Muscle Anatomy: Origins, Insertions, and Functions of Neck, Vertebral, Respiratory, and Abdominal Muscles

Sterno-Gleidomastoid

Origin: Sternum and clavicle; Insertion: Mastoid process; Function: Flexes the head from side to side and rotates it.

Splenius

Origin: Last 4 cervical vertebrae and the upper thoracic vertebrae; Insertion: Temporal and occipital bones, and upper cervical vertebrae; Function: Rotates the head and neck.

Scalenus Anterior

Origin: The third to sixth cervical vertebrae; Insertion: The crest of the first rib; Function: Elevates the first rib and rotates the neck. Also helps during forced breathing.

Scalenus Medius

Origin: The second to seventh cervical vertebrae; Insertion: The surface of the first rib; Function: Elevates the first rib and rotates the neck. Also helps during forced breathing.

Semispinalis Capitis

Origin: The first six thoracic vertebrae and the fourth to seventh cervical vertebrae; Insertion: Occipital bone (nuchal line); Function: Extends the neck.

Spinalis

Origin: The cervical and thoracic vertebrae; Insertion: The cervical and thoracic vertebrae above; Function: Extend and laterally flex the spine.

Longissimus

Origin: The cervical, thoracic, and lumbar vertebrae; Insertion: On the mastoid process and the cervical and thoracic vertebrae; Function: Extend and laterally flex the spine and head.

Illiocostalis

Origin: The sacrum, lumbar vertebrae, and the ribs; Insertion: The ribs and the cervical vertebrae; Function: Extend and laterally flex the spine.

Diaphragm

Origin: The sternum and the cartilage of the ribs and the lumbar vertebrae; Insertion: The central tendon; Function: Increases the volume of the thoracic cavity, decreasing pressure and drawing air in.

Intercostal Muscles

Origin: The inferior aspect of all the ribs; Insertion: The superior aspect of all the ribs; Function: Keeps the ribs elevating and depressing during expiration and inspiration.

Transversus thoracis

Origin: The xiphoid process and the sternum; Insertion: The cartilage of the second through to the sixth ribs; Function: Pulls the abdominal wall inwards.

Rectus Abdominis

Origin: The pubic crest and symphysis pubis; Insertion: The xiphoid process and the inferior ribs; Function: Flexes the trunk and aids in expiration, defecation, and childbirth.

External Obliques

Origin: The lower eight ribs; Insertion: The iliac crest and linea alba and pubis; Function: Flex and rotate the vertebral column and compress the abdomen during forced expiration.

Quadratus lumborum

Origin: The iliac crest and lower lumbar vertebrae; Insertion: The twelfth rib and upper lumbar vertebrae; Function: Extends and laterally bends the vertebral column and depresses and stabilizes the twelfth rib.