Y2 Prep Unit 1: NAVL of Abdomen and Pelvis

anterior abdominal wall innervation

• intercostal nerves

• subcostal nerve

• iliohypogastric nerve

• ilioinguinal nerve

intercostal nerves

spinal level: T1-T11

region supplied: anterior abdominal wall

the lumbar plexus

formed by: anterior rami of spinal nerves L1-L4 (and T12)

where: embedded in the posterior substance of the psoas major muscle

subcostal nerve

spinal level: T12

region supplied: below 12th rib

iliohypogastric nerve

spinal level: L1 (with branch from subcostal nerve at T12)

region supplied:

• motor: internal oblique, transversus abdominis

• sensory: lower anterior abdominal wall, gluteal skin, root of the penis, scrotum, labia majora

ilioinguinal nerve

spinal level: L1

region supplied:

• motor: internal oblique, transversus abdominis

• sensory: lower anterior abdominal wall, gluteal skin, root of the penis, scrotum, labia majora

genitofemoral nerve

spinal level: L1-L2

region supplied:

• genital branch: motor to cremaster muscle (tests cremasteric reflex)

• femoral branch: sensory to skin over the femoral triangle

lateral femoral cutaneous nerve

spinal level: L2-L3

region supplied: sensory to skin on outer thigh

• sensory:

what is meralgia paresthetica

compression of lateral cutaneous nerve

exiting the pelvis by passing under the inguinal ligament - near the ASIS

• because of this, can be easily compressed due to obesity, tight closes, or internal trauma (surgery)

• = entrapment

• = burning pain, tingling, numbness along lateral thigh

femoral nerve

spinal level: L2-L4

region supplied:

• motor: iliacus, quadriceps group, sartorius, and pectineus

• sensory: medial leg and foot

obturator nerve

spinal level: L2-L4

region supplied:

• motor: adductors (adductor longus, adductor brevis, gracilis), obturator externus

• sensory (minimal): medial thigh

muscular branches

spinal level: T12-L4

region supplied:

• motor: psoas major, psoas minor, quadratus lumborum

the sacral plexus

formed by: ventral rami of spinal nerves L4-S4

where: on the posterior pelvic wall, anterior on the piriformis muscle

innervates: posterior thigh, entire leg and foot, and parts of the gluteal region and perineum

superior gluteal nerve

spinal level: L4-S1

regions supplied:

• motor: gluteus medius, gluteus minimus, TFL (abductors)

inferior gluteal nerve

spinal level: L5-S2

regions supplied:

• motor: gluteus maximus

posterior femoral cutaneous nerve

spinal level: S1-S3

regions supplied:

• sensory: skin of gluteal, popliteal and posterior thigh regions

pudendal nerve

spinal level: S2-S4

regions supplied:

• motor: controls voluntary sphincters for urination and defecation

pathway: exits greater sciatic foramen, passes around ischial tuberosity, enters lesser sciatic foramen via pudendal canal

sciatic nerve

spinal level: L4-S3/S4

branches:

• common fibular nerve

• tibial nerve

sciatic nerve pathway

1. originates from sacral plexus

2. passes inferior to piriformis muscle (usually)

3. exits through greater sciatic foramen

4. bifurcates into tibial and common fibular nerves

5. innervates hamstring muscles in the posterior thigh

common fibular nerve (superficial and deep)

forms posterior (lateral) portion of sacral plexus

spinal levels: L4-S2

branches:

• superficial

• deep

regions supplied:

• superficial: motor - lateral leg muscles, sensory - dorsum of foot skin

• deep: motor - anterior leg muscles, dorsal foot muscles, sensory - web between great and second toe

tibial nerve

forms anterior (medial) portion of sacral plexus

spinal levels: L4-S3

regions supplied:

• motor: semimembranosus, semitendinosus, biceps femoris long head, posterior leg compartments, plantar foot muscles

• sensory: plantar foot surface, dorsal distal toes

lumbar and pelvic sympathetic chain

• continuous with thoracic

• descends along medial margin of psoas major

• right trunk = behind IVC

• left trunk = left side of abdominal aorta

• each lumbar trunk has 4 ganglia

• descend along ala of sacrum (deep to iliac vessels)

• unite in front of the coccyx = ganglion impar

gray rami communicantes

fiber type: sympathetic postganglionic

to: lumbar spinal nerves

white rami communicantes

fiber type: sympathetic preganglionic

from: T1-L2 only

lumbar splanchnic nerves

fiber type: sympathetic nerves

to: join abdominal autonomic plexuses

prevertebral plexuses

networks of autonomic nerves and ganglia located anterior to the abdominal aorta and its major branches, that receive both sympathetic and parasympathetic fibers

• celiac plexus

• superior mesenteric plexus

• inferior mesenteric plexus

• superior hypogastric plexus

• inferior hypogastric plexus

celiac plexus

spinal level: T12-L1

splanchnic input: greater splanchnic nerve (T5-T9), lesser splanchnic nerve (T9-T10)

region supplied:

• foregut

  • distal esophagus

  • stomach

  • liver

  • gallbladder

  • pancreas

  • spleen

  • proximal duodenum

  • adrenal glands

  • kidneys

superior mesenteric plexus

spinal level: L1

splanchnic input: / postganglionic from celiac ganglia, and preganglionic from vagus

region supplied:

• midgut

  • colon

  • duodenum

  • jejunum

  • ileum

inferior mesenteric plexus

spinal level: L3

splanchnic input: lumbar (sympathetic) splanchnic nerves (L1-L2) and pelvic (parasympathetic) splanchnic (S2-S4)

region supplied:

• hindgut

  • transverse colon

  • descending colon

  • sigmoid colon

  • rectum

  • superior anal canal

superior hypogastric plexus

spinal level: L5-S1

splanchnic input: aortic plexus and lumbar splanchnic nerves

branches:

• right and left hypogastric nerves (contribute to inferior hypogastric plexus)

region supplied:

• bladder

• rectum

• sexual organs

• urethral sphincters

*mostly sympathetic

inferior hypogastric plexus

spinal level: S2-S4

splanchnic input: hypogastric nerves (from superior hypo, sympa) joining with pelvic splanchnic nerves (S2-S4, parasymp)

regions supplied:

• bladder

• rectum

• sexual organs

• urethral sphincters

autonomic function in the pelvis - sympathetic

spinal level: T10-L2

function:

• innervate blood vessels

• contract internal urethral sphincter (males)

• contract internal anal sphincter

• contract smooth muscle in reproductive tract

• stimulate accessory reproductive glands

• terminal branches form cavernous nerves in males - innervating the erectile tissues of penis

autonomic function in the pelvis - parasympathetic

spinal level: S2-S4

function:

• vasodilation

• stimulate bladder contraction

• stimulate erection

• modulate enteric nervous system activity in colon distal to left colic flexure

pelvic splanchnic nerves carry parasympathetic fibers via ______ plexus

inferior hypogastric

dermatome

an area of skin supplied by sensory nerve fibers from a single spinal nerve root

landmark for T10 dermatome level

umbilicus

landmark for T4 dermatome level

nipple line

landmark for T7 dermatome level

xiphisternum

landmark for T12 dermatome level

costal margin

landmark for L1 dermatome level

inguinal ligament

landmark for L4 dermatome level

medial knee

landmark for S3-S5 dermatome level

perineum/saddle area

branches of the abdominal aorta

inferior phrenic (P)

celiac trunk (U)

middle suprarenal (P)

superior mesenteric (U)

renal (P)

gonadal (P)

lumbar (Post P)

inferior mesenteric (U)

median sacral (Post U)

celiac trunk

level: T1

branches and their supply:

• splenic - spleen

• common hepatic - kidney

• left gastric - stomach

supplies (overall): foregut

superior mesenteric artery

level: L1

branches:

• intestinal

• ileocolic

• right colic

• middle colic

supplies: midgut (jejunum, ileum, cecum, appendix, ascending and transverse colon)

inferior mesenteric artery

level: L3

branches:

• left colic

• sigmoidal

• superior rectal

supplies: hindgut (descending and sigmoid colon, superior rectum)

mesenteric ischemia

reduced bloodflow to intestines, caused by occlusion, narrowing, disease, etc., which can cause bowel injury or tissue death

arcade of riolan

an anastomose connecting the superior mesenteric artery and inferior mesenteric artery

• helps maintain bloodflow if one is blocked

marginal artery of drummond

a continuous artery channel running along the inner border of the colon

• connects the SMA and IMA

watershed area

an area (organ/tissue/structure) with limited overlapping/collateral arterial supply, making it more susceptible to ischemia should circulation decrease

renal arteries level and difference between R and L

level: L1-L2 (below the SMA)

right: usually longer than the left because it passes posterior to the IVC

common iliac arteries

level: L4

branches:

• internal common iliac

• external common iliac

supplies: to lower limbs and pelvis

internal common iliac

level: L5-S1

branches:

• anterior

  • Obturator

  • Middle rectal

  • Superior vesical (umbilical)

  • Uterine

  • Inferior vesical / vaginal

  • Inferior gluteal

  • Pudendal (internal)

• posterior

  • iliolumbar

  • lateral sacral

  • superior gluteal

supplies:

• pelvic organs + rectum

• gluteal region

• hip joint

• medial thigh (adductors)

external common iliac

level: L5-S1

branches:

• deep circumflex

• inferior epigastric

supplies: blood to lower limb

*continues as femoral artery below the inguinal ligament

inferior epigastric artery path and relations

origin: external iliac

path: ascends posterior to the rectus abdominis muscle within the abdominal wall

relation: the anastomosis between this and the superior epigastric artery forms a circulation pathway supplying the anterior abdominal wall

*the superior epigastric artery is a terminal branch of the internal thoracic artery

• and it descends posterior to the rectus abdominis to supply the anterior abdominal wall

portal vein

branches:

• superior mesenteric

• splenic

  • inferior mesenteric

• left gastric

• right gastric

• cystic (gallbladder)

• paraumbilical

drainage:

• drains digestive organs via hepatic veins and brings it to liver for detoxification

venous blood from intraperitoneal digestive organs primarily drain into the ____ vein, which then transports blood to the _____

heptatic portal vein / liver

the extraperionteal body wall above the umbilicus drains the to the _____ via veins like the _____ and _____

systemic pathway / lateral thoracic / axillary veins

below the umbilicus, systemic venous drainage occurs through the _____ via veins such as the _____ and _____ eventually reaching the _____

systemic pathway / superficial inguinal / great saphenous vein / heart

portal vein

valveless drainage system that drains abdominal organs and carries nutrient-rich blood to the liver for detoxification, prior to entering systemic circulation

systemic circulation

valved drainage system draining the body wall and tissues, bringing deoxygenated blood back to the heart to become oxygenated via systemic veinsp

portal hypertension

abnormal high blood-pressure within the hepatic portal vein / venous system usually due to reduced or blocked bloodflow to the liver

esophageal varices

collateral pathway - fragile, dilated veins in lower esophagus caused by portal HT and portosystemic shunting, can be life-threatening if ruptured

hemorrhoids

swollen venous “cushions” in anal canal resulting from increased pressure in renal venous plexus associated with PHT

caput medusae

dilated superficial veins stemming from the umbilicus, caused by PHT

portosystemic anastomoses

connections between portal venous system and system veins that allow blood to bypass the liver when portal pressure is elevated

inferior vena cava

level: L5

branches:

• hepatic (R, M, L)

• right suprarenal

• renal

  • left suprarenal

  • left gonadal

• right gonadal

• lumbar (L1-L5)

• common iliac (R, L)

drains:

*formed by the union of common iliac veins - left common iliac is longer and more oblique due to the IVC situated on right side

cisterna chyli

lymphatic duct

level: T12-L1

drains:

• abdomen

• lumbars

• intestinal trunks

thoracic duct

main lymphatic channel

begins at cisterna chyli and empties into left venous angle

venous angle

angle formed by union of subclavian vein and internal jugular vein at the root of the neck

lateral aortic nodes

drain organs like kidneys, gonads, and body wall

pre-aortic nodes

drain unpaired viscera

includes nodes:

• celiac

• superior and inferior mesenterics

common and internal iliac nodes

drain pelvic organs and lower limbs

batson’s venous plexus

plexus that connects pelvic veins with vertebral venous plexuses and intracranial dural sinuses
*valveless nature of batson’s plexus allows cancer from breast, bladder, or prostate to metastasize to spine and brain without passing through lungs