Lecture Notes - Anterior Triangle of the Neck

1. Bony landmarks and Surface Anatomy:
   1. Mastoid process
   2. Mandible
      1. Mental protuberance
      2. Angle
   3. Hyoid bone
   4. Thyroid cartilage, laryngeal prominence
   5. Cricoid cartilage
   6. Trachea
   7. Jugular notch
2. Cervical triangles:
   1. Anterior - Sternocleidomastoid, trapezius, mandible and midline
      1. Muscular - midline, sup. belly omohyoid, sternocleidomastoid
      2. Carotid - post. belly digastric, sup. belly omohyoid, sternocleidomastoid
      3. Submandibular - ant. and post. bellies of digastric, body of mandible
      4. Submental - both ant. bellies of digastrics, hyoid bone
   2. Posterior - Trapezius, sternocleidomastoid, clavicle
      1. Subclavian (Omoclavicular) - inf. belly omohyoid, clavicle, sternocleidomast.
      2. Occipital - trapezius, sternocleidomastoid, inf. belly omohyoid
3. Organization of fascial layers:
   1. Superficial - subcutaneous tissue - contains platysma muscle and cutaneous veins and nerves
   2. Deep cervical fascia:
      1. Superficial (investing) layer of deep cervical fascia - encloses trapezius and sternocleidomastoid.
      2. Infrahyoid (muscular) fascia - deep to sup. layer of deep, encloses infrahyoid (strap) muscles
      3. Carotid sheath - encloses carotid arteries, int. jugular v. and vagus n.
      4. Visceral fascia - encloses trachea, esophagus & thyroid
         1. Pretracheal - anterior, encloses thyroid and parathyroids
         2. Buccopharyngeal - back of pharynx
      5. Retropharyngeal space - interfascial plane between visceral and prevertebral
      6. Prevertebral fascia - encloses vertebral column and associated. m. (scalenes, etc.) roots of brachial and cervical plexi, sympathetic trunk.
4. Muscles:
   1. Platysma: subcutaneous, muscle of facial expression
   2. Sternocleidomastoid and trapezius muscles
   3. Infrahyoid (strap): act on larynx and pharynx
      1. Omohyoid (superior & inferior bellies)
      2. Sternohyoid
      3. Sternothyroid
      4. Thyrohyoid
   4. Cricothyroid (laryngeal muscle)
5. Nerves:
   1. Cervical plexus:
      1. Sensory (cutaneous): all emerge from posterior border of sternocleidomastoid m.
         1. Lesser occipital
         2. Great auricular
         3. Transverse cervical
         4. Supraclavicular
      2. Motor branches
         1. Ansa cervicalis
         2. Phrenic
   2. Cervical branch of facial n. (CN VII) to platysma
   3. Vagus nerve (X) branches
      1. External branch of superior laryngeal n. to cricothyroid
      2. Internal branch of superior laryngeal n. goes to interior of larynx
   4. Hypoglossal nerve (XII) - motor to tongue
6. Vessels:
   1. Superficial veins
      1. External jugular
      2. Anterior jugular
      3. Communicating
      4. Jugular venous arch
   2. Deep veins
      1. Internal jugular v. - in carotid sheath
   3. Common & external carotid arteries
      1. Superior thyroid a.
   4. Inferior thyroid a. - to thyroid gland, branch of thyrocervical trunk
7. Thyroid gland: endocrine glands control general metabolism, secrete thyroxin
   1. Right and left lobes
   2. Isthmus - connection between lobes
   3. Pyramidal lobe
8. Parathyroid glands - endocrine glands, spatially related to thyroid gland (NOT functionally)
9. Clinical Terms:
   1. Goiter - enlargement of thyroid gland
   2. Tracheostomy - creation of an airway in the trachea, usually an elective procedure
   3. Cricothyrotomy - creation of an emergency airway between thyroid an cricoid cartilages
   4. Thyroidectomy - removal of thyroid
   5. Thyroglossal duct cyst - a cyst along the tract of descent of the thyroid gland
   6. Torticollis - torsion or twisting of the neck and elevation of the chin due to shortening of sternocleidomastoid m.