anatomy of small and large intestines Flashcards
where does the jejunum begin
duodenojejunal flexure
where does the ileum end
ileo ceacal junction
how is digestion aided in the small intestine
addition of large amounts of fluid to the chyme
where is the jejunum
upper left abdomen
where is the ileum
lower right abdomen and pelvis
how can you tell the difference between the jejunem and the ileum
gradual change
The jejunum is wider bored,
thicker walled, and redder than the ileum; its wall feels thicker (shirt sleeve through jacket sleeve) because the permanent infoldings of the submucosa, the plicae circulares,
are larger, more numerous, and more closely set in the jejunum, whereas in the upper part
of the ileum they are smaller and more widely separated and in the lower part they are absent
jejunum has fewer arcades with long and infrequent vasa recta
where is the jejunal mesentery attached
post abdominal wall above and to the left of the aorta at L2
fat is deposited near the root and is scanty near the intestinal wall
where is the ileal mesentery attached
Attached below and to the right of the aorta at
the SI joint
fat is deposited through out
what is the name of the lymphoid tissue found in the mucous membrane of the lower ileum
Peyer’s patches
what does the ileocaecal valve consist of
two horizontal folds of mucous
membrane that project around
the orifice of the ileum
it stops colonic contents leaking back into the ileum
where do jejunal and ileal arteries branch from
superior mesenteric artery and its ileocolic branch
where does venous blood from the small intestine drain to
superior mesenteric
vein, which forms the portal vein
where is lymph drainage from the small intestine to
superior mesenteric
nodes, which are situated around the origin
of the SMA
what is the innervation of the small intestine
sympathetic, lesser splanchnic nerve T10
and 11, and parasympathetic (vagus) nerves
via the superior mesenteric plexus
referred pain is peri-umbilical
what is the origin of the SMA
arises from the aorta at L1 and carries nerves (sympathetic) derived from T10 and 11. It supplies the midgut
where are the lacteals
in the centre of each vilus for the absorption of fats and lipids (chyle)
where does the chyle from the lacteals go
cisterna chyli in the upper abdomen . first goes to mesenteric lymph channels that do not pass through lymph nodes but converge on the cisterna chyli
where does lymph from the nodes on the SMA pass to
cysterna chyli
what is meckel’s diverticulum
a remnant of the vitello-intestinal duct and may ulcerate
2 inches long,
2 feet from the end of the ileum, in
2% of people
it may ulcerate, create a fistula or a cyst
symptoms may be similar to appendicitis
how long is the colon
1.5 metres long
what are the internal differences between the small and large intestine
large intestine:
Lacks plicae circularis
Lacks villi
Lacks peyers patches
large intestine is larger in diameter, has omental appendages, 3 taenia coli and haustra
where is the caecum
right iliac fossa
may form recesses adjacent to it
the 3 taeniae coli converge here
covered by peritoneum but does not have a mesentery
where is the appendix
Mc burneys point
1/3 up from ASIS to umbilicus
can be found in many different positions: pelvic; subcaecal;
retrocaecal; retro-ileal; pre-ileal
describe the features of the appendix
a narrow blind ended tube hanging from the caecum
Its submucosa is packed full of lymphoid tissue
It is suspended on a short, but highly variable meso-appendix that transmits
the appendicular vessels
where does the appendicular artery arise from
the ileocolic branch of the
superior mesenteric, from the aorta
at L1 with nerves derived from
T10/11
describe the pain of appendicitis
refers pain to the peri umbilical region; the pain moves to right inguinal region later
describe the blood supply to the caecum
Anterior caecal artery
Posterior caecal artery
Appendicular artery (from posterior
caecal)
Lymph drainage is to nodes on the
SMA
where is the ascending colon
right lumbar region and is retroperitoneal. it is 13 cm long
how long is the transverse colon
38 cms long, across the umbilical region
intra peritoneal
where is the descending colon
left lumbar region
25 cms long
retroperitoneal
where is the sigmoid colon
25-38 cms long
in front of the pelivc brim
it becomes continuous with
the rectum in front of the 3rd sacral vertebra
intraperitoneal
where is the root of the transverse mesocolon
lies across the lower part of the pancreas
what is sigmoid volvulus
It may rotate upon itself
what is the ascending colon related to
the right kidney and duodenum with the ureter and major vessels medially
what is the descending colon related to
the left kidney with the duodeno-jejunal
flexure, ureter and major vessels medially
what are the branches of the SMA
Inferior pancreaticoduodenal intestinal arteries ileocolic, right colic and middle colic
what are the branches of the IMA
left colic
sigmoid branches
ends as the superior rectal artery
what structures are supplied by the IMA
1/3 of the transverse
colon, the splenic flexure, descending
colon and sigmoid colon
- hindgut
what structures are supplied by the SMA
inferior duodenum, small intestine head of pancreas caecum, ascending colon, hepatic flexure and 2/3 of the transverse colon
what does the IMA end as
uperior rectal
artery supplying the rectum and anal
canal
what does the IMA arise from
the aorta at L3 and carries sympathetic nerves derived from T12 (least splanchnic nerves) and parasympathetics from S 2, 3, 4 (NOT vagus)
how does SMA and IMA anastomose
the Marginal Artery
(of Drummond)
which may form a collateral
circulation should the IMA
become obstructed
what segments are associated with the coeliac trunk
(T7 – 9)
what segments are associated with the Superior mesenteric
T10/11
what segments are associated with the Inferior mesenteric
T12
what is the marginal artery of Drummond
an anastomosis with the SMA and IMA
this forms a collateral circulation should the IMA become obstructed
what are the branches of IMA
left colic artery supplies descending colon
sigmoid branches
superior rectal artery effectively the terminal branch of the IMA
arcades which supply the colon
where is Auerbach’s myenteric plexus of ganglia and nerves
lies between the muscular layers to control peristalsis
inner circular and outer longitudinal layer
what is Hirchsprung’s disease
Lack of normal development of the colonic innervation leads to a constricted, aganglionic segment of bowel, with a distended segment proximally (the innervation of which is normal)
where is the ileocaecal junction
right iliac fossa
what is the midgut
from the ampulla of Vater to 2/3rds along the transverse colon
how long is the rectum
13 cm long
begins infront of the 3rd sacral vertebra
retroperitoneal
where is the anal canal
rectal ampulla to anus
4 cm long
what does the inferior pancreaticoduodenal artery supply
head of the pancreas and the ascending and inferior parts of the duodenum
