Anterior Triangles of Neck

• 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

 

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

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 

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. 

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:

1. The floor is formed by
2. the mylohyoid muscle anteriorly,
3. the hyoglossus posteriorly.
4. A small part of the middle constrictor muscle of the pharynx, appears in the floor 

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. 

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:

1. The middle constrictor of pharynx.
2. The inferior constrictor of the pharynx
3. Thyrohyoid membrane. 

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. 

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 

Watch lectures on YouTube

Anterior Triangles of The Neck | Boundaries | Subdivisions | Muscular & Submental Triangles

Carotid Triangle of the Neck | Boundaries | Contents |

Features of Structures in the Carotid Triangle

Digastric Triangle of the Neck | Boundaries & Contents