A1 Abdominal Structures

Dorsal & Ventral Body Subdivisions

Muscles of Abdominal Wall

External Oblique

Origin & Insertion

-Origin: lower 8 ribs

-Insertion: Iliac crest & iliac alba

Function:

-unilateral: rotation & side flexion

-bilateral: flexion of lumber spine

Innervation: thoracic spine nerves

Internal Oblique

Origin & Insertion:

-Origin: lumbodorsal fascia, iliac crest, inguinal ligament

-Insertion: costal cartilage of last 3 ribs & linea alba

Functions:

-unilateral: rotation & side flexion

-bilateral: flexion of lumber spine

Innervation: thoracic spine nerves

Rectus abdominis

Origin & Insertion:

-Origin: Pubic Crest

-Insertion: costal cartilages 5-7 & xiphoid processes

Function: flexes lumber spine; compresses abdominal visceral

Innervation: thoracic spinal nerves

Rectus Abdominis (more functions)

Linea alba: formed by the fusion of the aponeuroses of the external oblique, internal oblique, and transversus abdominis muscles at the midline

Rectus sheath: formed by the fusion of the eponeuroses of the external oblique, internal oblique, and transversus abdominis muscles surrounding the rectus abdominis

Linea semilunaris: a tendinous line marking the lateral border of the rectus abdominis muscle; formed by the aponeuroses of the external oblique, internal oblique, and transversus Abdominis muscles

Tendinous intersections: transverse bands in the rectus muscle, dividing it into segments

Transverse Abdominis

Origin & Insertion:

-origin: lower 6 costal cartilages, lumbodorsal fascia, iliac crest, inguinal ligament

-insertion: linea alba

Actions: compresses and support abdominal viscera

Innervation: thoracic spinal nerves

Rectus Abdominis Sheath

The rectus Abdominis muscle lies in the rectus sheath, between the anterior and posterior layers of the sheath. The posterior layer is present superior to the arcuate line but absent inferior to it.

Arcuate lines: the lower border of the posterior layer of the rectus sheath

Inguinal ligament & Inguinal canal

Inguinal ligament

• formed by free inferior border of the external oblique aponeurosis

• extends from the anterior superior iliac spine to the pubic tubercle

Inguinal canal

• lies parallel and superior to the medial half of the inguinal ligament

• Openings:

-deep ring: an opening in the transversalis fascia

-superficial ring: an opening in the aponeurosis of external oblique

-main contents: spermatic cord (males) and round ligament of the uterus (females)

Erector Spinae Muscles

Erector spinae: Divides into three muscle columns

Iliacostalis: lateral

Longissimus: intermediate

Spinalis: medial

Origin:

-iliocostalis: iliac crest

-Longissimus: transverse processes

-Spinalis: spinous processes

Insertion:

-Iliocostalis: angle of lower ribs & cervical transverse processes

-Longissimus: transverse processes & mastoid process of temporal bone

-Spinalis: spinous processes of the upper vertebrae

Actions:

-unilaterally: laterally flex vertebral column

-bilaterally: extend vertebral column and head

Transversospinales Muscle Group

Transversospinales muscle group

• Deep to the erector spinae muscles

-Semispinalis: superficial; spanning 4-6 segments

-Multifidus: deeper; spanning 2-4 segments

-Rotatores: deepest; spanning 1-2 segments

Origin: Transverse processes

Insertion:

-Semispinalis: occipital bone and spinous processes

-Multifidus: spinous processes

-Rotatores: spinous processes

Actions:

unilaterally: spinal rotation and side flexion

bilaterally: extend the vertebral column and head