Head and Neck Anatomy Overview

Overview

This lecture covers key topics of head and neck anatomy, focusing on the scalp, triangles of the neck, major arteries, veins, nerves, important glands, deep cervical fascia, tongue, pharynx, larynx, and clinical correlations.

Scalp Anatomy

• The scalp has five layers: Skin, Connective tissue, Aponeurotic layer (epicranial aponeurosis), Loose connective tissue, and Pericranium (SCALP).
• The loose connective tissue (4th layer) is called the “dangerous layer” because emissary veins here can transmit infection to intracranial venous sinuses.
• The epicranial aponeurosis connects the frontalis (no bony attachment) and occipitalis (attached to superior nuchal line) muscles, both innervated by facial nerve branches.

Scalp Blood Supply and Nerves

• Sensory innervation: 8 nerves (4 anterior—supratrochlear, supraorbital, zygomaticotemporal, auriculotemporal; 4 posterior—great auricular, lesser occipital, greater occipital, third occipital).
• Motor innervation: facial nerve to frontalis and occipitalis.
• Arterial supply: Supratrochlear and supraorbital (ophthalmic/internal carotid); superficial temporal, posterior auricular, occipital arteries (branches of external carotid).
• Venous drainage involves facial veins, retromandibular vein (formed by superficial temporal and maxillary veins), and communication pathways with cavernous sinus.

Triangles of the Neck

• Posterior triangle: bounded by sternocleidomastoid (anterior), trapezius (posterior), and clavicle (base); roofed by investing fascia, floor by prevertebral fascia and underlying muscles.
• Contents include spinal accessory nerve, branches of cervical plexus, external jugular vein, occipital artery, and lymph nodes.
• Anterior triangle: bounded by anterior midline, sternocleidomastoid, and mandible; subdivided into muscular, carotid, submandibular (digastric), and submental triangles, each with specific boundaries and contents (e.g., carotid arteries, cranial nerves, glands, lymph nodes).

Major Arteries

• External carotid artery's 8 branches: Superior thyroid, Ascending pharyngeal, Lingual, Facial, Occipital, Posterior auricular, Maxillary, Superficial temporal (“Some Anatomists Like Freaking Out Poor Medical Students”).
• Maxillary artery has 3 parts (mandibular, pterygoid, pterygopalatine) with distinct branches.
• Facial artery has 4 branches in cervical and 4 in facial region.

Tongue Anatomy and Innervation

• Anterior 2/3: General sensation—lingual nerve (V3); taste—chorda tympani (VII).
• Posterior 1/3: General and taste—glossopharyngeal (IX).
• Motor: hypoglossal nerve (XII) to all muscles except palatoglossus (vagus, X).
• Lymphatic drainage crosses midline; tip—submental nodes, lateral—submandibular, posterior—jugulodigastric.
• Deviation of tongue toward the paralyzed side in hypoglossal nerve injury.

Deep Cervical Fascia

• Three layers: Investing, pretracheal, prevertebral; carotid sheath formed by contributions from these.
• Investing layer encloses sternocleidomastoid and trapezius, forms roof of neck triangles, splits to enclose submandibular and parotid glands, and creates suprasternal and supraclavicular spaces (“rule of twos”).

Pharynx and Larynx

• Pharynx: divided into nasopharynx, oropharynx, and laryngopharynx; important gaps allow passage of nerves and vessels.
• Larynx: nine cartilages (three paired/unpaired), membranes (thyrohyoid pierced by internal laryngeal n. & superior laryngeal a.), intrinsic and extrinsic muscles.
• Innervation: all intrinsic muscles by recurrent laryngeal nerve except cricothyroid (external laryngeal).
• Sensory above vocal cords by internal laryngeal n., below by recurrent laryngeal n.

Key Terms & Definitions

• SCALP — mnemonic for scalp layers: Skin, Connective tissue, Aponeurosis, Loose connective tissue, Pericranium.
• Dangerous area of scalp — loose connective tissue layer, pathway for infection spread.
• Carotid sheath — fascia enclosing carotid artery, IJV, vagus nerve.
• Rima glottidis — opening between the true vocal cords.
• Waldeyer’s ring — ring of lymphoid tissue in pharynx (tonsils).
• Ansa cervicalis — nerve loop providing motor to infrahyoid muscles (except thyrohyoid).

Action Items / Next Steps

• Review MCQs on head and neck anatomy, especially nerve injuries, vascular branches, and clinical scenarios.
• Study diagrams of neck triangles, scalp layers, tongue, and larynx.
• Read related textbook chapters on head and neck surface anatomy, vasculature, and cranial nerves.