The Small and Large Intestine Flashcards
The first part of the small bowel is the duodenum which is mostly retroperitoneal. is it fixed or mobile?
position is fixed and constant
The first part of the duodenum immediately beyond the pyloric sphincter is prone to peptic ulceration, why is this dangerous
the posterior wall lies directly in contact with a medium sized artery, the gastroduodenal artery.
how is the rest of the small intestine, the jejunum and ileum attached to the posterior of the abdomen, is it mobile or fixed
by a mesentery and is relatively mobile
What does the fact that the jejunum and ileum are mobile mean
This means that this part of the bowel is often involved in hernias and can become twisted (volvulus).
The small bowel is the organ of nutrient absorption and needs a high surface area;
what are the four things that help achieve this
it is long,
the mucosa has multiple mucosal folds (plicae circulares), there are villi on the mucosal folds
and microvilli on each individual epithelial cell.
The ileum is marked by
by the appearance of large submucosal lymph nodules known as Peyer’s patches.
The artery to the mid-gut is the
superior mesenteric artery, it is a branch off the front of the aorta just below the coelic trunk and supplies from the 3rd part of the duodenum to two thirds of the way along the transverse colon.
Where does the superior mesenteric artery come from and what does it supply
it is a branch off the front of the aorta just below the coelic trunk and supplies from the 3rd part of the duodenum to two thirds of the way along the transverse colon.
what is Meckel’s diverticulum
Occasionally the ileum bears a blind-ended diverticulum about 1 meter from its termination (Meckel’s diverticulum) this is an embryonic remnant of the attachment of the mid gut loop to the yolk sac.
To the right of the main superior mesenteric artery are branches to the colon;
the ileo-colic, right colic and middle colic branches
Note that the arteries (of jejunum and ileum) have accompanying veins, trace these upwards to where they pass over the third part of the duodenum, here they pass through
the pancreas, join the splenic vein to form the portal vein, and pass onto the liver.
what is the duodeno-jejunal flexure
the border between the duodenum and the jejunum,
Only after the duodenojejunal flexure does the small intestine become mobile.
The large intestine starts at the
ileo-caecal valve in the right iliac fossa.
the large intestine alternates between a retroperitoneal and a mesenteric disposition; the ascending and descending colon are normally
retroperitoneal
the transverse and sigmoid colon lie within
a mesentery
The outer longitudinal muscle layer forms three bands,
the taenia coli,
Between the longitudinal taenia coli the circular inner layer bulges repeatedly between them to form characteristic ‘haustrations’.
Away from the mesentry there are two rows of ear-like pads of fat; known as appendices epiploicia, these mark where the blood vessels penetrate the muscles of the bowel wall to supply the mucosa and sub mucosa.
the taenia coli arrangement
start at the base of the appendix and broaden out and fuse to form a continuous layer at the recto sigmoid junction.
what are appendices epiploicia and what do they mark
Away from the mesentry there are two rows of ear-like pads of fat; known as appendices epiploicia, these mark where the blood vessels penetrate the muscles of the bowel wall to supply the mucosa and sub mucosa.
McBurney’s point
The appendix arises from the base of the caecum at a fairly fixed position, whose surface marking is referred to as McBurney’s point but its distal end may lie in a variety of positions within the abdomen or pelvis giving rise to a range of symptoms when it becomes inflamed and involves adjacent structures during appendicitis.
The hind gut extends from
the distal third of the transverse colon to one third of the way down the anal canal
What is the hindgut supplied by and where does thus arise
supplied by the inferior mesenteric artery which arises from the lower aorta just above the bifurcation
The branches of the inferior mesenteric artery anastomose with each other and with a branch of the middle colic artery to form a vessel which runs along the wall of the colon
the marginal artery of Drummond.
the superior rectal artery enters the pelvic cavity posterior to the rectum and lies where
in the mesorectum beween the rectum and the sacrum.Within the mesorectum it divides into three branches.
Carcinoma of the colon and rectum are common in the western world. They spread directly via
the blood stream, through the portal circulation, to the liver but also through the lymph vessels to regional lymph nodes.
Which vein drains blood from the colon and where does it flow to?
Inferior mesenteric vein drains into the splenic vein.
Where does lymph from the small bowel drain?
Into the cisterna chyli and to the thoracic duct
Which foodstuffs are absorbed through the lymphatic system?
Lipids
What 4 anatomical features ensure the small bowel has a high surface area for absorption of nutrients?
Length, mucosal folds (plicae circularis), villi, micro-villi.
Where is the junction between the mid gut and the hind gut?
2/3 of the way along the transverse colon.
How do you distinguish a loop of large intestine from that of small intestine?
Large intestine has appendices epiploicae and tenea coli. The small bowel is centrally located and the colon round the sides.
Which part of the bowel is supplied by sacral nerves 2, 3 and 4?
The hind gut.
