Week 5 Flashcards
When is the primitive gut tube formed, and from what?
Body folding during week 4; from the top of the yolk sac
Also, during this time, the body cavity and anterolateral body wall are formed and the amnion encases the embryo
Which germ layer forms the epithelial lining of the gut tube?
endoderm
Which germ layer forms all other layers of the gut tube wall (except nerves and ganglia)?
mesoderm
What germ layer forms the serous membrane of the abdomen (peritoneum)?
mesoderm
What is a mesentery?
a double layer of peritoneum reflecting from the abdominal wall to enclose the viscera
What forms the boundaries of foregut, midgut, and hindgut?
The 3 arteries that branch off the anterior aorta: celiac trunk, superior mesenteric artery (SMA), and inferior mesenteric artery (IMA)
Liver buds
buds off the foregut into the ventral mesentery dividing it into the falciform ligament and the lesser omentum
What is septum transversum?
The mesoderm that the liver buds into; it forms the CT and blood vessels of the liver and also forms the diaphragm
Pancreas buds
off the foregut just above the midgut junction and has 2 buds: dorsal pancreas that buds into dorsal mesentery and ventral pancreas that buds into ventral mesentery
Stomach rotation in embryo development
it rotates 90 degrees clockwise on its longitudinal axis so the left side faces anteriorly
When the stomach rotates 90 degrees clockwise…
the dorsal mesentery of the stomach becomes the greater omentum, the liver moves to the right side of the abdomen and pushes the duodenum, pancreas, and part of the dorsal mesentery against the posterior body wall
Stomach growth and rotation creates the omental bursa or lesser peritoneal sac
spleen develops
from the mesoderm in the dorsal mesentery of the stomach. This makes the spleen a unique organ because it’s not derived from endoderm
Retroperitoneal organs
pancreas, most of the duodenum, ascending and descending colon, abdominal aorta, IVC
What are the names of the parts of the dorsal mesentery of the stomach that don’t fuse with the parietal peritoneum covering the posterior body wall?
splenorenal ligament, gastrosplenic ligament, and greater omentum
biliary duct system and gallbladder are formed from what?
the liver bud (hepatic diverticulum)
Physiological herniation
rapid growth of the midgut causes it to loop into the umbilical cord, where is it still connected to the rapidly resorbing yolk sac by the yolk stalk
Cranial limb of the midgut loop forms
the jenunum and upper ileum
the caudal limb of the midgut loop forms
the lower ileum through the proximal 2/3 of the transverse colon
Midgut loop rotation
by 10 weeks the midgut loop has rotated 270 degrees around the axis of the SMA
Order of organs returning to body cavity after physiological herniation
jejunum returns first, to the left side and then ileum to the right side. Cecum returns last, initially to the RUQ, but then moves dow the the RLQ
In rotation of the midgut, what happens to the mesenteries of the ascending and descending colon?
the mesenteries fuse with the posterior abdominal wall, so they become retroperitoneal
Transverse mesocolon fuses with
the greater omentum as the greater omentum passes anterior to it
What is mesentery proper
the mesentery of the small intestine
pyloric stenosis
results from hypertrophy of the muscularis externa of the pylorus, obstructing the pyloric canal and causing forceful (projectile) nonbilious vomiting
Etiology unclear, but may be multifactorial from both genetic and environmental factors. Symptoms usually begin 3-5 weeks of age
annular pancreas
sometimes ventral pancreatic bud has 2 lobes that move in opposite directions during foregut rotation. They form a ring around the 2nd part of the duodenum, which constricts the duodenum.
Can be asymptomatic, especially if incomplete. Symptoms present during neonatal period with feeding intolerance, vomiting, and abdominal distention. Vomit is usually nonbilious
omphalocele
results when the midgut loop fails to return to the abdominal cavity. The viscera herniate through the umbilical ring and are contained in a shiny sac of amnion covered parietal peritoneum at the base of the umbilical cord
It is often associated with genetic diseases and other congenital anomalies
gastroschisis
results when the abdominal viscera herniate through the body wall directly into the amniotic cavity, usually to the right of the umbilicus. Occurs due to a defect in the lateral folding of the embryo that leaves a gap or weakness in the anterior abdominal wall. It is usually an isolated defect
Meckel’s (ileal) diverticulum
persistence of the proximal portion of the yolk stalk (vitelline duct). It is present in 2% of the population and is 2x as common in males. Ectopic gastric mucosa may be present, leading to ulceration, perforation, or GI bleeding. Typically found about 2 ft from ileocecal junction
No rotation of the midgut
Causes the small intestine to end up on the right and large intestine on the left
What is malrotation of the midgut
mesentery doesn’t fuse correctly, so small intestine can twist around the SMA, resulting in volvulus (twisting). If SMA is obstructed, it can be life threatening. Babies present with vomiting, absence of stool and abdominal distention
Clockwise rotation of the midgut
large intestine enters first and is posterior to the duodenum
recanalization
lumen of midgut fills in from epithelial proliferation and then recanalizes to form villi and crypts.
Problems with recanalization can result in stenosis, atresia, septa, and cysts
duodenal atresia
an example of failed recanalization; it’s associated with polyhydramnios, bilious vomit, and a distended abdomen. Usually occurs distal to the major papilla
intussusception
occurs when a segment of intestine invaginates or telescopes into an adjacent semgent. It children, it may be caused by excessive peristalisis. Symptoms include intermittent abdominal pain, vomiting, bloating, and bloody stool
aganglionic megacolon (Hirschsprung’s disease)
results from lack of ganglia in the colon. Caused by a defect in the RET gene, a receptor tyrosine kinase involved in neural crest cell migration
Neural crest cells migrate to the gut during weeks 5-7 to form ganglia, but in this case, they fail to migrate to the hindgut.
80% of cases involve rectum to sigmoid colon leading to loss of peristalisis and immobility, fecal retention, and abdominal distention up to the transverse colon (megacolon)
lympatics of the stomach drain to
regional lymph nodes: splenic, gastric, gastro-omental, or pyloric
Where do the regional nodes of the stomach drain to?
celiac nodes
Where do celiac nodes drain?
the cisterna chyli and the thoracic duct
Regional lymph nodes for liver, gallbladder, pancreas, and duodenum
cystic, hepatic, pancreaticduodenal, and pancreatic
regional lymph nodes for liver, gallbladder, pancreas, and duodenum drain to
the celiac and superior mesenteric nodes
where do the superior mesenteric nodes drain
the cisterna chyli and the thoracic duct
regional lymph nodes of the small intestine and colon
mesenteric, ileocolic, right colic, middle colic, paracolic, sigmoid, and superior rectral
where do regional lymph nodes of the small intestines and colon drain
the superior and inferior mesenteric nodes
where do the inferior mesenteric nodes drain
the cisterna chyli and the thoracic duct
blood supply of foregut organs
branches of celiac trunk
what are the foregut organs
esophagus, stomach, proximal duodenum, liver, gall bladder, pancreas, spleen
blood supply of midgut organs
branches of superior mesenteric artery (SMA)
What are the midgut organs
distal duodenum, jejunum, ilium, cecum, appendix, ascending colon, proximal 2/3 transverse colon
Blood supply of the hindgut organs
branches of inferior mesenteric artery (IMA)
what are the hindgut organs
distal 1/3 of transverse colon, descending colon, sigmoid colon, rectum, anal canal
origin of sympathetic preganglionic neurons in foregut
T5-T9
origin of sympathetic preganglionic neurons in midgut
T5-T9 and T10-T11
origin of sympathetic preganglionic neurons in hindgut
L1-L2
sympathetic Preganglionic nerve fibers in foregut
greater splanchnic nerves
sympathetic Preganglionic nerve fibers in midgut
T5-T9: greater splanchnic nerves
T10-T11: lesser splanchnic nerves
sympatheticPreganglionic nerve fibers in hindgut
Lumbar and sacral splanchnic nerves
sympathetic Postganglionic nerve fibers in foregut
celiac plexus via the celiac ganglia
sympathetic Postganglionic nerve fibers in midgut
superior mesenteric plexus via the superior mesenteric ganglia
sympathetic Postganglionic nerve fibers in hindgut
inferior mesenteric plexus via the inferior mesenteric ganglia
Hypogastric plexus via the pelvic ganglia
area of referred pain from the foregut
epigastric via the greater splanchnic nerves
area of referred pain from the midgut
umbilical via the lesser splanchnic nerves
area of referred pain from the hindgut
pubic via the lumbar and sacral splanchnic nerves
parasympathetic preganglionic nerve fibers of foregut
vagus nerve
parasympathetic preganglionic nerve fibers of midgut
vagus nerve
parasympathetic preganglionic nerve fibers of hindgut
pelvic splanchnic nerves (S2-S4)
Four main layers of the GI tracts
hollow tube with lumen of variable diameter
Layers: mucosa, submucosa, muscularis, and serosa/adventitia
Mucosa of GI tract
consists of stratified squamous or columnar epithelial lining; lamina propria of loose CT rich in blood vessels, lymphatics, lymphocytes, and often containing small glands. It includes a thin layer of smooth muscle (muscularis mucosae) that separates it from the submucosa
Submucosa of GI tract
fibroelastic loose CT. contains larger blood vessels and lymphatics, often glands, and an important network of nerves and ganglia belonging to ANS (submucosal or meissner’s complex)
Muscularis of GI tract
consists of smooth muscle3 with inner circular and outer longitudinal orientations. Between the 2 layers is another network of nerves and ganglia known as the myenteric or Auerbach’s plexus. Contractions of the muscularis mix and propel luminal contents (peristalsis) and are generated and coordinated by myenteric plexus
adventitia/serosa
When facing the peritoneal cavity, this layer is encased with thin layer of simple squamous epithelium known as mesothelium. In this case the combined CT and mesothelium is called serosa.
In retroperitoneal surfaces where there is no mesotherlial lining and only CT is present, the outer tunic is called the adventitia
Unique qualities of esophagus
- lumen lined with thick, nonkeratinized stratified squamous epithelium to withstand abrasion
- submucosa has esophageal glands
- In distal 8 cm of esophagus, submucosal veins anastamose with branches of the portal vein
- proximal 1/3 of muscularis externa is skeletal muscle, middle 1/3 is a mix, and distal 1/3 is all smooth muscle
- thoracic esophagus has adventitia, abdominal esophagus has serosa
functions of stomach
- continued digestion of carbohydrates initiated by salivary enzyme amylase
- addition of acidic fluid to ingested fluids plus churning activity of muscularis to turn them into viscous mass called chyme
- continued digestion of triglycerides initiated by pancreatic enzyme lipase
- initial digestion of proteins with enzyme pepsin
unique qualities of stomach
•simple columnar mucosal lining consisting entirely of mucous-secreting cells
•surface epithelium invaginates into the lamina propria to make gastric glands
•in the fundus and body, gastric glands branch and open to gastric pits, which empty their contents into the lumen
has 3 layers of smooth muscle: inner oblique, middle circular, and outer longitudinal. Auerbach’s/myenteric plexus is between outer 2 layers
•submucosa has increased thickness, which is responsible for the rugae of the mucosa
•stomach has serosal layer
cell types in gastric glands
regenerative/stem cells, mucous cells, parietal cells, chief cells, and enteroendocrine cells
mucous cells of stomach
line the lumen of gastric pits and secrete thick, adherent, and highly viscous protective mucous layer that is rich in bicarbonate ions
parietal cells of stomach
predominate in the upper segment of the gastric gland; produce hydrochloric acid (important for the conversion of pepsinogen to pepsin) and intrinsic factor (essential for absorption of vitamin b12)
chief cells of stomach
secrete the inactive proenzyme pepsinogen, which is released into the lumen of the gland and then converted in the acidic environment of the stomach to pepsin
pepsin
a proteolytic enzyme capable of digesting most proteins
enteroendocrine cells
several types that secrete hormones and have effects on gut motility (serotonin) and HCl secretion (gastrin)
gastric glands in cardia and pyloric region of stomach
have roughly the same structure of those in the fundus and body, but primarily consist of mucus cells and a few enteroendocrine cells
small intestine function
a tube approx 5-7 meters long
it continues digestion of chyme from the stomach using pancreatic enzymes and liver bile AND absorbs the resulting nutrients
unique qualities of small intestine
- luminal surface is thrown into circular folds called plica circulares that contain villi and significantly increase the SA necessary for absorption of nutrients from digested food
- epithelium is simple columnar joined by extensive tight junctions. has enterocytes (absorptive), goblet cells (mucous-secreting), paneth cells (lysozyme secreting), enteroendocrine cells (hormone-secreting), and stem cells (replace enterocytes and goblet cells every 3-5 days)
enterocytes in small intestine
- to further increase the absorptive area, each is covered with numerous microvilli (brush border).
- they absorb carbohydrates, proteins, lipids, vitamins, Ca2+ and Fe2+
carbohydrate digestion in small intestine
digested to monosaccharides and transported to portal blood
protein digestion in small intestine
digested to amino acids, dipeptides, and tripeptieds. Some further digestion may occur in enterocytes, and then amino acids are transported to the portal blood
triglyceride digestion in small intestine
emulsified by bile salts and digested to fatty acids and monoacyclglycerols. Long chain fatty acids are packaged as chylomicrons that enter the lacteal center of the vilus. Short and medium chain fatty acids enter enterocytes directly and are delivered to portal blood
water soluble vitamin b12 in small intestine
absorbed in the ileum and requires intrinsic factor
Ca2+ in small intestine
requires vitamin d for absorption
goblet cells in small intestine
interspersed among enterocytes covering the villi. The secrete mucous for lubrication fo small intestine. The further down the GI tract, the greater number of goblet cells.
Goble cells in HandE section
appear clear
crypts of lieberkuhn
epithelium at base of villi in small intestine invaginates into the lamina propria to form these short glands
paneth cells
found at the base of crypts of lieberkuhn and stain orange-red color in HandE stain.
They have numerous cytoplasmic granules filled with lysosome (antibacterial), tumor necrosis factor-alpha (TNF-alpha, proinflammatory) and defensins (antibacterial and antiparasitic)
dysfunction of paneth cell biology
contributes to pathogenesis of chronic inflammatory bowel disease
What do enteroendocrine cells secrete in small intestine
cholecystokinin, secretin, gastric inhibitory peptide, and glucagon like peptide
cholecystokinin
secreted in response to small peptides, amino acids, and fatty acids in gut lumen. Stimulates secretion from pancreatic acinar cells and release of bile from gall bladder
secretin
secreted in response to H+ and fatty acids in gut lumen. Stimulates release of HCO3 from pancreas and biliary tract of liver
gastric inhibitory peptide
released in response to glucose, amino acids, and fatty acids in gut lumen. stimulates insulin secretion from pancreatic islets
glucagon like peptide
released in response to glucose, amino acids, and fatty acids in gut lumen. stimulates insulin secretion AND inhibits glucagon secretion
Brunner’s glands
found only in submucosa of duodenum adjacent to the stomach. They secrete alkaline mucus via ducts that empty into the bases of the crypts fo help neutralized th acidic chyme
lymphocytes in small intestine
large numbers are found throughout the lamina propria. Highest concentration will be present in the ileum, as individual cells or as groups of lymphoid nodules (peyer’s patches, also called gut associated lymphoid tissue GALT)
Large intestine function
a large diameter tube that absorbs about 4/5 of the water, Na+, and Cl- from the fluid presented to it by the ileum, concentrating it and solidifying to form solid feces
unique qualities of large intestine
- mucosa lacks villi and has no major folds, except in rectum
- Many goblet cells exist in glands created by invaginations of epithelium
- serosa has small, pendulous protuberances of adipose tissue called appendix epiploica
teniae coli
outer layer of smooth muscle in muscularis of large intestine is gathered into 3 longitudinal bands
epithelium of mucosa in large intestine
simple columnar
appendix
small blind ended diverticulum of the cecum. Characteristic features: accumulations of lymphoid tissues present within lamina propria
Salivary gland function
moisten and lubricate ingested food and oral mucosa, initiate digestion of carbohydrates and lipids with amylase and lipase
bile
made in liver, stored and concentrated in gallbladder
liver function
plays major role in carbohydrate and protein metabolism, inactivated many toxic substances and drugs, and synthesizes most plasma proteins and factors necessary for blood coagulation
exocrine portion of pancreas
make up about 80% of the organ; consist of numerous acinar cells aggregated into lobules that can be seen grossly.
pancreatic exocrine secretion
merocrine secretion of proenzymes by the acinar cells is regulated by secretin and cholecystokinin from the enteroendocrine cells of the duodenum and jejunum as well as stimulation from the vagus nerve
what stimulates secretin release
gastric acid in the intestinal lumen
what does secretin cause in the pancreas
ductal cells add water and bicarbonate to the fluid making it alkaline, rick in electrolytes, and poor in enzyme activity. This fluid naturalizes chyme so that pancreatic enzymes can function at optimal neutral pH
what stimulates the release of cholecystokinin
long-chain fatty acids, gastric acid, and some essential amino acids in the gut
what does the hormone cholecistokinin do
promotes secretion of an enzyme-rich (but less abundant) fluid
endocrine portion of pancreas
found in the aggregates of lightly staining cells called islets of langerhans that can only be seen histologically
3 major cell types in endocrine pancreas
alpha, beta, delta
they can only be recognized with special staining techniques
product of alpha cells in pancreatic islets
glucagon
product of beta cells in pancreatic islets
insulin
product of delta cells in pancreatic islets
somatostatin
function of glucagon
increases blood glucose, gluconeogenesis, and glycogenolysis
function of insulin
promotes decrease of blood glucose, stimulates storage of glucose as glycogen
function of somatostatin
inhibits secretion of glucagon and insulin
liver organization
liver parenchyma organized into hepatic lobules (hexagonal in shape). The center of the lobule is indicated by the presence of the efferent central vein, which is surrounded by hepatocytes arranged radially in plates or cords
portal triads
located at the periphery of a hepatic lobule; contain a branch of the hepatic artery, portal vein, and bile duct (with lymphatics and nerves)
3 functional zones of liver lobule
centrilobar (zone III), midlobar (zone II), and peripheral (zone I)
blood flow in lobule
always flows from the periphery to the center of each hepatic lobule
this means oxygen and metabolites reach the peripheral cells first
zone I hepatocytes
can rely on aerobic metabolism and are often more active in protein synthesis
zone III hepatocytes
exposed to lower concentrations of nutrients and oxygen and are more involved with detoxification and glycogen metabolism
bile production and flow
produced in hepatocytes and then flows into bile canaliculi that eventually connect to the small bile ducts in the portal triads. Bile flow progresses in a direction opposite to that of blood (center of lobule to periphery)
sinusoids of liver cell
- emerge where peripheral branches of portal vein and hepatic artery converge on lobules central vein.
- lined by fenestrated endothelial cells that allow plasma to move into space of disse
- contain phagocytic Kupffer cells
Kupffer cells
found in sinusoid of liver; important in phagocytosis of ages RBCs, bacteria and other debris in the portal blood
Ito cell
lives in the space of Disse and stores vitamin A and other fat-soluble vitamins
gallbladder
pear-shaped organ that occupies space on posterior aspect of right lobe of liver. Composed of a blindly ending fundus, central body, and narrow neck. concentrates, stores, and releases bile
bile volume per day
about 1000 mL flows into gallbladder and after concentration, about 30-50 mL is stored
unique qualities of gallbladder
- lacks muscularis mucosae and submucosa
- epithelial cells capable of secreting small amounts of mucous; have active sodium-transporting mechanism necessary for concentration of bile
epithelium of gallbladder
luminal folds lined by single layer of simple columnar
cholecystokinin function in gallbladder
its released in response to presence of dietary fats in small intestine and induces contraction of gallbladder
major types of salivary glands
parotid, submandibular, and sublingual
organization of salivary gland
surrounded by CT capsule; septa extend from capsule into gland to create lobes; CT septae further divide lobes into smaller lobules; secretory component organizes as an acinus; have myoepithelial cells (basket cells)
myoepithelial cells (basket cells)
flat and have long cytoplasmic processes that aid in contraction. they lie between epithelial cells and basal lamina of acini
duct system transport in salivary glands
transports saliva from gland to oral cavity and modifies its ionic composition by reabsorbing Na+ and Cl- making it more hypotonic.
intercalated duct of salivary glands
first segment out of acini and is lined with squamous or low cuboidal epithelium. empties into the striated or interlobar ducts located in CT septae that subsequently lead into main excretory duct system
parotid glands
serous acini consist of pear-shaped groups of epithelial cells surrounded by distinct basement membrane. have dense cytoplasm and basal nucleus in epithelial cells. Acini have central lumen
sublingual glands
mucous acini have abundant cytoplasm filled with clear mucus. cells are pyramidal with flattened basal nucleus
submandibular glands
mixed acini chan be characterized by crescent-shaped formation of serous cells capping a mucous acinis (serous demilune) or by a mixed pattern of serous and mucous acini
serous acini
secrete enzymes and other proteins
mucous acini
secrete mucins that provide lubricating properties to saliva
secretion of salivary glands
stimulated by ANS. Parasympathetic secretion, in response to taste or smell of food, promotes vasodilation and copious watery secretion. Sympathetic stimulation produces a small amount of viscous saliva
micturation
urination
defacation
bowel movement
parturition
childbirth
3 flat muscles of abdominal wall
external oblique, internal oblique, and transverse abdominus.
They are a continuation of the 3 intercostal muscle layers of the thorax
rectus abdominus
the vertical muscle on the abdominal wall and lies within the rectus sheath, which is the aponeurosis of the flat muscles
linea alba
“white line”
where the aponeurosis from each side interdigitate in the midline between paired rectus muscles
Has tendinous intersections that make the “six pack”
anterior rectus sheath
formed by aponeurosis of external oblique and part of that from internal oblique
posterior rectus sheath
formed by rest of aponeurosis from internal oblique and that of transverse abdominus
arcuate line
where the posterior rectus sheath ends. the inferior 1/3 is absent
layers of abdominal wall superficial to deep
skin, superficial fascia (split into Camper’s and Scarpa’s), external oblique, internal oblique, transverse abdominus, transversalis fascia, and a serous membrane (parietal peritoneum)
direct inguinal hernia
a weakening in the abdominal wall in an area called Hasselbach’s triangle that allows abdominal contents to protrude. Occurs above the inguinal ligament
indirect inguinal hernia
a congenital defect in the inguinal canal. Occurs above the inguinal ligament.
In males, the spermatic cords pass through here, which are bigger than the round ligament of the uterus in females. Thus more common in males.
femoral hernia
occurs more commonly in women and is below inguinal ligament. portion of abdominal contents protrude through the medial-most compartment of the femoral triangle
neurovascular supply of abdomen
nerves and vessels of anterolateral abdominal wall travel between deep and middle layers of muscle (transvers abdominus and internal oblique)
The nerve are the ventral rami of spinal nerves T7-L1
anterior rami of T7-T11
are continuations of the intercostal nerves
anterior rami of T12
the subcostal nerve
anterior rami of L1
splits into iliohypogastric and ilioinguinal nerves
superior and inferior epigastric arteries
run posterior to the abdominus muscle, within the posterior rectus sheath
transumbilical plane
level of T10, splits the upper and lower quadrants of abdomen
McBurney’s point
1/3 between anterior superior iliac spine and the umbilicus. It is where the appendix attaches to the cecum
abdominal regions
demarcated by 2 vertical midclavicular planes and 2 horizotal planes (subcostal and intertubercular planes)
right to left and top to bottom they are:
right hypochondrium, epigastric, left hypochondrium
right flank, umbilical, left flank
right groin, pubic, left groin
peritoneum
simple squamous (serous) epithelium lining abdominal cavity
What is found in the peritoneal cavity?
only serous peritoneal fluid, which allows the viscera to move without friction
Difference in men vs women for peritoneal cavity
its closed in men, but in women the uterine tubes open into the peritoneal cavity, creating a potential route for spread of infections
any organ that has mesentery is said to be
intraperitoneal
pain from parietal peritoneum
it shares sensory information with abdominal wall, spinal nerves T7-T11, so pain is sharp, somatic pain localized along a dermatome
pain from visceral peritoneum
it shares sensory innervation with the viscera, so pain is diffuse, referred pain
pain from foregut organs
refers to epigastric region
pain from midgut organs
refers to umbilical region
pain from hindgut organs
refers to pubic (aka hypogastric) region
epiploic foramen (of Winslow)
the entrance to the lesser sac of the peritoneal cavity; the greater and lesser sacs (aka omental bursa) communicate through this
ascites
excess peritoneal fluid accumulating due to pathology. In this case, it usually flows downward as opposed to the typical upward flow of peritoneal fluid
supracolic and infracolic compartments
the transverse mesocolon divides the greater sac into these 2 regions
anastamosis at the foregut-midgut junction
the superior pancreaticoduodenal artery (branch of celiac trunk) anastamoses with the inferior pancreaticoduodenal artery (branch of the SMA)
anastamosis at the midgut-hindgut junction
the middle colic artery (branch of SMA) anastamoses with the left colic artery (branch of the IMA)
If this anastamosis is not “robust,” this “watershed” area is vulnerable to ischemia
marginal artery
an arterial arch formed by anastamoses between left, middle, and right colic arteries
Why are loops of the small intestine suscepible to ischemia?
intestinal branches of the SMA do not anastamose with branches of the celiac trunk or IMA
anastamosis on the rectum (hindgut)
between superior rectal (terminal branch of IMA) and the middle and inferior rectal arteries (off the internal iliac artery)
cisterna chyli
the dilated proximal end of the thoracic duct where lymph is returned
blood entry to the liver
30% from hepatic artery and 70% from portal vein
it leave liver via hepatic veins, which drain into IVC
spleen
functionally a large lymph node that lies in the LUQ (hypochondrium)
engorged veins from increased blood flow at liver can cause
esophageal varices, hemorrhois, and caput medusae (cutaneous engorged veins around umbilicus)
cirrhosis of liver (fibrosis)
disrupts portal blood flow, leading to portal HTN and engorgement of portosystemic anastamoses
AAA (abdominal aortic aneurysm)
localized abnormal dilation of the aorta that occurs when the structure of the aortic wall is compromised (usually at the IMA)
HTN and atherosclerosis are the major causes
Symptoms can include abdominal and back pain, nausea, and early satiety. Up to 75% are asymptomatic. Sharp tearing pain accompanies rupture of AAA
SAD PUCKER
mnemonic to remember which organs are retroperitoneal: S = Suprarenal (adrenal) glands A = Aorta/Inferior Vena Cava D = Duodenum (second and third segments) P = Pancreas U = Ureters C = Colon (ascending and descending only) K = Kidneys E = Esophagus R = Rectum
