Anatomy of Large Bowel Flashcards
Parts of the large Bowel?
Caecum, appendix, ascending colon, hepatic flexure, transverse colon, splenic flexure, descending colon, sigmoid colon, rectum
Where are paracolic gutters?
Found on the lateral aspects of the ascending and descending colon, they are part of the greater sac
What are haustra?
Bumps formed by tonic contraction of teniae coli
Teniae coli?
3 longitudinal smooth muscle bands running from caecum to sigmoid colon
Primary functions of large bowel?
Net absorption of Na, Cl, H2O
Net sceretion of HCO3, mucus and K+
Colonic Flora role?
- Helps with intestinal immunity
- Promotes motility
- Synthesizes vit K and free fatty acids
- Helps in drug absorption
What does the levator ani muscle do for defaecation?
Relaxes
What does the levator ani do in
- resting conditions
- sneezing/coughing?
Tomically contracts to hold pelvic organs
Contracts further during cough/sneeze
What muscles is the levator ani made up of?
puborectalis
pubococcgyeus
ileococcygeus
What is the levator ani supplied by?
Pudendal nerve
S2,3,4
Where does the rectum become the anal canal?
Anterior to coccyx
Where does the sigmoid colon become the rectum?
Anterior to S3
Difference between rectal varrices and rectal haemorrhoids?
Varrices- dilation of collateral veins
Haemorrhoids- prolapse of rectal venous plexuses
What are haemorrhoids due to?
Increased pressure
What are rectal varices due to?
Related to portal hypertension
Common term for levator ani?
Pelvic floor
Contraction of which muscle helps maintain continence?
Puborectalis
The external anal sphincter is contracted all of the time. True or False?
FALSE
Internal is contracted all of the time
How is IAS contracted?
By sympathetic nerves
What type of muscle is the IAS?
Smooth muscle
What type of muscle is the EAS?
Skeletal
How is the extrenal sphincter contracted?
Puodendal nerve
Where is a risk site for abscess formation?
Ishioanal fossae (either side of anal canal)
What is the pectinate line?
Embryological line between endoderm (GI Tract) and ectoderm (skin)
What is above the pectinate line?
- Visceral (all hindgut)
- ANS
- IMA supply
- Venous drainage to HPV
- IM lymph nodes
Below pectinate line?
- Parietal
- Somatic & pudendal nerves
- Internal iliac artery
- Venous drainage to systemic veins
- Superficial inguinal nodes
Sympathetic nerve supply to rectum and AC?
Cause contraction of IAS
Inhibits peristalsis
Parasympathetic nerve supply to rectum and AC?
Inhibits IAS
Stimulates peristalsis
Visceral afferents for R & AC?
- Run with parasympathetics
- Sense stretch
Rhyme to help remember what vertebrae nerves for rectum and ac enter?
S2,3,4 keeps the 3 ps off the floor.
Pee, poo, penis
