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HEAD AND NECK - BDS 1st Year Anatomy Board Answers

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Q1. List out the layers of deep cervical fascia. Explain the vertical and horizontal tracing of the investing layer of deep cervical fascia. [2+2+2=6]

Layers of Deep Cervical Fascia

1. Investing (superficial) layer
2. Middle layer (pretracheal/muscular fascia)
3. Deep layer (prevertebral fascia)
4. Alar fascia - lies between the deep and middle layers

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Investing Layer - Horizontal Tracing

• Encloses the sternocleidomastoid muscle (anterolaterally)
• Encloses the trapezius muscle (posterolaterally)
• Forms the roof of both anterior and posterior triangles of the neck
• Splits to enclose the parotid gland and submandibular gland
• Encloses the posterior belly of digastric and stylohyoid muscles

Investing Layer - Vertical Tracing (Attachments)

• Superior nuchal line of occipital bone
• Mastoid process
• Zygomatic arch
• Inferior border of the mandible
• Hyoid bone
• Spinous processes of cervical vertebrae

• Manubrium sterni (splits to form the suprasternal space of Burns)
• Clavicle
• Acromion and spine of scapula

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Other Layers (Brief)

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Q2. Short Notes

(a) External Carotid Artery

• Arises from the common carotid artery at the level of the upper border of thyroid cartilage (C3-C4)
• Supplies structures outside the skull
• 8 branches (mnemonic: Some Anatomists Like Freezing Partly Over Ice Cold Beer):
  1. Superior thyroid artery
  2. Ascending pharyngeal artery
  3. Lingual artery
  4. Facial artery
  5. Occipital artery
  6. Posterior auricular artery
  7. Superficial temporal artery (terminal)
  8. Maxillary artery (terminal)

(b) Lacrimal Apparatus

• Consists of: lacrimal gland, lacrimal canaliculi (superior and inferior), lacrimal sac, nasolacrimal duct
• Lacrimal gland: in lacrimal fossa (superolateral orbit); secretes tears
• Tears drain medially through the puncta lacrimalia → canaliculi → lacrimal sac → nasolacrimal duct → inferior meatus of nose
• Nerve supply: secretomotor fibers from pterygopalatine ganglion via CN VII → zygomaticotemporal nerve → lacrimal nerve (CN V1)

(c) Carotid Sheath

• A fascial tube formed by contributions from all three layers of deep cervical fascia
• Contents:
  • Common + internal carotid artery (anteromedially)
  • Internal jugular vein (posterolaterally)
  • Vagus nerve (CN X) (between and behind the artery and vein)
  • Deep cervical lymph nodes (along the IJV)
  • Ansa cervicalis (on the anterior surface)
• Applied: Carotid triangle contains the superior part of the carotid sheath, carotid bifurcation, proximal ECA branches, and jugular chain lymph nodes

(d) Scalp

• Layers (mnemonic: SCALP):
  1. S - Skin (thick, hair-bearing)
  2. C - Dense Connective tissue (contains scalp arteries and veins; dangerous layer - infection/bleeding spreads here)
  3. A - Aponeurosis (epicranial/galea aponeurotica) - connects frontalis to occipitalis
  4. L - Loose areolar tissue (dangerous layer - allows spread of infection; "subaponeurotic space")
  5. P - Pericranium (periosteum of skull)
• Blood supply: Supratrochlear, supraorbital (from ophthalmic), superficial temporal, posterior auricular, occipital arteries
• Nerve supply: Supratrochlear, supraorbital (V1), zygomaticotemporal (V2), auriculotemporal (V3), lesser occipital (C2), greater occipital (C2), greater auricular (C2,3)

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Q3. Describe type, capsular attachments, and muscles causing different movements of temporomandibular joints. [1+2+4=6] (also Q5)

Type of Joint

• Synovial (modified hinge) joint - specifically a bicondylar, compound synovial joint
• The joint space is divided into two cavities (upper and lower) by an intra-articular fibrocartilaginous disc
• Unusual features: articular surfaces covered by fibrous tissue (not hyaline cartilage), reflecting intramembranous development

Articulating Bones

• Mandibular condyle (head of condyle) articulates with
• Mandibular (glenoid) fossa and articular eminence of the temporal bone
• The articular disc (meniscus) sits between them, dividing upper and lower compartments

Capsular Attachments

• Above: Attached to the mandibular fossa, extending anteriorly to just in front of the crest of the articular eminence; posteriorly to the squamotympanic and petrotympanic fissures
• Below: Attached to the neck of the condyle
• The capsule is reinforced laterally by the lateral (temporomandibular) ligament
• Inner surface lined by synovial membrane (does not cover articular surfaces)
• Upper compartment: gliding movements
• Lower compartment: hinge movements

Ligaments

Muscles Causing TMJ Movements

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Q4 & Q5. Give the Tracing of the Investing Layer with ILS Applied Anatomy of Deep Cervical Fascia [3+3+1=5 / 5]

1. The investing layer splits to enclose parotid gland - parotid abscesses are very painful because the unyielding fascia limits expansion
2. Splits to form the suprasternal space of Burns (contains the sternal heads of SCM, jugular venous arch, lymph nodes)
3. Acts as a barrier to infection, but deep to it, abscesses can track to the mediastinum via connected neck spaces
4. Forms the floor of the posterior triangle (covered by prevertebral fascia)

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Q6. Describe the Boundaries, Contents, and Applied Anatomy of Infratemporal Fossa. [2+2+1=5]

Boundaries

Contents

• Muscles: Medial pterygoid, lateral pterygoid
• Vessels: Maxillary artery (and its branches), pterygoid plexus of veins
• Nerves: Mandibular nerve (V3) and its branches (inferior alveolar, lingual, buccal, auriculotemporal nerves), chorda tympani (branch of CN VII), branches of glossopharyngeal nerve (CN IX)
• Ligament: Sphenomandibular ligament

Applied Anatomy

• Spread of infection from dental abscesses (especially lower molars) can track into the infratemporal fossa
• Tumours from adjacent nasopharynx or maxillary sinus can invade this fossa
• Access for nerve blocks: inferior alveolar nerve block (for mandibular anesthesia) is given near the mandibular foramen in this fossa
• Communications: via pterygomaxillary fissure with pterygopalatine fossa; with temporal fossa superiorly; with orbit via inferior orbital fissure

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Q7. Name the Muscles of Mastication with their Origin, Insertion, Action, and Nerve Supply. [6]

1. Masseter

2. Temporalis

3. Medial Pterygoid

4. Lateral Pterygoid

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Q8. Mention the Boundaries and Contents of Posterior Triangle of the Neck with the Help of a Labeled Diagram. [2+3=5]

Boundaries

• Occipital triangle (larger, superior)
• Omoclavicular/subclavian triangle (smaller, inferior)

Contents

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Q9. Describe the Histological Structure of Lymph Node with a Well-Labeled Diagram. [5]

Structure of a Lymph Node

Coverings

• Capsule: Dense connective tissue
• Trabeculae: Extensions of capsule into the node, dividing it into compartments

Zones (from outside to inside)

• Contains secondary follicles (germinal centers) = B-lymphocyte region
• Follicles show active B-cell proliferation in response to antigen

• T-lymphocyte region (thymus-dependent zone)
• Contains high-endothelial postcapillary venules through which lymphocytes enter from the bloodstream
• After differentiating, lymphocytes leave via efferent lymph vessels

• Contains medullary cords (plasma cells, macrophages) and medullary sinuses
• Lymph filters through sinuses here

Sinuses

• Subcapsular (marginal) sinus - just beneath the capsule
• Cortical (peritrabecular) sinuses - along trabeculae
• Medullary sinuses - between medullary cords

Vascular Supply

• Artery enters at the hilum → distributes through trabeculae → capillaries in cortex → high-endothelial venules in paracortex → drain via hilum
• Lymph enters via multiple afferent vessels → subcapsular sinus → cortical/medullary sinuses → exits via efferent vessel at hilum

Diagram label guide:
Afferent lymphatics → Capsule → Subcapsular sinus → Cortex (primary & 
secondary follicles/B-cells) → Paracortex (T-cells, HEVs) → Medulla 
(medullary cords + sinuses) → Efferent lymphatic at hilum
(Artery and vein also at hilum)

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Q10. Write Down the Boundaries, Contents, and Applied Anatomy of Carotid Triangle. [6]

Boundaries

Contents

• Common carotid artery + its bifurcation (at level of upper border of thyroid cartilage, C3-C4)
• Internal carotid artery (no branches in neck)
• External carotid artery with proximal branches: superior thyroid, ascending pharyngeal, lingual, facial, occipital arteries
• Carotid body (at bifurcation) - chemoreceptor
• Carotid sinus (at bifurcation) - baroreceptor (innervated by CN IX)

• Internal jugular vein and tributaries (facial, lingual, superior thyroid, pharyngeal veins)

• Vagus nerve (CN X) - in carotid sheath
• Hypoglossal nerve (CN XII) - crosses superficially
• Superior root of ansa cervicalis (from C1 via CN XII)
• Superior laryngeal nerve (branch of vagus) - divides into internal (sensory) and external (motor to cricothyroid) branches
• Glossopharyngeal nerve (CN IX) - to carotid sinus

Applied Anatomy

1. Carotid endarterectomy - surgical removal of atheromatous plaques from ICA is performed through this triangle
2. Carotid sinus hypersensitivity - pressure on the carotid sinus (e.g., tight collar) can cause bradycardia and syncope
3. Carotid angiography - puncture of the common carotid for cerebral angiography is through this triangle
4. Tracheostomy/emergency airway - structures here must be identified
5. Neck dissection - the carotid triangle is a critical zone during cervical lymph node dissection for head and neck cancers
6. Carotid body tumors (chemodectomas) - arise at the bifurcation in this triangle; present as pulsatile neck mass

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Q11. Common Facial Expression and the Muscle Producing It (Short Note)

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Q12. SCM - Sternocleidomastoid Muscle (Short Note)

Origin

• Sternal head: Arises from the superomedial part of the front of the manubrium sterni
• Clavicular head: Arises from the medial 1/3 of the superior surface of the clavicle

Insertion

• By a thick tendon into the lateral surface of mastoid process
• By a thin aponeurosis into the lateral half of the superior nuchal line of the occipital bone

Actions (NS: Accessory nerve CN XI + C2, C3)

• Unilateral: Tilts head to the same side (lateral flexion) + rotates face to the opposite side
• Bilateral: Flexion of the neck; if neck is fixed, elevates the thorax (accessory muscle of respiration)

Nerve Supply (NS)

• Motor: Accessory nerve (CN XI) - spinal root
• Proprioception: Anterior rami of C2 and C3

Arterial Supply

• 2 branches from occipital artery
• 1 branch from suprascapular artery
• 1 branch from superior thyroid artery

Relations / Applied

• Divides the neck into anterior and posterior triangles
• The SCM is used as a key landmark for all cervical triangles
• Torticollis (wry neck) - SCM fibrosis causes head tilt to affected side with face rotated to opposite side

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