Anterior triangle:

Superior: inferior border of mandible
Medial (anterior): midline
Lateral (posterior): anterior border of SCM

made up of:

the muscular triangle
the carotid triangle
the submental triangle
the submandibular triangle

Posterior triangle:

Anterior (medial): posterior border of SCM
Posterior (lateral): anterior border of trapezius
Inferior: middle ⅓ of the clavicle

venous drainage

External jugular vein lies extremely superficially over SCM

nerves

accessory nerve (CN XI) crosses the posterior triangle within the investing fascia
Cervical plexus forms within floor
- Phrenic nerve travels within prevertebral fascia

#anatomy-head-neck