The semispinalis muscles are a group of three
muscle
Skeletal muscles (commonly referred to as muscles) are Organ (biology), organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other ...
s belonging to the
transversospinales. These are the semispinalis capitis, the semispinalis cervicis and the semispinalis thoracis.
The semispinalis capitis (''complexus'') is situated at the upper and back part of the
neck
The neck is the part of the body on many vertebrates that connects the head with the torso. The neck supports the weight of the head and protects the nerves that carry sensory and motor information from the brain down to the rest of the body. In ...
, deep to the
splenius, and medial to the
longissimus cervicis and
longissimus capitis. It arises by a series of tendons from the tips of the
transverse processes
The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...
of the upper six or seven
thoracic and the
seventh cervical vertebrae
In tetrapods, cervical vertebrae (singular: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In ...
, and from the articular processes of the three cervical vertebrae above this (
C4-C6).
The tendons, uniting, form a broad muscle, which passes upward, and is inserted between the superior and inferior
nuchal lines of the
occipital bone
The occipital bone () is a cranial dermal bone and the main bone of the occiput (back and lower part of the skull). It is trapezoidal in shape and curved on itself like a shallow dish. The occipital bone overlies the occipital lobes of the c ...
. It lies deep to the
trapezius muscle and can be palpated as a firm round muscle mass just lateral to the cervical spinous processes.
The semispinalis cervicis (or ''semispinalis colli''), arises by a series of tendinous and fleshy fibers from the transverse processes of the upper five or six
thoracic vertebrae
In vertebrates, thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. In humans, there are twelve thoracic vertebrae and they are intermediate in size between the cervical ...
, and is inserted into the cervical
spinous processes, from the axis to the fifth
cervical vertebrae
In tetrapods, cervical vertebrae (singular: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In ...
inclusive. The semispinalis cervicis is thicker than the semispinalis thoracis. The fasciculus connected with the
axis is the largest, and is chiefly muscular in structure.
The semispinalis thoracis (or ''semispinalis dorsi'') muscle consists of thin, narrow, fleshy
fasciculi, interposed between
tendon
A tendon or sinew is a tough, high-tensile-strength band of dense fibrous connective tissue that connects muscle to bone. It is able to transmit the mechanical forces of muscle contraction to the skeletal system without sacrificing its ability ...
s of considerable length. It arises by a series of small tendons from the
transverse processes
The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...
of the sixth to the tenth
thoracic vertebrae
In vertebrates, thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. In humans, there are twelve thoracic vertebrae and they are intermediate in size between the cervical ...
, and is inserted, by tendons, into the
spinous processes of the upper four thoracic and lower two
cervical vertebrae
In tetrapods, cervical vertebrae (singular: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In ...
.
The semispinalis muscles are innervated by the dorsal rami of the
cervical spinal nerves.
See also
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List of muscles of the human body
Additional images
Image:Gray129.png, Occipital bone
The occipital bone () is a cranial dermal bone and the main bone of the occiput (back and lower part of the skull). It is trapezoidal in shape and curved on itself like a shallow dish. The occipital bone overlies the occipital lobes of the c ...
. Outer surface.
Image:Gray187.png, Base of skull
The base of skull, also known as the cranial base or the cranial floor, is the most inferior area of the skull. It is composed of the endocranium and the lower parts of the calvaria.
Structure
Structures found at the base of the skull are for ...
. Inferior surface.
File:Slide1ccc.JPG, Semispinalis capitis muscle
File:Gray384.png, Section showing cervicis and fascia
References
External links
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Image at ithaca.edu*
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{{Authority control
Muscles of the torso