Surface Anatomy of the Neck

Key Landmarks & Midline Structures - Neck's Notable Knobs

• Hyoid Bone: Mobile, U-shaped bone superior to larynx. Palpable above thyroid cartilage. Level: C3 vertebra.
• Thyroid Cartilage: Largest laryngeal cartilage ("Adam's apple"). Superior notch palpable. Level: C4-C5 vertebrae.
• Cricoid Cartilage: Complete cartilaginous ring inferior to thyroid cartilage. Level: C6 vertebra. Site for emergency cricothyrotomy.
• Tracheal Rings: Palpable in midline inferior to cricoid cartilage.
• Suprasternal Notch: (Jugular notch) Depression on superior border of manubrium sterni.
• Sternocleidomastoid (SCM) Muscle: Key muscular landmark; its borders define anterior and posterior triangles.

⭐ The cricoid cartilage, at the level of C6 vertebra, is a crucial landmark: it indicates the junction of the pharynx with the esophagus, and the larynx with the trachea. It's the narrowest part of a child's airway before puberty (subglottis).

Anterior Triangle & Subdivisions - Front Row Features

• Overall Boundaries: Midline (anteriorly), SCM (posteriorly), Mandible (superiorly).

• Four Key Subdivisions: (Defined by Digastric & Omohyoid muscles)

  • 1. Submental Triangle (Unpaired):

    • Borders: Ant. bellies of Digastric, Hyoid.
    • Key Contents: Submental lymph nodes.

  • 2. Submandibular Triangle (Paired):

    • Borders: Mandible, Ant. & Post. bellies of Digastric.
    • Key Contents: Submandibular gland, Facial artery, Hypoglossal n. (CN XII).

  • 3. Carotid Triangle (Paired):

    • Borders: Post. belly of Digastric, Sup. belly Omohyoid, SCM.
    • Key Contents: Carotid arteries (CCA, ECA, ICA), IJV, Vagus n. (CN X).

    ⭐ Contains Carotid Sheath (CCA/ICA, IJV, CN X) & site of carotid bifurcation.

  • 4. Muscular Triangle (Paired):

    • Borders: Sup. belly Omohyoid, SCM, Midline.
    • Key Contents: Infrahyoid muscles, Thyroid & Parathyroid glands.

Posterior Triangle & Subdivisions - Backstage Pass

• Boundaries:
  • Anterior: Sternocleidomastoid (posterior border)
  • Posterior: Trapezius (anterior border)
  • Inferior: Clavicle (middle third)
  • Apex: Superior nuchal line (SCM & Trapezius meet)
  • Roof: Investing layer of deep cervical fascia, Platysma
  • Floor: Prevertebral fascia; Muscles: Splenius capitis, Levator scapulae, Scalenus medius & posterior.
• Division: Inferior belly of Omohyoid divides into:
  • Occipital Triangle (superior, larger)
  • Supraclavicular/Subclavian Triangle (inferior, smaller)

• Key Contents:
  • Occipital Triangle:
    • Spinal Accessory Nerve (CN XI)
    • Sensory branches of Cervical Plexus (C2-C4)
    • Occipital artery (at apex)
  • Supraclavicular Triangle:
    • Brachial Plexus (Trunks)
    • Subclavian Artery (3rd part) & Vein
    • Suprascapular artery & nerve
    • External Jugular Vein (termination)

⭐ The Spinal Accessory Nerve (CN XI) is superficial in the posterior triangle, making it vulnerable to iatrogenic injury during procedures like lymph node biopsy.

Major Vessels, Nerves & Lymphatics - Neck's Network News

• Vessels:
  • Common Carotid A.: Bifurcates C4 (thyroid cartilage). Pulse: ant. to SCM, cricoid level.
  • Internal Jugular V. (IJV): Deep to SCM, lateral to carotid A.
  • External Jugular V. (EJV): Superficial, crosses SCM. Visible with ↑ intrathoracic pressure.
• Nerves:
  • Accessory N. (XI): Crosses post. triangle; SCM & Trapezius. Vulnerable.
  • Cervical Plexus: Sensory branches (Erb's point) post. to SCM.
  • Brachial Plexus: Trunks between ant. & mid. scalenes.
• Lymphatics:
  • Deep Cervical Nodes: Chain along IJV.

  ⭐ Virchow's node (L. supraclavicular) suggests gastric Ca. )

High‑Yield Points - ⚡ Biggest Takeaways

• Hyoid bone is palpable at the C3 vertebral level.
• Thyroid cartilage (Adam's apple) corresponds to C4-C5 vertebrae.
• Cricoid cartilage is a key landmark at C6 vertebra; trachea & esophagus begin.
• Carotid pulse is best felt anterior to SCM at thyroid cartilage level.
• External Jugular Vein (EJV) crosses SCM superficially; indicates JVP.
• Suprasternal notch is found at the superior margin of the manubrium.
• Apex of lung & subclavian artery are palpable in the supraclavicular fossa.