Human Anatomy
Anterior Triangle of the Neck
Anterior triangle of the neck for MBBS: submental, digastric, carotid and muscular triangles, carotid system, carotid sheath and ansa cervicalis, mapped to NMC codes AN32.1 and AN32.2.
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Anterior Triangle of the Neck
Anterior triangle of the neck for MBBS: submental, digastric, carotid and muscular triangles, carotid system, carotid sheath and ansa cervicalis, mapped to NMC codes AN32.1 and AN32.2.
The anterior triangle of the neck chapter divides the region into four smaller triangles and follows the carotid system, the internal jugular vein and the vagus nerve through the carotid sheath. It grounds the surgical anatomy of the neck and the reflexes based on the carotid sinus and body.
High-yield: Anterior Triangle of the Neck
- The anterior triangle is bounded by the anterior border of sternocleidomastoid, the midline of the neck and the lower border of the mandible.
- It is subdivided by the digastric and omohyoid muscles into submental, digastric, carotid and muscular triangles.
- The carotid triangle contains the common carotid artery dividing into internal and external carotid branches at the level of the upper border of the thyroid cartilage.
- The internal carotid artery gives no branches in the neck, while the external carotid gives eight branches to the head and neck.
- The carotid sinus is a baroreceptor at the origin of the internal carotid artery, supplied by the glossopharyngeal nerve.
- The carotid body is a chemoreceptor near the bifurcation that responds to falling oxygen tension.
- The internal jugular vein lies lateral to the carotid arteries within the carotid sheath.
- The vagus nerve lies behind and between the artery and vein inside the carotid sheath.
- The hypoglossal nerve crosses the carotid triangle superficial to both carotid arteries.
- The infrahyoid or strap muscles occupy the muscular triangle and are supplied by the ansa cervicalis, from C1 to C3.
- The submental triangle, between the two anterior bellies of digastric and the hyoid, contains submental lymph nodes.
- The digastric triangle contains the submandibular gland and the facial artery and vein.
- Ligation of the external carotid artery is possible in the carotid triangle to control facial and scalp bleeding.
- The ansa cervicalis has a superior root from C1 that travels with the hypoglossal nerve and an inferior root from C2 and C3.
Subdivisions of the anterior triangle
- **Carotid triangle:** Carotid bifurcation, internal jugular vein, vagus and hypoglossal nerves.
- **Digastric triangle:** Submandibular gland, facial vessels and lymph nodes.
- **Submental triangle:** Submental lymph nodes; drains the tip of the tongue and central lower lip.
- **Muscular triangle:** Infrahyoid strap muscles supplied by the ansa cervicalis.
NMC competencies in this chapter
- **AN32.1:** Subdivisions, boundaries and contents of the anterior triangle
- **AN32.2:** Applied anatomy of the anterior triangle including the carotid system
Frequently Asked Questions
Where does the common carotid artery divide?
It divides into the internal and external carotid arteries at the upper border of the thyroid cartilage, roughly at the fourth cervical vertebra, within the carotid triangle.
What is the difference between the carotid sinus and the carotid body?
The carotid sinus is a baroreceptor sensing blood pressure at the start of the internal carotid, while the carotid body is a chemoreceptor near the bifurcation sensing low oxygen.
Which nerve lies within the carotid sheath?
The vagus nerve runs in the sheath behind and between the carotid artery and the internal jugular vein, together with these two large vessels.
How does this chapter help in NEET-PG?
Carotid anatomy, the ansa cervicalis and the neck triangles are tested in surgery and medicine, so this dissection is a lasting reference well beyond the first year.
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