Anatomy: Midgut COPY Flashcards
location of the small intestine
gastrointestinal tract
extends from pylorus to ileocaecal junction to the large intestine at the ileocaecal valve
3 parts of the small intestine
duodenum
jejunum
ileum
general overview duodenum
most proximal portion
derived from duodenum digitorum= twelve fingers length
runs from pylorus to the duodenojejunal junction
what are the 4 parts of the duodenum
D1= superior
D2=descending
D3=inferior
D4=ascending
superior D1
first section, spinal level L1
known as the cap
ascends upwards from pylorus of the stomach
connected to liver by the hepatoduodenal ligament
most common site for duodenal ulceration
3cm covered anteriorly and posteriorly by visceral peritoneum and remainder is retroperitoneal
descending D2
L1-L3
curves inferiorly around head of the pancreas
lies posteriorly to the transverse colon and anterior to the right kidney
internally marked by the major duodenal papilla
what is the major duodenal papilla
opening at which bile and pancreatic secretions enter from the ampulla of Vater (hepatopancreatic ampulla)
Inferior D3
L3
travels laterally to the left
crosses over the inferior vena cava and aorta
located inferiorly to the pancreas
posteriorly to the superior mesenteric artery and vein
Ascending
L3-L2
after duodenum crosses aorta it ascends and curves anteriorly to join the jejunum at the duodenojejunal flexure
duodenojejunal flexure
located here is a muscle called the suspensory muscle of the duodenum
contraction of the muscle widens the angle of the flexure
aids movement of the intestinal contents into the jejunum
duodenal ulcers
most likely to occur in the superior portion
common causes are helicobacter pylori infection and chronic NSAID therapy
perforation may be complicated by:
-inflammation of the peritoneum (peritonitis): damages surrounding viscera
-erosion of the gasproduodenal artery: causes haemorrhage and potential hypovolaemia shock
contrasting the jejunum and the ileum to the duodenum
they’re intraperitoneal
what attaches the jejunum and ileum to the posterior abdominal wall
mesentery
jejunum
begins are the duodenojejunal flexure
ileum ends at ileocaecal junction
what occurs at the ileocaecal junction
the ileum invaginate into the cecum to form the ileocecal valve
can prevent reflux of material back into the ileum
characteristic features of the jejunum
located in the upper left quadrant
thick intestinal wall
longer vasa recta (straight arteries)
less arcades (arterial loops)
red in colour
characteristic features of the ileum
located in the lower right quadrant
thin intestinal wall
shorter vasa recta
more arcades
pink colour
arterial supply of the duodenum
proximal to the major duodenal papilla: supplied by the gastroduodenal artery
distal to the major duodenal papilla: supplied by the inferior pancreaticoduodenal artery
marks the change form foregut to midgut
veins of duodenum follow major arteries and drain into hepatic portal vein
lymphatic drainage of the duodenum
pancreatoduodenal
superior mesenteric nodes
arterial and venous supply of jejunum and ileum
from the superior mesenteric artery
venous drainage is from the superior mesenteric vein
lymphatic drainage of the jejunum and ileum
superior mesenteric nodes
where is the cecum located
most proximal part of the large intestine
located between the ileum and ascending colon
when can the cecum be palpated
if enlarged due to faeces, inflammation or malignancy
structure of the cecum
continuous with the ascending colon
is intraperitoneal
has a variable mesentery
ileocecal valve function
prevents reflux of large bowel contents into the ileum during peristalsis
thought to function passively rather than a defined muscular sphincter
cecum arterial supply
ileocolic artery- branch of the superior mesenteric
divides into anterior and posterior cecal arteries
cecum venous supply
ileocolic vein
then empties into the superior mesenteric plexus
lymphatic drainage of the cecum
drains into the ileocolic lymph nodes
what is the appendix
narrow blind-ended tube
attached to the posteromedial end of the cecum
large amount of lymphoid tissue
no vital functions
what is the appendix supported by
the mesoappendix
fold of mesentery which suspends the appendix from the terminal ileum
position of the free end of the appendix is highly variable and categorised into 7 main locations depending on relationship to the ileum, caecum or pelvis
what is the most common position of the appendix
retrocecal
positions of the appendix
pre-ileac
post-ileac
sub-ileal
pelvic
subecal
paracecal
retrocecal
pre-ileal
anterior to the terminal ileum
1 or 2 o clock
post-ileal
posterior to the terminal ileum
1 or 2 o clock
sub-ileal
parallel with the terminal ileum
3 o clock
pelvic
descending over the pelvic brim
5 o clock
subcecal
below the cecum
6 o clock