embryology of the abdomen Flashcards
what does the diaphragm develop from
the septum transversum in the neck close to the thoracic inlet also contributed to from: pleuroperitoneal membranes dorsal mesentary of the oesophagus ingrowth from the body wall
where do diaphragmatic muscles originate from
the xiphoid process
where does the left crus arise from
L1 and 2
where does the right crus originate from
L1,2 and 3
where is the median arcuate ligament found
in the midline at t12
describe the course of the right crus
fibres travel up and insert on the central tendon of the diaphragm
some cross the midline to form a loop around the oesophagus
where is the bare area of the diaphragm
posterior to the liver
is it not covered by peritoneum
what passes through the diaphragm at T8, through the central tendon
inferior vena cava
right phrenic nerve
what passes out of the diaphragm at T10 through the right crus
left gastric artery from the coeliac artery
oesophagus, ant and post vagal trunks, left gastric vein
what passes out of the diaphragm at T12 behind the median arcuate ligament
thoracic duct, azygous vein and hemiazygous vein
descending thoracic aorta
what passes through the crura
greater and lesser splanchnic nerves
what passes behind the median arcuate ligament
left and right sympathetic trunks
what is the most common type of hiatus hernia
sliding - 90% of cases
what happens in a sliding hernia
the intra abdominal part of the gastro-oesophageal junction rises above the oesophageal hiatus. This means some of the acid secreting parts of the stomach are above the diaphragm. leads to heart burn and dysphagia. may be asymptomatic
what is a rolling hernia
the fundus herniates but the gastro oesophageal junction is intact. May cause dysphagia, early satiety or inability to hold down food.
where are diarphragmatic hernias usually found
in neonates
presents with resp distress and cyanosis. Look for asymmetry on clinical examination
what is the purpose of the peritoneum
allows movement and distension of the GI tract
what is the difference in peritoneum between males and females
males- closed cavity
females- communication with the exterior through uterine tubes, the uterus and vagina
what is the consequence of female peritoneal arrangement
possible spread of infection from exterior to interior of peritoneal cavity
where is the extraperitoneal fascia
between the parietal peritoneum and the fascial lining of the abdominal wall (transversalis fascia)
it helps to support the kidneys
where is the lesser peritoneal sack
lies behind the stomach and lesser omentum. extends slightly into the greater omentum
what is the epiploic foramen (of Winslow)
allows communication between the greater and lesser sacs
what structures does the peritoneum form
omenta
mesenteries
ligaments
what is the greater omentum derived from
the dorsal mesentery
hangs from the greater curvature of the stomach and first part of the duodenum
overlies the transverse colon and small intestine
where is the lesser omentum
passes from the lesser curvature of the stomach and first part of duodenum to the inferior border of the liver
what is the hepatoduodenal ligament
the free edge of the lesser omentum containing the portal vein, hepatic artery and bile duct
what does epiploic mean
used to describe something associated with the omentum
what are mesenteries
double layered peritoneal folds that attach viscera to the posterior abdo wall
conduits for vessels, nerves and lymphatics
what are the different mesenteries
small intestine mesentery
transverse mesocolon
sigmoid mesocolon
what is the Mesentary
double layered fold of peritoneum that connects the jejunum and ileum to the posterior abdom wall
describe the course of the Mesentary
base starts left of L2 and passes obliquely downwards to the right, ending just above the sacro iliac joint,
it crosses the 3rd part of the duodenum, aorta and IVC, right gonadal vessels and right ureter
it contains branches of SMA and SMV, with nerves and lymphatics
describe the vasa recta of the jejunum
few arcades with long vasa recta to the intestine
describe the vasa recta of the ileum
many arcades with short vasa recta. This helps surgeons to identify it
what is the sigmoid mesocolon
the double layered fold of peritoneum that connects the sigmoid colon to the posterior abdom wall
where is the sigmoid mesocolon
root is in the left iliac fossa, crossing the birfurcation of the left common iliac vessels and the left ureter
it transmits the sigmoid branches of the inferior mesenteric vessels, plus nerves and lymphatics
what does the transverse mesocolon do
suspends the transverse colon from the posterior abdo wall
where is the transverse mesocolon
inferior to the pancreas
carries branches of the middle colic vessels
how does the transverse mesocolon divide the peritoneal cavity greater sac
divides it into supra and infra colic compartments
what does the supra colic compartment contain
liver stomach and spleen and part of the duodenum
what does the infra colic compartment contain
jejunum, ileum, ascending colon and descending colon. part of the duodenum
what divides the infracolic compartment
the Mesentary divides it into right and left halves, each has a paracolic gutter
what is Morison’s pouch also known as
right subphrenic recess or hepatorenal recess
where might pus collect and form abscesses when the patient is recumbent
Morison’s pouch
what seperates the rectum from the uterus in females
rectouterine pouch
what seperates the rectum from the bladder in males
rectovesical pouch
what separates the bladder and uterus in females
vesico uterine pouch
what is a peritoneal fold
a reflection of peritoneum with more or less sharp borders
usually covers blood vessels, ducts and obliterated foetal vessels
it connects two organs together
what is the importance of the lesser sack
allows distension of the stomach after a meal
what is the hepatogastric ligament
passes from the lesser curvature of the stomach to the liver
where may peritoneal folds or recesses form
where the intestine moves from being retro to intraperitoneal e.g. a paraduodenal recess
possible site for hernia
what is the significance of the peritoneal pouches, recesses, spaces and gutters
can house puss or blood or allow the spread of infection around the abdomen
where is the right hepatorenal pouch
behind the liver
above the kidney
puss can get into the space and form and abscess
it could overflow into the lesser sack
this is more likely if the patient is recumbent
this is due to the proximity to the epiploic foramen
what folds are visible on the anterior abdominal wall peritoneum
lateral umbilical folds, medial umbilical folds and median umbilical fold
what does the median umbilical fold contain
urachus which extends from the urinary bladder to the umbilicus
what do the medial umbilical folds contain
obliterated umbilical arteries extending from the internal iliac arteries to the umbilicus
what raises the lateral umbilical folds
inferior epigastric arteries
extending from the deep inguinal rings to the arcuate lines
what connects the liver to the diaphragm
falciform ligament, coronary ligament and the right and left triangular ligaments
what connects the spleen to the posterior abdominal wall and to the stomach
splenorenal and gastro splenic ligaments
part of the greater omentum
what is the allantois
a canal that drains the urinary bladder of the foetus and runs with the umbilical cord
it becomes the urachus
what does intra peritoneal mean
the organ is almost totally covered with visceral peritoneum and is suspended within the peritoneal cavity
what does retroperitoneal mean
organs lie outside or behind the peritoneum and are only partially covered with visceral peritoneum
is the ovary intraperitoneal?
yes- it has absorbed its peritoneal covering
what does secondarily retroperitoneal mean
the mesentery has been resorbed and lost
it used to be intra peritoneal but then moved out
what organs are 1o retroperitoneal
adrenal glands
kidneys
ureter
bladder
Aorta
IVC
oesophagus
rectum
what organs are 2o retroperitoneal
head, neck and body of the pancreas
the distal part of the duodenum
ascending and descending parts of the colon
where is the tail of the pancreas located
splenorenal ligament
where does appendix pain refer to
t10- peri umbilical
what is the parietal peritoneum sensitive to
pain, temperature, touch, and pressure
what is visceral peritoneum sensitive to
stretch and tear e.g. in inflammation
what is the parietal peritoneum in the pelvis supplied by
obturator nerve
L2,3,4
what is the visceral peritoneum supplied by
autonomic afferent nerves that supply the viscera or travel in the mesentery
where does gallbladder pain refer to
shoulder tip and right side
what is a coelom
a cavity
what happens to the conceptus 12 days post fertilisation
implants in uterine mucosa
forms bilaminar disc
what is the neural tube and body wall derived from
ectoderm
what is the cardiovascular, musculo skeletal system and coeloms derived from
mesoderm
what is the gastro-intestinal, respiratory and reproductive tracts derived from
endoderm
what does the notochord develop from
primitive node between endo and ectoderm
what is the peritoneal cavity derived from
intra embryonic coelom
what is the posterior abdo wall made from
mesoderm
what is exomphalos
failure of intestine to return to abdomen; lies within peritoneum and amnion, in umbilical cord
what is gastroschisis
failure of abdo wall, contents outside abdomen and not covered
what does the ventral mesenterary of the stomach and duodenum become
lesser omentum and falciform ligament
the falciform ligament and lesser omentum have free inferior borders
what is the foregut
the anterior part of the alimentary canal, from the mouth to the duodenum, just distal to the liver. The foregut develops from the folding primitive gut
what nerve supplies the foregut
coeliac trunk, refers pain to epigastrium T7-9
What does the foregut give rise to
oesophagus, respiratory diverticulum, stomach, proximal duodenum, liver, billary system, pancreas and spleen
what axes does the stomach rotate about
longitudinal axis and AP axis
when does the stomach appear
4th week of development as a dilation of the foregut
how does the stomach rotate
90 degrees clockwise around the longitudinal axis so that the left side faces anteriorly and the lesser curve faces to the right and greater to the left
AP axis so the pyloric part comes to lie on the right and oesophago-gastric junction slightly left so the greater curve faces left and inferior
how does the duodenum move during development
it is initially found in the midline but the rotations of the stomach cause it to rotate and swing on the right
it then falls onto the posterior abdominal wall and becomes retroperitoneal
describe the development of the duodenal lumen
proliferation of cells which destroys the lumen then it is re-canalised
when does the liver develop
3rd week
from and endodermal bud
describe the development of the liver
it penetrates the ventral mesentery and septum transversum and gives rise to the hepatic ducts and gallbladder
the liver develops in the ventral mesentery and grows up to reach the septum transversum
what does the pancreas form from
dorsal and ventral endodermal buds from the duodenum, the rotation of the latter causes the ventral bud to migrate around to lie behind and fuse with the dorsal bud so that the adult pancreas lies in the curve of the duodenum
the ducts of the dorsal and ventral buds unite to form the main pancreatic duct
the accessory duct is a remnant of the duct of the dorsal bud
what does the visceral peritoneum of the liver develop from
the ventral mesentery directly in contact with the liver
what is an annular pancreas
the ventral pancreas may become bifid which then form an obstructive ring around the duodenum
a bifid gallbladder is also possible
what does the liver divide the ventral mesentery into
lesser omentum and falciform ligament
how does rotation of the stomach affect the ventral mesentery
throws it to the right
where is the umbilical vein
the free edge of the falciform ligament
where is the bile duct
the free edge of the lesser omentum along with the hepatic artery and portal vein
where is the spleen
dorsal mesentery
where is the free edge of the lesser omentum
vertically between the liver and duodenum
where is the lesser sac
posterior to the stomach and the lesser omentum
what is the anterior boundary of the epiploic foramen
free border of the lesser omentum with the bile duct, hepatic artery and portal vein
what is the posterior border of the epiploic foramen
IVC
what is the superior border of the epiploic foramen
caudate process of the caudate lobe of the liver
what is the inferior border of the epiploic foramen
first part of the duodenum
what is Pringle’s manoevre
compress the hepatic artery and portal vein between the finger and thumb to control bleeding
what is the anterior border of the lesser sac
caudate lobe of liver, lesser omentum and stomach
what is the posterior border of the lesser sac
pancreas
what is the lateral border of the lesser sac
left kidney and adrenal gland, epiploic foramen
where is the lesser sac
extends upwards as far as the diaphragm and downwards a little way between the layers of the greater omentum
what is the dorsal mesentery
The portion of mesentery attached to the greater curvature of the stomach. it forms the greater omentum
what is the space within the greater omentum called
omental bursa which is the same as the lesser sac
where is the spleen
within the dorsal mesentery
What is the lienorenal ligament
double layers of peritoneum between the spleen and the posterior abdominal wall close to the kidney
what is the gastrolienal/ gastrosplenic ligament
the double layer between the spleen and the stomach
where is the tail of the pancreas
extends into the lienorenal ligament
where is the midgut
commences immediately distal to the entrance of the bile duct into the duodenum and ends 2/3rds along the transverse colon
what is the nerve supply of the midgut
superior mesenteric plexus- refers pain to the peri-umbilical region -T10
when does the midgut develop
week 5
what connects the midgut to the yolk sac
vitelline duct
through what angle does the midgut rotate
90 degrees anti clockwise in the hernia
a further 180 degrees as the loop drops back into the abdomen at 10 weeks
this leads to about 270 degrees rotation around the axis of the superior mesenteric artery
what does the cranial limb of the midgut form
jejenum and ileum
describe some congenital abnormalities related to the midgut
partial or abnormal rotation Meckel's diverticulum vitilline cyst vitilline fistula or patent duct (faecal discharge at umbilicus) failure of recanalization (narrowing or obstruction of the GI tract) gastrochisis Omphalocele umbilical hernia
when is development of the hindgut
end of the 3rd week
what develops from the hindgut
distal transverse colon
descending colon
sigmoid colon
rectum and upper anal canal
what is the innervation of the hind gut
inferior mesenteric plexus
refers pain to the suprapubic region -t12
what does the most inferior part of the hindgut develop from (anorectal canal)
cloaca
also develops into the urogenital system
what is the distal third of the anal canal derived from
ectoderm
marked by the pectinate line
what is the reason for imperforate anus
the anal membrane does not break down
what is the reason for urogenital - anal fistulae
common embryological origin
what types of anal-genital fistulae exist
uro-rectal fistulae
rectoperineal fistulae
rectovaginal fistulae
what is Hirchsprung disease
lack of normal colonic innervation leads to a constricted, aganglionic segment of bowel, with a distended segment proximally where the innervation is normal
describe the origins of the mesentery
base starts just left of L2 and passes obliquely downwards to the right ending above the sacroiliac joint
it crosses the 3rd part of the duodenum, aorta and IVC, right gonadal vessels and right ureter
describe the root of the sigmoid mesocolon
root is in the left iliac fossa, crossing the birfurcation of the left common iliac vesses and left ureter
it transmits the sigmoid branches of the inferior mesenteric vessels plus nerves and lymphatics
describe the root of the transverse mesocolon
fused to the inferior part of the greater omentum
root is inferior to the pancreas
transmits the middle colic vessels
what are the paracolic gutters
spaces between the colon and the abdominal wall
what is the innervation of the peritoneum lining the ant abdominal wall
lower six thoracic and first lumbar nerves
t7-12 and L1
what is the nerve supply of the diaphragm
ventral rami of c3,4,5
what are the components of the diaphragm
septum transversum
pleuroperitoneal membranes
dorsal mesentery of the oesophagus,
ingrowth from the body wall
which part of the diaphragm contributes to the oesophageal hiatus
the right crus
where does the left gastric artery pass through the diaphragm
t10
where do the anterior and posterior vagal trunks pass into the abdomen
t10, through the right crus but left of the midline
where does the right phrenic nerve enter the abdomen
t8, through the central tendon
where does the descending thoracic aorta enter the abdomen
t12, behind the median arcuate ligament
what structures pass through the crura
greater, lesser and least splanchnic nerves
what do the dorsal and ventral endodermal buds go on to form
pancreas
