Chapter 12 Flashcards
What is the main purpose of the colon?
Absorption of water and sodium
Tx of uncomplicated diverticulitis
IV abx and bowel rest
If complicated and/or recurrent: elective colectomy
What is the leading cause of LBO?
Cancer
Tx for ulcerative colitis
Can do total protocolectomy with end end ileostomy or total protocolectomy with ileal pouch and anastamosis
What is the most common form of intestinal volvulus?
Sigmoid volvulus
Tx of sigmoid volvulus
Detorsion via sigmoidoscopy followed by bowel prep and elective sigmoidoscopy with primary anastamosis or Hartmann’s procedure
What is the initial tx for anal squamous cell carcinoma?
Chemoradiation
What are the most common tumors of the appendix?
Carcinoid tumors
Where is the foregut? What is it supplied by?
End at 2nd portion of the duodenum
Supplied by the celiac artery
Where is the midgut?
What is it supplied by?
Duodenal ampulla to the 1st 2/3 of the transverse colon
Supplied by the SMA
Where is the hindgut?
What is it supplied by?
Distal transverse and descending colon as well as proximal rectum
Supplied by IMA
What supplies the distal rectum?
Internal iliac artery
How is the anus formed?
By an invagination of the ectomdermal anal pit and fuses with the distal rectum at the dentate line
What are the four major layers of the colon?
Mucosa (columnar epithelium)
Submucosa (muscularis mucosa)
Muscularis propria
Serosa
Muscularis propria
Inner circular
Outer longitudinal smooth muscle: forms three bands
-Teniae coli (run along the colon and converge distally at the top of the rectum)
-Produce haustra, which give the colon its appearance on X-ray
How long is the colon?
150 cm
Where does the colon start and end?
Starts at the cecum in the RLQ
Ends 15 cm from anal verge
How long is the rectum?
12-15 cm long
Where does the rectum start and end?
Peritoneal reflection to the dentate line (2-4 cm from anal verge)
What is the most common site of rupture secondary to obstruction or pseudo-obstruction?
Cecum
What is the average diameter of the cecum?
7.5 cm
Most capacious area of the colon
Where is the appendix?
Arises from base of cecum-within 2-3 cm of ileocecal valve
What is the MC position of the appendix tip?
Posterior to the cecum
Position of the right colon
Posterior surface is retroperitoneal and lies near the duodenum
Position of transverse colon
What is it suspended by?
Completely intraperitoneal
Suspended by broad mesentery
Which flexure is higher than the other?
Splenic flexure is higher than the hepatic flexure
Greater omentum
Gastrocolic ligament (coming from greater curve of the stomach) fuses to peritoneal covering of the colon
Position of the descending colon
Partially retroperitoneal and fixed
Position of the sigmoid colon
Intraperitoneal
How is the upper 1/3 of the rectum covered?
Anteriorly and laterally by peritoneum
How is the middle 1/3 of the rectum covered?
By peritoneum anteriorly
Position of the distal rectum
Entirely extra-peritoneal
How is the posterior rectum covered?
By fascia propria
What preserves the lymphatics during rectal cancer surgery?
Dissecting in the plan between the fascia propria of the rectum and sacrum
How many rectal ligaments are formed by the fascia propria?
What do they contain?
2
Middle rectal artery and mixed autonomic nerves
If the mixed autonomic nerves in the two rectal ligaments of the fascia propria get injured, what can result?
Erectile of bladder dysfunction
Where does the anus begin?
At dentate line
Surgically begins at the level of the pelvic floor muscle
What do the mucosa at the dentate line form?
Longitudinal folds called columns of Morgagni
If the bases of the columns of Morgagni are infected, what is the result?
Anorectal abscesses and fistulas
How is fecal continence controlled?
By muscles of the pelvic floor
What are the muscles of the pelvic floor that control fecal continence called?
Levator ani
Internal anal sphincter (involuntary smooth muscle)
External anal sphincter (striated voluntary muscle)
What supplies the right colon and first 2/3 of transverse via its branches (middle, right, and ileocolic)?
The SMA via the aorta
Where does the ileocolic branch of the SMA go to?
Appendiceal artery
What is the blood supply of the proximal and middle thirds of the transverse colon?
The middle colic artery branch of the SMA which branches off into left and right branches
What is usually ligated during a right colectomy?
Right branch of the middle colic branch of the SMA
What supplies the left colon and proximal rectum?
The IMA via the aorta, which branches into the left colic, sigmoidal, and superior rectal vessels
What supplies the distal rectum and anus?
The middle rectal artery via the internal iliac AND
the inferior rectal artery via the internal pudendal artery
Marginal artery of Drummond
Series of arterial arcades running along the mesenteric border of the entire colon
Arc of Rioland
Connects proximal SMA and IMA
What is at risk for ischemia because it lies between the SMA and IMA?
Splenic flexure
Venous drainage
IMV leads to splenic vein, joins with SMV to form the portal vein
Distal rectum and anus drained by the middle and inferior rectal veins, goes to internal iliac veins, goes to systemic circulation
Lymphatics
Follows blood supply
Tumor in mid/distal rectum goes to iliac nodal basins
Sympathetic innervation
Runs along blood vessels
Thoracic roots supply SMA distribution
Lumbar roots supply IMA distribution
Sacral roots supply tpelvic floor, distal rectum and anus
When can occur if the hypogastric nerve is injured when ligating the IMA?
Ejaculatory dysfunction
Parasympathetic innervation
Right vagus innervates the right and transverse colon
Sacral roots innervate left colon and rectum
