Anatomy Quiz 1

Function: Weakest segment of proximal humerus, closely in contact with axillary nerve and posterior circumflex humeral vessels
Clinical: Fracture at this site can directly injure the axillary nerve and/or posterior circumflex humeral artery and vein

Function: Bony shaft providing muscle attachment and protective groove (radial groove) for passage of radial nerve and deep brachial vessels
Clinical: Fracture of humerus body can directly injure the radial nerve and/or the profunda brachii artery. It can also present as Holstein-Lewis fracture if it occurs in the distal third of the humeral body.

Function: Distal bony reigon of the humeral shaft located immediately superior to the epicondyles
Clinical: Supercondylar fracture -> can entrap or tear the brachial artery and/or the median nerve

Function: Bony prominence on the distal medial humerus that acts as the origin for the common flecor tendon; its posterior aspect forms the ulnar groove for the ulnar nerve
Clinical: Fracture of the medial epicondyle can stretch or injure the ulnar nerve. Chronic strain here leads to medial epicondylitis (Golfers elbow) due to overuse of forearm flexors.

Function: Bony articulation site at the wrist joint
Clinical: Colles' fracture, which is a fracture of the distal radius caused by falling on an outstretched hand (palmar face)-> creates a characteristic "dinner fork deformity" that can compress the median nerve inside the carpal tunnel.

Function: Bondy shaft of the medial forearm
Clinical: Nightstick (cop) fracture, isolated fracture of the ulnar body from direct blunt trauma while raising the forearm to protect the face.

Function: Carpal bone located proximally on the lateral side of the wrist, key transitional pivot for force distribution across the carpus.
Clinical: Scaphoid fracture (most common carpal bone fracture) carries a high risk of developing avascular (aseptic) necrosis due to compromised retrograde blood flow.

Function: Proximally located carpal bone central to the wrist joint axis
Clinical: Most dislocated carpal bone, acts as space-occupying mass that can crush or injure median nerve when dislocated.

Function: multiaxial ball and socket joint designed for maximum mobility of the upper extremity
Clinical: Glenohumeral joint dislocation (largest and most frequent dislocated large joint in adults, 95-98% anterior dislocations), presents with epaulette sign (flattened deltoid contour) and frequently damages the axillary nerve.

Function: Fibriocartiliginous ring attached to the rim of the glenoid cavity to deepen the socket and stabilize the humeral head
Clinical: Bankart lesion (tear or seperation of the glenoid labrum from its attachment rim) odten results from recurrent anterior dislocations of the shoulder joint.

Function: Rotator cuff component passing through the subacromial space to initiate arm abduction (0-15 degrees) and stabilize the humeral head
Clinical: Shoulder impingement syndrome, characterized by calicification and compression of this degenerated tendon within the subacromial space. It is reliably reproduced by a painful arc during 60-120 degrees of passive or active arm abduction.

Function: Hinge component of the elbow joint responsible for flexion and extension movements
Clinical: Posterior elbow dislocation, occuring when the ulna dislocates posteriorly during ulnar abduction, frequently accompanied by a fracture of the coronoid process, medial epicondyle avulsion and ulnar nerve injury

Function: Fibrous band encirciling the head of the radius to keep it attached in the radial notch of the ulna during pronation and supination
Clinical: Nursemaid's elbow (pulled elbow). Sudden axial pulling of a child's extended and pronated forearm causes the small radial head to slip out, tearing and trapping the anular ligament between the radial head and capitulum. Foreshortened forearm remains passively pronated/flexed; supination is highly restricted and painful.

Function: Anatomical gateway bounded by teres minor (superior), teres major (inferior), humeral surgical neck (lateral), and long head of the triceps brachii (medial)
Clinical: Space compression directly compromises the structures traversing it: the axillary nerve and posterior circumflex humeral artery/vein.

Function: Path bounded by teres minor (superior), teres major (inferior), and the long head of the triceps brachii (lateral)
Clinical: Vulnerable site where space-occupying pathology can compromise the circumflex scapular artery and vein

Function: Pyramidal zone providing safe conduit for the major neurovascular bundle of upper extremity
Clinical:
- Inner medial wall: Built by the first 4 ribs, intercostals and the serratus anterior muscle. It is the least dangerous wall and chosen for surgical access, but surgical error risk involves the long thoracic nerve.
-Ouer lateral wall: Formed by humerus intertubercular groove, biceps brachiim and coracobrachialis. Most dangerous wall bc branches of the brachial plexus and axillary vessels run directly against it.

Function: Motor nerve providing exclusive innervation to the serratus anterior muscle to protract and stabilize scapula against the thoracic wall.
Clinical: Winged scapula (scapula alata). Commonly injured during axillary surgeries like radical mastectomies or via prolonged heavy pressure on the shoulder. Results in an inability to abduct the arm beyond 90 degrees and causes the medial border of the scapula to painfully flare out like a wing when pushing against the wall.

Function: Motor innervation of the deltoid and teres minor muscles; carries sensory fibers to the skin over the upper-outer region of the arm
Clinical: Injury results in deltoid muscle atrophy (loss of rounded shoulder contour), severe weakness in arm abduction between 15-90 degrees, and patchy sensory loss over the lateral arm.

Function: Exclusive motor supply to all extensor muscles of the arm and forearm
Clinical: Injury inside the acilla or along the humeral body causes wrist drop (drop hand). The wrist and fingers remain passivley flexed due to unopposed flexor activity. extension of the elbow is preserved if the injury occurs in the humeral shaft because triceps long/medial head branches split off early in the axilla. (aka saturday night/honeymoon palsy)

Function: Motor division traversing the supinator canal to provide motor command to deep forearm extensors
Clinical: Supinator syndrome -> entrapment neuropathy caused by compression of this nerve branch within the supinator canal as it slides past the arcade of Frohse.

Function: Core motor innervation to the forearm pronators, long wrist/finger flexors (lateral half), thenar eminence, and the 1st and 2nd lumbricals.
Clinical:
-High level proximal lesions leave the forearm fixed in supination with weak hand flexion and loss of thum flecion/opposition
- Presents as ape hand or a baptismlessing hand deformity when attempting to close a fist (digits 2 and 3 fail to flex)
- Compression can occur proximally under Struthers' ligament (pronator syndrome)

Function: inelastic pathway bounded to the carpal bones posteriorly and the flexor retinaculum anteriorly. safley trasnmits 9 tendons (1 flexor pollicis longus, 4 flexor digitorum superficialis, 4 flexor digitorum profundus) and the median nerve
Clinical: Carpal tunnel syndrome -> entrapment neuropathy from high pressure inside tunnel, diagnosed via tinel's sign (percussing the retinaculum triggers paresthesia) and the Phalen test (sustained full wrist flexion for 1 minute reproduces symptoms)

Function: Motor control to the medial half of flexor digitorum profundus, flexor carpi ulnaris, all interosseous muscles (abduction and adduction of fingers), adductor pollicis, and the hypothenar eminence.
Clinical: Laceration or entrapment produces Claw hand, characterized by hyperextension of the metacarpophalangeal joints and fixed flexion of the interphalangeal joints of digits 4 and 5 due to lumbrical loss. Features hypothenar eminence flatenning and positive Froment's sign

Function: Retromalleolar passageway at the elbow through which the ulnar nerve passes
Clinical: Cubital tunnel syndrome, caused by ulnar nerve entrapment as it passes betwen the humeral and ulnar heads of the flexor carpi ulnaris muscle

Function: Specialized canal located between the pisiform, hamate and pisohamate ligament that houses the ulnar nerve and artery
Clinical: Guyon's canal syndrome -> typically causes a pure motor neuropathy affecting the intrinsic hand muscles in ,anular laborers using heavy machinery or long-distance motorcyclists. Sensation is intact because palmar/dorsal cutaneous sensory branches split off proximal to this canal.

Function: dense connective tissue walls dividing the forearm muscles and neurovascular packages into high-pressure tight spaces.
Clinical: Acute compartment syndrome -> forearm bine fractures causes local edema or bleeding, raising interstitial pressure above 35-40mmHg, marked by classic 6Ps (pain,pallor,paralysis, pulselessness, paresthesia and pain on passive stretch). requires immediate emergency fasciotomy to save the limb.

Function: 6 fibrous tunnels that guide extensor tendons onto the hand
Clinical:
-Canal 1 (Abductor pollicis longus + Extensor pollicis brevis): Site of De Quervian's tenosynnovitis (painful thickening of the sheath due to repetitive gripping/wringing movements)
-Canal 2 (Extensor carpi radialis logusrevis): The brevis sheath is the most common site in the entire wrist for a synnovial cyst (ganglion)

Function: Origin point for the common forearm extensor muscle tendon
Clinical: Lateral epicondylitis (tennis elbow)-> overuse tendon injury causing inflammation at the epicondyle due to repetitive wrist extension or continuous foreceful forearm supination and pronation.

Function: thich protective layer of deep fascia stabilizing skin of the palm and protecting underlying tendons
Clinical: Dupuytren's contracture, progressive fibrotic disease characterized by chronic thickening, hyperplasia, and shortening of the palmar aponeurosis. It draws the ring and little finger into a permanent fixed flexion

Function: Dual terminal vascular trees supplying the superficial and deep palmar arcges of the hand
Clinical: Assesed using the Allen test, where both vessels are manually compressed while the patient makes a tight fist. Releasing one artery should instantly flush the balanced hand red; failure to fo so indicates partial or complete occlusion of that specific vascular tree

Function: Major pelvic outlet partitioned by the piriformis muscle into 2 spaces, acting as a gateway for gluteal and sciatic neurovascular bundles
Clinical: Space compression or pathology alters transit elements:
- Suprapiriform foramen: transmits superior gluteal nerve, artery and vein. Injury causes Trendelenburg sign (pelvis drops on the unsupported side when standing on the affected leg)and a duck-like waddling gait due to gluteus medius/minimus paralysis
- Infrapiriform foramen: Transmits the sciatic nerve, inferior gluteal neurovascular bundle, pudendal nerve and internal pudendal vessels

Function: Pelvic transit route housing the obturator internus muscle tendon, internal pudendal artery/vein, and pudendal nerve
Clinical: Provides a re-entry loop into the perineum(pudendal nerve and internal pudendal vessels are unique because they pass through both the greater and lesser sciatic foramina

Function: Neck of the lateral leg bone, acting as direct physical conduit for the common fibular nerve
Clinical: Bony fracture at the fibular head or neck can directly crush, sever or stretch the common fibular (peroneal) nerve

Function: Deep ball and socket joint designed for heavy axillay weight-bearing load
Clinical: Hip dislocation, most commonly caused by high impact motor vehicle accident (force strikes a flexed, adducted thigh -> driving femoral head out posteriorly through capsule). If the acetabular rim fractures during this exit, the sciatic nerve can be injured

Function: Insertion point for the patellar ligament. trasmits extension forces of quadriceps femoris muscle complex
Clinical: Osgood- Schlatter disease, presents as painful micro-avulsion fractures along the tibial tuberosity surface. It is caused by chronic, repetitive pulling forces from the patellar ligament in skeletally immature adolescent athletes.

Function: deepest vascular structure running centrally through the popliteal fossa, providing the primary arterial blood supply to the leg and foot
Clinical: Popliteal artery injury or rupture (carries a high risk of limb loss) it is the single most vulnerablle structure during knee joint dislocations (typically due to severe hyperextension)

Function: Strong flat medial stabilizer band anchored to the medial epicondyle of the femur and the tibia, securely attached to the medial meniscus
Clinical: Tear or rupture from violent valgus stress forces, often presenting as unhappy (O'Donoghues) triad: tearing of the TCL + ACL + medial meniscus at the same time. Tear is clinically demonstrated by abnormal passive abduction of the leg

Function: Intracapsular ligament preventing abnormal passive forward displacement (anterior translation) of the tibia relative to the femur
Clinical: ACL rupture or tear, clinically confirmed via a positive anterior drawer test (leg moves more than 2cm when pulled forward with the knee flexed at 90 degrees)

Function: Strong intracapsular ligament that prevents posterior displacement of the tibia relative to the femur
Clinical: PCL rupture or tear, clinically confirmed via a positive Posterior Drawer Test (tibia sags or displaces more than 2 cms when pushed posteriorly)

Function: Fluid-filled synovial sac located anterior to the patella, minimizing fiction between skin and bone during knee movement
Clinical: Prepatellar bursitis (housemaid's/ Miner's knee) is an acute or chronic inflammation/infection of the bursa caused by friction from prolonged working on ones knees

Function: Small medial channel within the femoral sheath that trasmits lymphatic tracking vessels and houses the Cloquet/Rosenmuller lymph node. the abdominal opening to this canal is the femoral ring
Clinical: Femoral hernia, where abdominal contents push through the femoral septum and descend into the canal. presents as mass protruding through the saphenous opening. more common in females

Function: Exclusivley sensory nerve passing under the inguinal ligament to supply the skin over the lateral aspect of the thigh
Clinical: Meralgia paresthetica, a painful entrapment neuropathy where the nerve is compressed as it pierces the fascia lata or passes under the inguinal ligament. ommon in obese indiviuals and during pregnancy

Function: Massive nerve trunk eciting the infrapiriform space to supply all hamstring muscles and all muscles below the knee
Clinical: Commonly damaged in posterior hip dislocations or incorrect intramuscular injections into the gluteal region. Results in foot drop, severe weakness in leg flexion and sensory loss below the knee (except medial strip-> supplied by saphenous nerve)

Function: Travels through the popliteal fossa to provide motor control to all muscles in the posterior compartment of the leg and sole of foot
Clinical: Injury results in Calcaneovalgus, foot is fixed in dorsiflexion and eversion due to unopposed extensor muscles. Patient cant stand on tiptoe and has total sensory loss on the sole of the foot

Function: tunnel below the medial malleolus covered by the flexor retinaculum. it trasmits the tibialis posterior, flexor digitorum longus, and flexor hallucis longus tendons, along with the posterior tibial vessels and tibial nerve.
Clinical: Tarsal tunnel syndrome. entrapment neuropathy caused by localized edema within the tunnel that copresses the tibial nerve. Causes a burning pain and paresthesia across the sole of the foot, typically more severe at night

Function: Curves around the lateral neck of the fibula to supply all muscles in the anterior (dorsiflexors) and lateral (evertors) compartments of the leg
Clinical: Most frequently injured nerve in the lower extremity. Injury from fibular neck fractures or tight casts results in Equinovarus and foot drop. The foot remains stuck in plantar flecion and inversion

Function: Thick fibrous sheet of the fascia lata stabilizing the lateral thigh and knee
Clinical: Illiotibial band contracure -> passive shortening of the tract causing severe lateral thigh pain. Diagnosed using the Ober test: patient on their side, leg is abducted and extended; when released, a contracted band leaves the leg abnormally suspended in the air

Function: Powerful superficial posterior compartment muscle executing explosive plantar flexion of the foot
Clinical: Tennis leg-> painful partial tear of the medial head at the musculocutendinous junction. It is caused by overstretching the muscle when the knee is fully extended while the foot is forced in sudden dorsiflexion

Function: Thick common terminal insertion tendon for the triceps surae complex into the calcaneus bone
Clinical: Achilles tendon rupture, often seen in middle aged athletes following sudden, forceful dorsiflexion, presenting with audible pop and acute pain. Clinically confirmed via Thompson test: when calf muscle is squeezed while patient is prone, a ruptured tendon will fail to produce passive plantar flexion

Function: thick connective tissue supporting the longitudinal arches of the foot and absorbing mechanical shock during walking
Clinical: Plantar fasciitis-> most common cause of heel pain. caused by microtearing and chronic strain along the fascia due to the biomechanical imbalances It is common in indiviuals that stand for long periods