Small Intestine and Large Intestine Flashcards
What regulates and coordinates numerous GI tract activities?
enteric nervous system
What are the activities that the enteric nervous system regulates and controls?
- gastric secretory activity
- GI blood flow
- peristalsis
Where is the ENS located?
between the walls of the GI tract
What is generally independent of CNS and receives input from sympathetic and parasympathetic innervation?
ENS
What is the sympathetic abdominal innervation and associated levels?
- greater splanchnic (T5-T9)
- lesser splanchnic (T10-T11)
- least splanchnic (T12)
- lumbar splanchnic (L1-L2/L3)
The greater splanchnic nerves run to the (1) ganglion which distribute to the (2)
- celiac
- foregut
The lesser and least splanchnic nerves run to the (1) and (2) which distribute to the (3)
- superior mesenteric ganglion
- aorticorenal ganglia
- midgut
The lumbar thoracic splanchnic nerves run to the (1) which distribute to the (2)
- inferior mesenteric ganglion
- hindgut
The celiac, superior mesenteric, aorticorenal, and inferior mesenteric plexus communicate via what?
intermesenteric plexus
What is the parasympathetic abdominal innervation and associated postganglionic distribution?
- vagus n. (CN X) - foregut and midgut
- pelvic splanchnic (S2-S4) - hindgut
Descending sympathetic innervation to the pelvic organs is via what plexuses?
superior hypogastric plexuses
What receives pelvic splanchnic nn. (parasympathetics)?
hypogastric nn (inferior hypogastric plexus)
What are the sympathetic activities of the abdominal organs and what do they go to?
- vasoconstriction
- decreased peristalsis
- decreased hormonal secretion
- goes to smooth muscle and glands
What are the parasympathetic activities of the abdominal organs and what do they go to?
- vasodilation
- increased peristalsis
- increased hormonal secretion
- goes to smooth muscle and glands
Pre-synaptic sympathetic fibers synapse directly into what?
suprarenal gland
What travels with sympathetic fibers (GSA)
pain (GVA)
What is the function of the small intestine?
absorption of nutrients
What are the parts of the small intestine?
- duodenum
- jejunum
- ileum
What does the small intestine extend from?
from pylorus to ileocecal junction
What do the jejunum and ileum contain that increase surface area for absorption?
elaborate folds of mucosa
What part of the small intestine doesn’t absorb any nutrients?
duodenum
What vertebral levels does the duodenum travel from?
L1 to L3
How many parts of the duodenum are there and what are their associated vertebral levels?
- 1st: superior part (L1)
- 2nd: descending part (L2-L3)
- 3rd: horizontal part (L3)
- 4th: ascending part (L3)
What is the most movable part of the duodenum?
superior part (first)
What is the very first part of the duodenum called?
duodenal cap (ampulla)
What attaches the superior part (1st part) of the duodenum to the porta hepatis of the liver and what is contained in it?
hepatoduodenal ligament:
- portal triad
**common bile duct
**hepatic artery
**portal vein
What parts of the duodenum are retroperitoneal?
the 2nd and 3rd part
What part of the duodenum attaches to the pancreas?
2nd part
What is located in the 2nd part of the duodenum and is where the bile duct + main pancreatic duct connect to the duodenum and drain into?
hepatopancreatic ampulla
What is the landmark located halfway along the second part of the duodenum that marks the transition from foregut to midgut?
hepatopancreatic ampulla (ampulla of Vater)
The hepatopancreatic ampulla connects to the duodenum via what?
major duodenal papilla
What is the opening of the accessory pancreatic duct into the 2nd part of the duodenum?
minor duodenal papilla
What part of the duodenum is important for the hepatobiliary tract?
2nd part of the duodenum
What does the 3rd part of the duodenum run in front of?
IVC and aorta
What runs in front of the 3rd part of the duodenum?
superior mesenteric vessels
What is the duodenojejunal junction?
where the 4th part of the duodenum meets and continues as the jejunum
What is a thin band of tissue that connects the duodenojejunal junction to the right crus of the diaphragm?
ligament of Treitz
What is the ligament of Treitz critical in ruling out?
malrotation of the gut in children
A GI bleed above the ligament of Treitz will lead to (1)
vomiting up blood
A GI bleed below the ligament of Treitz will lead to (1)
dark, tarry, maybe purplish stool
What two arteries supplies the duodenum and what does this mark the transition of?
- celiac trunk via gastroduodenal a
- superior mesenteric artery via inferior pancreaticoduodenal a
marks transition between foregut and midgut
What branches off the gastroduodenal artery to supply the upper portion of duodenum and head of pancreas?
ant. and post. superior pancreaticoduodenal a
What branches off the superior mesenteric artery and supplies the lower portion of the duodenum?
ant. and post. inferior pancreaticoduodenal a
What is the direct venous drainage of the duodenum?
hepatic vein
What is the indirect venous drainage of the duodenum?
- superior mesenteric vein
- splenic vein
The anterior lymphatic vessels of the duodenum drain into the (1) located alone the superior and inferior pancreaticoduodenal arteries and into the (2) which lie along the gastroduodenal artery, and then drains into (3)
- pancreaticoduodenal lymph nodes
- pyloric lymph nodes
- celiac lymph nodes
The posterior lymphatic vessels of the duodenum pass posterior to the head of the pancreas and drain into the (1); efferent lymphatic vessels from the duodenal lymph nodes drain into the (2)
- superior mesenteric lymph nodes
- celiac lymph nodes
What is the parasympathetic innervation of the duodenum?
vagus n
What is the sympathetic innervation pathway of the duodenum?
- spinal cord T5-T11
- greater and lesser splanchnic
- celiac and superior mesenteric plexuses
- peri-arterial plexuses extending to pancreaticoduodenal aa
- duodenum
What does the jejunum begin at and what part of the small intestine is considered the jejunum?
- begins at duodenojejunal flexure
- proximal 2/5 of intestine
Where does the ileum end at and what part of the small intestine is considered the ileum?
- ends at ileocecal junction
- distal 3/5 of intestine
What keeps the jejunum and ileum attached to the posterior abdominal wall?
mesentery
What is the function of the jejunum?
lipid and protein digestion
What are in the jejunum but not in the ileum?
plicae circulares
How does the jejunum differ from the ileum?
- thicker walls
- larger diameter
- arteries
What is the function of the ileum?
absorption of most digested nutrients
What has peyer’s patches?
ileum
How does the ileum differ from the jejunum?
- thinner walls
- smaller diameter
- arteries
What is the caliber of the jejunum in relation to the ileum?
jejunum : greater
ileum : lesser
What is the plicae of the jejunum in relation to the ileum?
jejunum : many
ileum : few
What is the mesentery length of the jejunum in relation to the ileum?
jejunum : shorter
ileum : longer
What is the peyer’s patches of the jejunum in relation to the ileum?
jejunum : few
ileum : present
What is the vascularity of the jejunum in relation to the ileum?
jejunum : greater
ileum : less
What is the length of vasa recta in the jejunum in relation to the ileum?
jejunum : longer
ileum : shorter
How many arcades are there in the jejunum in relation to the ileum?
jejunum : few
ileum : many
what extends from the duodenojejunal flexure obliquely downwards and to the right to the ileocecal junction?
root of the mesentery
What is the arterial supply of the jejunum and ileum?
superior mesenteric artery
- jejunal aa
- ileal aa
What are the characteristics of the jejunal aa?
- less arcades
- longer vasa recta
What are the characteristics of the ileal aa?
- more arcades
- shorter vasa recta
The jejunal and ileal aa unite to form loops or arches, called (1), which give rise to straight arteries, called (2)
- arterial arcades
- vasa recta
Why are arterial arcades important?
may help maintain arterial perfusion of the gut if the mesentery is twisted or stretched
What are the 6 branches of the SMA and mnemonic?
“In my room, I’m in jail”
I: inferior pancreaticoduodenal
M: middle colic
R: right colic
I: ileocolic
I: ileal
J: jejunal
What does the inferior pancreaticoduodenal aa supply?
duodenum
What does the middle colic a supply?
transverse colon
What does the right colic a supply?
ascending colon
What does the ileocolic a supply?
- ascending colon
- small portion of ileum
- cecum
What do the ileum aa supply?
ileum
What do the jejunal aa supply?
jejunum
What is the position of the SMV in relation to the SMA?
lies anterior and to the right of the SMA
Where does the SMV end?
posterior to the neck of the pancreas
What unites to form the hepatic portal vein?
SMV & splenic vein
Where are lacteals found?
in intestinal villi (only in the jejunum and ileum)
What is the function of lacteals?
absorb fat and drain into lymphatic plexuses in walls
What do lacteals drain into?
cisterna chyli
What are the 3 groups of lymph nodes in the lymphatic drainage of the jejunum and ileum and what do they drain into?
- juxta-intestinal
- mesenteric
- central superior
drain into superior mesenteric nodes
Where are juxta-intestinal lymph nodes located?
close to the intestinal wall
Where are mesenteric lymph nodes located?
scattered in arterial arches
Where are central superior lymph nodes located?
along proximal SMA
What do lymph nodes of the terminal ileum drain into?
ileocolic lymph nodes
What is the pattern of sympathetic innervation of the jejunum and ileum?
- spinal cord T8-T10
- greater, lesser, least splanchnic nn
- superior mesenteric nerve plexus
- synapse on celiac and superior mesenteric ganglia
- pre-arterial nerve plexuses on SMA branches
What provides parasympathetic innervation to the jejunum and ileum (specific trunk)?
- vagus nerve (posterior vagal trunks)
preganglionic synapse with postganglionic in myenteric and submucosal plexuses in intestinal wall
What type of fibers does the parasympathetic innervation provide to the jejunum and ileum?
intestine sensory fibers (GVA)
Intestine sensory fibers (GVA) are (1) to most pain stimuli, including cutting and burning; but are (2) to sudden distention (gas) and transient ischemia from abnormally long contractions (colic, spasmodic abdominal pains)?
- insensitive
- sensitive
What is the function of the large intestine?
water absorption and create feces
- helps reabsorb electrolytes and makes vitamins
Without enough electrolytes, what can happen?
small bowel obstruction
What does the large intestine span from?
ileocecal fold to the anus
What are the large intestine characteristics?
- omental appendices
- teniae coli
- haustra
- great internal diameter
What are small, fatty, omentum-like projects in the large intestine?
omental appendices
What is a thickened band of smooth muscle in the large intestine that is absent in the rectum and appendix?
teniae coli
What are the sacculations of the wall of the colon between the teniae?
haustra
What are the retroperitoneal organs and mnemonic?
SAD PUCKER
S: suprarenal gland
A: aorta/IVC
D: duodenum (2nd and 3rd)
P: pancreas (except tail)
U: ureters
C: colon (ascending/descending)
K: kidneys
E: esophagis
R: rectum
What parts of the large intestine are retroperitoneal structures?
- ascending colon
- descending colon
- rectum
Most tumors of the large intestine occur in the (1) and (2) or (3)
- sigmoid colon
- rectum
- ascending colon
Tumors in the ascending colon are more common among (1) and (2)
- women
- older patients
Rectosigmoidal tumors are more common among (1) and (2)
- men
- younger patients
With suspected GI bleeds, where is a person scoped first and why?
from above because an upper GI bleed is more life threatening
The interior of the colon can be observed and photographed in a procedure called (1) or (2)
- colonoscopy
- coloscopy
The interior of the sigmoid colon is observed with a (1), a shorter endoscope, in a procedure called (2)
- sigmoidoscope
- sigmoidoscopy
What is a blind-ended pouch in the RLQ that has no mesentery so it may be displaced?
cecum
What is suspended from the cecum and contains masses of lymphoid tissues?
appendix
What is the portion of mesentery connecting the ileum to the appendix?
meso-appendix
What can contain blind diverticulum?
appendix
What is found 2/3 of the way from umbilicus to ASIS?
McBurney’s point
Acute inflammation of the appendix, (1), is a common cause of an acute abdomen
- appendicitis
Digital pressure over the (1) registers maximum abdominal tenderness in appendicitis?
McBurney point
What is appendicitis in young people usually caused by?
hyperplasia of lymphatic follicles in appendix that occludes the lumen
What is appendicitis in older people usually caused by?
an obstruction from fecalith, a cocreation formed around fecal matter
The pain of appendicitis usually commences as vague pain in the (1) because of afferent pain fibers entering the spinal cord at T10 level; later the sever pain transmits to (2) from irritation of parietal peritoneum lining the posterior abdominal wall
- umbilical region
- right lower quadrant
Acute infection of the appendix may result in (1) in the (2) artery
- thrombosis
- appendicular
The ascending colon is covered anteriorly and on both sides with (1)
- peritoneum
What is located between the lateral aspect of the ascending colon and adjacent abdominal wall AND extends between right subphrenic space to the pelvis?
right paracolic gutter
What is the right colic flexure?
where the ascending colon turns into transverse colon
Why are the paracolic gutters clinically important?
allow for passage for infectious fluids from different compartments of abdomen
- ex: fluid from infected appendix can track up to the right paracolic gutter to hepatorenal recess
What is found between right and left colic flexures, and is horizontally oriented?
transverse colon
What is the transverse colon suspended from the posterior abdominal wall by?
transverse mesocolon
What is the most mobile part of the large intestine?
transverse colon
What is found between the left colic flexure to the left side of the groin?
descending colon
What covers the colon anteriorly and laterally, binding it to the posterior abdominal wall?
peritoneum
What is found between the lateral aspect of the descending colon and adjacent abdominal wall?
left paracolic gutter
What is “S” shaped, and begins at the pelvic inlet and descends to the level of S3?
sigmoid colon
What is the sigmoid attached to the pelvic wall by?
sigmoid mesocolon (mesentery)
What does the sigmoid colon have and why it is important?
- considerable freedom of movement
- important because this part of colon can get firm/hard as bowel moves through so you need the sigmoid colon to be able to move around
What is the most common site for diverticulitis?
sigmoid colon
What is a fixed, retroperitoneal organ that is continuous with the sigmoid colon at S3?
rectum
What is the rectum continuous with inferiorly?
anal canal
What branches off the aorta at L3?
inferior mesenteric artery
What are the 3 branches of IMA?
- left colic a
- sigmoid aa
- superior rectal artery
What is the main artery that gives off the marginal artery?
left colic artery
What gives off an appendicular artery that is important for the appendix?
ileocolic artery
What does the left colic artery supply?
descending colon
What do the sigmoidal arteries supply?
sigmoid colon
What does the superior rectal artery supply?
rectum
What provides collateral circulation to the large intestine?
marginal artery
What is the venous drainage of the large intestine?
portal system of veins
- superior mesenteric vein
- splenic vein
- inferior mesenteric vein
portal vein
- splenic v + SMV; R and L branches
What joins the splenic vein and drains blood from the hindgut?
inferior mesenteric vein
What is the lymphatic drainage of the cecum and appendix?
lymph nodes in meso-appendix drain to ileocolic nodes
What is the lymphatic drainage of the ascending colon?
- epicolic and paracolic nodes drain to:
- ileocolic and intermediate right colic nodes which drain to:
- superior mesenteric nodes
What is the lymphatic drainage of the transverse colon?
- middle colic nodes drain to
- superior mesenteric nodes
What is the lymphatic drainage of the descending and sigmoid colons?
- epicolic and paracolic drain to intermediate colic nodes which drain to inferior mesenteric nodes
- left colic flexure nodes drain to superior mesenteric nodes
What is the sympathetic innervation of the large intestine?
- superior mesenteric plexus
**cecum and appendix
**ascending colon
**transverse colon - lumbar part, inferior mesenteric plexus, and peri-arterial plexuses following IMA:
**descending and sigmoid colon
What is the parasympathetic innervation of the large intestine proximal to the left colic flexure?
vagus nerve
What is the parasympathetic innervation of the large intestine distal to the left colic flexure?
pelvic splanchnic nerves (S2-S4)
- via inferior hypogastric plexus and nn