Master First-Year Anatomy: Must-Know Essays OmpathStudy

ANATOMY EXAMINATION — COMPLETE REWRITE --- Q1 — FACIAL NERVE LESIONS a) UMN vs LMN Lesion — Clinical Difference UMN lesion: contralateral lower face weakness; forehead spared (bilateral cortical input to upper face nucleus). LMN lesion: ipsilateral complete facial paralysis — upper and lower face, including forehead. b) Anatomical Basis The facial motor nucleus lies in the pons. Its upper division (forehead) receives bilateral corticobulbar input; its lower division receives only contralateral input. A UMN lesion (e.g. stroke) destroys one corticobulbar tract — the lower face loses its only cortical input contralaterally, but the forehead remains functional via the intact opposite tract. An LMN lesion (e.g. Bell's palsy) destroys the nerve distal to the nucleus, cutting off all ipsilateral motor supply — full ipsilateral paralysis results. c) Posterior Column Sensory Modalities Fine (discriminative) touch Proprioception (position sense) --- Q2 — OESOPHAGUS a) Three Constrictions Cervical — cricopharyngeus muscle at C6 Thoracic (broncho-aortic) — aortic arch and left main bronchus at T4–T5 Diaphragmatic — oesophageal hiatus at T10 b) Four Relations in the Superior Mediastinum Anterior: trachea and left recurrent laryngeal nerve Posterior: vertebral column and thoracic duct Right: azygos vein and right pleura Left: aortic arch, left subclavian artery, left pleura c) Lymphatic Drainage Cervical part → deep cervical nodes Thoracic part → posterior mediastinal nodes Abdominal part → left gastric and coeliac nodes --- Q3 — JEJUNUM vs ILEUM & INGUINAL CANAL a) Four Differences — Jejunum vs Ileum Feature Jejunum Ileum --- --- --- Position Upper left abdomen Lower right abdomen Wall thickness Thicker, more vascular Thinner, less vascular Villi Taller, more numerous Shorter, fewer Peyer's patches Absent/sparse Prominent b) Inguinal Canal — Boundaries Anterior wall: external oblique aponeurosis (reinforced laterally by internal oblique) Posterior wall: transversalis fascia (reinforced medially by conjoint tendon) Roof: arching fibres of internal oblique and transversus abdominis Floor: inguinal ligament (medially supported by lacunar ligament) --- Q4 — POPLITEAL FOSSA & FEMORAL TRIANGLE a) Popliteal Fossa Boundaries: Superolateral: biceps femoris Superomedial: semimembranosus and semitendinosus Inferolateral: lateral head of gastrocnemius Inferomedial: medial head of gastrocnemius Floor: popliteal surface of femur, knee joint capsule, popliteus Roof: skin and popliteal fascia Contents (superficial to deep): tibial nerve → popliteal vein → popliteal artery; common peroneal nerve runs along biceps femoris tendon; small saphenous vein terminates here; lymph nodes and fat. b) Femoral Triangle Boundaries: Base (superior): inguinal ligament Lateral: sartorius Medial: adductor longus Floor: iliopsoas (lateral) and pectineus (medial) Roof: fascia lata and skin Contents (lateral to medial) — mnemonic NAVEL: Femoral Nerve, Femoral Artery, Femoral Vein, Empty space (femoral canal with Cloquet's node), Lymphatics --- Q5 — MEDIAN NERVE A. Course Origin: medial and lateral cords of brachial plexus (C5–T1); roots unite anterior to the third part of the axillary artery. Arm: runs lateral then crosses medial to brachial artery at mid-arm. No branches in arm. Cubital fossa: enters medial to biceps tendon and brachial artery; passes between two heads of pronator teres. Forearm: travels between FDS and FDP; gives anterior interosseous nerve (AION); becomes superficial at wrist. Hand: passes through carpal tunnel (deep to flexor retinaculum); divides into recurrent branch (thenar muscles) and digital branches (lateral 3½ fingers). B. Motor and Sensory Distribution Motor — forearm: all anterior compartment muscles except flexor carpi ulnaris and medial half of FDP. Hand: abductor pollicis brevis, opponens pollicis, superficial head of flexor pollicis brevis, lumbricals 1 and 2. Sensory: lateral palm; palmar and dorsal fingertip surfaces of thumb, index, middle, and lateral half of ring finger. C. Injury Deficits At elbow (e.g. supracondylar fracture): loss of pronation, weak wrist flexion with ulnar deviation, loss of lateral finger and thumb flexion, hand of benediction on attempted fist. At wrist (e.g. carpal tunnel): thenar wasting, loss of thumb opposition, sensory loss over lateral 3½ fingers, ape hand deformity. AION injury: inability to make OK sign (weak flexor pollicis longus and lateral FDP). --- Q6 — STOMACH a) Blood Supply Lesser curvature: left gastric artery (coeliac trunk) + right gastric artery (proper hepatic artery) Greater curvature: left gastroepiploic (splenic artery) + right gastroepiploic (gastroduodenal artery) Fundus: short gastric arteries (splenic artery) Venous drainage follows arteries → portal vein via left/right gastric, splenic, and superior mesenteric veins. b) Innervation Parasympathetic (vagus CN X): left vagus → anterior wall; right vagus → posterior wall. Stimulates secretion, motility, sphincter relaxa