Jejunum, Ileum and large intestine Flashcards
Where do the jejunum and ilem lie in the abdomen?
- Jejunum in the upper left abdomen
- Ileum lower right and partly in the pelvis
After the duodenum how much of the small intestine is jejunum and ileum?
- Proximal 40% jejunum
- Distal 60% ileum
Gradual change from jejunum to ileum
What is the border of the jejunum and duodenum called?
The duodenojejunal junction
What does the jejunum and ileum hang from the posterior abdominal wall by?
The mesentary
What structures does the mesentary cross near the midline?
- Its base crosses the 3rd part of the duodenum
- Aorta
- IVC
- Right gonadal vessels
- Right ureter
What structures are found within the mesentary?
- Branches of the superior mesenteric artery, forming anastomotic arteries
- Branches of the superior mesenteric vein
- Lymph vessels
- Nerves
How many layers does the mesentary have?
2
What are the differences between the jejunum and ileum?
- Jejunum wide, ileum narrow
- More plica circulares in jejunum
- The ileum contains MALT as well as numerous peyer’s patches
Describe the shape of the ileocaecal valve
- Rudimentary structure
- Consists of 2 horizontal folds of mucous membrane that project aroun the orifice of the ileum
What is the function of the ileocaecal valve?
To limit the reflux 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
What does the superior mesenteric artery supply?
The midgut (from the ampulla of Vater in duodenum to 2/3 along the transverse colon)
What are the differences between the vascular supply of the jejunum and ileum?
- Ileum
1 or 2 arcades with long vasa recta in its mesentary - Ileum
Many arcades with short vasa recta in its mesentary
What do the jejunal and ileal veins drain into?
The superior mesenteric vein that eventually forms the portal vein
What is the lymph drainage from peyer’s patches to the cisterna chyli?
- Peyer’s patches
- Superior Mesenteric nodes
- Intestinal trunk
- Cisterna chyli
lacteals drain into lymph vessels then cisterna chyli
What is the NERVE SUPPLY of jejunum and ileum?
- Sympathetic from greater and lesser
- Vagus
Combine to make coeliac plexus -> superior mesenteric plexus -> myenteric and submucosal plexus
What parts of the colon are in the peritoneum and what parts are not?
- The ascending and descending colon are secondarily retroperitoneal
- Transverse and sigmoid colon
What are the 3 taenia coli?
Thickened smooth muscle fibres
- Free
- Mesenteric
- Omental
What are haustra?
small segmented pouches of bowel separated by the haustral folds. They are formed by circumferential contraction of the inner muscular layer of the colon
mobile
What are peyer’s patches?
Small masses of lymphatic tissue found throughout the ileum region of the small intestine
What are appendices epiploicae?
Small pouches of the peritoneum filled with fat and situated along the colon, but are absent in the rectum
Where is the caecum located in the large intestine?
- Inferior to the opening of the ileocecal valve
- In the right iliac fossa
- Covered by peritoneum but not on a mesentary
Where do the 3 taeniae coli converge?
The appendix
What is the submucosa of the veriform appendix full of?
Lymphoid tissue
What is at McBurney’s point?
The root of the appendix
Where can the appendix be found?
One of numerous anatomical positions:
- Retrocaecal (65%)
- Pelvic (30%)
- Subcaecal
- Retroileal
- Pre-ileal
What does the large intestine include?
- Caecum
- Ascending colon
- Hepatic (right coli) flexure
- Transverse colon
- Splenic (left colic) flexure
- Descending colon
- Sigmoid colon
Where are there portocaval anastomoses in the colon?
Posteriorly to ascending and descending colon
Where is the ascending colon found?
- Right lumbar region
- Between caecum nd hepatic flexure
- Secondarily retroperitoneal
Where is the right paracolic gutter formed?
Between the right side of the ascending colon and posterior abdominal wall
What is the transverse colon suspended by?
Transverse mesocolon, it is intraperitoneal
What is the mesocolon?
The mesentary of the colon
Where does the transverse mesocolon cross the pancrease?
The root of the transverse mesocolon crosses the inferior edge of the pancreas
What is a paracolic gutter?
Recesses between the abdominal wall and the colon. - Clinically important because they allow a passage for infectious fluids from different compartments of the abdomen
Where is the left paracolic gutter formed?
Between the left side of the descending colon and posterior abdominal wall
Is the sigmoid colon intra or retroperitoneal
Intraperitoneal
What is the sigmoid colon suspended by?
- Sigmoid mesocolon
- Long; making volvulus more common in sigmoid colon
Where does the sigmoid colon become continous with the rectum?
The 3rd sacral vertebra
Where does the rectum end?
The pelvic diaphragm
How long is the anal canal?
~ 4cm
Where is the rectum located in relation to the peritoneum?
- Upper 1/3 intraperitoneum
- Lower 2/3 retroperitoneal
What structures does the rectum lack?
- Taenia
- Haustra
- Appendices epiploica
What is the function of the rectum?
To store faeces
Where does the superior mesenteric artery originate?
Lower border of L1 vertebra
Where are the nodes roughly located?
Origins of the superior and inferior mesenteric arteries
What does the superior mesenteric artery supply?
- Part of large intestine:
from veriform appendix to
proximal 2/3 of transverse colon
What are the branches of the superior mesenteric artery and what do they supply?
- Middle colic artery: Transverse colon - Right colic artery Ascending colon - Illeocolic artery CAecum - Appendicular artery A terminal artery that runs close and parallel to the appendix
Where does the inferior mesenteric artery arise?
From the aorta at L3
What do the branches of the inferior mesenteric artery supply?
- Distal 1/3 of the transverse colon
- Splenic fissure
- Descending colon
- Sigmoid colon
What are the main branches of the inferior mesenteric artery?
- Left colic artery
Splenic fissure, descending colon - Sigmoid artery
Sigmoid colon
Where does the inferior mesenteric artery end?
At the superior rectal artery supplying the rectum and anal canal
What is the marginal artery?
- An anastomosis between inferior and superior mesenteric arteries
- Forms a collateral circulation should the inferior mesenteric artery become obstructed
What do the veins of the colon eventually drain into?
Portal vein
Nerve supply of the colon
Greater lesser and least splanchnic nerves
VAgus or sacral 2 -4
What is the coeliac trunk/foregut nerve supply?
- Symp T5-9 (greater splanchnic)
- Vagus
What is the superior mesenteric/midgut nerve supply?
- Symp T10-11 (lesser splanchnic)
- Vagus
What is the inferior mesenteric/hindgut nerve supply?
- Symp T12-L3 (least splanchnic and lumbar splanchnic nerves)
- Para: S2-4
Where will celiac trunk pain refer?
Epigastric region (T7-9)
Where will superior mesenteric pain refer?
Periumbilical region (T10-11) - Appendicitis pain in first 6-8hrs
Where will pain from the inferior mesenteric refer?
T12
Where will pain from the inferior mesenteric refer?
T12
Where is pain referred from the Jejunum and ileum?
Periumbilical (T10)