1st Year MBBS Anatomy - Important Questions

Mysore Medical College & Research Institute (RGUHS)

Based on II Internal Assessment Exam Paper 2024-25

LONG ESSAY (10 marks)

Q1. Thyroid Gland - Hyperthyroidism / Thyroidectomy Case

• Location: In front of the neck at the level of C5-T1 vertebrae
• Parts: Two lateral lobes + isthmus (at 2nd-4th tracheal rings) + pyramidal lobe (in 50%)
• Coverings:
  • True capsule: fibrous condensation of the gland itself
  • False capsule (surgical sheath): derived from pretracheal fascia - this is the surgical plane
• Key Relations:
  • Anterolateral: Sternothyroid, sternohyoid, omohyoid
  • Posterior: Parathyroid glands (behind posterior border), recurrent laryngeal nerve (in tracheo-esophageal groove)
  • Medial: Trachea, esophagus, cricothyroid muscle

• Superior thyroid artery (1st branch of external carotid) - enters upper pole
• Inferior thyroid artery (from thyrocervical trunk of subclavian)
• Thyroidea ima artery (in 10%, from arch of aorta / brachiocephalic)
• Veins: Superior + middle drain to internal jugular; inferior thyroid vein drains to left brachiocephalic vein

• The recurrent laryngeal nerve (branch of vagus) runs in the tracheo-esophageal groove
• It is closely related to the inferior thyroid artery - the artery and nerve may cross
• It enters larynx by passing under the lower border of the inferior constrictor
• Damage during thyroidectomy causes hoarseness (unilateral) or aphonia (bilateral)
• Surgeons must identify and preserve it by ligating inferior thyroid artery lateral to the nerve

SHORT ESSAYS (5 marks each)

Q2. Muscles of Mastication

• Key diagram: Draw masseter with its two heads and the parotid duct overlying it
• Masseter is the key muscle - it relates to parotid gland, facial nerve, parotid duct (crosses it at right angles at anterior border)

Q3. Cavernous Sinus - Location, Relations, Connections

• Location: On either side of the sella turcica, from the superior orbital fissure to the apex of petrous temporal bone
• Contents (within the sinus wall):
  • Oculomotor nerve (CN III) - in lateral wall
  • Trochlear nerve (CN IV) - in lateral wall
  • Ophthalmic division of trigeminal (V1) - in lateral wall
  • Maxillary division (V2) - in lateral wall (lower part)
  • Abducens nerve (CN VI) - passes through the sinus itself, lateral to ICA
  • Internal carotid artery (with sympathetic plexus) - passes through sinus
• Connections: Communicates with opposite side via intercavernous sinuses; drains to superior/inferior petrosal sinuses; receives superior ophthalmic vein (route for spread of facial infections - "danger area of face")
• Clinical: Cavernous sinus thrombosis - proptosis, chemosis, ophthalmoplegia, pain in V1/V2 distribution

Q4. Internal Capsule - Location, Parts, Constituent Fibres

• Location: Between thalamus/lentiform nucleus (medially) and caudate nucleus/lentiform nucleus
• Parts and fibre arrangement (anterior to posterior):
  • Anterior limb: Frontopontine fibres, anterior thalamic radiation, thalamocaudate fibres
  • Genu: Corticobulbar (corticonuclear) fibres - for motor cranial nerves
  • Posterior limb: Corticospinal fibres (anterior 2/3), thalamocortical (sensory) fibres
  • Retrolenticular: Optic radiation (Meyer's loop), parietopontine fibres
  • Sublenticular: Auditory radiation, temporopontine fibres
• Blood supply: Lenticulostriate branches of MCA - these are "arteries of stroke"
• Clinical: MCA territory stroke causes contralateral hemiplegia (face, arm > leg), hemisensory loss, homonymous hemianopia

Q5. Sick Sinus Syndrome / Neck Tie Case (Carotid Sinus)

• A 32-year-old male gets giddy when wearing a neck tie = Carotid sinus syncope
• Affected structure: Carotid sinus - a dilation at the bifurcation of the common carotid artery
• Location: At the level of the upper border of thyroid cartilage (C3-C4)
• Nerve supply: Carotid sinus nerve (branch of glossopharyngeal nerve, CN IX) - Hering's nerve
• Boundaries of carotid triangle:
  • Anterior: Superior belly of omohyoid
  • Posterior: Anterior border of sternocleidomastoid
  • Superior: Posterior belly of digastric + stylohyoid
• Other structures in carotid triangle: Common carotid, internal/external carotid, internal jugular vein, vagus nerve, hypoglossal nerve (CN XII), accessory nerve (CN XI)

SHORT NOTES (5 marks each)

Q6. Extracranial Course of Facial Nerve + Clinical Significance

• Exits stylomastoid foramen → enters parotid gland → divides at pes anserinus into:
  • Temporal, Zygomatic, Buccal, Marginal mandibular, Cervical branches
• Branches before entering parotid: Posterior auricular, nerve to posterior belly of digastric, nerve to stylohyoid
• Clinical significance:
  • Bell's palsy: LMN facial nerve paralysis - all muscles of face affected ipsilaterally
  • Parotid surgery / parotidectomy: risk of damage
  • Forceps delivery: pressure at stylomastoid foramen in neonates
  • Ramsay Hunt syndrome: herpes zoster of geniculate ganglion affects facial nerve

Q7. Fontanelles - Names, Time of Closure, Significance

• Physiological significance: Allow moulding during birth; allow rapid brain growth in infancy; anterior fontanelle used to assess ICP (bulging = raised ICP, sunken = dehydration)
• Clinical: Delayed closure in hypothyroidism, rickets, hydrocephalus; premature closure = craniosynostosis

Q8. Layers of Scalp, Blood Supply, Nerve Supply, Clinical Importance

• S - Skin (thick, hair-bearing)
• C - Connective tissue (dense, with vessels and nerves)
• A - Aponeurosis (epicranial/galea aponeurotica)
• L - Loose areolar tissue - "dangerous layer" (emissary veins, infection can spread to intracranium)
• P - Pericranium
• Blood supply: Supratrochlear + Supraorbital (ophthalmic a.) anteriorly; Superficial temporal (ECA) laterally; Posterior auricular + Occipital (ECA) posteriorly - vessels run in layer C
• Nerve supply: Supratrochlear + Supraorbital anteriorly; Zygomaticotemporal + Auriculotemporal laterally; Greater + Lesser occipital + Greater auricular posteriorly
• Clinical: Scalp wounds bleed profusely (vessels in dense CT can't retract); infections in loose layer spread to dangerous area; scalp avulsion; subgaleal hematoma (crosses suture lines)

Q9. Middle Ear Cavity - Relations and Applied Anatomy

• Roof (tegmental wall): Tegmen tympani - separates from middle cranial fossa
• Floor (jugular wall): Jugular bulb below
• Anterior (carotid wall): Internal carotid artery, Eustachian (auditory) tube opening
• Posterior (mastoid wall): Aditus to mastoid antrum, pyramid (stapedius), facial nerve canal
• Lateral (membranous wall): Tympanic membrane
• Medial (labyrinthine wall): Oval window (fenestra vestibuli), round window (fenestra cochleae), promontory (1st turn cochlea), lateral semicircular canal
• Applied: Otitis media can spread to: mastoid (mastoiditis), intracranium via tegmen (meningitis, brain abscess), facial nerve palsy, labyrinthitis

SHORT ANSWERS (5 marks each)

Q10. Role of Cadaver in Learning Anatomy

• First-hand 3D understanding of spatial relationships
• Variation anatomy - textbooks describe "normal" but cadavers show real-life variations
• Surgical anatomy and planes of dissection
• Develops professional attitude (respect for human body)
• Enhances clinical palpation and examination skills

Q11. Structures Affected in Paramedian Medulla (at Sensory Decussation)

• Medial lemniscus fibres as they decussate = loss of proprioception, fine touch, vibration on ipsilateral side (fibres haven't crossed yet)
• Corticospinal tract (pyramidal decussation) - below this level = ipsilateral hemiplegia
• Hypoglossal nucleus/fibres - ipsilateral tongue paralysis
• Anterior spinal artery territory

Q12. Pharyngeal Pouches - Derivatives and Anomalies

• Anomalies: DiGeorge syndrome (3rd + 4th pouch failure = no thymus + no parathyroids); Branchial cyst/fistula (failure of obliteration of 2nd cleft/pouch)

Q13. Microscopic Structure of Trachea and Function

• Epithelium: Pseudostratified ciliated columnar (respiratory epithelium) with goblet cells
  • Function: Mucociliary escalator - traps dust, propels mucus upward
• Lamina propria: Loose CT with elastic fibres
• Submucosa: Seromucous glands
• C-shaped hyaline cartilage rings (16-20): Maintain patent lumen; open posteriorly
• Trachealis muscle: Smooth muscle closes the gap posteriorly; allows food bolus to pass in esophagus behind
• Adventitia: Fibroelastic

Q14. Development of Hard Palate and Associated Anomalies

• Primary palate: From median nasal process (premaxilla - anterior 1/3, carries upper incisors)
• Secondary palate: From paired palatine processes of maxilla (posterior 2/3) - they grow medially and fuse with each other and with primary palate at 8-10 weeks
• Fusion: Palatine processes fuse at midline; nasal septum fuses with palate from above
• Anomalies:
  • Cleft palate: Failure of fusion of palatine processes (posterior hard palate affected)
  • Cleft lip: Failure of fusion of maxillary process with medial nasal process (primary palate)
  • Cleft uvula: Minor form of cleft palate
  • Complete cleft: Both primary and secondary palate fail - associated with cleft lip

REASONING QUESTIONS (3 marks each)

Q15. Nerve Supply of Tongue Correlated with Development

• Developmental correlation: The nerve that accompanies each pharyngeal arch in development stays with that tissue even after migration - hence the seemingly complex innervation

Q16. Cornea Histology and Maintenance of Transparency

• Layers: Epithelium (stratified squamous non-keratinized), Bowman's membrane, Stroma (90% - collagen lamellae), Descemet's membrane, Endothelium
• Factors maintaining transparency:
  • Regular arrangement of collagen fibrils (uniform diameter + spacing)
  • Avascularity (no blood vessels - nourished by aqueous humor and limbal vessels)
  • Active dehydration by endothelial Na-K ATPase pump
  • No myelinated nerve fibres in stroma
  • Intact epithelial barrier

Q17. Anatomical Basis of Severe Pain in Mumps

• Mumps = viral infection of parotid gland
• Parotid gland is enclosed in a tight fascial sheath (parotid capsule = dense layer of investing cervical fascia)
• The sheath is inextensible - therefore inflammation causes intense pressure pain
• In addition, parotid gland sends a deep process through the stylomandibular gap - swelling here irritates auriculotemporal nerve (branch of V3) causing severe referred ear pain
• Also: facial nerve passes through the parotid - hence risk of facial paralysis in severe parotitis

Q18. Anatomical Basis of Control of Secretions from Anterior and Posterior Pituitary

• Anterior pituitary (adenohypophysis):
  • No direct neural control
  • Controlled by hypothalamic-pituitary portal system (hypothalamo-hypophyseal portal veins)
  • Hypothalamus releases/inhibits releasing hormones → carried via portal blood → anterior pituitary
• Posterior pituitary (neurohypophysis):
  • Direct neural connection via hypothalamo-hypophyseal tract (axons of neurons in supraoptic + paraventricular nuclei)
  • ADH (vasopressin) and Oxytocin are made in hypothalamic nuclei, travel down axons, stored and released from posterior pituitary

Q19. Submental Lymph Nodes - Areas to Examine for Focal Infection

• Submental lymph nodes drain:
  • Tip of tongue
  • Floor of mouth (anterior)
  • Central lower lip and chin
  • Lower incisor teeth and adjacent gums
  • Skin of chin
• Areas to examine:
  • Tip and anterior tongue (look for ulcer/carcinoma)
  • Floor of mouth
  • Central lower lip
  • Chin skin for infected cuts/acne
  • Lower anterior teeth for dental caries/periapical abscess
  • Sublingual gland

High-Priority Topics for Final Exam (RGUHS Pattern)

1. Thyroid gland (location, blood supply, RLN injury) - appears almost every exam
2. Cavernous sinus (contents, relations, clinical) - repeated topic
3. Facial nerve (course, branches, Bell's palsy)
4. Scalp layers (SCALP mnemonic, dangerous layer)
5. Internal capsule (parts, fibres, blood supply, stroke)
6. Pharyngeal arches and pouches (derivatives and anomalies)
7. Fontanelles (types, closure times, clinical relevance)
8. Middle ear (walls and relations, clinical)
9. Hard palate development + cleft palate
10. Pituitary gland (blood supply, portal system, anatomy)
11. Parotid gland (bed, contents, relations, mumps)
12. Medullary syndromes - paramedian vs lateral

Exam Tips for RGUHS:

• Always draw a neat labelled diagram wherever asked - diagrams carry separate marks
• For clinical reasoning questions (like the neck tie case and thyroidectomy case), always name the specific structure, then explain the mechanism
• In embryology questions, always include the anomaly/clinical correlation
• In histology questions, always correlate structure with function