Q9 Sternomastoid

Question 1

Give the position of this muscle

Answer 1

Long strap-like muscle that arises by two heads and runs around the anterolateral aspect of the neck close to midline anteriorly

Question 2

State the attachments of the sternomastiod muscle

Answer 2

Sternal head arises by a narrow rounded tendon from the upper part of the anterior surface of the manubrium sternum.
Clavicular head arises by a flattened muscular attachment from the surface of the medial two thirds of the clavicle
The tendon attaches to the lateral surface of the mastoid process of the temporal bone and by a thin aponeurosis to the lateral third of the superior nuchal line of the occipital bone.

Question 3

List the unilateral action of this muscle

Answer 3

Working alone: tilts head to same side- lateral flexion of neck, whilst rotating head to opposite side.

Question 4

List the bilateral action of this muscle

Answer 4

Working together: flex the neck and extend head at atlanto-occipital joint
When head and neck are fixed-raise clavicle and manumbrium sterni and ribs assisting respiration.

Question 5

Give 2 functional activities when this muscle is active

Answer 5

Raising head from lying supine. (getting in and out of bed)
Looking over your shoulder when reversing a car
Accessory muscle of respiration