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Sterno- attaches to the sternumFlat bone forming the center of the chest; anchor for ribs and clavicles. Appears as a vertical dagg. Cleido- attaches to the clavicleS-shaped collarbone; connects sternum to scapula; helps brace the shoulder.. Mastoid attaches to the mastoid processLarge, rounded bump behind the ear; attachment for neck muscles.. This muscle lifts your headRounded proximal end that fits into the acetabulum of the hip bone. when you are laying down.
Origin
The sternocleidomastoidFlexor / Rotator From sternum and clavicle to skull behind the ear; turns and bends the head. muscle originates from two distinct sites:
The manubriumSuperior, triangular portion of the sternum; articulates with clavicles and first ribs. of the sternum, which is the upper part of the breastbone.
The medialToward the midline of the body third of the clavicle, one of the long bones in the shoulder girdle.
Insertion
The sternocleidomastoid muscle inserts on the mastoid process of the temporal boneBones on the sides of the skull near the ears; house structures of hearing and balance.. This is a prominent bony projection on the skull, located behind the ear.
Actions
Head Rotation
Neck Flexion
Lateral Flexion of the Neck
The name sternocleidomastoid literally tells you where it goes:
- Sterno– → from the manubrium of the sternum
- Cleido– → from the medial third of the clavicle
- –mastoid → to the mastoid process of the temporal bone (that big bump just behind your ear) and part of the superiorAbove or toward the upper part of the body. nuchal line of the occipitalPosterior and base of the skull; curves under to form the back of the head. bone
So you’ve got two heads (sternal and clavicular) fanning upward and converging on the mastoid. Because it’s so large and superficialNear the surface of the body., you can easily see or feel it when you turn your head.
Turgery. Clinicians often palpate just in front of the SCM to feel the carotid pulse.
Torticollis (“wry neckNarrow region just below the head; common fracture site.”) is a condition where the SCM is shortened or spasms, twisting the head to one side. In newborns, this can result from birth trauma or positioning.
Why It’s Famous:
It’s one of the most visible muscles in the human body. You can see it stand out when someone turns their head. It is also noticeable when they strain their neck. Artists love drawing it. Doctors use it as a landmark. Anyone who’s ever sung, shouted, or gasped has relied on it to assist in lifting
Photography, text, and labels by Rob Swatski, Assistant Professor of Biology, Harrisburg Area Community College – York Campus, York, PA.
Identify More Muscles
Link to more Muscle Identification
Upper Arm Muscles
Forearm Muscles
Calf Muscles
Anterior Thigh Muscles
Posterior Thigh Muscles
Knee Structures
Chest Muscles
Back Muscles
Abdominal Muscles
Neck Muscles
Head Muscles
List of terms
- sternum
- clavicle
- mastoid process
- head
- sternocleidomastoid
- manubrium
- medial
- temporal bone
- superior
- occipital
- superficial
- neck