Sternocleidomastoid muscle
| Sternocleidomastoid muscle |
|---|
|
| Neck and neck muscles |
| origin |
| Caput laterale: upper edge and front surface of the medial third of the clavicle , caput mediale: front surface of the manubrium sterni of the sternum |
| approach |
| Outside of the mastoid process of the temporal bone and the superior nuchal line of the occiput |
| function |
|
Unilateral: Lateral flexion in ipsilateral direction and rotation of the head in contralateral direction with simultaneous reclination
both sides: extension (reclination) of the neck and forced inspiration |
| Innervation |
| Accessor nerve and cervical plexus |
| Spinal segments |
| C1-C4 |
The sternocleidomastoid muscle (Latinized form of ancient Greek : muscle between the sternum , collarbone and the base of the skull ; "big head turner" or "head nod") is a skeletal muscle of the superficial layer of the ventral ( ventral ) neck muscles. It is a two-headed muscle on which one can distinguish a lateral head ( caput laterale ) and a head towards the middle of the body ( caput mediale ). Both heads are sloping across the side surface of the neck . Every person has two large heads: a left ( sternocleidomastoideus sinister muscle ) and a right ( sternocleidomastoideus dexter muscle ). The blood supply takes place via the ramus sternocleidomastoideus .
course
origin
The origin of the lateral head (the two-headed muscle) lies on the upper edge and front surface of the third of the collarbone ( clavicle ) located towards the middle of the body . From there its fleshy and tendon-plate-like ( aponeurotic ) fibers run almost vertically upwards.
The muscle head, which is located towards the middle of the body, arises on the front surface of the so-called handle ( manubrium sterni ) of the breastbone ( sternum ). From there, its fibers run headward ( cranial ), to the side ( lateral ) and backward ( dorsal ).
The origins of both muscle heads are separated from each other by a triangular gap (Fossa supraclavicularis minor). In the further course they unite in the middle of the neck to form a thick, rounded muscle belly.
approach
The attachment of the large head turn is largely on the outside of the so-called mastoid process ( processus mastoideus ) of the temporal bone ( os temporale ). It continues to attach to the lateral half of the upper neck line ( Linea nuchae superior ) of the occipital bone ( Os occipitale ) via a thin tendon plate .
topography
The muscle is visible through the skin on the stretched neck. The neck area above it is known as the sternocleidomastoid region and separates the lateral and front neck area .
function
In the case of one-sided contraction, the large head turn causes the head to tilt sideways ( lateral flexion ) towards the shoulder on the same side, as well as a slight stretching ( extension or reclination ) backwards. At the same rotation (place rotation ) rather than the opposite side.
Varieties
Occasionally, the area where the muscle attached to the collarbone widened. Then the trapezius muscle , which attaches to the arm side of the bone , usually also widens; sometimes they even grow together. The prominent pit on the front of the shoulder (between the back line and the collarbone) then becomes significantly smaller or even disappears completely.