chapter 11 axial muscles eh

Illustrate the organization and function of the muscles that support and move the axial skeleton

Organization and Function of Muscles Supporting and Moving the Axial Skeleton

The axial muscles support the head, neck, and trunk, providing stability and mobility to the spine and core. These muscles are organized into several groups based on function and location:

Muscles of the Head and Neck:

Function: Support and move the head and neck, assist in facial expressions, mastication, and swallowing.

Examples: Orbicularis oculi (closes eyes), orbicularis oris (closes mouth), and sternocleidomastoid (rotates and flexes the head).

Muscles of the Vertebral Column:

Function: Stabilize, flex, extend, and rotate the spine.

Examples: Erector spinae group (spinal extension and posture), multifidus (stabilizes vertebrae), and quadratus lumborum (lateral flexion of the spine).

Muscles of Respiration:

Function: Facilitate breathing by controlling the rib cage and diaphragm.

Examples: Diaphragm (primary muscle of inhalation), external intercostals (elevate ribs for inhalation), and internal intercostals (depress ribs for forced exhalation).

Muscles of the Abdominal Wall:

Function: Compress abdominal contents, stabilize the spine, and flex and rotate the trunk.

Examples: Rectus abdominis (trunk flexion), external oblique (trunk rotation), and transverse abdominis (core stabilization).

Specified Muscles, Their Actions, Origins, and Insertions That Support and Move the Axial Skeleton

Below are some key muscles in the axial skeleton, along with their specific actions, origins, and insertions.

Sternocleidomastoid:

Action: Flexes and rotates the head.

Origin: Sternum and clavicle.

Insertion: Mastoid process of the temporal bone.

Erector Spinae Group (Iliocostalis, Longissimus, Spinalis):

Action: Extends and laterally flexes the vertebral column.

Origin: Iliac crest, sacrum, lumbar vertebrae.

Insertion: Ribs, cervical and thoracic vertebrae.

Diaphragm:

Action: Contracts and flattens to expand the thoracic cavity for inhalation.

Origin: Xiphoid process, lower ribs, and lumbar vertebrae.

Insertion: Central tendon.

Rectus Abdominis:

Action: Flexes the vertebral column and compresses the abdominal contents.

Origin: Pubic crest and symphysis.

Insertion: Xiphoid process and costal cartilages of ribs 5-7.

External Oblique:

Action: Flexes and rotates the trunk; compresses the abdominal wall.

Origin: Outer surface of lower eight ribs.

Insertion: Linea alba, pubic crest, and iliac crest.

Transverse Abdominis:

Action: Compresses the abdominal contents to stabilize the core.

Origin: Iliac crest, lower six ribs, lumbar fascia.

Insertion: Linea alba and pubic crest.

These muscles work in tandem to support the spine, enable movement of the trunk and head, and facilitate critical functions like respiration and core stability.