Head & Neck Anatomy - Quick Reference Brief

1. Temporomandibular Joint (TMJ)

• Modified synovial hinge joint (ginglymoarthrodial)
• Articular surfaces: head (condyle) of mandible + mandibular fossa of temporal bone + articular eminence
• Articular disc: fibrocartilage - divides joint into upper and lower compartments
• Ligaments: Lateral (TM), Sphenomandibular, Stylomandibular
• Movements: Elevation, Depression, Protrusion, Retrusion, Side to side
• Nerve: Auriculotemporal n., Masseteric n. | Blood: Superficial temporal a., Maxillary a.
• Applied: Dislocation, Ankylosis, Clicking

2. Muscles of Mastication (all supplied by Mandibular n. - V3)

3. Facial Nerve (VII)

• Mixed nerve; 4 components: Branchial motor, Parasympathetic, Taste, General sensory
• Course: Pons → internal acoustic meatus → facial canal → stylomastoid foramen → parotid gland
• Branches in parotid (T-Z-B-M-C): Temporal, Zygomatic, Buccal, Marginal mandibular, Cervical
• Motor: muscles of facial expression, stapedius, stylohyoid, post. belly of digastric
• Parasympathetic: Greater petrosal n. → lacrimal gland; Chorda tympani → submandibular & sublingual glands
• Taste: Anterior 2/3 of tongue

4. Trigeminal Nerve (V)

• Largest cranial nerve; 3 divisions:
  • V1 Ophthalmic (pure sensory): forehead, cornea, nose, upper eyelid
  • V2 Maxillary (pure sensory): midface, maxillary sinus, upper teeth
  • V3 Mandibular (mixed): lower teeth/lip, tongue (general sensation); motor to muscles of mastication, mylohyoid, ant. belly of digastric, tensor tympani, tensor veli palatini
• Important V3 branches: Lingual, Inferior alveolar, Buccal, Auriculotemporal, Masseteric
• Trigeminal ganglion in Meckel's cave

5. Facial Artery

• Origin: External carotid artery
• Course: Carotid triangle → crosses lower border of mandible anterior to masseter → winds upward deep to SMAS
• Neck branches: Ascending palatine, Tonsillar, Glandular, Submental
• Face branches: Inferior labial, Superior labial, Lateral nasal, Angular (terminal)
• Anastomoses: Angular a. with dorsal nasal branch of ophthalmic a.
• Applied: Severe bleeding, facial flap

6. Cavernous Sinus

• Paired venous sinus on either side of body of sphenoid
• Extent: Superior orbital fissure to apex of petrous temporal bone
• Contents: Internal carotid artery, Abducent nerve (VI)
• Nerves in lateral wall (top to bottom): III, IV, V1, V2
• Tributaries: Superior & inferior ophthalmic v., superficial middle cerebral v., sphenoparietal sinus
• Communications: Facial v. → internal jugular v. → pterygoid plexus
• Applied: Cavernous sinus thrombosis

7. Parotid Gland

• Largest salivary gland; situated in front of and below ear
• Parts: Superficial & deep
• Duct: Stensen's duct - emerges from anterior border, pierces buccinator, opens opposite upper 2nd molar
• Nerve supply: Parasympathetic - Glossopharyngeal n. (via tympanic n. → lesser petrosal n. → otic ganglion); Sympathetic - Superior cervical ganglion
• Blood supply: External carotid a. (superficial temporal & maxillary a.)
• Applied: Parotitis, facial nerve injury in parotid surgery

8. Submandibular Gland

• Mixed gland; situated in submandibular triangle
• Duct: Wharton's duct - opens at summit of sublingual papilla
• Nerve: Parasympathetic - Facial n. (via chorda tympani); Sympathetic - Superior cervical ganglion
• Blood: Facial a., submental a.
• Applied: Sialoadenitis, stones in duct

9. Maxillary Artery

• Branch of external carotid artery; gives 3 parts in infratemporal fossa
• 1st part (Mandibular): Deep auricular, Anterior tympanic, Middle meningeal, Accessory meningeal
• 2nd part (Pterygoid): Inferior alveolar, Posterior superior alveolar, Masseteric, Pterygoid, Buccal
• 3rd part (Pterygopalatine): Sphenopalatine, Infraorbital, Descending palatine

10. Scalp & Dangerous Area

• 5 layers: SCALP - Skin, Dense connective tissue, Aponeurosis (galea), Loose areolar tissue, Pericranium
• Blood supply: Supratrochlear, Supraorbital, Superficial temporal, Posterior auricular (from ECA)
• Dangerous area: Triangle from bridge of nose to angles of mouth - infection spreads via Facial v. → Angular v. → Ophthalmic v. → Cavernous sinus → Thrombosis, meningitis

11. Thyroid Gland

• Butterfly-shaped; in front of trachea (C5-T1)
• Parts: Right lobe, Left lobe, Isthmus
• Nerve: Sympathetic - superior, middle & inferior cervical ganglia; Parasympathetic - vagus
• Blood: Superior thyroid a., Inferior thyroid a.
• Applied: Goitre, Thyroidectomy

12. Carotid Triangle

• Boundaries: Ant. border of SCM (post.), Post. belly of digastric (sup.), Sup. belly of omohyoid (inf.)
• Floor: Hyoglossus, Thyrohyoid, Middle constrictor, Carotid sheath
• Contents: Carotid sheath (Common carotid a., Internal jugular v., Vagus n.), External carotid a. & branches, Hypoglossal n., Superior thyroid a., Ansa cervicalis

13. Tongue - Muscles & Nerve Supply

• Intrinsic muscles: Superior longitudinal, Inferior longitudinal, Transverse, Vertical
• Extrinsic muscles: Genioglossus, Hyoglossus, Styloglossus, Palatoglossus
• Nerve supply: Motor - Hypoglossal n. (XII) to all except palatoglossus (X)
• Sensory: Ant. 2/3 - Lingual n. (V3) general + Chorda tympani (taste); Post. 1/3 - Glossopharyngeal n. (IX); Epiglottic region - Internal laryngeal n. (X)

14. Soft Palate

• Muscular part (posterior to hard palate); muscular & mucous parts
• Muscles (medial to lateral): Tensor veli palatini (V3), Levator veli palatini (X), Palatoglossus (X), Palatopharyngeus (X), Musculus uvulae (X)
• Nerve: Motor - Pharyngeal plexus (X); Sensory - Greater palatine (V2) for mucous membrane
• Function: Closes nasopharynx during swallowing & speaking

15. Pharynx

• Muscles: Constrictors (sup., middle, inf.), Stylopharyngeus, Palatopharyngeus, Salpingopharyngeus
• Nerve: Motor - Pharyngeal plexus (X) except stylopharyngeus (IX); Sensory - Pharyngeal plexus
• Parts: Nasopharynx, Oropharynx, Laryngopharynx
• Functions: Passage for air & food, phonation, swallowing

Key PYQs (Previous Year Questions) are flagged throughout - focus on TMJ type/surfaces/ligaments, muscles of mastication with origins/insertions, facial nerve course/branches, trigeminal divisions/branches, salivary gland ducts/nerve supply, cavernous sinus contents, and scalp layers.

Interpretation of Lab Findings

Pathophysiology

Glycogen / Gluconeogenesis
         ↓
    Glucose-6-phosphate  ←── G6Pase DEFICIENT
         ↓ (cannot dephosphorylate)
   Cannot release free glucose into blood
         ↓
   Hypoglycemia → counter-regulatory hormones ↑
         ↓
   Excess G6P diverted to:
   • Glycolysis → Lactate (lactic acidosis)
   • Lipogenesis → ↑Triglycerides → fatty liver (hepatomegaly)
   • Pentose phosphate pathway → ↑Purines → Hyperuricemia

Clinical Clues in This Case

• 12-year-old girl - presents in childhood (typically presents in infancy/early childhood)
• Grossly enlarged abdomen + enlarged liver - hepatomegaly due to glycogen + fat accumulation
• Weakness, sweating, pallor disappearing on eating - classic fasting hypoglycemia symptoms
• Slow developmental milestones - chronic hypoglycemia affecting brain development
• Family history - autosomal recessive inheritance (mother's history suggests carrier state or affected sibling pattern; elder brother with slow milestones)

Key Biochemical Triad (Classic PYQ points)

"FLUK" - Fasting hypoglycemia + Lactic acidosis + Uric acid elevated + Ketones + Triglycerides elevated

• All 4 metabolic derangements stem from a single enzyme defect: G6Pase
• Enzyme located on ER membrane of liver, kidney, intestine
• Gene: G6PC on chromosome 17q21

Treatment

• Frequent feeds / nocturnal continuous feeds
• Corn starch therapy (slow-release glucose)
• Allopurinol for hyperuricemia
• Avoid fructose and galactose (cannot bypass G6Pase)