Abdominal Muscles

Question 1

psoas major

Answer 1

origin: lateral surface of bodies of T12 and L1-L5, transverse processes of lumbar vertebrae, and IVDs b/w T 12 and L1-L5

insertion: lesser trochanteric of the femur

innervation: anterior rami of L1-L3

function: flexion of thigh at hip joint

Question 2

psoas minor

Answer 2

origin: lateral surface of bodies of T12 and L1 and IVD

insertion: pectineal line of the pelvic brim and illiopubic eminence

innervation: anterior rami of L1

function: weak flexion of lumbar vertebral column

Question 3

quadratus lumborum

Answer 3

origin: transverse process of L5, illiolumbar ligament, and iliac crest

insertion: transverse process of L1-L4 and inferior border of rib 12

innervation: anterior rami of T12 and L1-L4

function: depress and stabilize rib 12 and some lateral bending of the trunk

Question 4

illiacus

Answer 4

origin: upper 2/3 of iliac fossa, anterior SI and iliolumbar ligaments, and upper lateral surface of
sacrum

insertion: lesser trochanter of femur

innervation: femoral nerve (L2-L4)

function: flexion of thigh at hip joint

Question 5

external oblique

Answer 5

origin: muscular slips from the outer surfaces of the lower 8 ribs

insertion: lateral lip of iliac crest; aponeurosis ending in midline raphe (linea alba)

innervation: anterior rami of lower 6 thoracic spinal nerves

function: compress abdominal contents; both muscles flex trunk; each muscle bends trunk to same side

Question 6

internal oblique

Answer 6

origin: thoracolumbar fascia, iliac crest b/w attachments of external oblique and transversus abdominis; lateral 2/3 of inguinal ligament

insertion: inferior border of the lower 3-4 ribs; aponeurosis ending in linea alba; pubic crest and pectineal line

innervation: anterior rami of lower 6 thoracic spinal nerves and ilioinguinal and iliohypogastric nerves

function: compress abdominal contents; both muscles flex trunk; each muscle bends trunk to same side

Question 7

transversus abdominis

Answer 7

origin: thoracolumbar fascia; medial lip of iliac crest; lateral one-third of inguinal ligament; costal cartilages lower six ribs

insertion: aponeurosis ending in linea alba; pubic crest and pectineal line

innervation: Anterior rami of lower six thoracic spinal nerves and ilioinguinal and iliohypogastric nerves

function: compress abdominal contents

Question 8

rectus abdominis

Answer 8

origin: pubic crest, pubic tubercle, and pubic symphysis

insertion: costal cartilages of ribs 5 to 7; xiphoid process

innervation: anterior rami of lower seven thoracic spinal nerves

function: compress abdominal contents; flex vertebral column; tense abdominal wall

Question 9

pyramidalis

Answer 9

origin: front of pubis and pubic symphysis

insertion: into linea alba

innervation: anterior ramus of T12

function: tenses the linea alba