 a) Difference in Clinical Presentation between Upper and Lower Motor Neuron Lesions of the Facial Nerve (3 marks) Upper Motor Neuron (UMN) Lesion: - Causes contralateral weakness of the lower half of the face - The forehead muscles are spared due to bilateral cortical innervation Lower Motor Neuron (LMN) Lesion: - Causes ipsilateral weakness of both the upper and lower facial muscles, including the forehead Summary: UMN lesion = contralateral lower face weakness with forehead sparing; LMN lesion = ipsilateral complete facial paralysis. b) Anatomical Basis for the Difference Between UMN and LMN Lesions (5 marks) - Facial nucleus location: The facial nerve motor nucleus is located in the pons and gives rise to the lower motor neurons. - Cortical innervation: The upper part of the facial nucleus (which controls the forehead) receives bilateral corticobulbar innervation, while the lower part (which controls the lower face) receives only contralateral corticobulbar innervation. - UMN lesion (e.g., stroke): Since the upper facial muscles have bilateral input, they remain functional when one corticobulbar tract is damaged. However, the contralateral lower face loses its only source of cortical input, resulting in weakness. - LMN lesion (e.g., Bell's palsy): The lesion affects the facial nerve after it exits the brainstem, disrupting all motor supply to ipsilateral facial muscles, both upper and lower. - Resulting clinical difference: This anatomical pattern explains why UMN lesions spare the forehead, while LMN lesions cause complete ipsilateral facial paralysis. c) Two Sensory Stimuli Conveyed by the Posterior Columns of the Spinal Cord (2 marks) - Fine (discriminative) touch - Proprioception (position sense) --- QUESTION 2 - Esophagus (10 Marks) a) Three Areas of Constriction (3 marks - 1 mark each) - Cervical constriction: At the origin of the esophagus, behind the cricoid cartilage (C6), caused by the cricopharyngeus muscle. - Thoracic (broncho-aortic) constriction: Where the esophagus is crossed by the aortic arch and the left main bronchus (~T4–T5). - Diaphragmatic constriction: Where the esophagus passes through the esophageal hiatus of the diaphragm at T10. b) Four Relations in the Superior Mediastinum (4 marks - 1 mark each) - Anteriorly: Trachea and left recurrent laryngeal nerve. - Posteriorly: Vertebral column and thoracic duct. - To the right: Azygos vein and right pleura/lung. - To the left: Arch of the aorta, left subclavian artery, and left pleura/lung. c) Lymphatic Drainage (3 marks) The lymphatic drainage of the esophagus is segmental and drains into different nodal groups: - Cervical part: Drains into deep cervical lymph nodes. - Thoracic part: Drains into posterior mediastinal lymph nodes. - Abdominal part: Drains into left gastric and celiac lymph nodes. --- QUESTION 3 - Jejunum vs Ileum and Inguinal Canal (10 Marks) a) Name 4 Differences Between Jejunum and Ileum (4 Marks - 1 mark each) b) Describe the Boundaries of the Inguinal Canal (6 Marks - 1.5 marks each for boundaries) The inguinal canal is an oblique passage in the lower anterior abdominal wall, about 4 cm long, running from the deep to the superficial inguinal ring. - Anterior Wall: Mainly formed by the aponeurosis of the external oblique muscle throughout - Reinforced laterally by internal oblique muscle fibers - Posterior Wall: Formed by the transversalis fascia - Reinforced medially by the conjoint tendon (fusion of internal oblique and transversus abdominis aponeuroses) - Roof (Superior Wall): Formed by the arching fibers of the internal oblique and transversus abdominis muscles - Floor (Inferior Wall): Formed by the inguinal ligament - Medially supported by the lacunar ligament --- QUESTION 4 - Popliteal Fossa and Femoral Triangle (10 Marks) a) Boundaries and Contents of the Popliteal Fossa (5 Marks) Boundaries: - Superolateral: Biceps femoris muscle - Superomedial: Semimembranosus and semitendinosus muscles - Inferolateral: Lateral head of gastrocnemius - Inferomedial: Medial head of gastrocnemius - Floor: Popliteal surface of femur, capsule of knee joint, and popliteus muscle - Roof: Skin and deep fascia (popliteal fascia) Contents (from superficial to deep/posterior to anterior): - Tibial nerve - Popliteal vein - Popliteal artery - Common peroneal (fibular) nerve - Small saphenous vein (termination) - Lymph nodes and fat b) Boundaries and Contents of the Femoral Triangle (5 Marks) Boundaries: - Superior (base): Inguinal ligament - Lateral: Sartorius muscle - Medial: Adductor longus muscle - Floor: Iliopsoas (laterally) and pectineus (medially) - Roof: Fascia lata and skin Contents (from lateral to medial - NAVEL mnemonic): - Femoral Nerve - Femoral Artery - Femoral Vein - Femoral canal (contains lymph node of Cloquet) - Deep inguinal lymph nodes and fat --- QUESTION 5 - Median Nerve (10 Marks) A. Course of the Median Nerve in the Upper Limb - Origin: Formed by two roots from the medial and lateral cords of the brachial plexus (C5–T1) - Roots unite anterior to the third part of the axillary artery - In the Arm: Runs lateral to the brachial artery initially, then crosses over to become medial to it near the mid-arm - Does not give any branches in the arm - In the Cubital Fossa: Enters the cubital fossa medial to the biceps tendon and brachial artery - Passes between the two heads of pronator teres - In the Forearm: Travels between flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) - Gives off the anterior interosseous nerve (AION), supplying deep forearm muscles - At the wrist, it becomes superficial, passing through the carpal tunnel - In the Hand: Enters the hand deep to the flexor retinaculum (in the carpal tunnel) - Divides into recurrent branch (to thenar muscles) and digital branches (to lateral 3½ fingers for motor and sensory innervation) B. Distribution of the Median Nerve - Motor Supply: Forearm muscles (anterior compartment): All except flexor carpi ulnaris and medial half of FDP - Thenar muscles: Abductor pollicis brevis, opponens pollicis, flexor pollicis brevis (superficial head) - Lumbricals 1 and 2 (index and middle fingers) - Sensory Supply: Skin over the lateral palm - Palmar surface and dorsal tips of the lateral 3½ fingers (thumb, index, middle, and half of ring finger) C. Deficits Following Median Nerve Injury - At the Elbow (e.g., supracondylar fracture): Loss of forearm pronation - Weak wrist flexion with ulnar deviation - Loss of flexion of the lateral fingers and thumb opposition - Hand of Benediction when attempting to make a fist (only ulnar-side fingers flex) - At the Wrist (e.g., carpal tunnel syndrome, laceration): Thenar muscle wasting - Loss of thumb opposition - Sensory loss over lateral 3½ fingers - Ape hand deformity: Flattened thenar eminence, thumb held in same plane as fingers - Anterior Interosseous Nerve Injury: Weakness of flexor pollicis longus, FDP (lateral half), and pronator quadratus - Inability to make an "OK sign" (due to weak flexion of thumb and index finger tips) --- QUESTION 6 - Stomach (10 Marks) a) Blood Supply of the Stomach (4 Marks) The stomach receives a rich arterial supply from branches of the celiac trunk: - Lesser Curvature: Left gastric artery (from the celiac trunk) - Right gastric artery (from the proper hepatic artery) - These anastomose along the lesser curvature - Greater Curvature: Left gastroepiploic artery (from splenic artery) - Right gastroepiploic artery (from gastroduodenal artery) - Anastomose along the greater curvature - Fundus and Upper Body: Short gastric arteries (from splenic artery) Venous drainage: Corresponds to the arteries and drains into the portal vein via the left and right gastric veins, splenic vein, and superior mesenteric vein. b) Innervation of the Stomach - Parasympathetic Innervation: From the vagus nerve (CN X) - Left vagus supplies the anterior wall, ri