MSK Flashcards
What is an avulsion fracture? Where does it commonly occur?
A piece of bone is torn away by a tendon due to trauma. Greater tubercle of the humerus/ medial malleolus
What innervates serratus anterior?
Long thoracic nerve (Nerve of Bell) from C5 c6 and c7
Where would a you find a Colles fracture?
Radius protrudes through anterior face of wrist
Distal fragment (hand) moves posterior to radius
Caused by falling on an outstretched hand.
Name the 8 carpal bones.
PROXIMAL Scared - Scaphoid Lovers - Lunar Try - Triquetrum Positions - Pisiform
DISTAL That - trapezium They - trapezoid Can't - capitate Handle - hamate
Name the 3 components of a synovial joint.
Articular capsule (membrane)
Synovial fluid
Articular, hyaline cartilage
Identify 3 types of fibrous joints and give an example of each.
Sutures - skull bones
Gomphosis - teeth
Syndesmosis - flat sheath of connective tissue between the radius and ulna
What is the difference between primary and secondary cartilaginous joints?
Primary - hyaline - eg growth plates
Secondary - fibrocartilage eg pubic symphysis or intervertebral discs
What is a saddle joint?
A type of synovial joint where a concave and convex bone meet. Eg 1st carpometacarpal (base of thumb)
What is a condyloid joint?
A very motile synovial joint which allows flexion, extension, adduction, abduction and circumduction. Eg metacarpophalangeal (knuckles)
What is a compartment?
A bundle of muscles enclosed by a fascial membrane or septum. It also contains nerves and blood vessels.
What is compartment syndrome?
When there is an increase in pressure in a muscle compartment due to a bleed or a blockage. It can lead to ischaemia. It causes 6P's: Pain Parasthesia Palor Perishingly cold Pulseless Paralysis
What is a motor unit?
A motor neuron and the fibres it innervates
Why are the motor units in the eye very small, and in the buttock they are very large?
The fewer fibres per neuron, the finer the control
Give four differences between fast twitch and slow twitch muscle fibres.
Fast- Anaerobic
Slow- aerobic
Fast - few mitochondria
Slow - lots of mitochondria
Fast- few myoglobin
Slow - lots of myoglobin
Fast - suited to intense exercise
Slow - suited to prolonged exercise
Give two ways a muscle can increase the force it exerts.
Recruiting more neurons
Increasing the frequency of action potentials
What are two possible causes of low muscle tone and how would you differentiate between them?
Decreased neuronal activity - eg polyneuritis
Decreased muscle elasticity - eg myopathy
Differentiate by noting loss of reflexes for nerve damage
What is the difference between isotonic and isometric muscle contraction?
Isotonic has a constant tension but variable length
Isometric has a variable tension but constant length eg hand grip
Where does the clavicle tend to fracture and why?
Mid 1/3 shaft where it is weakest. Designed to stop forces travelling to the neck and causing damage where it is more dangerous.
What are the boundaries of the axilla?
Apex - clavicle, scapula, 1st rib Posterior - latissimus dorsi and teres major and minor Anterior - pectoralis major and minor Lateral - humerus Medial - serratus anterior Base - armpit skin
Give 3 possible causes of a winged scapula.
Describe the nerve fully
- Weak Serratus anterior - Long thoracic nerve damage C5 6 and 7
- Or other muscle wasting eg muscular dystrophy or MS - Idiopathic
- Scoliosis
Which structures can be found in the cubital fossa?
Medial to lateral Median nerve Brachial artery Biceps tendon Median cubital vein
What are the borders of the cubital fossa?
Superior - imaginary line between the epicondyles
Medial - pronator teres
Lateral - brachioradialis
What is painful arc syndrome? Name three possible causes.
Pain when raising the arm above 90 degrees due to rubbing of the supraspinatus tendon under the acromion. Can be caused by subacromial bursitis, repetitive overuse or degeneration of the tendons with old age.
Why does the shoulder tend to dislocate easily?
Weak joint because shallow glenoid fossa, little support from ligaments inferiorly, lax capsule and not much contact between articulate surfaces.
Which nerve is most at risk of damage when the shoulder dislocates and how would you test for its function?
Axillary nerve because shoulders tend to make anterior dislocations. Test axillary nerve by checking loss of sensation at the regimental badge area.
Which muscles are found in the anterior compartment of the upper arm and which nerve innervates them?
BBC - biceps, brachialis and coracobrachialis. Innervates by the musculocutaneous nerve.
Which muscles are found in the posterior compartment of the upper arm and which nerve innervates them?
Triceps
Radial nerve
Which nerves innervate the muscles of the cubital fossa?
Brachioradialis innervated by radial nerve
Pronator teres innervated by median nerve
Describe the venous drainage of the arm.
Cephalic - Subclavian vein brachiocephalic
Basilica - axillary - subclavian - brachiocephalic
Median cubital vein between basilic and Cephalic in the cubital fossa
What are the four rotator cuff muscles?
SITS Supraspinatus Infraspinatus Teres minor Subscapularis
What are the six ligaments of the rotator cuff? (3 inside and 3 outside the capsule)
Superior, middle and inferior glenohumeral ligaments inside the capsule. Plus outside the capsule ... Coracoacromial Coracohumeral Transverse humeral
Which nerves originate in the lateral cord of the brachial plexus?
Musculocutaneous and medial nerves
Which nerves originate in the medial cord of the brachial plexus?
Medial and ulnar nerves
Which nerves originate in the posterior cord of the brachial plexus?
Axillary and radial
Which germ layer do the somites arise from and what do they develop into?
Paraxial mesoderm - somites - dermatomes, myotomes, sclerotomes
What germ layer do the limb buds arise from?
Somatic mesoderm
What initiates the formation of the primitive hands and feet “paddles”?
The apical ectodermal ridge. An area of thick ectoderm at the apex of the limb bud.
By what process do the primitive hands and feet interdigitate?
Apoptosis - programmed cell death
Which direction do the upper and lower limbs rotate as they form? (Think about the anatomical position)
Upper - laterally
Lower - medially
What embryological disorder was caused by thalidomide?
Phocomelia - a type of Meromelia which is a partial absence of a limb
What are the defining symptoms of syndactyly and polydactyly?
Syndactyly - fusion of the digits (at the bone or skin level)
Polydactyly - extra digits
Where does the axillary artery become the brachial artery?
After it passes teres major
Which artery and nerve are most at risk when the humerus is fractured?
Surgical neck - Circumflex artery and axillary nerve
Mid shaft - Deep brachial artery and Radial nerve (in the spiral groove)
Which muscles are involved in the abduction of the arm?
Supraspinatus - first 15 degrees
Deltoid - up to 90 degrees when the humerus bumps into acromion
Trapezius and serratus anterior - up to 180 degrees
Recite the rhyme which reminds you the roots which supply the nerves of the brachial plexus.
3 musketeers Assassinate 5 rats 5 mice And 2 unicorns
Outline the motor and sensory function of the musculocutaneous nerve. Plus its nerve roots.
Motor - BBC above elbow
Sensory - lateral anterior forearm
C5, C6, C7
Outline the motor and sensory function of the axillary nerve. Plus its nerve roots.
Motor - deltoid, teres minor, triceps
Sensory - regimental badge
C5, C6
Outline the motor and sensory function of the median nerve.
Motor - forearm flexors, lateral hand (thenar eminence and 2 lateral lumbricals)
Sensory - lateral Palm
C5 - T1
Outline the motor and sensory function of the radial nerve. Plus its nerve roots.
Motor - extensors of the arm
Sensory - posterior hand
C5 - T1
Outline the motor and sensory function of the ulnar nerve. Plus its nerve roots.
Motor - hand (except lateral)
Sensory - 3rd and 4th fingers
C8 - T1
Outline the motor and sensory function of the femoral nerve.
Motor - anterior thigh
Sensory - anterior thigh and medial leg
L2 - L4
Outline the motor and sensory function of the obturator nerve. Plus its nerve roots.
Motor - medial thigh
Sensory - medial thigh
L2 - L4
Outline the motor and sensory function of the pudendal nerve.
Motor - s2 3 and 4 keeps the shit off the floor
Sensory - penis and clitoris
Outline the motor and sensory function of the sciatic nerve. Plus its nerve roots.
Motor - posterior thigh
Sensory - n/a
L4 - S1
Outline the borders of the anatomical snuff box.
Medial - Extensor pollicis longus
Lateral - Extensor pollicis brevis and Abductor pollicis longus
What passes through the carpal tunnel?
Recurrent branch of Median nerve and the intermediate and deep tendons
(Flexor pollicis longus
Flexor digitorum profundus
Flexor digitorum superficialis)
Which artery runs alongside the medial nerve?
Brachial
Which artery runs alongside the radial nerve?
Profunda brachii
Which artery runs alongside the ulnar nerve?
Ulnar artery
Which artery runs alongside the axillary nerve?
Circumflex artery
What runs just above the carpal tunnel?
Guyon’s canal - ulnar artery and nerve
Describe the motor innervation of the hand.
Ulnar except
LOAF
Are median
Describe the sensory innervation of the hand.
FRONT
Thumb, first 2 fingers and medial palm are median
Last 2 fingers and lateral palm are ulnar
BACK
Last 2 fingers and lateral dorsum are ulnar
Tips of thumb and first 2 fingers are median
Dorsum of thumb and first 2 fingers are radial
What is the difference between a sensory nerve territory and a dermatome?
Sensory nerve territory is an area whose sensory nerve function is supplied by an individual nerve.
Dermatome is an area whose sensory function is supplied by an individual nerve root.
Where can the dermatome for c4 be found?
Skin above deltoid
Where can the dermatome for c7 be found?
Fingers and central forearm
Where can the dermatome for t2 be found?
Armpit
Which muscle does the lumbar plexus travel through?
Psoas major
What nerve roots make up the lumbar plexus?
L1 to L5