Muscles that Move the Head and Vertebral Column

Paired muscles in the neck and back flex, extend, and rotate the head and hold the torso erect (figs. 9.24 and 9.26 and table 9.5). They include the following:

Sternocleidomastoid Semispinalis capitis

Splenius capitis Erector spinae

The sternocleidomastoid (ster"no-kli"do-mas'toid) is a long muscle in the side of the neck that extends upward from the thorax to the base of the skull behind the ear. When the sternocleidomastoid on one side contracts, the face turns to the opposite side. When both muscles contract, the head bends toward the chest. If other muscles fix the head in position, the sternocleidomastoids can raise the sternum, aiding forceful inhalation (fig. 9.26 and table 9.5).

The splenius capitis (sple'ne-us kap'i-tis) is a broad, straplike muscle in the back of the neck. It connects the base of the skull to the vertebrae in the neck and upper thorax. A splenius capitis acting singly rotates the head and bends it toward one side. Acting together, these muscles bring the head into an upright position (fig. 9.24 and table 9.5).

The semispinalis capitis (sem"e-spi-na'lis kap'i-tis) is a broad, sheetlike muscle extending upward from the vertebrae in the neck and thorax to the occipital bone. It extends the head, bends it to one side, or rotates it (fig. 9.24 and table 9.5).

Erector spinae muscles run longitudinally along the back, with origins and insertions at many places on the axial skeleton. These muscles extend and rotate the head and maintain the erect position of the vertebral column. Erector spinae can be subdivided into medial, intermediate, and lateral groups (table 9.5).

Splenius capitis (cut) Longissimus capitis

Semispinalis capitis (cut) Longissimus cervicis lliocostalis cervicis_

Semispinalis capitis Spinalis capitis Splenius capitis Spinalis cervicis

Longissimus thoracis

Splenius capitis (cut) Longissimus capitis

Longissimus thoracis

Vertebral Column And Muscles

Semispinalis capitis Spinalis capitis Splenius capitis Spinalis cervicis

_lliocostalis thoracis

Spinalis thoracis lliocostalis lumborum

Figure

Deep muscles of the back and the neck help move the head (posterior view) and hold the torso erect. The splenius capitis and semispinalis capitis are removed on the left to show underlying muscles.

_lliocostalis thoracis

Spinalis thoracis lliocostalis lumborum

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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Responses

  • giorgia lucciano
    Does the splenius capitus hold the head erect?
    5 years ago
  • Bartolomeo
    Which muscle extends the vertebral column and rotates it to the opposite side?
    4 years ago
  • Obo
    What muscles hold the head erect?
    4 years ago
  • franziska
    Which muscles connects the vertebral column?
    4 years ago

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