Unit 1 Anterior Muscles Origins, Insertion, Action, Innervation

Origins, Insertion, Action, Innervation for the unit 1 anterior muscles

Rectus Abdominis Origin

Pubic crest and pubic symphysis.

Rectus Abdominis Insertion

Cartilage of ribs 5–7 and xiphoid process.

Rectus Abdominis Action

Flexes vertebral column, especially lumbar portion, and compresses abdomen to aid in defecation, urination, forced exhalation, and childbirth. RMA: Flexes pelvis on the vertebral column.

Rectus Abdominis Innervation

Thoracic spinal nerves T7–T12

External abdominal oblique Origin

Ribs 5–12.

External abdominal oblique Insertion

Iliac crest and linea alba

External abdominal oblique Action

Acting together (bilaterally), compress abdomen and flex vertebral column; acting singly (unilaterally), laterally flex vertebral column, especially lumbar portion, and rotate vertebral column.

External abdominal oblique Innervation

Thoracic spinal nerves T7–T12 and the iliohypogastric nerve.

Internal abdominal oblique origin

Iliac crest, inguinal ligament, and linea alba

Internal abdominal oblique Insertion

Cartilage of ribs 7–10 and linea alba.

Internal abdominal oblique Action

Acting together, compress abdomen and flex vertebral column; acting singly, laterally flex vertebral column, especially lumbar portion, and rotate vertebral column (B)

Internal abdominal oblique Innervation

Thoracic spinal nerves T8–T12, the iliohypogastric nerve, and ilioinguinal nerve.

 

 

Tranversus Abdominis Origin

Iliac crest, inguinal ligament, lumbar fascia, and cartilages of ribs 5–10.

Tranversus Abdominis Insertion

Xiphoid process, linea alba, and pubis

Tranversus Abdominis Action

Compresses abdomen.

Tranversus Abdominis Innervation

Thoracic spinal nerves T8–T12, iliohypogastric nerve, and ilioinguinal nerve. (transversus)

External Intercostals Origin

Inferior border of rib above.

External Intercostals Insertion

Superior border of rib below

External Intercostals Action

Contraction elevates ribs and increases anteroposterior and lateral dimensions of thoracic cavity, resulting in inhalation; relaxation depresses ribs and decreases anteroposterior and lateral dimensions of thoracic cavity, resulting in exhalation.

External Intercostals Innervation

Thoracic spinal nerves T2–T12.

Internal Intercostals Origin

Superior border of rib below.

Internal Intercostals Insertion

Inferior border of rib above.

Internal Intercostals Action

Contraction draws adjacent ribs together to further decrease anteroposterior and lateral dimensions of thoracic cavity during forced exhalation.

Internal Intercostals Innervation

Thoracic spinal nerves T2–T12

Diaphragm Origin

Xiphoid process of sternum, costal cartilages and adjacent portions of ribs 7–12, lumbar vertebrae and their intervertebral discs.

Diaphragm Insertion

Central tendon.

Diaphragm Action

Contraction of diaphragm causes it to flatten and increases vertical dimension of thoracic cavity, resulting in inhalation; relaxation of diaphragm causes it to move superiorly and decreases vertical dimension of thoracic cavity, resulting in exhalation.

Diaphragm Innervation

Phrenic nerve, which contains axons from cervical spinal nerves (C3–C5).

Platysma Origin

Fascia over deltoid and pectoralis major muscles

Platysma Insertion

Mandible, blends with muscles around angle of mouth, and skin of lower face.      

Platysma Action

Draws outer part of lower lip inferiorly and posteriorly as in pouting; depresses mandible.

Platysma Innervation

Facial (VII) nerve

Sternocleidomastoid Origin

Sternal head: manubrium of sternum; clavicular head: medial third of clavicle.

Sternocleidomastoid Insertion:

Mastoid process of temporal bone and lateral half of superior nuchal line of occipital bone.

Sternocleidomastoid Action

Acting together (bilaterally), flex cervical portion of vertebral column, extend head at atlanto-occipital joints; acting singly (unilaterally), laterally flex neck and head to same side and rotate head to side opposite contracting muscle. Laterally rotate and flex head to opposite side of contracting muscle. Posterior fibers of muscle can assist in extension of head. RMA: Elevate sternum during forced inhalation.

Sternocleidomastoid Innervation

Accessory (XI) nerve, C2, and C3.

 

Pectoralis Major Origin

Clavicle (clavicular head), sternum, and costal cartilages of ribs 2–6 and sometimes ribs 1–7 (sternocostal head).

Pectoralis Major Insertion

Greater tubercle and lateral lip of intertubercular sulcus of humerus.

Pectoralis Major Action

As a whole, adducts and medially rotates arm at shoulder joint; clavicular head flexes arm, and sternocostal head flexes the extended arm to side of trunk.

Pectoralis Major Innervation

Medial and lateral pectoral nerves

Pectoralis Minor Origin

Ribs 2–5, 3–5, or 2–4.

Pectoralis Minor Insertion

Coracoid process of scapula.

Pectoralis Minor Action

Abducts scapula and rotates it downward. RMA: Elevates ribs 3–5 during forced inhalation when scapula is fixed.

Pectoralis Minor Innervation

Medial and lateral pectoral nerve

Scalenus anterior Origin

Transverse processes of C3–C6.

Scalenus anterior Insertion

Rib 1

Scalenus anterior Action

Acting together, right and left scalenus anterior and scalenus medius muscles elevate first ribs during deep inhalation.

Scalenus anterior Action

Acting together, right and left scalenus anterior and scalenus medius muscles elevate first ribs during deep inhalation.

Scalenes Middle Origin

Transverse processes of C2–C7.

Scalenes Middle Insertion

Rib 1.

Scalenes Middle Action

RMA: Flex cervical vertebrae; acting singly, laterally flex and slightly rotate cervical vertebrae

Scalenes Middle Innervation

Cervical spinal nerves.

Scalenes Posterior Origin

Transverse processes of C4–C6.

Scalenes Posterior Insertion

Rib 2.

Scalenes Posterior Action

Acting together, right and left scalenus posterior elevate second ribs during deep inhalation. RMA: Flex cervical vertebrae; acting singly, laterally flex and slightly rotate cervical vertebrae.

Scalenes Posterior Innervation

Cervical spenial nerves