8. ► Insertion: Lateral surface of mastoid
process and lateral 1/2 of the superior
nuchal line.
► Action:
1. Acting on one side, it tilts the head to
the same side and rotates the face to the
opposite side.
2. Acting together, the muscles of the
two sides flexes the neck forwards.
9. ► Nerve supply:
motor Spinal accessory nerve (XI)
sensory supply from C2 & C3 (for
proprioception).
10. The side of the neck is divided by the sternomastoid muscle into:
• Anterior triangle in front of the muscle.
• Posterior triangle behind the muscle.
11.
12. Digastric muscle
Origin:
The Anterior belly Arises from a depression on
the inner side of the lower border of the mandible
(digastric fossa).
The Posterior belly arises from mastoid notch of
the temporal bone.
Insertion: the two bellies meet in an intermediate
tendon
perforates the stylohoid muscle and runs in a
fibrous sling attached to the body of hyoid bone.
13. Digastric muscle
Action: Elevates the hyoid bone; depresses the
mandible.
Nerve supply:
the anterior belly is supplied by mylohyoid
nerve, because it is a muscular derivative of
the first pharyngeal arch.
The posterior belly is supplied by facial nerve
(VII) because it is a muscular derivative of the
second pharyngeal arch.
14. Omohyoid muscle
Origin:
- Superior belly: from lower border of
body of hyoid bone.
- Inferior belly: from upper border of
scapula and suprascapular ligament.
Insertion: By an intermediate tendon
which lies on internal jugular vein and
held in position by a fascial sling
connecting it to clavicle.
Nerve supply: ansa cervicalis.
15. POSTERIOR TRIANGLE OF THE NECK
Boundaries:
- Anterior: Posterior border of the sternomastoid muscle.
- Posterior: Anterior border of trapezius muscle.
- Base: Intermediate third of the clavicle.
- Apex: at the superior nuchal line.
- Roof: The investing layer of deep cervical fascia.
16. POSTERIOR TRIANGLE OF THE NECK
Boundaries:
- Floor: Is formed of the following muscles
covered with prevertebral fascia:
(muscles are arranged from below
upwards)
1. Scalenus medius. S M
2. Levator scapulae. L S
3. Splenius capitis. S C
4. Semispinalis capitis. S S C
17. Contents of posterior triangle
1. Arteries
Subclavian artery (3rd part).
Suprascapular artery.
Transverse cervical artery.
Occipital artery.
Notice that the suprascapular and the
transverse cervical arteries are branches
from the thyrocervical trunk of the first part
of subclavian artery.
18. Contents of posterior triangle
2. Veins:
Subclavian vein.
External jugular vein& its tributaries.
19. Contents of posterior triangle
3. Nerves:
• Roots and trunks of the brachial plexus& their
branches :
From the roots: N. to rhomboids & N. to serratus
anterior muscle.
From the upper trunk: Suprascapular n. & N. to
subclavius muscle.
• Spinal part of accessory nerve.
• Cutaneous branches of the cervical plexus:
Great auricular nerve.
Transverse cervical (cutaneous) nerve.
Lesser occipital nerve.
Supraclavicular nerve.
24. • Fascia forming the roof of posterior triangle is ………
• Fascia forming the roof of posterior triangle is ………
• Motor cranial nerve present in posterior triangle is ……
• 2 veins present in posterior triangle are ……
• The muscle which present in posterior triangle is …
