GI- physiology and anatomy Flashcards
What is the foregut?
pharynx to duodenum
What is the midgut?
duodenum to proxima 2/3 of transverse colon
What is the hidngut?
distal 1/3 of transverse colon to anal canal above pectinate line
When does the midgut herniate through the umbilical ring?
6th week
What does the midgut return to the abdominal cavity and rotate around the SMA?
10th week
Compare gastroschisis to omphalocele. What fold is defective in both?
Lateral fold
Gastroschisis- not covered by peritoneum (defect in abd wall)
omphalocle- covered by peritoneum (persistent herniation)
What chromosomal abnormality is duodenal atresia associated with?
Trisomy 21
What congenital abnormality presents as an olive mass and nonbilious projectile vomiting at 2-6 weeks?
congenital pyloric stenosis
What is the uncinate process formed from?
ventral pancreatic bud only
What is an annular pancreas
ventral pancreatic bud encircles 2nd part of duodenum- duodenal narrowing
what is a pancreas divisum
ventral and dorsal parts fail to fuse
What parts of the colon and rectum are intraperitoneal and retroperitoneal?
ascending, descending, upper rectum- secondarily retropertioneal
transverse colon, sigmoid colon- intraperitoneal
lower rectum, anal canal- primary retropartineum
What ligament is the portal triad contained in?
hepatoduodenal
What vessels are contained in the gastrohepatic ligament?
gastric arteries
What vessels are contained in the gastrocolic ligament?
gastroepiploic arteries
What vessels are contained in the gastrosplenic ligament?
short gastrics, left gastroepiploic
What vessels are contained in the splenorenal ligament?
splenic artery and vein, tail of pancrease
What directions do the inner and outer muscle layers of the digestive tract face?
Inner- circular
outer- longitudinal
Where is the myenteric/auerbach plexus located? What does it do?
in muscularis externa, controls muscle contractions
Where is the Meissner plexus located? What does it do?
submucosa, controls secretory activity
Where are brunner glands located?
duodenum
What are the levels of the celiac trunk, SMA, IMA, Renal arteries
Celiac: T12
SMA/renal: L1
IMA: L3
What is the parasympathetic innervation of the foregut, midgut, and hindgut?
foregut, midgut- vagus
hindgut- pelvic
What area of the colon is particularly susceptible to ischemia?
splenic flexure (jxn midgut + hindgut)
What are the 3 branches of the celiac trunk?
common hepatic, splenic, left gastric
What arteries supply the greater vs lesser curvature of the stomach?
lesser curvature- gastric
greater curvature- gastroepiploic
What is the embryologic and circulatory significance of the pectinate line?
above pectinate- endoderm, portal venous
below- ectoderm, systemic circ
How does an external vs internal hemorrhage differ?
internal- not painful, drain deep nodes
external- painful, drain superficial inguinal
Describe blood flow and bile flow of the liver
Glood flows from portal ven to central vein
bile flows towards portal triad
What area of the liver is most likely to be damaged by viral hepatitis?
Periportal zone (zone I)
What area of the liver is most likely to be damaged by ingested toxins?
Periportal zone (zone I)
What area of the liver is most likely to be damaged by ischemia?
centrilobular zone (zone III)
What area of the liver is most likely to be damaged by alcohol hepatitis?
centrilobular zone (zone III)
What area of the liver contains the cytochrome P450 system?
centrilobular zone (zone III)
Describe the locations of the medial and median umbilical ligaments
Medial lig- located just lateral to the rectus abdominus
median lig- located just medial to the rectus abdominus
Where would the inferior epigastric artery be in relation to a direct and indirect hernia?
Medial to- direct hernia
lateral to- indirect hernia
Which inguinal ring(s) does an indirect hernia pass through?
deep and superficail rings
What is the underlying defect for an indirect hernia?
failure of processus vaginalis to close
Which inguinal ring(s) does a direct hernia pass through?
superficial ring only
What hernia is most common in women? Where is it located?
femoral hernia
below femoral canal and lateral to pubic tubercle
What cells produce cholecystokinin?
I cells (duodenum, jejunum)
What stimulates CCK?
fatty acids, amino acids
What cells produce gastrin?
G cells (antrum of stomach)
What stimulates gastrin?
stomach distention, alkalinization, vagal stim, amino acids
What does motilin do?
produces migrating motor complexes, increased in fasting state
What cells produce GIP
K cells (duodenum, jejunum)
What are the symptoms of a VIPoma
watery diahrrhea, hypokalemia, achlorhydria
What cells produce VIP?
parasympathetic ganglia in sphincters, gallbladder, SI
What cells produce secretin?
S cells (duodenum)
What stimulates secretin?
acid, fatty acids in lumen of duodenum
What cells secrete somatostatin?
D cells (pancreatic islets, GI mucosa)
What stimulates somatostatin?
incr acid, decr vagal stim
What intestinal hormones affect insulin and glucagon secretion?
GIP- increases insulin
somatostatin- decreases insulin and glucagon
What intestinal hormones affect gastric acid secretion?
Gastrin (+ histamine, vagal stim)- incr H+ secr
GIP, Secretin, somastostatin- decr acid secr
What GI hormones affect pancreatic secretion?
CCK- incr secr
secretin- incr HCO3 secr
somatostatin- decreases
What two amino acids are potent stimulators of gastrin?
phenylalanine, tryptophan
What do parietal cells produce (2)
intrinsic factor, gastric acid
What cells produce pepsin?
chief cells of stomach
How does is gastrin stimulation of acid secretion mediated?
act directly on ECL cells which produce histamine
How do pancreatic secretions compare with high and low flow?
low flow- high Cl
high flow- high HCO3
What is the purpose of the D-xylose absorption test?
distinguishes GI mucosal damage from other types of malabsorption
How are glucose, galactose, and fructose absorbed? transported to blood?
glucose, galactose- taken up by SGLT1
froctuse- by GLUT-5
all taken to blood- GLUT-2
Where are iron, folate and B12 absorbed?
Iron- duodenum
floate- jejunum and ileum
Bqw- terminal ileum
What enzyme catalyzes the rate-limiting step of bile synthesis?
cholesterol 7a-hydroxylase
Compare direct to indirect bilirubin?
direct- conjugated with glucoronic acid, water sol
indirect- unconjugated, water insol
