Lower GI Tract - Jejunum, Ileum, Colon, Rectum and Anal Canal Flashcards
Are the small intestines intra or retroperitoneal?
Intraperitoneal
How are the jejunum and ileum attached to the posterior abdominal wall?
Via mesentery
What is the blood supply to the small intestines?
Superior Mesenteric Artery
Sends 15-18 branches into the jejunum and ileum mesentery
What happens to the arteries in the mesentery of the small intestine?
They anastomose to form loops called Arcades
What are vasa recta?
Long, straight arteries arising from the arcades in the mesentery of the small intestine
What is the venous drainage of the small intestines?
Superior mesenteric vein
What happens to the SMV at the head of the pancreas?
Unites with the splenic vein to form the hepatic portal vein
What is the lymphatic drainage of the small intestine?
Lymph drains into the superior mesenteric nodes
Name the 4 superior mesenteric nodes?
Mesenteric
Ileocolic
Right colic
Middle colic
What is the para and symp innervation of the small intestine?
Para - coeliac plexus
Symp - greater and lesser splanchnic nerves
What is the difference in colour between the jejunum and ileum?
Jejunum - deep red
Ileum - paler pink
What is the difference in walls of the jejunum and ileum?
Jejunum - thick, heavy walls
Ileum - thin, light walls
What is the difference in vasculature between the jejunum and ileum?
Jejunum - greater vasculature
Ileum - less vasculature
What is the difference in vasa recta between the jejunum and ileum?
Jejunum - long vasa recta
Ileum - short vasa recta
What is the difference in aracdes between the jejunum and ileum?
Jejunum - few, large arcades
Ileum - many arcades
What are tenia coli?
3 thickened longitudinal bands of smooth muscle in the intestines
What does contraction of tenia coli cause?
Contractions shorten the associated intestinal wall, forming haustra
Name all the parts of the large intestine
Cecum, appendix, ascending, transverse, descending and sigmoid colon, rectum and anal canal
What is the cecum?
The cecum is an intestinal pouch continuous with the ascending colon
What does the cecum act as?
Acts as a reservoir for chyme which it receives from the ileum
What is the appendix? What does it contain?
The appendix is a vermiform projection of lymphoid tissue - contains large amount of lymphoid tissue but has no vital functions in the human
What is the blood supply of the cecum and appendix? Why is this? What are the specific arteries?
Superior Mesenteric Artery
Because they are derived from the midgut
Ileocolic artery - divides into anterior and posterior cecal arteries
What is the venous drainage of the cecum and appendix?
Ileocolic vein, which empties in to the Superior Mesenteric Vein
Where does lymph from the cecum drain to? Where are these nodes located?
The ileocolic lymph nodes
They surround the ileocolic arteries
What is the para and symp innervation of the cecum and appendix?
Para - vagus
Symp - superior mesenteric plexus
Are the ascending, transverse, descending and sigmoid colon retro or intraperitoneal?
Ascending - retro
Transverse - intra
Descending - retro
Sigmoid - intra
When does the ascending colon turn 90 degrees? What is this bend called?
When ascending colon reaches the right lobe of the liver
This is the right colic flexure
What encloses the transverse colon?
The transverse mesocolon
When does the transverse colon turn 90 degrees inferiorly? What is this called?
When transverse colon meets the spleen
This is called the left colic flexure
When does the sigmoid colon start?
When the descending colon moved medially
How is the sigmoid colon attached to the posterior pelvic wall?
By the sigmoid mesocolon
Where are the paracolic gutters located?
Between the ascending/ descending colon and the posterolateral abdominal wall
What is the blood supply to the colon?
Ascending colon and proximal 2/3 of the transverse colon - SMA
Distal 1/3 of the transverse , descending and sigmoid colon - inferior mesenteric artery
What is the blood supply of the ascending colon?
Ileocolic artery (SMA) Right colic artery (SMA)
What is the blood supply of the transverse colon?
Right and middle colic arteries (SMA)
Left colic artery (IMA)
What is the blood supply of the descending colon?
Left colic artery (IMA)
What is the blood supply of the sigmoid colon?
Sigmoid arteries (IMA)
What is the venous drainage of the ascending colon?
Ileocolic vein
Right colic vein
Both drain into SMV
What is the venous drainage of the transverse colon?
Middle colic vein
Drains into SMV
What is the venous drainage of the descending colon?
Left colic vein
Drains into IMV
What is the venous drainage of the sigmoid colon?
Sigmoid veins
Drain into IMV
Where do the superior and inferior mesenteric veins drain into?
Hepatic portal vein
What is the innervation of the ascending colon and proximal 2/3 of the colon?
Superior mesenteric plexus
What is the innervation of the distal 1/3 of the transverse, descending and sigmoid colon? Para and symp
Inferior mesenteric plexus
Symp - lumbar splanchnic nerves
Para - pelvic splanchnic nerves
What is the lymphatic drainage of the ascending and transverse colon?
Superior mesenteric nodes
What is the lymphatic drainage of the descending and sigmoid colon?
Inferior mesenteric nodes
Where do the inferior and superior mesenteric lymph nodes drain to?
Interstitial lymph trunks
Drains to cistena chyli
Ultimately empties into the thoracic duct
What are 2 flexures of the rectum? Are they concave or convex anteriorly?
Sacral flexure - concave anterior
Anorectal flexure - convex anterior
What is the blood supply of the rectum?
Superior, middle and inferior rectal artery
What is the venous drainage of the rectum?
Superior, middle and inferior rectal veins
Where are the anastomoses between portal and systemic venous system located?
In the wall of the anal canal
What surrounds the upper 2/3 of the anal canal?
Internal anal sphincter - involuntary control
What surrounds the lower 2/3 of the anal canal?
External anal sphincter - voluntary control
Where is the anorectal ring located?
At the junction of the rectum and the anal canal
What is the anorectal ring formed from?
Fusion of the internal and external anal sphincters
What is the blood supply to the anal canal?
Above pectinate line - superior rectal artery and anastomosing branches from the middle rectal artery
Below pectinate line - inferior rectal artery and anastomoses from the middle rectal artery
What is the venous drainage of the anal canal?
Above the pectinate line - superior rectal vein
Below the pectinate line - inferior rectal vein
What is the lymphatic drainage of the anal canal?
Above pectinate line - internal iliac lymph nodes
Below pectinate line - superficial inguinal lymph nodes
What is the innervation of the anal canal?
Above the pectinate line - inferior hypogastric plexus
Below the pectinate line - inferior rectal nerves
What is above the pectinate line sensitive to?
Stretch
What is below the pectinate line sensitive to?
Pain, temperature, touch and pressure
What does the pectinate line divide?
Proximal 2/3 and distal 1/3 of the anal canal
