Q: Answer these questions for bds 1st year anatomy board exam of kathamndu university each question holds 5 to 7 marks A: Here are complete, board-exam-level answers for all questions. Each is written for BDS 1st year Kathmandu University standard. --- UPPER LIMB - ANATOMY BOARD EXAM ANSWERS --- Q1. Formation of Brachial Plexus with Diagram + Two Applied Anatomy 4+1=5 Formation of the Brachial Plexus The brachial plexus is a somatic nerve plexus formed by the anterior rami ventral rami of C5, C6, C7, C8, and T1. Occasionally C4 contributes prefixed plexus or T2 contributes postfixed plexus. The plexus originates in the neck, passes laterally and inferiorly over the 1st rib, and enters the axilla. It is organized into four parts: Roots → Trunks → Divisions → Cords → Branches mnemonic: "Robert Taylor Drinks Cold Beer". Parts: 1. ROOTS 5: Anterior rami of C5-T1, lying between the anterior and middle scalene muscles. They receive gray rami communicantes from the sympathetic trunk. 2. TRUNKS 3: Trunk Formation ------ Superior trunk C5 + C6 unite Middle trunk C7 alone continues Inferior trunk C8 + T1 unite The trunks cross the posterior triangle of the neck and pass over Rib I, posterior to the subclavian artery. 3. DIVISIONS 6: Each trunk divides into an anterior division and a posterior division total 6 divisions. They are located posterior to the clavicle. - Anterior divisions - supply flexor anterior compartments - Posterior divisions - supply extensor posterior compartments 4. CORDS 3: Named by their relationship to the 2nd part of the axillary artery: Cord Formation Position --------- Lateral cord Anterior divisions of Superior + Middle trunks C5-C7 Lateral to axillary artery Medial cord Anterior division of Inferior trunk C8-T1 Medial to axillary artery Posterior cord All three posterior divisions C5-T1 Posterior to axillary artery 5. BRANCHES major terminals: - Lateral cord → Musculocutaneous nerve, Lateral root of median nerve, Lateral pectoral nerve - Medial cord → Ulnar nerve, Medial root of median nerve, Medial pectoral nerve, Medial cutaneous nerves of arm and forearm - Posterior cord → Radial nerve, Axillary nerve, Thoracodorsal nerve, Upper and lower subscapular nerves Branches from roots: Dorsal scapular nerve C5, Long thoracic nerve C5-C7 Branches from trunks Superior trunk only: Suprascapular nerve, Nerve to subclavius Diagram of Brachial Plexus: C5 ─┐ C6 ─┴─ SUPERIOR TRUNK ──── Anterior div ─┐ ├── LATERAL CORD C7 ─── MIDDLE TRUNK ──── Anterior div ─┘ └── Posterior div ─┐ C8 ─┐ ├── POSTERIOR CORD T1 ─┴─ INFERIOR TRUNK ─── Anterior div ── MEDIAL CORD └── Posterior div ─┘ LATERAL CORD → Musculocutaneous N. Lateral root of Median N. MEDIAL CORD → Ulnar N. Medial root of Median N. POSTERIOR CORD → Radial N. Axillary N. Gray's Anatomy for Students, p. 858 Applied Anatomy of Brachial Plexus 1 mark each - 2 total: 1. Erb's Palsy Upper trunk injury - C5, C6: Caused by excessive stretching of the neck away from the shoulder e.g., during difficult delivery, motorcycle accidents. The superior trunk C5+C6 is damaged. This paralyzes the deltoid, biceps brachii, brachialis, brachioradialis, and supraspinatus muscles. The limb hangs in the characteristic "Waiter's tip" position - arm adducted, internally rotated, elbow extended, forearm pronated. 2. Klumpke's Palsy Lower trunk injury - C8, T1: Caused by excessive abduction of the arm e.g., grabbing a branch during a fall. The inferior trunk C8+T1 is damaged, affecting small intrinsic muscles of the hand supplied by ulnar nerve and long flexors of the fingers. Results in "Claw hand" deformity. If T1 sympathetic fibers are also damaged, Horner's syndrome ptosis, miosis, anhidrosis, enophthalmos occurs due to interruption of cervical sympathetics. --- Q2. Short Notes a External Carotid Artery Origin: Arises from the common carotid artery at the level of the upper border of the thyroid cartilage C3-C4 vertebral level, within the carotid triangle. Course: Initially anteromedial to the internal carotid artery, then curves posterolaterally to enter the parotid gland where it divides into its two terminal branches. Branches mnemonic: "Some Anatomists Like Feeding Our Poor Medical Students": Branch Distribution ------ Superior thyroid artery Thyroid gland, larynx Ascending pharyngeal artery Pharynx, meninges Lingual artery Tongue, floor of mouth Facial artery Face, lips, nose Occipital artery Scalp occipital region Posterior auricular artery Ear, scalp behind ear Maxillary artery terminal Deep face, teeth, dura Superficial temporal artery terminal Scalp, temples Applied: Ligation of external carotid is done in severe facial hemorrhage. The facial artery pulse is felt at the lower border of the mandible at the anterior edge of masseter. --- b Facial Nerve CN VII Origin: Arises from the lower border of the pons at the cerebellopontine angle. Course: - Enters the internal acoustic meatus - Passes through the facial canal in the petrous temporal bone - Gives branches within the canal: Greater petrosal nerve parasympathetic to lacrimal gland, Nerve to stapedius, Chorda tympani taste to anterior 2/3 of tongue + submandibular/sublingual gland supply - Exits the skull at the stylomastoid foramen - Enters the parotid gland and divides into five terminal branches Five terminal branches mnemonic: "Two Zebras Bit My Cat": 1. Temporal 2. Zygomatic 3. Buccal 4. Marginal mandibular 5. Cervical Applied Anatomy: - Bell's palsy: Idiopathic LMN facial nerve palsy causing unilateral facial paralysis - all muscles of facial expression affected on the same side. - Upper vs Lower motor neuron lesion: In UMN lesion, forehead is spared bilateral cortical representation; in LMN lesion, entire ipsilateral face including forehead is paralyzed. - The nerve is at risk during parotid surgery. --- c Carotid Triangle Location: A subdivision of the anterior triangle of the neck. Boundaries: - Anteroinferiorly: Superior belly of omohyoid - Posteriorly: Anterior border of sternocleidomastoid - Superiorly: Posterior belly of digastric Floor: Hyoglossus, thyrohyoid, inferior and middle constrictors of pharynx. Roof: Investing layer of deep cervical fascia + platysma + skin. Contents: - Common carotid artery bifurcates into internal and external carotid arteries here - Carotid sinus at bifurcation - baroreceptor, supplied by CN IX - Carotid body chemoreceptor - Internal jugular vein - Vagus nerve CN X in carotid sheath - Hypoglossal nerve CN XII - crossing superficially - Superior root of ansa cervicalis Applied: Carotid sinus massage slows the heart used in supraventricular tachycardia. Atherosclerosis at the carotid bifurcation is a common cause of stroke/TIA. --- d Carpal Tunnel Syndrome Definition: Compression of the median nerve within the carpal tunnel at the wrist. Anatomy of Carpal Tunnel: - Floor & walls: Carpal bones arranged as a groove - Roof: Flexor retinaculum transverse carpal ligament - Contents: Median nerve + 4 tendons of FDS + 4 tendons of FDP + tendon of FPL 9 tendons + 1 nerve Note: The ulnar nerve and artery pass superficial to the flexor retinaculum through Guyon's canal - NOT through the carpal tunnel. Causes: Pregnancy, hypothyroidism, rheumatoid arthritis, diabetes, repetitive hand movements, acromegaly. Clinical Features: - Pain and paresthesia burning/tingling in the lateral 3½ fingers thumb, index, middle, lateral half of ring finger - Worse at night, relieved by shaking the hand - Wasting of thenar eminence LOAF muscles affected: Lateral two Lumbricals, Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis - Weak thumb opposition Tests: Phalen's test wrist flexion, Tinel's sign percussion over carpal tunnel. Treatment: Splinting, corticosteroid injection, surgical division of flexor retinaculum. --- e Axillary Artery Definition: Continuation of the subclavian artery beginning at the lateral border of the 1st rib and ending at the lower border of teres major where it becomes the brachial artery. Relations: The pectoralis minor muscle divides it into 3 parts. Branches: Part Branches ------ 1st part medial to pectoralis minor Superior thoracic artery 2nd part posterior to pectoralis minor Thoracoacromial artery, Lateral thoracic artery 3rd part lateral to pectoralis minor Subscapular artery, Anterior circumflex humeral, Posterior circumflex humeral artery Mnemonic: "Scorch That Lazy SA's Poor Ass" 1-2-3 branches per part. Applied: - Axillary artery aneurysm can compress the brachial plexus cords causing upper limb neurological symptoms. - It is the basis for axillary nerve block used for upper limb surgeries. --- f Sympathetic Nervous System Overview: The thoracolumbar outflow T1-L2/L3 - the "fight or flight" system. Components: - Pre-ganglionic neuron: Cell bodies in the lateral horn of spinal cord T1-L2. Short myelinated fibers travel via white rami communicantes to sympathetic chain ganglia. - Post-ganglionic neuron: Long unmyelinated fibers from the ganglia travel to effector organs via gray rami communicantes to all spinal nerves or along blood vessels. Sympathetic Chain: Two parallel chains of ganglia 22-24 ganglia each running lateral to the vertebral column from base of skull to coccyx. Preganglionic fibers may: 1. Synapse in the ganglion at the same level 2. Ascend or descend to synapse at a different level 3. Pass through without synapsing to reach collateral prevertebral ganglia - celiac, superior/inferior mesenteric Effects of Sympathetic Stimulation: - Pupil dilation mydriasis, decreased secretions, bronchodilation - Tachycardia, increased force of cardiac contraction - Vasoconstriction skin, viscera, vasodilation skeletal muscle - Decreased gut motility, sphincter contraction - Piloerection, sweating Applied: Horner's syndrome damage to cervical sympathetics - ptosis, miosis, anhidrosis, enophthalmos. Raynaud's disease treated by cervical sympathectomy. --- g Elbow Joint Type: A compound hinge joint synovial. Articulations 3 in one joint cavity: 1. Humero-ulnar joint trochlea of humerus + trochlear notch of ulna - hinge 2. Humero-radial joint capitulum of humerus + head of radius - hinge 3. Superior radio-ulnar joint head of radius + radial notch of ulna - pivot Ligaments: - Medial ulnar collateral ligament - triangular; limits valgus stress - Lateral radial collateral ligament - limits varus stress - Annular ligament - holds head of radius in radial notch Movements: - Flexion 0-145° and Extension: Flexion by biceps brachii, brachialis, brachioradialis; Extension by triceps brachii, anconeus - Supination and Pronation occur at the superior radioulnar joint Blood Supply: Anastomosis around elbow profunda brachii, radial recurrent, ulnar recurrent, interosseous recurrent arteries. Nerve Supply: Musculocutaneous, radial, ulnar, and median nerves Hilton's law. Applied: - Pulled elbow Nursemaid's elbow: Subluxation of radial head through annular ligament in children under 5 years due to sudden pulling of the arm. - Lateral epicondylitis Tennis elbow: Overuse injury of common extensor origin. - Medial epicondylitis Golfer's elbow: Overuse of common flexor origin. - Cubitus valgus after lateral condyle fracture can cause tardy ulnar nerve palsy. --- h Cubital Fossa Definition: A triangular hollow in front of the elbow the "antecubital fossa". Boundaries: - Medially: Pronator teres medial border - Laterally: Brachioradialis lateral border - Base superiorly: Imaginary line joining the medial and lateral epicondyles - Apex inferiorly: Where pronator teres and brachioradialis meet Floor: Brachialis muscle + supinator muscle lateral part Roof: Deep fascia of arm reinforced by the bicipital aponeurosis, and overlying skin/superficial fascia containing the median cubital vein. Contents medial to lateral - mnemonic "TAN" or "BAN": Structure Notes ------ Brachial artery Divides into radial and ulnar arteries at the apex of cubital fossa Median nerve Lies medial to the brachial artery Biceps brachii tendon Central, passes to radial tuberosity Radial nerve Lies lateral; divides into superficial radial and posterior interosseous nerves here Applied: - The median cubital vein in the roof is the most common site for venipuncture/IV cannulation. - Brachial artery is palpated/auscultated in cubital fossa for blood pressure measurement. - Supracondylar fractures in children can damage the brachial artery and median nerve. --- Q3. Boundaries, Contents and Applied Anatomy of Axilla 5 Axilla - Shape and Overview The axilla is a pyramidal space between the upper limb and the thoracic wall. It acts as a passageway for nerves, vessels, and lymphatics traveling to and from the upper limb. Boundaries: Wall Formed By ------ Apex Bounded by 1st rib medially, clavicle anteriorly, and superior border of scapula posteriorly - the gateway to the axilla Base floor Axillary fascia + skin + subcutaneous tissue axillary fossa Anterior wall Pectoralis major superficial, pectoralis minor and clavipectoral fascia deep. The anterior axillary fold = lower margin of pectoralis major Posterior wall Subscapularis upper, teres major and latissimus dorsi lower. The posterior axillary fold = teres major + latissimus dorsi Medial wall Upper thoracic wall ribs 1-4 + intercostal muscles + serratus anterior Lateral wall Intertubercular bicipital groove of the humerus narrowest wall Fischer's Mastery of Surgery, p. 1552; Gray's Anatomy for Students, p. 845 Contents of Axilla: 1. Axillary artery continuation of subclavian; divided into 3 parts by pectoralis minor 2. Axillary vein formed by union of venae comitantes of brachial artery + basilic vein 3. Cords and terminal branches of brachial plexus lateral, medial, posterior cords + their branches 4. Axillary lymph nodes 5 groups: anterior/pectoral, posterior/subscapular, lateral/humeral, central, apical 5. Axillary fat 6. Long thoracic nerve on surface of serratus anterior 7. Intercostobrachial nerve T2 - pierces the medial wall Axillary Lymph Nodes 5 groups: Group Location Drainage --------- Anterior pectoral Along lateral thoracic artery Breast lateral and central Posterior subscapular Along subscapular vessels Back, neck, scapular region Lateral humeral Along axillary vein Most of upper limb Central Central fat Receives from anterior, posterior, lateral groups Apical Above pectoralis minor All other groups → drains to subclavian trunk Applied Anatomy: 1. Breast cancer and axillary clearance: Axillary lymph nodes are the primary route of spread of breast carcinoma. Surgical axillary lymph node dissection Level I, II, III is performed in breast cancer staging. The surgical boundaries are: axillary vein superiorly, latissimus dorsi laterally, and chest wall medially. 2. Damage to long thoracic nerve: During axillary surgery or mastectomy, the long thoracic nerve nerve to serratus anterior can be injured, causing "winging of the scapula" - the medial border of the scapula lifts off the chest wall when the patient pushes against a wall. 3. Axillary nerve injury: Fracture of the surgical neck of the humerus or dislocation of the shoulder joint can damage the axillary nerve, causing loss of deltoid function inability to abduct the arm beyond 15° and loss of sensation over the "regimental badge" area of the shoulder. --- Q4. Origin, Course, and Applied Anatomy of Radial Nerve 3+2=5 Origin The radial nerve arises from the posterior cord of the brachial plexus C5, C6, C7, C8 - with variable T1 contribution. It is the largest branch of the brachial plexus. Course In the Axilla: - Lies posterior to the axillary artery and anterior to the subscapularis, teres major, and latissimus dorsi. - Gives branches to the long and medial heads of triceps brachii in the axilla. Entering the Arm: - Crosses the inferior margin of teres major with the profunda brachii deep brachial artery. - Enters the posterior compartment of the arm by passing through the triangular interval bounded by: shaft of humerus, lower border of teres major, lateral head of triceps. In the Posterior Compartment Radial/Spiral Groove: - Winds around the humerus in the radial groove spiral groove, lying directly on bone. - Travels with the profunda brachii artery from medial to lateral. - Gives branches to all three heads of triceps brachii and to the anconeus. - Gives cutaneous branches: posterior cutaneous nerve of the arm and inferior lateral cutaneous nerve of the arm, and posterior cutaneous nerve of the forearm. Entering the Anterior Compartment: - Pierces the lateral intermuscular septum to enter the anterior compartment of the arm. - Lies between brachialis medially and brachioradialis laterally. - Innervates the brachioradialis and extensor carpi radialis longus here. At the Elbow: - Enters the forearm anterior to the lateral epicondyle, deep to the brachioradialis. - Divides into two terminal branches within the cubital fossa or at the level of the lateral epicondyle: Terminal Branch Nature Distribution --------- Superficial branch superficial radial nerve Sensory only Dorsum of hand lateral 3½ fingers, dorsal web space Deep branch posterior interosseous nerve Motor only All extensor muscles of forearm except ECRL already supplied; terminates as posterior interosseous nerve in posterior interosseous canal Gray's Anatomy for Students, p. 881 Applied Anatomy: 1. Radial Nerve Injury in the Radial Groove Midshaft Humerus Fracture - "Saturday Night Palsy": The radial nerve is tightly bound with the profunda brachii artery in the radial groove. Fracture of the midshaft of the humerus or prolonged compression e.g., sleeping with arm over a chair - "Saturday night palsy" stretches or transects the nerve. Results in: - Wrist drop - inability to extend the wrist due to denervation of wrist extensors - Inability to extend the fingers at the MCP joints - Sensory loss over dorsum of hand dorsal web space between thumb and index finger - Triceps is usually spared branches given off before the spiral groove 2. Posterior Interosseous Nerve PIN Palsy: PIN can be compressed as it passes through the Arcade of Frohse fibrous arch at the proximal edge of supinator. Causes weakness of finger extension but NO wrist drop ECRL is supplied before the PIN branches and no sensory loss PIN is purely motor. Seen in radial head fractures, lipomas, rheumatoid arthritis. --- Q5. Origin, Insertion, Nerve Supply, and Actions of Deltoid Muscle 1+1+1+2=5 Origin 1 mark The deltoid has three parts arising from: Part Origin ------ Anterior clavicular part Lateral 1/3 of the anterior surface and inferior border of the clavicle Middle acromial part Lateral surface of the acromion process Posterior spinal part Inferior lip of the crest of the spine of the scapula The three parts converge to form a multipennate arrangement. Insertion 1 mark All three parts insert into the deltoid tuberosity on the middle of the lateral surface of the shaft of the humerus. Nerve Supply 1 mark The deltoid is supplied by the axillary nerve C5, C6 - from the posterior cord of the brachial plexus. The axillary nerve winds around the surgical neck of the humerus within the quadrilateral space, giving muscular branches to the deltoid and teres minor, and a sensory branch - the upper lateral cutaneous nerve of the arm - supplying skin over the lower deltoid "regimental badge area". Actions 2 marks Part Action ------ Middle entire muscle Abduction of the arm initiates after 15° initiated by supraspinatus - up to 90° Anterior part Flexion, medial rotation, and horizontal adduction of the arm Posterior part Extension, lateral rotation, and horizontal abduction of the arm Together, the deltoid is the main abductor of the arm supraspinatus initiates the first 15°, then deltoid continues to 90°; beyond 90° requires scapular rotation by trapezius and serratus anterior. Applied: - Axillary nerve injury surgical neck of humerus fracture or shoulder dislocation paralyzes the deltoid, resulting in inability to abduct the arm beyond 15°. - Loss of the deltoid contour gives the shoulder a "flat" or squared-off appearance. - Intramuscular injections are given into the middle part of deltoid safe from the axillary nerve which is 5 cm below the acromion. - Deltoid is tested by asking the patient to abduct the arm against resistance. --- Q6. Formation, Extent of Clavipectoral Fascia and Structures Piercing It 2+2+1=5 Formation 2 marks The clavipectoral fascia is a strong sheet of connective tissue deep fascia that lies deep to the pectoralis major muscle and pectoral fascia. It is formed as follows: - Superiorly: Splits to enclose the subclavius muscle, and is attached above to the clavicle on both sides of the subclavius. - Inferiorly: After enclosing the subclavius, the two layers reunite below it as a single dense sheet, which then descends to enclose the pectoralis minor muscle splitting again to surround it. - Below pectoralis minor: The two layers reunite again as the suspensory ligament of the axilla axillary fascia, which connects to the axillary fascia floor of axilla and holds the axillary floor open. So in summary: It encloses subclavius above, spans the gap between subclavius and pectoralis minor as a single sheet, and then encloses pectoralis minor below. Gray's Anatomy for Students, p. 845; THIEME General Anatomy Atlas Extent 2 marks Region Extension ------ Superiorly Clavicle attached to both lips of the subclavian groove Inferiorly Continues as the axillary fascia suspensory ligament of axilla, blending with the deep fascia of the armpit Medially Continuous with the fascia covering the first and second intercostal spaces Laterally Blends with the capsule of the shoulder joint and coracoid process The fascia is pierced by structures that travel between the pectoral region and the axilla. Structures Piercing the Clavipectoral Fascia 1 mark Structures pass through in two locations: Between subclavius and pectoralis minor: 1. Cephalic vein - draining into the axillary vein 2. Thoracoacromial artery and its branches 3. Lateral pectoral nerve C5-C7 from lateral cord - supplies pectoralis major Below pectoralis minor: 4. Lateral thoracic artery - passes through fascia inferior to pectoralis minor Note: The medial pectoral nerve pierces the pectoralis minor directly rather than the fascia Applied: - The cephalic vein is an important landmark in the deltopectoral groove deltopectoral triangle and is the preferred vein for central venous catheter insertion via the deltopectoral approach. - The clavipectoral fascia keeps the axillary vein patent by exerting traction on its wall facilitated by the pectoralis minor making the fascia taut, which aids venous return. - During surgical approaches to the shoulder joint, the clavipectoral fascia must be divided to access the axillary contents. --- Sources: Gray's Anatomy for Students p. 845, 858, 881; Fischer's Mastery of Surgery 8th ed. p. 1551-1552; THIEME General Anatomy and Musculoskeletal System Atlas; Campbell's Operative Orthopaedics 15th Ed.
