The Abdomen

rectus abdominis muscle (ventral)

Tendinous intersections

• Interrupts muscle belly to create “abs”— there are 10 sections created

Linea alba

• THICK dense irregular CT

Rectus sheath

• CT envelope around the abs

Lumbar-vertebral flexion (bending forward)

External oblique muscle - superficial lamina

part 1 of 2

Aponeurosis

• flat, sheet-like tendon that covers the abs

Inguinal ligament

• bone-to-bone on os coxae

External oblique muscle - deep lamina

part 2 of 2

Doesn’t cover ribs; is in the same plane as ribs, under them

Function:

1. Bilateral: flex lumbar vertebral column

2. Unilateral: flexion & contralateral rotation (to opposite sides)

Internal oblique muscle

The aponeurosis splits— half in front of the abs, half behind

function:

1. flexion of lumbar-vertebral column

2. flexion & ipsilateral rotation

contralateral

to opposite sides

ipsilateral

to the same side

Transverse abdominis muscle

aponeurosis is posterior to abs

function:

• giant abdominal sphincter

• core stabilization

Quadratus lumborum muscle

function:

1. Unilateral: lateral flexion

2. Bilateral: extends lumbar-vertebral column (holds posture)

Psoas major muscle

hip flexion

Psoas minor muscle

weak vertebral flexor

• only in 40% to 60% of people

dynamic retaining wall

the muscles of the abdomen work together to fight gravity and keep a lot of vital organs in place!

rectus sheath

above the belly button, the rectus sheath is as programmed.

below the belly button, all parts of the rectus sheath switch to in front of the abs to create a stronger retaining wall where there is the most pressure

inferior phrenic arteries

lumbar arteries

where would you find the lumbar arteries?

in between the middle and internal layers

internal thoracic arteries

—> turn into superior epigastric arteries

superior epigastric arteries

• down to the belly button

inferior epigastric arteries

• up to the belly button

• branches from external iliac artery

lumbar veins

ascending lumbar veins

venous collateral flow

blood can travel any-which way it wants back to the heart, typically the path of least resistance but can take detours

internal thoracic veins come together from superior epigastric veins

superior epigastric veins

anastomose

to join together

bifurcate

to branch or split

inferior epigastric veins

inferior phrenic veins

thoracic spinal nerves

lumbar spinal nerves

urogenital ridges

• develops to be part of the urinary and genital system

Peritoneal organs…

are organs that are in front of the peritoneum

• SALT C JISS? (something like that)

Retroperitoneal organs…

are organs towards the posterior cavity wall and are behind the mesenteric layer of the peritoneum

• Primary retroperitoneal: has been retroperitoneal since development (not gut tube)

• Secondarily retroperitoneal: started peritoneal and migrated to become retro (gut tube)

what kind of organs are visible?

peritoneal

what kind of organs are visible?

retroperitoneal

List peritoneal organs:

stomach, liver, spleen, ileum, jejunum, cecum, appendix, transverse colon, sigmoid colon

List retroperitoneal organs:

pancreas, duodenum, ascending colon, descending colon, rectum

tip for remembering large intestine (retro)peritoneal

the large intestine sews in and out:

• when vertical: retroperitoneal

• when horizontal: peritoneal

parietal peritoneum

visceral peritoneum

mesentery

greater omentum:

• attaches from the greater curvature of the stomach, covers abdominal organs, and attaches to the transverse colon

omentum

runs visceral to visceral peritoneum (organs to organ)

lesser omentum

• runs from the lesser curvature of the stomach to the liver

This image represents the arteries that branch off of the aorta; cranial end on the left, caudal on the right. F = foregut, M = midgut, H = hindgut

• The celiac trunk supplies the foregut, from the esophagus to the duodenum

• The superior mesenteric artery supplies the midgut, from the jejunum to the transverse colon

• The inferior mesenteric artery supplies the hindgut, from the descending colon to the rectum

ADoral arteries branch cranially

ABoral arteries branch caudally

what is this showing?

collateral flow between adoral and aboral arteries

celiac trunk —> foregut

superior mesenteric artery —> midgut

inferior mesenteric artery —> hindgut

renal arteries

gonadal arteries (up high because gonads start up here and drop with development)

celiac trunk

left gastric artery

esophageal artery (ADoral)

left gastric artery (ABoral)

splenic artery

short gastric artery (ADoral)

left gastro-omental artery (ABoral)

hepatic artery

right gastric artery (ADoral)

gastro-duodenal artery (ABoral)

right gastro-omental artery (ADoral)

pancreaticoduodenal artery (ABoral)

hepatic veins: drain the liver

renal veins

gonadal veins

**do NOT match the arteries

• right —> IVC

• left —> left renal vein

hepatic portal system

1. first capillary beds are all in the abdominal viscera

2. second is the liver

hepatic portal vein

• all roads lead to here

**not a hepatic vein— is part of the portal system, not drainage

left gastric vein

• left side of lesser curvature of stomach

right gastric vein

• right side of lesser curvature of stomach

splenic vein

• from the spleen

short gastric vein

• off the fundus of the stomach

left gastro-omental vein

inferior mesenteric vein

• from hindgut

superior mesenteric vein

• from midgut

right gastro-omental vein

Hepatic sinusoids

the capillary system inside of the liver

hepatic veins

sympathetic splanchnic nerves…

go to smooth muscle in blood vessels of organs

Parasympathetic nerves…

go to smooth muscle in the wall of organs via either:

1. Vagus nerve (innervates the foregut & midgut)

2. Pelvic splanchnic nerves (innervate the pelvis & hindgut)