small and large intestines Flashcards
what makes up the SI?
duodenum, jejunum and ileum
what are the boundaries of the SI?
pylorus of stomach to ileocalceal junction where it meets the LI at the ileocalceal valve
what are the boundaries of the duodenum?
pylorus of stomahc to duodenojejunal junction
what are the parts of the duodenum?
superior, descending, horizontal, ascending
what shape is the duodenum?
C
what does the duodenum wrap around?
head of the pancreas
what is the 1st section of the duodenum called?
the ‘cap’
what connects the superior part of the duodenum to the liver?
hepatoduodenal ligament
what is the most common site of duodenal ulceration?
the superior part
is the duodenum retro or intra peritoneal?
only the superior part is intraperitoneal, the rest is retroperitoneal (only covered anteriorly)
the descending section of the duodenum lies posteriorly/anteriorly to what?
posterior to the transverse colon and anterior to the right kidney
what is the descending duodenum marked internally by?
the major duodenal papilla - the opening at which bile and pancreatic secretions enter from the ampulla of Vater (hepatopancreatic ampulla)
what does the inferior duodenum cross when it travels laterally to the left?
IVC and aorta
what is the inferior duodenum located inferiorly and posteriorly to?
inferiorly to the pancreas and posteriorly to the superior mesenteric artery and vein
after the duodenum crosses the _____, it ascends and curves _______ to join the jejunum at a sharp turn known as the ___________________
- aorta
- anteriorly
- duodenojejunal flexure
what slip of muscle is located at the duodenojejunal junction?
suspensory muscle of the duodenum — contraction of this muscle widens the angle of the flexure, and aids movement of the intestinal contents into the jejunum
at what vertebral levels are each of the duodenal parts?
superior = L1
descending = L1-L3
horizontal = L3
ascending = L3-L2
are the jejunum and ileum intra or retro peritoneal?
intraperitoneal
what attaches the jejunum and ileum to the posterior abdominal wall?
mesentery (a double layer of peritoenum)
where does the jejunum begin?
duodenojejunal flexure
where does the ileum end?
ileocaecal junction
what does the ileum do at the ileocaecal junction?
invaginates into the caecum to form the ileocaecal valve — although it is not developed enough to control movement of material from the ileum to the cecum, it can prevent reflux of maternal back into the ileum
what is the arterial supply of the duodenum proximal to the major duodenal papilla?
gastroduodenal artery = branch of common hepatic from coeliac trunk
what is the arterial supply of the duodenum distal to the major duodenal papilla?
inferior pancreaticoduodenal artery = branch of superior mesenteric
what marks the transition from the embryological foregut to midgut?
major duodenal papilla
the veins of the duodenum follow the major arteries and drain into what?
the hepatic portal vein
lymphatic drainage of the duodenum is to what nodes?
pancreatoduodenal and superior mesenteric nodes
arterial supply of the jejunum and ileum is from what?
superior mesenteric artery
the SMA arises from the aorta at what vertebral level?
L1 (immediately inferior to the coeliac trunk)
describe how arcades and vasa recta form
the SMA moves between layers of mesentery, splitting into approx 20 branches — these branches anastomose to form loops called arcades — from the arcades, long and straight arteries arise, called vasa recta
venous drainage of the jejunum and ileum is via ______________ - unites with the _____________ at the neck of the pancreas to form the _________________
venous drainage via superior mesenteric vein - unites with the splenic vein at the neck of the pancreas to form the hepatic portal vein
lymphatic drainage of the jejunum and ileum is to what nodes?
superior mesenteric nodes
identify A-C. what happens at B? function of C?
A = head of pancreas
B = major duodenal papilla = where hepatopancreatic ampulla empties bile and pancreatic juice into the duodenum
C = folds called plicae circulares — increase SA for absorption
identify A-C. where does C extend?
A = jejunum
B = ileum
C = mesentery — attaches A and B to posterior body wall. extends from the duodenojejunal junction (left side of L2) to the ileocecal junction (right sacroiliac joint)
what does the root of the mesentery cross?
• ascending and horizontal parts of duodenum
• aorta
• IVC
• right ureter
• right psoas major
• right testicular/ovarian vessels
what lies between the 2 layers of the mesentery?
superior mesenteric vessels, lymph nodes, autonomic nerves, fat
jejunum vs ileum : colour
the jejunum is darker red due to increased vascularity
jejunum vs ileum : caliber
the jejunum has greater caliber
jejunum vs ileum : wall thickness
the jejunum has a thicker wall
jejunum vs ileum : number of plicae
the jejunum has large, tall and closely packed plicae. plicae are sparse and low in the ileum
jejunum vs ileum : vasa recta
the vasa recta supplying the jejunum are long and the ileum short
jejunum vs ileum : arcades
the jejunum has a few large loops, the ileum has many short loops
jejunum vs ileum : fat in mesentery
there is less fat in the mesentery of the jejunum compared to that of the ileum
what does the superior mesenteric vein unite with to form the portal vein?
splenic vein
what nerve transmits preganglionic sympathetic fibres to the jejunum and ileum?
lesser splanchnic nerve
what ganglion do the post ganglionic sympathetic fibres suppling the midgut and hindgut arise in?
superior mesenteric ganglion
lymph from the jejunal and ileal lymph nodes drain to what nodes?
superior mesenteric nodes
identify A-D
A = superior mesenteric artery
B = jejunal arteries
C = ileal arteries
D = superior mesenteric vein
where does the LI extend?
from the cecum to the anal canal
function of colon (aka LI)
revives digested foods from the SI, from which it absorbs water and electrolytes to form faeces
what are the 4 parts of the colon?
ascending, transverse, descending and sigmoid colons — these form an arch which encircles the SI
is the ascending colon intra or retro peritoneal?
retroperitoneal
what does the ascending colon ascend superiorly from?
cecum
what happens when the ascending colon meets the right lobe of the liver?
it turns 90 degrees to move horizontally = right colic flexure aka hepatic flexure — marks the start of the transverse colon
where does the transverse colon extend?
extends from the right colic flexure to teh spleen, where it turns another 90 degrees to point inferiorly = left colic flexure aka splenic flexure
at the left colic/splenic flexure, the colon is attached to the diaphragm by what?
phrenicocolic ligament
what is the least fixed part of the colon?
the transverse colon is the least fixed part of the colon, and is variable in position (it can dip into the pelvis in tall, thin individuals)
is the transverse colon intra or retro peritoneal?
unlike the ascending and descending colon, it is intraperitoneal and is enclosed by the transverse mesocolon
is the descending colon intra or retro peritoneal?
retroperitoneal in most individuals, but is located anteriorly to the left kidney, passing over its lateral border
what quadrant is the sigmoid colon in?
left lower quadrant
the sigmoid colon extends from the left iliac fossa to the level of what vertebra?
S3
the sigmoid colon is attached to the posterior pelvic wall by what?
sigmoid mesocolon (mesentery)
what permits the sigmoid colon the be particularly mobile?
the long length of the mesentery
what are paracolic gutters?
they are 2 spaces between the ascending/descending colon and the posterolateral abdominal wall. clinically important as they allow material that has been released from inflamed or infected abdominal organs to accumulate elsewhere in the abdomen
what are attached to the surface of the LI?
omental appendices = small pouches of peritoneum filled with fat
what run longitudinally along the surface of the large bowel?
3 strips of muscle called teniae coli = mesocolic, free and omental coli
what are haustra?
sacculations in the wall of the LI formed from the contraction of the teniae coli that shortens the bowel wall
LI vs SI diameter?
LI has a much wider diameter
what happens at the rectosigmoid junction?
the special features of the LI (omental appendices, teniae coli, haustra) cease at this junction where the smooth muscle of the tenaie coli broaden to form a complete layer within the rectum
where does the greater omentum lie in relation to the colon?
lies anterior to the colon
where do the kidneys lie in relation to the colon?
right kidney posterior to ascending colon
left kidney posterior to descending colon
where does the urinary bladder lie in relation to the colon?
anterior to the sigmoid colon
where do the duodenum and head of the pancreas lie in relation to the colon?
posterior to the transverse colon
ascending colon and proximal 2/3 of the transverse colon = derived from _________
distal 1/3 transverse colin, descending colon and sigmoid colon = derived from ________
- midgut
- hindgut
as a general rule, midgut-derived structures are supplied by the _____________ artery and hindgut-derived structures by the ______________ artery
s a general rule, midgut-derived structures are supplied by the superior mesenteric artery and hindgut-derived structures by the inferior mesenteric artery
the ascending colon receives arterial supply from what 2 branches of the SMA?
the ileocolic and right colic arteries
the ileocolic artery gives rise to what branches? what do they all supply?
colic, anterior cecal, and posterior cecal branches — all supply the ascending colon
what is the arterial supply of the transverse colon and why?
derived from midgut and hindgut therefore supplied by branches of both the SMA and IMA
• right colic artery (from SMA)
• middle colic artery (from SMA)
• left colic artery (from IMA)
the descending colon is supplied by what single branch of the IMA?
the left colic artery
arterial supply of the sigmoid colon?
sigmoid branches of the IMA
describe the marginal artery (of Drummond)
- clinically important as it provides collateral supply to the colon (thereby maintaining arterial supply in the case of occlusion or stenosis in one of the major vessels)
- forms a major anastomotic network between the SMA and IMA
venous drainage of the ascending colon
ileocolic and right colic veins - empty into the superior mesenteric vein
venous drainage of the transverse colon
middle colic vein — empties into the SMV
venous drainage of the descending colon
left colic vein - drains into the inferior mesenteric vein
venous drainage of the sigmoid colon
drained by the sigmoid veins into the IMV
what do teh SMV and IMV ultimately drain into? what does this allow?
hepatic portal vein — allows toxins absorbed from the colon to be processed by the liver for detoxification
midgut derived structures — receive their sympathetic, parasympathetic and sensory supply via nerves from the ________________
superior mesenteric plexus
hindgut derived structures — receive their sympathetic, parasympathetic and sensory supply via nerves from the ________________
parasympathetic/sympathetic via what nerves?
inferior mesenteric plexus
• PS via pelvic splanchnic nerve
• S via lumbar splanchnic nerve
lymphatic drainage of the ascending and transverse colon?
superior mesenteric nodes
lymphatic drainage of the descending and sigmoid colon?
inferior mesenteric nodes
most of the lymph from the superior and inferior mesenteric nodes passes into the ____________, and on to the _____________ - where it ultimately empties into the ___________
most of the lymph from the superior and inferior mesenteric nodes passes into the intestinal lymph trunks, and on to the cisterna chyli - where it ultimately empties into the thoracic duct
A = caecum
B = ascending colon
C = hepatic flexure
D = transverse colon
E = splenic flexure
F = descending colon
G = sigmoid colon
H = right paracolic gutter
I = left paracolic gutter
what are the 3 gross distinguishing features of the LI?
= haustra, teniae coli and epiploic appendages
what is the branch of the SMA that supplies the caecum?
ileocolic artery
what is the branch of the iliocolic artery that supplies the appendix?
appendicular artery
identify A-D and where do they all arise from?
A = ileocolic artery
B = marginal artery
C = right colic artery
D = middle colic artery
these all arise from the superior mesenteric artery
A = aorta
B = inferior mesenteric artery
C = left colic artery
D = sigmoid arteries
draw the superior mesenteric and inferior mesenteric arteries with their branches
The root of the mesentery is attached to the posterior wall along a line that extends from the left side of the second lumbar vertebra to the region of which joint?
sacroiliac
Which part of the duodenum has part of the lesser omentum attached to its superior border and part of the greater omentum attached to its inferior border?
superior/first
Which part of the duodenum is supported by the suspensory muscle of the duodenum (ligament of Treitz)?
ascending/fourth
The parts of the duodenum proximal to the major duodenal papilla are supplied by a branch of the gastroduodenal artery which arises from the coeliac trunk. What is the name of this branch?
superior pancreaticoduodenal
Most absorption occurs in the jejunum but the terminal ileum is the only site of absorption for which substance?
vitamin B12
what is the region of the small intestine with the highest abundance of plicae circulares?
proximal jejunum
Histologically the duodenum can be differentiated from other parts of the small intestine by the presence of what?
Brunner’s glands
Histologically the ileum can be differentiated from other parts of the small intestine by the presence of what?
Peyer’s patches
In relation to surface anatomy the base of the appendix is located at McBurney’s point.
McBurneys’s point is located two-thirds of the way along an imaginary line that extends laterally from the umbilicus to which structure?
ASIS
Afferent pain fibres from the appendix accompany the sympathetic fibres and enter the spinal cord at the level of T10. Which abdominal region is pain from the appendix perceived?
umbilical
The ilioinguinal and iliohypogastric nerves cross behind the ascending colon. From which spinal segment do these nerves arise?
L1
The transverse colon is suspended by the transverse mesocolon from the anterior border of which structure?
pancreas
The transverse mesocolon attaches to the superior border of the transverse colon. Which structure is attached to the lower border of the transverse colon?
greater omentum
Which 4 nerves cross posterior to the descending colon?
Femoral
Iliohypogastric
Ilioinguinal
Lateral cutaneous nerve of the thigh
At which vertebral level does the sigmoid colon meet the rectum?
S3
