4. Sternohyoid
• Origin :Back of manubrium
& medial end of clavicle.
• Insertion :Medial part of
the lower border of hyoid
bone.
• Nerve supply : Ansa
Cervicalis
• Action: Depression of
hyoid bone
5. Sternothyroid
• Origin :Back of
manubrium sterni.
• Insertion: Oblique line of
thyroid cartilage.
• Nerve supply : Ansa
cervicalis.
• Action :Depression of the
larynx.
6. Thyrohyoid
• Origin: Oblique line of the
thyroid cartilage.
• Insertion :Lower border of
hyoid bone.
• Nerve supply :hypoglossal
nerve(C1fibers).
• Action:Depression of hyoid
or elevation of larynx.
7. Ansa Cervicalis
Def It is a loop of cervical nerves which lies on the surface
of carotid sheath.
It is formed by the union of:
• Descending hypoglossi :consist of fibers from C1.
• Descending cervicalis : consist of fibers from C2&C3
Branches:
• Sternohyoid
• Sternothyroid
• Omohyoid(both belies)
9. Carotid Triangle
Boundaries
• Superiorly(A) Posterior
belly of digastric
muscle.
• Inferiorly(C) Superior
belly of omohyoid.
• Posteriorly(B) Anterior
border of
sternomastoid.
10. Roof:
• Skin &superficial fascia
• Platysma & deep fascia
Floor:
•Thyrohyoid
•Hyoglossus
•Middle& Inferior constrictors of the pharynx.
11. Contents:
1- Internal jagular vein:
descends vertically in the lateral part of the triangle
2-common & internal carotid triangle:
both lie medial to the internal jagular vein
3-external carotid artery:
it gives 8 branches, 5 of them are given off in the
triangle ( superior thyriod, ascending pharyngeal,
lingual, facial, occipital)
4-vagus:
it descends within the carotid sheath
12. 5- Cervical part of the sympathetic trunk:
Lies behind the carotid sheath
6-Accessory nerve:
runs downwards and backwards either superficial or
deep to the internal jagular vein.
7- Hypoglossal nerve:
descends between internal jagular vein and internal
carotid artery.
cross the external carotid artery and the loop of the
lingual artery.
13. 8- Deep cervical lymph nodes:
lie along the carotid sheath
9-Ansa cervicalis
10-Common facial vein
