Abdominal Midgut and Hindgut Flashcards
What makes up the midgut?
the jejunum, the ileum, the cecum, the ascending colon, and the transverse colon
what makes up the hindgut?
the descending colon, the sigmoid colon, and the rectum and anus
what type of organ is the jejunum?
intraperitoneal- it is supported by the mesentery
what does the jejunum and the ileum contain?
mucosal folds called plicae circulares
what is the arterial supply of the jejunum?
it is supplied by arterial arcades with long vasa recta (straight arteries) off branches of the SMA
what type of organ is the ileum?
intraperitoneal- it is supported by the mesentery
what is the arterial supply of the ileum?
it is supplied by compound arterial arcades with short vasa recta (straight arteries) branches of SMA
where does the colon begin?
at the ileocecal junction
what are the external features of the colon?
3 outer bands of longitudinal smooth muscle (tenia coli)
what do the tenia coli cause?
outpocketings (haustra) with attached outer fatty appendages (appendices epiploicae)
what is the blind pouch of the colon that contain ileal papilla?
cecum
what are ileal papilla?
cone-like projections of the ileum
what valve regulates the passage of ileal contents into the cecum?
ileocecal valve
what type of organs are the ascending and descending colon?
secondarily retroperitoneal
what type of organ is the transverse colon?
intraperitoneal
what is the transverse colon suspended to the posterior wall by?
transverse mesocolon mesentery
what is the sigmoid colon suspended by?
sigmoid mesocolon
where is the appendix attached to?
posterior-medial part of the cecum
what is the appendix supported by?
mesoappendix
what does the appendix contain?
several lymphoid nodules
what type of organ is the rectum?
retroperitoneal and sub-peritoneal
what does the rectum contain?
3 transverse rectal folds/rectal valves (superior, middle, and inferior)
what is the rectum continuous with?
the anal canal
what is the anal canal surrounded by?
2 anal sphincters
what is the internal anal sphincter comprised of?
smooth muscle
what is the external anal sphincter comprised of?
skeletal muscle
what does the anal canal contain?
anal columns, anal valves, and anal sinuses
in the anal canal, what is the transition point of the different epithelium known as?
pectinate line
what does the epithelium transition from in the anal canal?
it transitions from columnar epithelium to nonkeratinized squamous epithelium
what is the external opening of the anal canal known as?
anus
What is the primary arterial supply to the midgut and hindgut?
the SMA and IMA
what does the SMA supply?
pancreas and duodenum, small intestines, cecum, and ascending and transverse colon
what does IMA supply?
the descending and sigmoid colon and the superior rectum
what does the SMA arise from?
the abdominal aorta at the level of L1- posterior to the neck of the pancreas; then passes inferiorly to the anterior horizontal portion of the duodenum
what is the first thing that branches off of the SMA?
the inferior pancreaticoduodenal artery
what does the inferior pancreaticoduodenal artery branch into?
branches into the anterior and posterior inferior pancreaticoduodenal arteries
what do the anterior and posterior inferior pancreaticoduodenal arteries anastamose with?
the anterior and posterior superior pancreaticoduodenal arteries
what do the anterior and posterior superior pancreaticoduodenal arteries branch from?
the gastroduodenal artery (which comes from the celiac trunk)
besides the inferior pancreaticoduodenal artery, what else branches off of the SMA?
jejunal branches, ileum branches, ileocolic artery, right colic artery, and middle colic artery
where does the IMA come from?
it branches off the abdominal aorta at the L3 level
what branches off the IMA?
left colic artery, sigmoidal artery, the superior rectal artery
what is the anastomosis between the SMA and the IMA known as?
marginal artery
the superior rectal artery will anastamose with what other blood supply to the rectum?
the middle rectal artery and the inferior rectal artery
what does the middle rectal artery come from?
it is a branch of the internal iliac artery
what does the inferior rectal artery come from?
branch of the internal pudendal artery
venous return from the peritoneal viscera is eventually drained into what?
the hepatic portal vein
where does the hepatic portal vein begin?
where the superior mesenteric vein and the splenic vein join together
why is the venous supply sent to the liver?
it processes the nutrients from our digestive system and it filters the toxins before we send it into systemic circulation
where does the portal venous system have anastomoses with the systemic system at?
the gastroesophageal plexus, the umbilicus, and the rectal venous plexus
when do varicosities occur?
due to decreased blood flow through the liver (e.g. when there is hepatic hypertension)
what do the thoracic splanchnics do?
they carry presynaptic axons from the spinal cord to postsynaptic neurons that are located in aortic collateral ganglia
what nerve fibers do the greater splachnics carry?
presynaptic axons from T5-T9
where do the greater splachnics travel?
to the celiac ganglion
what nerve fibers do the the lesser splanchnics carry?
presynaptic axons from T10-T11
where do the lesser splanchnics travel?
to the superior mesenteric ganglion
what nerve fiber does the least splanchnic carry?
presynaptic axons from T12
where does the least splanchnic travel?
to the aorticorenal ganglion
Where do the lumbar splanchnics (L1 and L2) travel?
to the inferior mesenteric ganglion
where do the lumbar splanchnics (L3, L4, L5) travel?
to the inferior hypogastric plexus/ganglion
what do the sacral splanchnics do?
carry presynaptic axons from sacral sympathetic chain to the hypogastric ganglion
where do the post-synaptic sympathetic axons from the celiac ganglion target?
gallbladder, stomach, pancreas, liver
where do the post-synaptic sympathetic axons from the superior mesenteric ganglion target?
small intestine, cecum, appendix, ascending colon, and transverse colon
where do the post-synaptic sympathetic axons from the aorticorenal ganglion target?
kidney and the suprarenal glands
where do the post-synaptic sympathetic axons from the inferior mesenteric ganglion target?
descending colon, sigmoid colon, and the rectum
where do the post-synaptic sympathetic axons from the hypogastric plexus/ganglion target?
the rectum, anus, and pelvic organs
where are the postsynaptic neurons found for the parasympathetics?
in the walls of the organs
the vagus nerve carrying presynaptic parasympathetic fibers will pass through what?
celiac ganglion and superior mesenteric ganglion
what nerve fibers do the pelvic splanchnics carry?
S2-S4
where do the pelvic splanchnics travel to and pass through?
the hypogastric plexus/ganglion and then travel into the anus, rectum, descending colon, and sigmoid colon
what are the sacral splanchnic nerves associated with?
spinal nerves S1-S5
what artery does the post synaptic neurons from the inferior hypogastric plexus/ganglion travel with to reach the pelvic viscera and perineum?
the internal iliac artery
What are the two types of referred pain?
somatic afferent pain or visceral afferent pain
what is somatic afferent pain?
it is due to the organs that are inflamed irritating the parietal peritoneum and the brain interprets the pain as though the irritation occurred in the skin of the region supplied by the same sensory ganglia and spinal cord segments as that region of the affected peritoneum
how can somatic afferent pain be described?
acute and well-localized
what is visceral afferent pain?
pain from the organ itself; pain is transmitted via splanchnic nerves to spinal cord
