The anterior triangle of the neck is divided into four smaller triangles by the digastric muscle and omohyoid muscle. The submental triangle is bounded by the digastric muscles and hyoid bone, and contains submental lymph nodes and veins. The digastric triangle contains the submandibular gland and lymph nodes, as well as the hypoglossal and lingual nerves. The carotid triangle contains the common carotid artery and its branches, internal and external jugular veins, and the vagus, accessory, and hypoglossal nerves. The muscular triangle contains the infrahyoid muscles - sternohyoid, sternothyroid, thyrohyoid, and omohyoid.

1. Anterior Triangles of
Neck

2. BOUNDARIES
Medial: The anterior median plane
of the neck
Lateral: sternocleidomastoid
Superior: Base of the mandible
and a line joining the angle of the
mandible to the mastoid process

3. SUBDIVISIONS
The anterior triangle is subdivided (by the
digastric muscle and the superior belly of
the omohyoid into:
a. Submental
b. Digastric
c. Carotid
d. Muscular triangles

4. SUBMENTAL TRIANGLE
This is a median triangle.
It is bounded as follows.
• On each side, there is the anterior belly of the
digastric muscles.
• base is formed by the body of the hyoid bone.
• apex lies at the chin.
• floor of the triangle is formed by the right and
left mylohyoid muscles and the median raphe
uniting them

5. Contents
1. Two to four small submental lymph nodes
are situated in the superficial fascia between
the anterior bellies of the digastric muscles.
They drain:
a. Superficial tissues below the chin.
b. Central part of the lower lip.
c. The adjoining gums.
d. Anterior part of the floor of the mouth.
e. The tip of the tongue. Their efferents pass to
the submandibular nodes.
2. Small submental veins join to form the
anterior jugular veins.

6. DIGASTRIC TRIANGLE
Boundaries
The boundaries of the digastric triangle are as follows.
Anteroinferiorly : Anterior belly of digastric.
Posteroinferiorly: Posterior belly of digastric and the
stylohyoid.
Superiorly or base: Base of the mandible and a line
joining the angle of the mandible to the mastoid process
Roof:
The roof of the triangle is formed by:
1. Skin.
2. Superficial fascia, containing:
a. The platysma.
b. The cervical branch of the facial nerve.
c. The ascending branch of the transverse or anterior
cutaneous nerve of the neck.
3. Deep fascia, which splits to enclose the submandibular
salivary gland
Floor:
The floor is formed by
• the mylohyoid muscle anteriorly,
• the hyoglossus posteriorly.
• A small part of the middle constrictor muscle of the
pharynx, appears in the floor

7. Contents
Anterior Part of Triangle
• Structures superficial to mylohyoid are:
1. Superficial part of the submandibular salivary gland
2. The facial vein and the submandibular lymph nodes are
superficial to it and the facial artery is deep to it.
3. Submental artery
4. Mylohyoid nerve and vessels.
5. The hypoglossal nerve.
• Posterior Part of Triangle
1. Superficial structures are:
a. Lower part of the parotid gland.
b. The external carotid artery before it enters the parotid gland.
2 Deep structures, passing between the external and internal
carotid arteries are:
a. The styloglossus.
b. The stylopharyngeus.
c. The glossopharyngeal nerve
d. The pharyngeal branch of the vagus nerve.
e. The styloid process.
f. A part of the parotid gland.
3 Deepest structures include:
a. The internal carotid artery.
b. The internal jugular vein.
c. The vagus nerve.

8. Carotid Triangle
BOUNDARIES
Anterosuperiorly: Posterior belly of the
digastric muscle and the stylohyoid.
Anteroinferiorly: Superior belly of the
omohyoid.
Posteriorly: Anterior border of the
sternocleidomastoid muscle.
Roof
1 Skin.
2 Superficial fascia containing:
a. The plastysma.
b. The cervical branch of the facial nerve.
c. The transverse cutaneous nerve of the neck.
3 Investing layer of deep cervical fascia.
FIoor
It is formed by parts of:
a. The middle constrictor of pharynx.
b. The inferior constrictor of the pharynx
c. Thyrohyoid membrane.

9. CONTENTS
Arteries
1 The common carotid artery with the carotid sinus and the
carotid body at its termination;
2 Internal carotid artery; and
3 The external carotid artery with its superior thyroid,
lingual, facial, ascending pharyngeal and occipital branches.
Veins
1 The internal jugular vein.
2 The common facial vein draining into the internal jugular vein.
3 A pharyrgeal vein which usually ends in the internal jugular
vein.
4 The lingual vein which usually terminates in the internal jugular
vein.
Nerves
1. The vagus running vertically downwards.
2. The superior laryngeal branch of the vagus, dividing into the
external and internal laryngeal nerves.
3. The spinal accessory nerve running backwards over the
internal iugular vein.
4. The hypoglossal nerve running forwards over the external and
internal carotid arteries.
The hypoglossal nerve gives off the upper root of the ansa
cervicalis or descendens hypoglossi, and another branch to the
thyrohyoid.
5. Sympathetic chain runs vertically downwards posterior to the
carotid sheath.

10. Muscular Triangle
BOUNDARIES
Anteriorly: Anterior median line of the
neck from the hyoid bone to the sternum.
Posterosuperiorly: Superior belly of the
omohyoid muscle
Posteroinferiorly: Anterior border of the
sternocleidomastoid
muscle.
Contents
The infrahyoid muscles are:
a. Sternohyoid
b. Sternothyroid
c. Thyrohyoid
d. Omohyoid