Jejunum, Ileum and Large Intestines Flashcards
What is the longest part of the GI tract?
jejunum and ileum
Describe the jejunum and ileum?
convoluted tube that runs from the duodenojejunal junction to the ileocecal valve
What best describes the change from jejunum to ileum?
gradual - no clear boundary
Where does the jejunum lie?
upper left abdomen
Where does the ileum lie?
lower right abdomen and partly in the pelvis
What is the ratio of jejunum to ileum?
40% jejunum - 60% ileum
What do the jejunum and ileum had from and what are they suspended by?
posterior abdominal wall by the mesentery
What structures does the small intestine cross?
- base crosses 3rd part of the duodenum
- aorta
- inferior vena cava
- right gonadal vessels
- right ureter
What is contained within the mesentery?
- branches of the superior mesenteric artery, forming anastomatic arcades
- branches of the superior mesenteric vein
- lymph vessels
- nerves
Describe the jejunum?
- wide
- more plica circulares
- no peyer’s patches
- MALT (mucous associated lymphoid tissue)
Describe the ileum
- narrow
- fewer plic circulares
- numerous Peyer’s patches (aggregations of lymphoid tissue along the antimesenteric border)
- MALT
What does the ilecocecal valve consist of?
2 horizontal folds of mucous membrane that project around the orifice of the ileum
Where is the ileocecal valve situated?
at the junction of the small intestine and the large intestine (caecum)
What is the function of the ileocecal valve?
limit the refluc of colonic contents into the ileum and possibly control the flow of ileal contents into the caecum
What are jejunal and ileal arteries branches of?
superior mesenteric artery
Where does the superior mesenteric artery arise from?
aorta at the lower border of L1
What does the superior mesenteric artery supply?
Supplies the midgut (from ampulla of Vater in duodenum to 2/3 along the transverse colon)
What does the superior mesenteric artery form within the mesentery?
series of vascular anastomotic arcades
What has one pr two arcades with long vasa recta in the mesentery?
jejunum

What has many arcades with short vasa recta in its mesentery?
ileum

Where do jejunal and ileal veins drain into? And what does this eventually form?
superior mesenteric vein
portal vein

Draw a diagram indicating the lymphatic drainage of the small intestine

How is the mucous memrbane of the small intestine adapted to increase asbsoprtive SA?
raised in multiple villi (finger-like projections)
What is the function of the lacteal at the centre of each villus?
absoption of digested fats and lipids (chyle)
Where does chyle pass from and to?
- pass from lacteals into mesenteric lymph channels
- don’t pass through lymph nodes
- coverge on cisterna chyli
Where does cisterna chyli lie and where does it pass through?
- lies in upper abdomen
- pass through diaphragm as the thoracic duct
Draw a diagram showing the nerve supply of the small intestine

Where is pained referred from the small intestine
periumbilical (T10)
What are the functions of the large intestine?
- fluid-electrolyte balance - absorbs fluids and salts
- Dries out the chyme to form faeces
Where does the LI run between?
caecum to the rectum and anal canal
How long is the LI?
approximately 1.5m long
What are the components of the LI?
Caecum, ascending colon, hepatic (right colic) flexure, transverse colon, splenic (left colic) flexure, descending colon, sigmoid colon
What parts of the LI are retroperitoneal?
ascending & descending colon
What parts of the LI are on the mesentery? (intraperitoneal)
transverse & sigmoid colon
How does the diameter of the LI compare with the SI?
larger unless contracted by a wave of peristalsis
What do longitudnal smooth muscle fibres thicken to form?
3x taenia coli
What length are taenia coli?
shorter than the LI
What are the sacculations/pouches of the LI known as?
haustra
mobile
What is the name for the tags of fat in the LI?
Possesses epiploic/omental appendices (appendices epiploicae)
What does the LI lack that is present in the SI?
Peyer’s patches
What is the widest and first part of the LE?
caecum
Where is the caecum located?
Lies below the junction of the ileum with the large intestine in the right iliac fossa
What is the caecum continous with?
Continuous with the ascending colon
What is the caecum covered by?
Covered by peritoneum but not on a mesentery
How does the ileum enter the caecum?
enters the caecum obliquely and partly invaginates into it, forming ileocaecal orifice
What is the veriform appendix?
A blind intestinal diverticulum, from the posteromedial aspect of the caecum
What cinverge of the root of the veriform appendix? And what is the name of this point?
The 3 taeniae coli converge at the root of the vermiform appendix
Root of vermiform appendix is at McBurney’s point
Describe the submucosa of the veriform appendix
packed full of lymphoid tissue
Where is the veriform appendix suspended?
suspended on a short but highly variable mesoappendix that transmits the appendicular vessels
What are the differnet anatomical positions the veriform appendix can be found in?
retrocaecal (65%); pelvic (30%); subcaecal; retroileal; pre- ileal
Where does the base of the appendix most often lie deep to?
a point that is one third of the way along the oblique line joining the right anterior superior iliac spine to the umbilicus (McBurney point).
Where is the ascending colon located?
in the right lumbar region
What is the ascending colon between?
caecum and hepatic flexure
Describe the attachment of the ascending colon
secondarily retroperitoneal
Where is the right parabolic gutter formed?
between ascending colon and posterior abdominal wall
Where does the transverse colon extend between?
hepatic and splenic flexures
What is the transverse colon suspended by?
transverse mesocolon
Describe the attachment of the transverse colon
intraperitoneal
What is the hepatic (right colic) flexture related to?
liver
What is the splenic (left colic) flexture related to?
spleen
What is the transverse mesocolon?
mesentery of the ytransverse colon
What does the root of the transverse mesoclon cross?inferior edge of the pancreas in the left lumbar region
Where is the descending colon located?
left lumbar regiom, hidden anteriroly by the small intestine
What forms the left paracolic gutter?
descending colon and posterior abdominal wall
What is the sigmoid colon a continuation of?
Continuation of the descending colon in front of the pelvic inlet
What is the sigmoid colon suspended by?
sigmoid mesocolon
What is the sigmoid colon continous with?
Continuous with the rectum in front of the 3rd sacral vertebra
Where is the rectum located within the peritoneum?
Retroperitoneal
Where does the rectum begin?
in front of 3rd sacral vertebra
What does rhe rectum follow the curve of?
sacrum and coccyx
Where does the rectum end?
Ends in front of the tip of the coccyx by piercing the pelvic diaphragm & becoming continuous with the anal canal
What does the rectum lack?
Lacks taenia, haustra or appendices epiploica
What is the function of the rectum?
Stores faeces
How long is the anal canal
approx. 4cm
What is the anal canal
canal from pelvic diaphragm to the anus
conduit to the outside world
Where does the superior mesenteric artery originate
lower border of L1 vertebra
What do branches of the superior mesenteric artery supply?
part of the large intestine, from vermiform appendix to proximal 2/3 of the transverse colon
What are the 3 main branches of the superior mesenteric artery that form anastomoses in the LI
− Ileocolic artery: Caecum; appendicular artery
− Right colic artery: Ascending colon
− Middle colic artery: Transverse colon
Describe the appendicular artery
a terminal artery that runs close and parallel to the appendi
Where does the inferior mesenteric artery arise from?
arises from aorta at L3
What do the branches of the inferior mesenteric artery supply?
supply distal 1/3 of the transverse colon, the splenic flexure, descending colon & sigmoid colon
What are the branches of the inferior mesenteric artery and what do they supply?
− Left colic artery: Splenic flexure, descending colon
− Sigmoid artery: Sigmoid colon
What does the inferior mesenteric artery end as?
ends as the superior rectal artery supplying the rectum & anal canal
What nerves run with the coeliac trunk to the foregut?
− Sym from T5-9 (greater splanchnic)
− PSym from vagus
What nerves run with the superior mesenteric artery to the midgut?
− Sym from T10-11 (lesser splanchnic)
− PSym from vagus
What nerves run with the inferior mesenteric artery to the hindgut?
− Sym. from T12-L3 (least splanchnic and lumbar splanchnic nerves)
− Psym. from S2-4
Where does pain from areas supplied by the coeliac trunk refer to?
epigastric region (T7-9)
where does Pain from areas supplied by Superior
mesenteric artery refer to?
Periumbilical region (T10-11)
− Appendicitis pain in the first 6-8h
Where does pain from areas supplied by the inferior mesenteric artery refer to?
suprapubic region (T12)