Anatomy - Abdomen Lecture 1

what is the purpose of the abdominal walls

contract to increase intra-abdominal pressure and distend to accommodate expansion from viscera

what are the membranes of the abdominal walls

serous membrane and the double layers reflection

what is the purpose of serous membrane

membrane on posterial wall that reflects onto abdominal viscera; forms a bursal sac/lined potential space (peritoneal cavity); just enough fluid to lubricate linings

what is the purpose of double layered reflection

provide passage for blood vessels, lymphatics and nerves

what is the purpose of abdominal cavity

protects superior abdominal organs; has no floor (continuous with pelvic cavity)

what is the purpose of the greater pelvis

supports and protects lower abdominals

what is the abdominal cavity

between thoracic diaphragm and pelvic diaphragm; extends superiorly into thoracic cage to fourth intercostal space

what does the t7-t9 dermatome supply

supplies skin of epigastrium superior to umbilicus

what is the t10 dermatome

high-yield; level of umbilicus; classic landmark for appendicitis referred pain

what does the L1 segment supply

supplies inguinal fold, anterior scrotum/labium via ilioinguinal and iliohypogastric nerves

clinical vignette: 21 male presents with periumbilical dull, aching visceral pain shifting to sharp RLQ pain 12 hours laters

initial visceral sensory afferents travel with sympathetics to t10 spinal cord level; somatic parietal peritoneal irritation localized sharply to McBurney's point

what is the anterolateral abdominal bound by superiorly

cartilage of 7th-10th ribs and xiphoid process

what is the anterolateral abdominal bound by inferiorly

inguinal ligament and superior margins of anterolateral aspects of pelvic girdle

what are the layers of the anterolateral abdominal wall

skin, subcutaneous tissue (superficial fascia); fat, muscles, and aponeuroses; deep fascia, extraperitoneal fat, parietal peritoneum

what are the musculotendinous layers

three layers; fibers of each layer run in different direction (similar to thorax)

what is the fascia of anterolateral abdominal wall

subcutaneous tissue -> variable and is a major site of fat storage

what are the two layers of the deep subcutaneous tissue in the fascia of anterolateral abdominal wall

superficial fatty layer (Camper fascia) and deep membranous layer (Scarpa fascia)

what is the investing fascia of anterolateral abdominal wall

superifical, intermediate, and deep layers; cover external aspects of the three muscle layers of anterolateral abdominal wall and their aponeuroses; thin and not easily separated

what is endoabdominal fascia

transversalis fascia; internal aspect of abdominal wall; continuous and named according to muscle or aponeurosis it is covering

what is the extraperitoneal fat

separates parietal peritoneum and transversalis fascia

what is the order of the abdominal wall

skin -> camper fascia -> scarpa fascia -> superficial investing fascia -> external oblique -> intermediate investing fascia -> internal oblique -> deep investing fascia -> transversus abdominis -> extraperitoneal fat -> parietal peritoneum

what is the importance of scarpa fascia and surgery

closing lower abdominal skin incisions includes closure of this layer

where fluid may accumulate and spread if surgery is done wrong on the abdominal wall

potential space between scarpia fascia and deep fascia covering rectus abdominis and external oblique muscles (cannot spread inferiorly into thigh due to fascia lata)

what is the important of endoabdominal fascia and surgery

potential space/fat-filled space provides a plane that can be opened —→ surgeron can approach structures in this area without entering membraneous peritoneal sac containing abdominal viscera

what is the benefit of laproscopic surgery

limited risk of contamination; small incision and camera equipped tube to diagnose and treat conditions inside abdomen and pelvis

what are the nerves of abdomen distribution

peripheral nerve distribution is virtually identical to the dermatome map of anterolateral wall

what are the exceptions of the peripheral nerve distribution

anterior rami of spinal nerves (t7-t11) do not participate in plexus formation; l1 bifurcates into two peripheral nerves

what are the nerves of the anterolateral abdominal wall supplied by

thoracoabdominal nerves (t7-t11); lateral thoracic cutaneous branches; subcostal nerve; iliohypogastric and ilioinguinal nerves

why are the nerves injury risk?

susceptible to injury from trauma or surgery; causes weakness of muscles and may predispose to inguinal hernia; loss of sensation

what are the paraumbilical veins

small tributaries of portal vein; parallel obliterated umbilical vein (round ligament of the liver)

where do the intricate subcutaneous venous plexus drain to

drains superiorly to internal throacic vein; drains laterally to medial and lateral throacic vein; drains inferiorly to epigastric veins

what is the thoracoepigastric vein

exist or develops between superficial epigastric vein and lateral thoracic vein

what are the four primary blood vessels (artery and veins)

superior epigastric vessel and musculophrenic arteries; inferior epigastric and deep circumflex iliac vessels; superficial circumflex iliac and superficial epigastric vessels; posterior intercostal vessels

what are the superficial lymphatic vessels

accompany subcutaneous veins; superior to transumbilical plane (drain primarily to axillary lymph nodes/few drain to parasternal lymph nodes); inferior to transumbilical plane

what are the deep lymphatic vessels

accompany deep veins of abdominal wall; drain to external iliac, common iliac, and right and left lumbar lymph nodes

what are the functions and actions of the anterolateral abdominals muscles

strong, expandable support, protect the abdominal viscera from injury, compress the abdominal contents to maintain or increase intra-abdominal pressure and oppose diaphragm, contraction of diaphragm anterolateral muscles relax to make room for organs, elevates the relax diaphragm to expel air during respiration, provides force for defecation, vomiting, move the trunk and maintain posture, powerful flexion of thoracic and lumbar regions

what is the external oblique

hands-in-pocket fiber orientation; inferior edge forms inguinal ligament

what is the internal oblique

fans out perpendicularly; forms conjoint tendon with transerse abdominis

what is the transverse abdominis

deepest horizontal compression layer; elevates intra-abdominal pressure

what is the superior 2/3 of rectus sheath

internal oblique aponeurosis splits around rectus abdominis; anterior and posterior walls present

what is inferior 1/3of rectus sheath

arcuate line; all three aponeuroses pass anterior to rectus; posterior sheath deficient (transversalis fascia only_

what is the neurovascular supply of rectus sheath

superior and inferior epigastric vessels anastomose within posterior rectus

what is linea alba

runs vertically the entire length of anterior abdominal wall; seperates bilateral rectus sheaths; transmits small vessels and nerves to the skin

what is umbilical ring

middle of linea alba, underlying umbilicus; defect in linea alba through which fetal umbilical vessel passed to and from umbilical cord

where do all layers of the abdominal wall fuse at

umbilicus

for abdominal surgical incisions, what should you do

follow cleavage lines which leads to adequate exposure and best cosmetic effect when closing -> must consider direction of muscle fibers, location of aponeuroses and nerves

what should you never transect during abdominal surgery

muscles -> causes irreversible necrosis; better to split them in direction of the fibers (only exception is rectus abdominis)

when are longitudinal incision used

primarily centrally in abdomen; muscles and vasculature are longitudinal

what are the longitudinal incisions called

medial or midline incisions; paramedian incision

when should oblique and transverse incisions be used

most common on one side of midline in more peripheral abdomen -> most often used in appendectomy

what are oblique and transverse incisions called

gridion (muscle splitting) and McBurney incisions; suprapublic incision

what is the incisional hernia

protrusion of omentum or an organ through a surgical incision -> muscular or aponeurotic layers do not heal properly -> factors: age, obesity, infection

what are the positives of endoscopic surgery

decreased risk for nerve injury, incisional hernia, and decreased healing time

when an organ is inflammed or injured, the abdomen produces what

involuntary spams of the muscle: intense guarding -> board-like reflexive muscular rigidity that cannot be willfully suppressed; protecting viscera from pressire

what are protuberances of the abdomen

increase amount of air in GI tract, muscle gaining strength, large liver

what are the six common causes of protrusion

flood, fluid, fat, feces, flatus, fetus

what are umbilical hernias

common in newborns; wake anterior abdominal wall in umbilical ring; result from intra-abdominal pressure

what is an epigastric hernia

hernia is epigastric region through linea alba occurs in midline

what is a spigelian hernia

occur along semilunar lines

what are the five umbilical folds

1 medial fold, 2 medial folds, 2 lateral folds

what is the 1 medial fold

midline apex of bladder to umbilicus; covers remnant urachus

what are the 2 medial folds

covers obliterated umbilical arteries (fetal placental return)

what are the 2 lateral folds

covers inferior epigastric vessels (active bleeding risk if transected)

what are the peritoneal fossae

supravesical fossa, medial injuinal fossa lateral inguinal fossa

what is the supravesical fossa

between median and medial umbilical folds

what is the medial inguinal fossa

inguinal (Hesselbach) triangle; site of direct inguinal hernias

what is the lateral inguinal fossa

lateral to lateral fold; contains deep ring (site of indirect hernias)

where is the inguinal canal

canal in between the deep inguinal ring and the superficial inguinal ring - true canal for blood vessel and spermatic cord and point of weakness at the rings causes hernias

what are the border of the inguinal canal

MALT: roof (M); anterior (A); floor (L); posterior (T)

what does roof (M) in MALT for the inguinal canal mean

arching muscular fibers of internal oblique and transverse abdominis

what does anterior (A) in MALT for the inguinal canal mean

aponeurosis of external oblique (plus internal oblique laterall)

what does floor (L) in MALT for the inguinal canal mean

inguinal ligament and lacunar ligament medially; iliopublic tract

what does posterior (T) in MALT for the inguinal canal mean

transversalis fascia reinforced medially by conjoint tendon

what is the deep ring

evagination in transversalis fascia lateral to inferior epigastric vessels

what is the superficial ring

triangular opening in external oblique aponeurosis superolateral to public tubercle

what are the canal contents

spermatic cord (males) / round ligament (females) plus ilioinguinal nerve

what is the dynamic defense for the inguinal canal

increased intra-abdominal pressure (coughing) depresses canal roof against floor

what is the Hesselbach's triangle for the inguinal canal

boundaries: medial (rectus margin) lateral (inferior epigastric vessels) inferior (inguinal ligament)

what is the finger occlusion test

occlude deep ring with index finger; ask patient to cough -> hernia controlled = indirect / hernia continues to bulge medial to finger = direct

what is a indirect inguinal hernia

persistent processus vaginalis; enters deep inguinal ring LATERAL to epigastrics; transverses entire length of canal inside spermatic cord layers into scrotum; most common hernia in both male and females espeically neonates/young adults

what is a direct inguinal hernia

protrudes MEDIAL to inferior epigastric vessels through Hesselbach's triangle; pushes directly forward through attenuated transversalis fascia; rarely descends into scrotum; elderly men with chronic increased abdominal pressure