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Sternocleidomastoid muscle

 

 
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Sternocleidomastoid muscle
 
 
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In human
Human

A human being, also human or man, is a member of a species of bipedalism primates in the family Hominidae . Mitochondrial DNA evidence indicates that modern humans originated in east Africa about 200,000 years ago....
 anatomy
Anatomy

Anatomy is a branch of biology that is the consideration of the body plan. It is a general term that includes human anatomy, animal anatomy and plant anatomy ....
, the sternocleidomastoid (pronounced ) muscle, also known as sternomastoid and commonly abbreviated as SCM, is a paired muscle in the superficial
Superficial

Superficial is a general term meaning "regarding the surface", often metaphorically. Both in the literal as in the metaphorical sense the term has often a negative connotation based on the idea that deeper parts are also important to consider....
 layers of the anterior portion of the neck
Neck

The neck is the part of the body on many limbed vertebrates that distinguishes the head from the torso or trunk. The scientific term signifying "of the neck" is nuchal....
. It acts to flex and rotate the head.

It also acts as an accessory muscle of inspiration, along with the scalene muscles
Scalene muscles

The scalene muscles are a group of three pairs of muscles in the lateral neck, namely the scalenus anterior, scalenus medius, and scalenus posterior....
 of the neck.

s given the name sternocleidomastoid because it originates at the manubrium of the sternum
Sternum

The sternum is a long flat bone located in the center of the chest . It connects to the rib via cartilage, forming the rib cage with them, and thus helps to protect the lungs, heart and major blood vessels from physical trauma....
 (sterno-) and the clavicle
Clavicle

In human anatomy, the clavicle or collar bone is classified as a flat bone that makes up part of the shoulder girdle . It receives its name from the Latin clavicula because the bone rotates along its axis like a key when the shoulder is Abduction ....
 (cleido-), and has an insertion at the mastoid process
Mastoid process

The mastoid process is a conical prominence projecting from the undersurface of the mastoid portion of the temporal bone. It is located just behind the external acoustic meatus, and lateral to the styloid process ....
 of the temporal bone
Temporal bone

The temporal bones are situated at the sides and base of the skull.The temporal bone supports that part of the face known as the temple ....
 of the skull
Skull

The skull is a bone structure found in the head of many animals. The skull supports the structures of the face and protects the head against injury....
.

sternocleidomastoid passes obliquely across the side of the neck.

It is thick and narrow at its central part, but broader and thinner at either end.





The two heads are separated from one another at their origins by a triangular interval, but gradually blend, below the middle of the neck, into a thick, rounded muscle which is inserted, by a strong tendon, into the lateral surface of the mastoid process
Mastoid process

The mastoid process is a conical prominence projecting from the undersurface of the mastoid portion of the temporal bone. It is located just behind the external acoustic meatus, and lateral to the styloid process ....
, from its apex to its superior border, and by a thin aponeurosis
Aponeurosis

Aponeuroses are layers of flat broad tendons. They have a shiny, whitish-silvery color, and are histologically similar to tendons, but are very sparingly supplied with blood vessels and nerves....
 into the lateral half of the superior nuchal line of the occipital bone
Occipital bone

The occipital bone, a saucer-shaped membrane bone situated at the back and lower part of the skull, is trapezoid in shape and curved on itself. It is pierced by a large oval aperture, the foramen magnum, through which the cranial cavity communicates with the vertebral canal....
.

sternocleidomastoid is innervated by the ipsilateral accessory nerve
Accessory nerve

In anatomy, the accessory nerve is a nerve that controls specific muscles of the neck. As a part of it was formerly believed to originate in the brain, it is considered a cranial nerve....
.






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Encyclopedia


In human
Human

A human being, also human or man, is a member of a species of bipedalism primates in the family Hominidae . Mitochondrial DNA evidence indicates that modern humans originated in east Africa about 200,000 years ago....
 anatomy
Anatomy

Anatomy is a branch of biology that is the consideration of the body plan. It is a general term that includes human anatomy, animal anatomy and plant anatomy ....
, the sternocleidomastoid (pronounced ) muscle, also known as sternomastoid and commonly abbreviated as SCM, is a paired muscle in the superficial
Superficial

Superficial is a general term meaning "regarding the surface", often metaphorically. Both in the literal as in the metaphorical sense the term has often a negative connotation based on the idea that deeper parts are also important to consider....
 layers of the anterior portion of the neck
Neck

The neck is the part of the body on many limbed vertebrates that distinguishes the head from the torso or trunk. The scientific term signifying "of the neck" is nuchal....
. It acts to flex and rotate the head.

It also acts as an accessory muscle of inspiration, along with the scalene muscles
Scalene muscles

The scalene muscles are a group of three pairs of muscles in the lateral neck, namely the scalenus anterior, scalenus medius, and scalenus posterior....
 of the neck.

Etymology

It is given the name sternocleidomastoid because it originates at the manubrium of the sternum
Sternum

The sternum is a long flat bone located in the center of the chest . It connects to the rib via cartilage, forming the rib cage with them, and thus helps to protect the lungs, heart and major blood vessels from physical trauma....
 (sterno-) and the clavicle
Clavicle

In human anatomy, the clavicle or collar bone is classified as a flat bone that makes up part of the shoulder girdle . It receives its name from the Latin clavicula because the bone rotates along its axis like a key when the shoulder is Abduction ....
 (cleido-), and has an insertion at the mastoid process
Mastoid process

The mastoid process is a conical prominence projecting from the undersurface of the mastoid portion of the temporal bone. It is located just behind the external acoustic meatus, and lateral to the styloid process ....
 of the temporal bone
Temporal bone

The temporal bones are situated at the sides and base of the skull.The temporal bone supports that part of the face known as the temple ....
 of the skull
Skull

The skull is a bone structure found in the head of many animals. The skull supports the structures of the face and protects the head against injury....
.

Origin and insertion

The sternocleidomastoid passes obliquely across the side of the neck.

It is thick and narrow at its central part, but broader and thinner at either end.

  • The medial or sternal head is a rounded fasciculus
    Fasciculus

    Fasciculus can refer to:* nervous tissue** Superior longitudinal fasciculus*** Arcuate fasciculus** Dorsal longitudinal fasciculus** Medial longitudinal fasciculus...
    , tendinous in front, fleshy behind, which arises from the upper part of the anterior surface of the manubrium sterni, and is directed superiorly, laterally, and posteriorly.


  • The lateral or clavicular head, composed of fleshy and aponeurotic fibers, arises from the superior border and anterior surface of the medial third of the clavicle
    Clavicle

    In human anatomy, the clavicle or collar bone is classified as a flat bone that makes up part of the shoulder girdle . It receives its name from the Latin clavicula because the bone rotates along its axis like a key when the shoulder is Abduction ....
    ; it is directed almost vertically upward.


The two heads are separated from one another at their origins by a triangular interval, but gradually blend, below the middle of the neck, into a thick, rounded muscle which is inserted, by a strong tendon, into the lateral surface of the mastoid process
Mastoid process

The mastoid process is a conical prominence projecting from the undersurface of the mastoid portion of the temporal bone. It is located just behind the external acoustic meatus, and lateral to the styloid process ....
, from its apex to its superior border, and by a thin aponeurosis
Aponeurosis

Aponeuroses are layers of flat broad tendons. They have a shiny, whitish-silvery color, and are histologically similar to tendons, but are very sparingly supplied with blood vessels and nerves....
 into the lateral half of the superior nuchal line of the occipital bone
Occipital bone

The occipital bone, a saucer-shaped membrane bone situated at the back and lower part of the skull, is trapezoid in shape and curved on itself. It is pierced by a large oval aperture, the foramen magnum, through which the cranial cavity communicates with the vertebral canal....
.

Innervation

The sternocleidomastoid is innervated by the ipsilateral accessory nerve
Accessory nerve

In anatomy, the accessory nerve is a nerve that controls specific muscles of the neck. As a part of it was formerly believed to originate in the brain, it is considered a cranial nerve....
. It supplies only motor fibres. The cervical plexus supplies sensation including proprioception.

Variations

The sternocleidomastoid varies much in the extent of its origin from the clavicle: in some cases the clavicular head may be as narrow as the sternal; in others it may be as much as 7.5 cm in breadth.

When the clavicular origin is broad, it is occasionally subdivided into several slips, separated by narrow intervals. More rarely, the adjoining margins of the Sternocleidomastoid and Trapezius are in contact. This would leave no posterior triangle.

The Supraclavicularis muscle arises from the manubrium behind the Sternocleidomastoid (also known as the wing and named after a large prehistoric bird) and passes behind the Sternocleidomastoid to the upper surface of the clavicle.

Relations

The sternocleidomastoid is within the investing fascia of the neck, along with the trapezius muscle, with which it shares its nerve supply (the accessory nerve
Accessory nerve

In anatomy, the accessory nerve is a nerve that controls specific muscles of the neck. As a part of it was formerly believed to originate in the brain, it is considered a cranial nerve....
). Anterior to sternocleidomastoid is the anterior cervical triangle. Posterior to it is the posterior cervical triangle.

Many important structures relate to the sternocleidomastoid, including the common carotid artery, accessory nerve, and brachial plexus.

Cultural significance


  • Tom Wolfe
    Tom Wolfe

    Thomas Kennerly Wolfe, Jr. , known as Tom Wolfe, is a best-selling United States author and journalist. He is one of the founders of the New Journalism movement of the 1960s and 1970s....
    's The Bonfire of the Vanities
    The Bonfire of the Vanities

    The Bonfire of the Vanities is a 1987 novel by Tom Wolfe. The story is a drama about ambition, racism, social class, politics, and greed in 1980s New York City and centers on four main characters: WASP bond trader Sherman McCoy, Jewish Assistant District Attorney Larry Kramer, British expatriate journalist Peter Fallow and black activist...
     featured a lawyer
    Lawyer

    A lawyer, according to Black's Law Dictionary, is "a person learned in the law; as an Attorney at law, counsel or solicitor; a person licensed to practice fraud." Law is the system of rules of conduct established by the sovereign government of a society to correct wrongs, maintain stability, and deliver justice....
     fond of clenching his sternocleidomastoid muscles.
  • In the Portuguese movie A Canção de Lisboa
    A Canção de Lisboa

    A Can??o de Lisboa is a Portugal film comedy from 1933 in film, directed by Jos? Cottinelli Telmo, and starring Vasco Santana, Beatriz Costa, Ant?nio Silva, Alfredo Silva, Ana Maria, Artur Rodrigues, Coralia Escobar, Eduardo Fernandes, Elvira Coutinho, Fernanda Campos, Francisco Costa, Henrique Alves, Ivone Fernandes, Jos? Victor, J?lia...
    , the main character, Vasco, who is studying medicine, is asked in his final exam where the Sternocleidomastoid muscle is located. The name of the muscle became famous in Portugal after this movie.


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