(10) Posterior Abdominal Viscera & Wall

contents of posterior abdominal wall

- L1-L5

- Diaphragm (posterior/inferior)

- Posterior abdominal wall muscles

- Lumbar plexus

- Kidneys, ureters, suprarenal glands

Posterior abdominal wall muscles

- Iliacus

- Psoas major/minor

- Iliopsoas (iliacus & psoas major)

- Quadratus lumborum

- Transversus abdominis

- Oblique muscles (laterally)

retroperitoneum

anatomical space behind peritoneal cavity where peritoneal structures exist. much of the space is filled with pararenal & perirenal fat to protect the kidneys.

(primary) retroperitoneal structures

-kidneys

-adrenal/suprarenal glands

-ureters

-aorta

-IVC

-anal canal

*have peritoneum on their anterior surface ONLY

Diaphragm

Muscle of ventilation that shifts pressure in the thoracic cavity. Essentially air-tight. Divides thoracic & abdominal cavities. Anchored to lumbar vertebrae by crua. Innervated by the phrenic nerve.

Hemidiaphragms

fuse at the central tendon to make the diaphragm

central tendon

fuses hemidiaphragms

crura of diaphragm

muscular sections of the diaphragm that attach it to the upper lumbar vertebrae. right & left.

right crus of diaphragm

larger crus that is attached to L1-L4 vertebrae. acts as a functional sphincter at the esophageal hiatus (not air-tight bc gas needs to come out from stomach)

left crus of diaphragm

smaller crus that is attached to L1-L3 vertebrae

muscular regions of the diaphragm

- xiphoid

- costal

- lumbar

Arcuate ligaments of the diaphragm

arches of fascia that connect the diaphragm to lumbar vertebrae. median, medial, lateral.

median arcuate ligament

connects right & left crura across the midline. Anterior to the aorta so it doesn't get constricted by muscle

medial arcuate ligament

fibrous band of tissue on the diaphragm that arches over the psoas major muscle

lateral arcuate ligament

fibrous band of tissue on the diaphragm that arches over quadratus lumborum

Aperatures/Hiatuses of the diaphragm

caval opening, esophageal hiatus, aortic hiatus

caval opening

opening in the diaphragm at the T8 level that allows the inferior vena cava & right phrenic nerve to pass through

esophageal hiatus

opening in the diaphragm at the T10 level where the esophagus and anterior & posterior vagus trunks pass through. right crus acts as a sphincter here.

aortic hiatus

opening in diaphragm at the T12 level posterior to the median arcuate ligament where the aorta, azygos vein, and thoracic duct pass through

pericardiophrenic artery

branch of internal thoracic artery that supplies blood to the superior surface of the diaphragm

superior phrenic artery

branch of the thoracic aorta that supplies blood to the superior surface of the diaphragm

inferior phrenic arteries

Branches of the abdominal aorta or celiac trunk that supply blood to the inferior surface of the diaphragm

location of the kidneys

-T12-L3

-5cm from median plane

-superior poles at ribs 11 & 12

-Right kidney is 5cm lower than left (due to size of liver), with its inferior pole of one finger width from iliac crest

structures anterior to the right kidney

Suprarenal gland

Liver

Right colic Flexure

2nd part of duodenum

structures anterior to left kidney

Suprarenal gland

Stomach

Spleen

Distal part of transverse colon

Tail of pancreas

structures posterior to the kidneys

posterior abdominal wall muscles

fibrous renal capsule

protective membrane that directly encloses the kidneys

renal fascia

outer layer of dense fibrous connective tissue that anchors the kidney

perirenal fat

fatty tissue surrounding the fibrous renal capsule deep to the renal fascia

pararenal fat

fatty tissue external to renal fascia

hilum of kidney

opening for renal artery, renal vein, & ureter. renal veins run anterior to renal arteries.

renal artery

Supplies blood to the kidneys.

renal vein

Drains blood from the kidneys.

renal cortex

outer portion of the kidney deep to renal capsule

renal medulla

Inner portion of the kidney consisting of renal pyramids & renal columns

renal pyramids

triangular-shaped areas in the medulla of the kidney that drain little bits of urine to minor calyces

renal columns

extensions of renal cortex in between renal pyramids

minor calyces

small tubes that collect urine from renal pyramids & merge to form major calyces

major calyces

collect urine from minor calyces & empty it into renal pelvis

renal pelvis

funnel-shaped reservoir that collects urine from the kidney and passes it to the ureter

ureter

tube that carries urine from the kidney to the urinary bladder

arcuate arteries

small arteries found at the base of the renal pyramids between the cortex & medulla that bring waste-filled blood into the glomerulus

Nephron

Functional unit of the kidney within renal pyramids, consisting of a glomerulus, renal tubule, and collecting tubule.

suprarenal glands (adrenal glands)

glands attached to the superior pole of each kidney. surrounded by a capsule.

cortex of adrenal gland

outer layer derived from mesoderm that releases hormones in response to long-term stress (Androgens and corticosteroids)

medulla of adrenal gland

inner layer derived from neural crest cells, which form a specialized sympathetic ganglion that releases hormones in response to short-term stress (Epinephrine and norepinephrine)

Unpaired visceral branches of abdominal aorta

celiac trunk, superior mesenteric artery, inferior mesenteric artery. supply GI tract.

Paired visceral branches of abdominal aorta

suprarenal arteries, renal arteries, and gonadal arteries. supply urogenital & endocrine organs.

paired parietal branches of the abdominal aorta

Inferior phrenic arteries, subcostal arteries, lumbar arteries. supply diaphragm & body wall.

right renal artery

Branch of aorta that supplies blood to the right kidney. Crosses posterior to IVC.

left renal artery

Branch of aorta that supplies blood to the left kidney.

right renal vein

Drains blood from the right kidney into the IVC

left renal vein

Drains blood from the left kidney into the IVC. Crosses anterior to aorta & posterior to SMA.

Superior suprarenal arteries

left & right branches of the inferior phrenic arteries that supply the adrenal glands

middle suprarenal arteries

right and left branches of the aorta that supply the adrenal glands

inferior suprarenal arteries

right & left branches of the renal arteries that supply the adrenal glands

right suprarenal vein

drains blood from the right adrenal gland into the inferior vena cava

left suprarenal vein

drains blood from the left adrenal gland into the left renal vein

right and left gonadal arteries

left & right branches of the aorta that supply the gonads

right gonadal vein

drains blood from the right ovary or testis into the inferior vena cava

left gonadal vein

drains blood from the left ovary or testis into the left renal vein

lumbar arteries

left & right branches that supply lumbar vertebrae, spinal cord, & posterior abdominal wall. 1st-4th branch off aorta, 5th branches off median sacral artery.

median sacral artery

branch of aorta that supplies the sacrum and coccyx. NOT paired.

1st-4th lumbar veins

drain blood to ascending lumbar veins

ascending lumbar veins

Drain blood from the posterior abdominal wall into azygos & hemiazygos veins

median sacral vein

Drains blood from the sacral region into the left common iliac vein

why there are less veins draining into the IVC than there are arteries from the aorta

1. 80% of blood passing through the celiac trunk, SMA, & IMA returns to portal system

2. 1-4th lumbar veins return primarily to ascending lumbar veins then to azygos/hemiazygos veins

3. On the left side, some veins first dump into renal vein

4. Median sacral vein goes to left common iliac vein

ureterovesical valves

prevent urine in the ureters from flowing back towards the kidneys

path of ureters

Cross UNDER gonadal vessels, then OVER the iliac vessels, then UNDER the uterine artery or artery to vas deferens

Differences in sympathetic innervation of the adrenal medulla vs the rest of the abdominal organs

- provided by LOWER THORACIC SPINAL CORD LEVELS (T5-T11)

- Preganglionic fibers in thoracic splanchic nerves pass through subdiaphragmatic ganglia/plexuses WITHOUT SYNAPSING

- Preganglionic fibers SYNAPSE DIRECTLY ON CELLS of the adrenal medulla, stimulating the release of epinephrine &

norepinephrine

abdominal plexus

a mix of sympathetic & parasympathetic fibers, which travel along the arteries

there are no parasympathetics to the

kidney & suprarenal glands

T12-L4 ventral rami

enter psoas major immediately after leaving their intervertebral foramina

lumbar plexus

L1 to L4. Supplies a mix of motor and sensory innervation to abdominal wall, anterior thigh, and genitalia.

subcostal nerve

T12 ventral ramus that enters abdomen beneath lateral arcuate ligament. Has anterior & lateral cutaneous branches.

-Motor: anterolateral abdominal wall muscles + rectus abdominis

-Sensory: hypaxial part of T12 Dermatome

iliohypogastric nerve

Superior of two branches of L1 ventral ramus that does not pierce/innervate rectus abdominis or enter inguinal ring. Has anterior & lateral cutaneous branches.

-Motor: anterolateral abdominal wall muscles

-Sensory: skin over its path, ending superior to pubic symphysis, over iliac crest

ilioinguinal nerve

Inferior of two branches of L1 ventral ramus. Pierces transversus abdominis & internal abdominal oblique & then passes through superficial inguinal ring & travels with (NOT inside) spermatic cord. Has an anterior scrotal branch.

-Motor: anterolateral abdominal wall muscles

Sensory: upper inner thigh, mons pubis & anterior part of labia majora in females, and root of penis & anterior skin of scrotum in males

genitofemoral nerve

L1-L2 ventral rami that branches into a genital branch & femoral branches.

-Motor: genital branch enters deep inguinal ring (& therefore enters spermatic cord) to innervate cremaster muscle in

males

-Sensory: femoral branch passes deep to inguinal ligament to supply skin and superficial fascia of anterior thigh. Sometimes (33%) the genital branch takes over sensory territory of ilioinguinal nerve.

Lateral Femoral Cutaneous Nerve

L2-L3 ventral rami that runs anterior to psoas & crosses illiacus. Passes under inguinal ligament

-Sensory: lateral thigh

femoral nerve

L2-L4 ventral rami that runs deep to psoas. Passes under inguinal ligament.

Sensory: Inner Leg

Motor: muscles of anterior thigh

obturator nerve

L2-L4 ventral rami that runs inferior to the pubic ramus. Tight & round.

Sensory: portion of inner thigh

Motor: Muscles of medial thigh

lumbosacral trunk

L4-L5 ventral rami that joins the sacral plexus & contribute to the sciatic nerve, which innervates muscles of posterior thigh, leg, & foot. Most medial & deep portion of the lumbar plexus. Under psoas.

Illiacus

posterior abdominal wall muscle that flexes the hip & stabilizes the hip joint.

Origin: iliac fossa

Insertion: lesser trochanter of femur

Innervation: Femoral nerve (L2-L4)

psoas major

posterior abdominal wall muscle that flexes the hip & trunk, and laterally flexes the vertebral column.

Origin: T12-L4, associated intervertebral discs

Insertion: lesser trochanter of femur

Innervation: Lumbar Plexus (L1-L4)

psoas minor

posterior abdominal wall muscle present in only half the population that (weakly) flexes the trunk.

Origin: T12-L1 and associated intervertebral discs

Insertion: iliopubic eminence

Innervation: L1-L2

Quadratus Lumborum

posterior abdominal wall muscle that extends and laterally flexes the vertebral column

Origin: 12th rib, L1-L4 vertebrae (costal processes)

Insertion: iliac crest, iliolumbar ligament

Nerve: T12 (subcostal nerve), L1-L4

kidney stones

Mostly insoluble calcium salts that can get stuck where the renal pelvis narrows, in the ureter at the sacroiliac joint where ureters cross into pelvis, and where the ureters enter the bladder

polycystic kidney

An autosomal dominant condition in which the kidney contains many cysts and is enlarged. Can lead to kidney failure, so patients may need dialysis or a kidney transplant.

kidney transplant

replacement of a diseased kidney with one that is supplied by a donor. Donor kidney is usually placed on the common iliac region, as it is easier for the surgeon to get to.