Introduction to Regional Anatomy

The posterior cutaneous nerve of the arm originates exclusively from spinal nerve T1.

The triceps brachii muscle is innervated by three distinct branches of the radial nerve.

The radial nerve branches to the heads of the triceps brachii typically arise in the following sequence: medial, long, lateral, and medial.

The first branch of the radial nerve to the medial head of triceps is identified as the radial collateral nerve.

The second branch of the radial nerve to the medial head of triceps brachii ultimately provides innervation to the coracobrachialis muscle.

The lower lateral cutaneous nerve of the arm, originating from C6, emerges after the radial nerve pierces the lateral intermuscular septum.

Avulsion of the brachial plexus roots, leading to complete plexus damage, is most commonly caused by car accidents involving forceful neck flexion.

In cases of complete brachial plexus root damage, the affected limb typically presents with hypermobility and heightened sensation.

When assessing the musculocutaneous nerve, flexion of the elbow by the brachioradialis muscle is the definitive test to confirm its integrity.

The epidermis is composed of stratified cuboidal epithelium.

Sebaceous glands are responsible for producing sweat.

Fat solvents can stiffen the horny layer of the skin.

The dermis contains bundles of elastin fibers and blood vessels.

Thick skin, like that on the sole of the foot, is characterized by a thick stratum corneum but a relatively thin dermis.

The 'claw hand' deformity arises from the unopposed action of the flexors and flexor digitorum profundus muscles.

To assess the small muscles innervated by the ulnar nerve, one should test for adduction of the index finger using the first dorsal interosseous.

In a high ulnar nerve lesion, testing the flexion of the proximal interphalangeal joint of the little finger assesses the action of the ulnar half of flexor digitorum profundus.

Surgically exposing the ulnar nerve in the upper arm involves an incision along the lateral border of the biceps brachii.

In lesions at or above the elbow affecting the median nerve, fingers tend to be more flexed due to the inaction of the ulnar portion of flexor digitorum profundus.

For median nerve lesions at the wrist, assess abductor pollicis longus function instead of abductor pollicis brevis due to its more reliable nerve supply.

The median nerve in the upper arm is surgically approached via an incision along the lateral aspect of the biceps brachii, adjacent to the brachial artery.

To display the median nerve in the forearm during surgery, detach the ulnar head of flexor digitorum superficialis from the radius.

In carpal tunnel release surgery, the flexor retinaculum is incised longitudinally on the radial side of the median nerve to avoid damaging the muscular branch.

Red marrow is primarily found in the cancellous ends of limb bones in young adults.

The periosteum's blood vessels are essential for nourishing the bone underneath it.

Sharpey's fibers weaken the connection between the periosteum and the bone, especially at tendon and ligament attachment points.

The periosteum plays a vital role in bone repair but loses its bone-producing ability after growth is complete.

Intramembranous ossification involves the formation of bone within an existing cartilage structure.

The clavicle, like the bones of the skull vault and face, develops through intramembranous ossification.

Bone growth, excluding the thickening of existing bones, primarily occurs via endochondral ossification.