36 - Colorectal Flashcards
Colon secretes _ and absorbs _
Secretes - K
Absorbs - water and Na
Layers of colon
Mucosa, submucosa, muscularis propria, serosa
Small interwoven inner muscle layer below mucosa but above basement membrane in colon
Muscularis mucosa
Portions of colon that are retroperitoneal
Ascending, descending and sigmoid
Peritoneum cover this portion of rectum
Anterior upper and middle 1/3
Transverse bands forming haustra
Plicae semilunaris
3 bands running longitudinally along the colon
Taenia coli
Distance of dentate line from anal verge
2cm
SMA supplies which portions of the colon (name branches)
Ascending - ileocolic, right colic
2/3 Transverse - middle colic
IMA supplies which portions of the colon/rectum (name branches)
1/3 Transverse - left colic
Descending - left colic
Sigmoid - sigmoidal branches
Upper rectum - superior rectal
Collateral flow connecting SMA and IMA
Marginal artery
Short direct connection between SMA and IMA
Arc of Riolan
Superior, middle and inferior rectal artery branches from
Superior - IMA
Middle - Internal iliac
Inferior Internal pudendal (branch of internal iliac)
Watershed areas of colon and there junctions
Splenic flexure (Griffith's point) - SMA and IMA junction Rectum (Sudaks point) - superior and middle rectal junction
Anal sphincter with voluntary control
External sphincter
Anal sphincter with involuntary control
Internal sphincter
External anal sphincter innervation and muscle (type)
Inferior rectal nerve (internal pudendal nerve branch) Levator ani (skeletal)
Internal anal sphincter innervation and muscle (type)
Pelvic splanchnic nerves Muscularis propria (smooth)
The inner and outer nerve plexus of the colon, respectively
Inner - Meissner’s plexus
Outer - Auerbach’s plexus
What forms the anal verge
0-5cm anal canal, 5-15cm rectum, 15-18cm rectosigmoid junction
Mucin secreting goblet cells of colon
Crypts of Lieberkuhn
Slow transit time of the colon
colonic inertia
Main nutrient of colonocytes
Short chain fatty acids
Tx for stump/diversion pouchitis of colon
Short chain fatty acid enema
Tx for infectious pouchitis
Metronidazole
Anterior colorectal fascia (rectovesicular/rectoprostatic - men; rectovaginal - women)
Denonvilliers fascia
Posterior colorectal fascia (rectosacral)
Waldeyer’s fascia
Most common colon polyp
Hyperplastic polyp
Most common neoplastic intestinal polyp
Tubular adenoma
Most likely to produce sxs, more often cancerous (50%0
Villous adenoma
Indications for increased cancer risk of intestinal polyps (3)
> 2cm, sessile, villous
Screening age for colon cancer, normal risk and family hx
Normal risk - 50yo Intermediate risk (fam hx) - 40yo or 10 yrs before youngest fam member
Screening options for colon cancer
- Colonoscopy q10 yrs
- Fecal occult blood testing (FOBT) q3yrs AND flex sigmoidoscopy q 5yrs
- FOBT annually
Definition of invasive cancer (T1) lesion in colorectal
Invasion INTO submucosa (past basement membrane)