|Neck and neck muscles|
|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
|Outside of the mastoid process of the temporal bone and the
superior nuchal line of the occiput
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
|Accessor nerve and cervical plexus|
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 .
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.
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 .
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.
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.