Lecture 6: Anterior triangle of neck

Question 1

Anterior triangle boundaries? superficial structures?

Answer 1

Midline of the neck

Anterior boarder of the SCM

inferior boarder of the mandible

(nb: although it is not clinically important there is an anterior jugular vein that lies superficial to the strap muscles)

Question 2

Muscles of the anterior triangle?

Answer 2

Infrahyoid muscles

Most superficial is the sternohyoid muscle

Below this is the sternothyroid and the thyrohyoid attaching to the sternum, thryoid cartilage and hyoid bone.

lastly there is the omohyoid out to the side and deep to sternohyoid

Question 3

Cervical plexus? supplies

Answer 3

Ansa cervicalis - only motor components formed by C1,2 and 3 and innervates the infra-hyoid muscles

Lesser occipital and greater aurciular nerve come from here and go to erbs point.

Superior root of ansa cervicalis (C1) = thyrohyoid

Inferior root of ansa cervicalis (C2,3) = Sternohyoid, sternothyroid, omohyoid

Question 4

Thyoid gland components? A,V,L,N supply?

Answer 4

• Left and right lobe connected by the isthmus that sits ontop of the 2nd and 3rd tracheal cartilage rings.
• From the foramen cecum of tongue and migrates through the thyroglossal duct.
• parathyroid glands sit on the back of the thryoid

Blood supply and drainage

• Superior thyroid vein drains to the internal jugular
• middle (variable) and inferior thyroid vein drain to to the brachiocephalic
• The isthmus artery may come off the arch of aorta but not present in everyone (IMA)

Lymph drainage

• Drain to either the paratracheal and/or deep cervical lymph nodes

Nerve supply

• Sympathetic supply: middle cervical gaglion (runs with arteries)
• Parasympathetic: VAGUS (recurrent laryngela nerve)

Question 5

Relations of the thyroid?

Answer 5

Question 6

Suprahyoid muscles? nerve innervations and route?

Answer 6

Most superficial is the anterior belly of digastric that attaches to posterior part of mandible and then wraps around a ligament and heads to the mastoid process as the posterior belly of digastic.

Deep to this is the mylohyoid muscle and the stylohyoid muscle

Deep to all of this is the geniohyoid muscle

The facial nerve goes through the stylomastoid foramen to innervate the posterior belly of digastric and stylohyoid.

V3 (mandibular branch) innervates mylohyoid and anterior belly of digastric

Geniohyoid is actually part of thryohyoid in a child and so is innervated by C1

Question 7

What forms the venous drainage?

Answer 7

The internal and external jugular both flow out but in this case the clinically important one is the External jugular vein made from the retromandibular and posterior auricular

Question 8

Vagus nerve, Glossopharyngeal and hypoglossal

1. Exits through?
2. Travels through?
3. At root of neck?
4. Gives of branches?

Answer 8

Vagus (CN X) -

• leaves via jugular foramen between IX and XI
• travels in the carotid sheath
• stays close to the midline at the root of the neck

Glossopharyngeal (CN IX)

• through the jugular foramen
• deep to posterior belly of digastric and stylohyoid
• runs between ext and int carotid
• hooks around stylopharyngeus muscle to post 1/3 tongue

Hypoglossal (CN XII)

• exits through the hypoglossal canal
• deep to posterior belly of digastric and stylohyoid
• runs between IJV and int carotid
• runs to tongue