subdivisions of the anterior triangles

submental, digastric (submandibular), carotid and muscular

what are the subdivisions of the anterior triangles?

1. submental triangle

2. digastric (submandibular) triangle

3. carotid triangle

4. muscular triangle

what are the boundaries of the submental triangle?

• apex: the meeting point of the the anterior bellies of the digastric muscles meet, just below the symphysis menti

• base: body of the hyoid bone

• laterally: anterior bellies of right and left digastric muscles

• floor: two mylohyoid muscles, meeting in the median plane and forming the diaphragma oris.(mylohyoid)

what are the contents of the submental triangle?

• submental lymoh nodes

• submental artery, which arises from the facial artery

• nerve to mylohyoid muscle

• submental veins, which unite to form the anterior jugular vein

what are the boundaries of the digastric (submandibular) triangle?

• anterior border: anterior belly of the digastric

• posterior border: posterior belly of the digastric and stylohyoid muscles

• base (above): the lower border of the mandible

• floor: mylohyoid muscle anteriorly, hyoglossus muscle posteriorly

what are the contents of the digastric triangle?

1. submandibular salivary gland

2. submandibular lymph nodes

3. part of the facial artery and its branch called the submental artery, which passes on the mylohyoid to the submental triangle

4. facial vein, which runs along the submandibular gland before joining the anterior branch of the retromandibular vein

5. hypoglossal nerve, runs deep to the submandibular gland and travels over the surface of the hyoglossus muscle.

6. nerve to the mylohyoid muscle

what occupies the greater part of the digastric triangle?

submandibular salivary gland

what lies along the base of the mandible?

the submandibular lymph nodes

what are the boundaries of the carotid triangle?

• anteriorly and inferiorly: superior belly of omohyoid

• anteriorly and superiorly: posterior belly of the digastric

• posterior: anterior border of the sternocleidomastoid muscle

• floor: hyoglossus and thyrohyoid muscles anteriorly and the middle and inferior constrictors of the pharynx posteriorly

what are the contents of the carotid triangle?

1. terminal part of the common carotid artery

2. proximal parts of the internal and external carotid arteries

3. internal jugular vein

4. vagus nerve

5. sympathetic trunk that are posteriorly embedded in the substance of the carotid sheath

6. deep cervical nodes arranged along the carotid sheath

7. hypoglossal nerve

8. ansa cervicalis

9. branches of the external carotid artery

10. accessory nerve

11. tributaries of the internal jugular vein

what is the carotid sheath?

a tubular fascial sheath that encloses as follows:

• common carotid artery

• internal carotid artery (medially)

• internal jugular vein (laterally)

• vagus nerve (posterior in position and between the artery and vein)

where does the hypoglossal nerve appear at?

at the lower border of the posterior belly of the digastric muscle, curving forward and crossing the carotid arteries, passing deep to the posterior belly of the digastric muscle to reach the digastric (submandibular) triangle

what is the ansa cervicalis?

a nerve loop which lies on the common carotid artery. it is formed of the fiber from the ventral rami of C1-C3 and the descending hypoglossal nerves

what are the branches of the external carotid artery?

1. ascending pharyngeal artery, ascending upwards on the wall of the pharynx

2. superior thyroid artery, passing upwards and forwards to the superior pole of the thyroid gland

3. lingual artery, which arches behind the tip of the hyoid bone and passing under the hyoglossus muscle

4. facial artery, ascending deep to the posterior belly of the digastric muscle to pierce the triangle

5. occipital artery, which runs along the lower border of the posterior belly of digastric

where does the accessory nerve cross?

it crosses the upper angle of the carotid triangle, deep to the internal jugular vein, passing under the sternocleidomastoid muscle

what are the tributaries of the internal jugular vein?

1. facial vein, which crosses the posterior belly of the digastric, uniting with the anterior division of retromandibular vein to form common facial vein, draining into the internal jugular vein

2. lingual vein, which is formed by the union of several veins from the tongue at the posterior border of the hyoglossus, draining into the internal jugular vein

3. superior thyroid vein, which runs along the artery, draining into the internal jugular vein

what are the boundaries of the muscular triangle?

• anteriorly: midline of the neck

• posteriorly and superiorly: superior belly of the omohyoid

• posteriorly and inferiorly: anterior border of the sternocleidomastoid muscle

• floor: formed by the infrahyoid muscles, which are:

  • thyrohyoid

  • sternohyoid

  • sternothyroid

what is the only triangle that does not contain any major vessels or nerves?

the muscular triangle