Muscles Of The Abdominal And Pelvic Walls

Front 1

Bony Landmarks

Back 1

1) rib cage - xiphoid process of sternum; ribs and costal cartilages
2) pelvis
a) pubic bone - pubic symphysis, pubic tubercle
b) ilium - iliac crest, iliac fossa, anterior superior iliac spine
c) ishiopubic rami
3) Femur - lesser trochanter

Front 2

Abdominal and Pelvic Cavities

Boundaries

Back 2

1) Rib cage & thoracic diaphragm - superior
2) pelvis & pelvic diaphragm - inferior
3) anterior-lateral abdominal wall muscles - ventral (anterior)
4) vertebral column, and psoas major & quadratus lumborum muscles - dorsal (posterior)

Front 3

Muscles of Anterior-Lateral Abdominal Wall

Back 3

1) lateral abdominal wall consists of 3 overlapping layers of sheetlike muscle - external abdominal oblique, internal abdominal oblique, and transvers abdominis muscles
a) muscles form either side become aponeurotic anteriorly and insert into each other at anterior midline of body- forms a raphe called the linea alba (runs from xiphoid process of sternum to pubic symphysis of pelvis)
2) fourth abdominal wall muscle is rectus abdominis muscle - paired muscles running superior-inferior on wither side of anterior midline
3) abdominal muscles innervated by lower intercostal nerves or upper lumbar nerves

Front 4

External Oblique Muscle

Back 4

fibers run down and medial
Origin - lower borders of last 8 ribs (ribs 5-12)
Insert - linea alba, pubic tubercle, anterior half of iliac crest

Front 5

Internal Abdominal Oblique Muscle

Back 5

fibers run up & medial
Origin - from anterior iliac crest, lateral inguinal ligament, & thoracolumbar aponeurosis of back (tendinous layer arising from spines of lower thoracic and all lumbar vertebrae; provides origin for litissimus dorsi, internal abdominal oblique, & transversus abdominis muscles
Insert - lower ribs, linea alba, pubic bone

Front 6

Tranversus Abdominis Muscle

Back 6

fibers run lateral to medial
Origin - lower ribs, thoracolumbar aponeurosis, anterior iliac crest, & lateral inguinal ligament
Insert - linea alba, pubic bone

Front 7

Rectus Abdominis Muscle

Back 7

runs vertically next to anterior midline
Origin - pubic bone
Insert - xiphoid process and ribs 5-7
-- muscles divide into sections of muscle fibers seperated by tendinous intersections
-- rectus muscle covered superficially by anterior rectus sheath and deep by posterior rectus sheath
-- rectus sheath formed by fused aponeurosis of external & internal abdominal oblique and transverse abdominis muscle layers

Front 8

Actions of Abdominal Wall Muscles

Back 8

1) all 4 muscles act to hold abdominal viscera in place and to compress abdomen
2) rectus abdominis flexes trunk of body (flexes vertebral column)
3) external & internal abdominal oblique muscles:
a) unilateral action - primary rotators of body of trunk
1) contraction of external muscle on right side of body plus contraction of internal muscle on left side of body - rotate to left (rotates toward side of internal abdominal oblique muscle)
b) unilateral action - contraction of both muscles on same side - lateral bending of trunk
c) bilateral action - contraction of both muscles on both sides - flexion of trunk (bending forward0
** commom question, "rotation to " " side requires " " muscle use **

Front 9

Inguinal Ligament

Back 9

1) formed by rolled under inferior margin of external abdominal oblique aponeurosis
2) spans from anterior superior iliac spine to pubic tubercle
3) passes over and attaches to deeper structures that are exiting abdominal cavity to enter thigh:
a) iliacus and psoas major muscle - from single iliopsoas tendon inferior to inguinal ligament
b) femoral arter, vein, and nerve

Front 10

Inguinal Canal

Back 10

1) for passage of spermatic cord (in males) between abdominal cavity and testis
a) spermatic cord contains testicular artery & vein, & ductus deferens
2) canal formed by openings through muscles of abdominal wall (external & internal abdominal oblique muscles & transversus abdominis muscle)
a) inguinal canal runs just above and parallel within abdominal cavity; deep ring formed by opening through transversus abdominis muscle
c) canal continues through opening in internal abdominal oblique muscle
d) superficial inguinal ring - exit of canal; superficial ring formed by opening through external abdominal oblique muscle

Front 11

Inguinal Hernias

Back 11

inguinal canal potential site for hernias (evagination of abdominal contents out of abdominal cavity, passing down inguinal canal toward scrotum)

Front 12

Muscles of Posterior Wall
x 3

#1 Quatratus Lumborum

Back 12

Origin - posterior iliac crest
Insert - rib 12 and lumbar vertabrae
Action - anchors 12th rib during inspiration (resists upward pull of diaphragm)

Front 13

Muscles of Posterior Wall
x 3

#2 Psoas Major

Back 13

Origin - vertebrae T12, L1 - L5
Insert - lesser trochanter of femur
-- psoas major passes over quadratus lumborum, then runs caudally & under the inguinal ligament into thigh

Front 14

Muscles of Posterior Wall
x 3

#3 Iliacus

Back 14

Origin - iliac fossa
Insert - lesser trochanter of femur
-- psoas major & iliacus muscles fust to form single iliopsoas tendon inferior ro level of inguinal ligament
-- iliacus & psoas major are primary flexors of the hip joint

Front 15

Pelvic Diaphragm

Back 15

1) funnel-shaped muscle layer that closes off inferior opening of pelvis (forms inferior floor of pelvic cavity; supports pelvic viscera)
a) has larger, superior opening - arises from U shaped line around inner margins of true pelvic cavity (opening of U is in anterior direction)
b) narrow, inferior opening of diaphragm allows for passage for rectum
1) rectum becomes anal canal at passage through pelvic diaphragm
2) anal canal terminates as anus - surrounded by muscle of external anal sphincter
3) rectum, anal canal, anus exit pelvis in downward & posterior direction
2) gap in anterior wall of diaphragm (anterior opening of U shape) = urogenital hiatus
a) allows for passage of urethra (male) or urethra & vagina (female) - exit pelvis in downward & anterior direction