10/12 Anterolateral Abdominal Wall

How do abdominal muscles effect pressure?

1. Muscles decrease abdominal cavity volume / increase intraabdominal pressure 2. Abdominal organs increase pressure in thorax and pelvis

Inferior epigastric artery

Comes from external iliac artery. Enters rectus sheath, underneath arcuate line, enters the rectus sheath on the deep surface of the rectus abdominis muscle. Comes up and has an anastomosis with the superior epigastric artery.

Superficial half of rectus sheath above the Arcuate line (top 3/4)

EAO and IAO

What is the path of the EAO aponeurosis above the Arcuate line (top 3/4)

EAO is always superficial to rectus abdominis muscles

How do the fibers run in the rectus abdominis?

Fibers run vertically.

Flexion of the trunk via abdominal wall muscles

Flexion (pure) - bilateral

Deep half of rectus sheath above the Arcuate line (top 3/4)

IAO and TA.

Blood supply for the rectus abdominis

In addition to intercostal arteries... Superior epigastric artery from internal thoracic Majority comes from inferior epigastric artery, comes from external iliac artery. Inferior is way more important, main blood supply

Blood supply for the anterior abdominal wall

Intercostal arteries for the most part, run between IAO and TA. Rectus abdominis has an additional blood supply of the superior and inferior epigastric arteries.

Arteries supplying intercostal muscles run between:

Internal abdominal oblique and TA. (see lateral side of picturee)

What happens to the back wall below the arcuate line?

It disappears. IAO and TA layers join the EAO running superiorly to the rectus abdominis. So only thick superficial wall and no posterior wall.

What is the path of the IAO aponeurosis above the Arcuate line (top 3/4)?

Its aponeurosis will split into two layers, one running superficial and one running deep to the rectus abdominis. The superficial branch fuses with the aponeurosis of the EAO, while the deep branch fuses with the aponeurosis of the TA.

Lateral flexion of the trunk via abdominal wall muscles

Lateral flexion - unilateral

Internal Abdominal Oblique Muscles

Muscle is fan shaped. O: Relatively small, long top of iliac crest as far as ASIS. Extends inferiorly onto the deep surface of the inguinal ligament. (So lower fibers of IAO come from inguinal ligament) so top of iliac crest and part of inguinal ligament I: fades into aponeurosis which fades into linea alba Notice fibers run in multiple directions. also pubis and some ribs

Rectus Abdominis

O: Origin on pubis I: -Insertion on costal cartilages and xiphoid processes -4 tendinous insertions into the superficial division of the rectus sheath

Tranversus Abdominis Muscle

O: in the back, from the lateral edge of the transversalis fascia. Inferiorly, has some origins from iliac crest. Below ASIS, lower fibers that arise from something other than bone, fascia on the deep surface of internal abdominal oblique/inguinal ligament. Has horizontal fibers that insert into the midline. Also inserts into pubis O: 1/3 of inguinal ligament, iliac crest, posterior of lower ribs I: Turns into aponeurosis. Upper 3/4 form the back of the rectus sheath and insert on the linea alba, the lower 1/4 forms the front of the rectus sheath and attaches to the pubis

External Abdominal Oblique Muscles

O: lateral surface of thoracic cage from ribs and costal cartilages Fibers run downward and inward towards midline (same as external intercostals) Hands in gloves I: -bony pelvis, on top of the iliac crest, as far forward as the ASIS. -Some fades (abruptly) into aponeurosis, which will fade into linea alba. -Lower most fibers of aponeurosis insert into bone of pubis.

Rectus Sheath Organization Above Arcuate line (top 3/4)

On right side of the person, we see EAO, IAO, TA, from superficial -> deep. Extending to the midline of these muscles is a grey aponeurosis. EAO aponeurosis passes superficial to rectus abdominis, meets in the center at the linea alba IAO aponeurosis branches into a superficial and deep branch, wrapping around the rectus abdominis TA aponeeurosis passes deep to rectus absominis

Rectus Sheath Organization Below Arcuate line (bottom 1/4)

Only the aponeurosis of the EAO is seen All muscle layers cross superiorly to the rectus abdominis. So thick outer layer, and no back wall.

Rotation of the trunk via abdominal wall muscles

Rotation (twisting) - unilateral

Anterior abdominal wall somatic motor innervation

Same as skin sensory innervation. Provided by ventral rami: lower 5 intercostal nerves (T7-11), subcostal nerve (T12), and iliohypo- gastric/ilioinguinal nerves (L1).

Anterior abdominal wall SKIN sensory innervation

Sensory innervation of skin over the anterior abdominal wall is provided by ventral rami: lower 5 intercostal nerves (T7-11), subcostal nerve (T12), and iliohypo- gastric/ilioinguinal nerves (L1).

Scarpa's fascia

also called membranous layer of anterior abdominal wall. Fibers tightly arranged. Forms thin membrane

Lymph from skin above the umbilicus (including the back and upper limb) drains to

axillary nodes

Superior epigastric artery

branches off of internal thoracic artery. Runs on the deep surface of rectus abdominis muscle.

Inguinal ligament is made by

external oblique

transversalis fascia

lines the three overlying skeletal muscle layers. Distributed wherever you see overlying muscle. Attached to thoracic cage above, iliac crest and inguinal ligament below.

Linea alba

midline tendinous seam joining the abdominal muscles xiphoid process to pubic symphesis

Campers fascia

superficial fatty layer Where a persons subcutaneous fat will be stored. Has fat cells. Will also have cutaneous nerves Loosely oriented

Lymph from skin below the umbilicus (including the back, pelvis, perineum, and lower limb) drains to

superficial inguinal nodes.

Less obvious functions of the abdominal wall muscles are the ones that do not produce trunk movements, but are related to changes in intra-abdominal pressure:

• Stabilization of the trunk during strenuous physical effort (Valsalva's maneuver) • Forceful expiration • Coughing and sneezing • Urination and defecation • Labor and delivery

How does the superior part of the rectus abdominis compare to the inferior part?

About 3 times as wide superiorly as inferiorly

How do the superior and inferior epigastric arteries run?

Arteries run in the rectus sheath deep to the muscle.

Describe the abdominal wall below the inguinal ligament

abdominal wall stops abruptly, we have this gap to allow neurovascular structures to pass into lower limb. So there is a weak spot under the inguinal ligament.