Chapter 93 Colon Flashcards
Where is the caecocolic orifice in relation to the iliocolic orifice in dogs?
And in cats?
Dogs: Caecocolic orifice 1cm distal to iliocolic orifice
Cats: Caecocolic and iliocolic orifices adjacent to each other

What structures does the duodenocolic join (be specific)
Ascending duodenum - descending colon
What arteries supply the colon and what artery do they originate from?
Cranial mesenteric artery:
- Iliocolic a
- Right colic
- Middle colic
Caudal mesenteric
- Left colic
- (Caudal rectal)

Label the diagram


What is the name of the small individual arteries branching off colic arteries?
Vasa recta
The colon contains two arterial netweors - what are they
Sub-serous
Mural (predominantly within submucosa)
What LNs drain the colon?
Left, middle and right colic LNs

Label the diagram


What are the three cell types of the colonic mucosa
- Epithelial
- Goblet
- Enterocromafffin (5% of cells)
How does colonic mucosa differ from Si mucosa?
- No villi
- No aggregated lymph nodules (instead have large solitary lymphoglandular complexes (3mm. In cats the lymphoglandular complexs ate only present in the caecum)
List 3 functions of the colon
- Faecal storage
- Resevoir for microbial ecosystem
- Maintaining fluid and electrolyte balance
List 4 things that are absorbed in colon and 3 things that are excreted
Absorbed:
- Water
- Na+
- Cl-
- Short chain fatty acids
Excreted:
- K+
- HCO3-
- Mucous
What is the main driving force nehind salt and solute transport mechanism in colon?
Electrical gradients
What volume of fluid does the colon absorb (a total figure)
Up to 1.5 L/day
What is the net direction of eectrolytes in colon, under normal conditions
Absorbtion of electrolytes
What drives water movement across colon
Osmosis and active absorbtion
What cells produce mucous in coloon?
Goblet cells and columnar epithelial cells
(i.e. 2/3 cell types present in mucosa. Other type is enterochromaffin cell, making up 5% of cells)
What are the three short chain fatty acids?
Butyrate, acetate, propionate
List two mechanisms leading to mixing of faeceal contents in the dog.
And an additional mechanism in cats
- Segmentation
- Propulsion
- (Retrograde peristalsis in cats)
What is major control of colonic wall dependent on?
Intrinsic nerve plexuses (myenteric and sub-mucous)
List 3 factors that make the barrier created by colonocytes a major contributor to immunity (ie how does epithelium confer immunity)
- Rapidly renews
- Is constantly moving
- Protected by mucous and antimicrobial molecules
Whatare the three stages of wound/colonic healing?
- Lag phase (/Inflammation phase)
- Proliferative phase
- Maturation phase
What material prevents anastomotic leakage during lag phase of healing?
Fibrin
What cell type predominates in early lag phase of healing?
How does this change after 2-3 days?
Neutrophils initially –> macrophages/monocytes after 2-3 d






