) zone of polarizing activity
1) apical ectodermal ridge - regulates outgrowth (proximal to distal)
2) dorsal ectoderm - regulates dorsal-ventral patterning
3) zone of polarizing activity - controls anterior-posterior patterning
Cell death in what region (apical ectodermal ridge, dorsal ectoderm or zone of polarizing activity) causes the transformation of paddles to hands with separate digits?
AER (AER maintained over each future fingertip)
What is ‘syndactyly’?
Fusion of digits
What is ‘polydactyly’?
Extra digits
What is ‘amelia’?
Complete absence of a limb
What is ‘meromelia’?
Partial absense of 1 or more limb structures
What is the difference between ‘deformation’ and ‘malformation’?
Deformation - healthy formation but pieces of limbs cut off
Malformation - intrinsic error in coordination of morphogenesis
In the 8th week of pregnancy, how do the upper limb and lower limb rotate?
Upper limb - dorsally/laterally 90°
Lower limb - ventrally/medially 90°
Define ‘dermatome’
Area of skin supplied by a single spinal nerve
What is the difference between a dermatome and a myotome?
Dermatome - Area of skin supplied by a single spinal nerve
Myotome - group of muscles supplied by a single spinal nerve
Define ‘myotome’
group of muscles supplied by a single spinal nerve
What is the specific type of tissue that differentiates into somites?
Paraxial mesoderm
What nerve root supplies the middle finger? (sensory)
C7
What nerve root supplies the region of skin over the shoulder?
C4
What nerve root supplies medial two digits?
C6
What nerve root supplies the medial leg?
L4
What nerve root supplies the skin over the knee?
L3
What nerve root supplies plantar surface of foot?
S1
What nerve root supplies back of leg?
S2
What nerve root supplies skin at level of nipples?
T4
What is a spinal nerve?
Parallel bunch of axons encased in connective tissue that have both MOTOR and SENSORY functions
What do the ventral and dorsal ramus supply?
Ventral - muscles and skin of lower and upper limbs; ventral and lateral trunk
Dorsal - deep muscles and skin of dorsal trunk
Which branch of the spinal nerve is given off and reenters the spinal canal through intervertebral foramen to supply vertebrae, ligaments, etc.?
Meningeal branch
What is the difference between the peripheral nerve distributions and dermatomes?
In one peripheral nerve, there may be fibres from MORE THAN ONE SPINAL NERVE (unlike dermatomes)
What is the action of the C5 myotome?
elbow flexion
What is the action of the C6 myotome?
wrist extension
What is the action of the C7 myotome?
elbow extension
What is the action of the C8 myotome?
finger flexion
What is the action of the T1 myotome?
finger abduction
What is the action of the L2 myotome?
hip flexion
What is the action of the L3 myotome?
knee extension
What is the action of the L4 myotome?
ankle dorsiflexion
What is the action of the L5 myotome?
great toe extension
What is the action of the S1 myotome?
ankle plantarflexion
What is a motor unit?
Motor neuron + skeletal muscle fibres it innervates
What is the difference between a motor unit and a spinal nerve?
Spinal nerve = supplies ONE MYOTOME but contains the neurons of MANY MOTOR UNITS
What is the difference between endoneurium, epineurium and perineurium?
Endoneurium - around each axon
Perineurium - around each fascicle
Epineurium - around each spinal nerve (fascicles + blood vessels)
Spinal nerves leave the spinal cord via which region of the vertebrae?
Intervertebral foramina
C8 spinal nerve exits between which two vertebrae?
C7 and T1
What is the typical pattern of herpes zoster infection?
It always affects skin of a single dermatome only
Persons who get shingles are likely to have been infected by what virus?
Varicella zoster previously and had chicken pox. Then the virus remains dormant. When host is immunosuppressed, VZV reactivates and travels through peripheral nerve to skin of a single dermatome.
The clavicle forms 2 joints with surrounding bones. What are these 2 joints?
Sternoclavicular joint
Acromioclavicular joint
Where do fractures of the clavicle usually occur?
Middle third of clavicle
When a fracture of the clavicle occurs, explain how the fragments move and why?
Lateral fragment pulled inferiorly due to weight of arm
Medial fragment pulled upward by sternocleidomastoid muscle
What is the name of the piece of cartilage on the glenoid fossa to deepen the fossa and increase joint stability?
Glenoid labrum
Fracture of the surgical neck of the humerus can lead to damage of which major vessels/nerves?
Axilliary nerve
Circumflex humeral artery damage
Fracture of the humerus mid-shaft can lead to damage of which major vessels/nerves?
Brachial artery
Radial nerve
Trochlea on the humerus articulates with which bone of the forearm?
Ulna
Coracoacromial arch is a protective arch formed by which three elements?
inferior aspect of acromion
coracoid process of scapula
coracoacromial ligament between the two of them
What is the importance of the coracoacromial arch?
Prevents upward dislocation of the head of the humerus from the glenoid fossa
A supraepicondylar fracture of the humerus is likely to cause damage of which nerve?
Median nerve
Give one similarity between Colles fracture and Smiths fracture
both are transverse fractures of the distal radius
What deformity does Colles’ fracture produce?
dinner fork deformity due to posterior displacement of the distal fragment
How does a Smith’s fracture of the distal humerus occur?
A fall onto a flexed wrist causing anterior displacement of the distal fragment
In patients with scaphoid fractures, what area tends to be tender?
anatomical snuff box
What is a major risk in patients with scaphoid fractures?
avascular necrosis of the proximal fragment as the blood supply to the scaphoid is from one distal blood vessel only (so reunion cannot be done)
What is a “boxer’s fracture”?
Break in the neck of either/or the 4th or 5th metacarpals
What is the collective name of the muscles that contribute to glenohumeral stability?
rotator cuff muscles
What are the borders of the anatomical snuff box?
Ulnar / medial border - tendon of extensor pollicis longus
Radial / lateral border - tendon of extensor pollicus brevis
Proximal border - styloid process of radius
What is the floor and the roof of the anatomical snuff box?
floor - scaphoid and trapezium
roof - skin
What are the four muscles of the pectoral region?
Pectoralis major
Pectoralis minor
Subclavius
Serratus anterior
Winged scapula occurs as a result of damage to which nerve?
Long thoracic nerve
Which muscle is paralysed in “winged scapula”?
Serratus anterior
What is the role of the subclavius muscle?
Anchors and depresses clavicle
Pectoralis minor inserts where?
The coracoid process of the scapula, so it obviously draws the scapula anteriorly and inferiorly, against the thoracic wall
What is the insertion point of pectoralis major?
intertubercular sulcus
What are the four main muscles of the back?
Trapezius
Latissimus dorsi
Levator scapulae
Rhomboid major and minor
Which muscle is the most superficial of all the back muscles?
Trapezius
What can you ask a patient to do in order to test the function of the accessory nerve?
Shrug the shoulders
as if the accessory nerve is compromised, the trapezius muscle will be paralysed and patient will not be able to shrug his or her shoulders
Where does the trapezius insert (NB there are THREE insertions)?
Lateral clavicle
Acromion
Spine of scapula
To what does the latissimus dorsi muscle insert?
intertubercular sulcus of the humerus, just like the pectoralis major!
What are the origins of the latissimus dorsi muscle? (NB there are 4 origins)
spinous processes of T6 to T12
iliac crest
inferior 3 ribs
thoraco-lumbar fascia
What is the role of the levator scapulae muscle?
elevate and rotate scapula
What is the origin of the levator scapulae muscle?
C1-C4 transverse processes
Rhomboid major and minor both insert to what structure?
The medial border of the scapula
What are the medial, lateral, anterior and posterior borders of the axilla?
Medial - thoracic call and serratus anterior
Lateral - intertubercular sulcus
Anterior - pectoralis major and minor
Posterior - scapularis, teres major, latissimus dorsi
6 things are contained in the axilla. Name them.
axillary artery axillary vein axillary lymph nodes brachial plexus biceps brachii tendons coracobrachialis tendon
In axillary clearance, which nerve can be damaged and if damaged what is the name of the clinical findings?
Long thoracic nerve
Winged scapula
The deltoid muscle inserts where specifically on the humerus?
Deltoid tuberosity
The deltoid muscle is supplied by which nerve?
axillary nerve
Which nerve supplies the teres major muscle?
Lower subscapular nerve
The teres major muscle has what actions on the arm?
adducts
medially rotates
Name the four muscles of the rotator cuff
Supraspinatus
Infraspinatus
Teres minor
Subscapularis
Supraspinatus, infraspinatous and teres minor all attach to ___________. They all have a common role as well which is ___________
Attachment - greater tubercle
Role - External rotation
Name the three flexor muscles of the anterior arm
Biceps brachii
Brachialis
Coracobrachialis
Abduction of the arm: name the muscles that allow movements at the following angles:
0-15° - ________
15-90° - ____________
90°+ - ______________
0-15° - supraspinatous muscle
15-90° - deltoid (middle fibres)
90°+ - trapezius and serratus anterior (scapular rotation)
Which nerve supplies all the flexors of the arm?
Musculocutaneous nerve
Biceps brachii has which 2 roles in arm movement?
flexion of the arm at elbow and shoulder
supinator
Where does the brachialias muscle insert?
coroNoid process of the ulna
“Popeye sign” on flexion of the arm is a sign that which tendon has been ruptured?
tendon of the long head of biceps brachii
Branches of which artery supply the flexors of the anterior arm?
brachial artery
Which artery supplies the posterior compartment of the arm?
profunda brachii artery
What are the lateral, medial and superior borders of the cubital fossa?
Lateral - medial border of brachioradialis
Medial - lateral border of pronator teres
Superior - imaginary line between the two epicondyles
Which vein is in the roof of the cubital fossa?
medial cubital vein (connects the basilic and cephalic veins)
What are the contents of the cubital fossa?
radial nerve biceps brachii tendon brachial artery median nerve (really need beer to be at my nicest)
The medial cubital vein situated in the roof of the cubital fossa connects which two veins of the arm?
basilic
cephalic
Supracondylar fractures can lead to which condition, common in children?
Volksmann’s ischaemic contracture
How does a supracondylar fracture lead to Volksmann’s ischaemic contracture?
Post fracture swelling compresses brachial artery
so ischaemia of muscles of the forearm, muscles become fibrotic and short
arm flexes uncontrollably
