Anatomy

Human Anatomy

posteriorly

anteriorly
superiorly

Submental Triangle

Above and laterally, this triangle is bounded on each side (right and left) by the anterior belly of the digastric muscle. The third side of the triangle (base) is formed by the hyoid bone. The floor of the triangle is formed by the mylohyoid muscle.
The only contents of the triangle are the submental lymph nodes, and some small blood vessels.

superiorly

anteriorly
posteriorly

Its floor of submandibular triangle is formed by the mylohyoid and hyoglossus muscles, and by the anterior part of the middle constrictor of the pharynx. The roof of the triangle is formed by skin, superficial fascia (containing the platysma, the cervical branch of the facial nerve and some cetaceous nerves) and the investing layer of deep fascia. The main content of this triangle is the submandibular gland.

Carotid Triangle

This triangle is bounded
posteriorly by the anterior margin of the sternocleidomastoid muscle
superiorly by the posterior belly of the digastric muscle,
anteroinferiorly by the superior belly of the omohyoid muscle.
Its roof is formed by skin, superficial and deep fascia. The floor of the triangle is formed by the thyrohyoid and hyoglossus muscles, and the middle and inferior constrictors of the pharynx.

Contents:

The carotid triangle contains several important blood vessels
and nerves. These are as follows:
1. Common carotid artery, along with carotid sinus and carotid body.
2. Internal carotid artery.
3. External carotid artery and the following branches arising from it.
(a) Superior thyroid artery.
(b) Lingual artery.
(c) Facial artery.
(d) Ascending pharyngeal artery.
(e) Occipital artery.

4. Internal jugular vein, and some tributaries draining into it.

5. Vagus nerve, and its superior laryngeal branch dividing into external and internal laryngeal nerves.
6. Spinal accessory nerve.
7. Hypoglossal nerve and upper root of ansa cervicalis.
8. Sympathetic trunk.
The common carotid and internal carotid arteries, the internal jugular vein and the vagus nerve are surrounded by the carotid sheath.

Muscular Triangle

This triangle is bounded
posteroinferiorly by the sternocleidomastoid muscle.
posterosuperiorly by the superior belly of the omohyoid muscle.
anteriorly (or medially) by the anterior middle line of the neck.
The triangle contains the infrahyoid muscles. Deep to these muscles it contains the thyroid gland, the larynx and the trachea. On either side of the trachea we see the carotid sheath and its contents.