Rabbit GI anatomy and physiology

Question 1

Name the rabbit salivary glands (and if you upgrade to PRO, add a picture to label)

Answer 1

Sublingual
buccal
Parotid
mandibular

Question 2

What percentage of the GIT volume is the stomach?

Answer 2

15%

Question 3

What does the ampulla (just past the pylorus) do?

Answer 3

AKA ampulla of Vater. It’s where the pancreatic/common bile ducts empty.

Question 4

what is the sphincter of Oddi?

Answer 4

muscle that controls secretion from the pancreatic/common bile ducts into the ampulla

Question 5

How fast do rabbit incisors grow?

Answer 5

up to 2 mm/wk

Question 6

Basic function of the colon?

Answer 6

separates first-pass fibers into nondigestible (to be pooped out) and digestible (to stay as a substrate for fermentation, mostly in the cecum. also reabsorbs water and makes poop.

Question 7

Do rabbits see their food as they eat it?

Answer 7

nope, they select food & textures via vibrissae & taste etc. Prey eyes.

Question 8

How many teeth do rabbits have and what are they for?

Answer 8

28 total
6 incisors (2 real upper, 2 peg teeth upper, 2 lower): to slice food
22 PM/Ms: grind the food.

Question 9

what are normal pH ranges in rabbits

Answer 9

Pre-weaning: 5.0-6.5 (helps establish flora)
Post weaning, eating first pass food: 1.0-2.0 (Jesus)
Post weaning, eating a cecotrope: 3.0

Question 10

Normal GI transit time in a rabbit?

Answer 10

3-6 hours for first pass

Question 11

Main function of duodenum?

Answer 11

Mix in bicarb and digestive enzymes (esp to cecotropes)

Question 12

Main functions of jejunum & ileum?

Answer 12

Actual absorption of nutrients from the cecotrophs; some bacterial fermentation occurs in the ileum as well.

Question 13

What’s the thingy between the ileum and the colon?

Answer 13

ileocolic valve - reduces reflux from lower GIT to upper

Question 14

General transit time of the small intestines?

Answer 14

10-20 min in jejunum, 30-60 min in ileum

Question 15

Where are the gut-associated lymphoid tissues found in rabbits?

Answer 15

Peyer’s patches (Jejunum & distal ileum)
Sacculus rotundus at the ICJ
Vermiform appendix (distal cecum)
Lymphoid follicles along the colon

Question 16

which organ makes up 49% (but not 50%, that would apparently be way too much) of the GIT volume

Answer 16

seekum you shall findum

but takes up >50% of abdominal volume. how the hell does that math work either??

Question 17

Twisty coils on the right side, huge, thin walled

Answer 17

Is a cecum!

Question 18

what’s at the end of the cecal rainbow?

Answer 18

The vermiform appendix (secretes bicarb and makes immune cells)

Question 19

What are the 4 regions of the rabbit colon?

Answer 19

1) Anterior part 1: about 10 cm. 3 taeniae, 3 haustrae
2) Anterior 2: about 20 cm. 1 ea taenia/haustra
3) Fusus coli
4) Distal colon: 80-100 cm long, no t/h, short crypts, many goblet cells

Question 20

what’s the function of the fusus coli and where is it

Answer 20

3rd region of the rabbit colon, 4 cm band of muscle & innervation, controls pass-through of multiple areas of large intestine. Lots of goblet cells, which package up cecotrophs in mucus and squish them down.

Question 21

describe how particles move through the cecum and colon (ideally with picture/Pro)

Answer 21

homogenous first-pass schmoo goes from ileum and get spread evently between cecum and colon. Cecum moves stuff over to the colon, which divides it into save vs poop. Save gets refluxed to the cecum to ferment. Cecum has different contractions for cecotrope vs excrete.

Question 22

what plant fibers can the cecal microbes ferment?

Answer 22

mostly cellulose, pectin, and hemicellulose; last 2 are more important

Question 23

what are the main products of cecal fermentation and where do they go?

Answer 23

volatile fatty acids - 75% acetate, 10% propionate, 15% butyrate.
Butyrate: feeds the colon
Others: bloodstream, go to liver & get made into other things there.
Overall this is 30% of the rabbit’s metabolic needs!

Question 24

How does the fusus coli affect cecotropes?

Answer 24

1) secretes prostaglandins to STOP haustral contractions and START distal cecal contractions
2) cecotrope goes FWOOSH down the cecum, prox colon
3) Fusus coli goblet cells package it in mucus and squish it into shape
4) Colon goes PEW PEW PEW

Question 25

What is the percentage makeup of a cecotrope?

Answer 25

By weight: 34% Dry matter, 66 % water
Dry matter subdivides into 18% fiber, 30% protein, and 52% PURE MAGIC
The protein subdivides into 80% microbial origin, 20% directly from food

Question 26

What nutrients does a cecotrope contain?

Answer 26

Amino acids - especially lysine, threonine, and the sulfur-containing AAs
B vitamins (lots of them)
Vitamin K
Various minerals, potassium etc
Magic

Question 27

3 broad categories of small intestinal motility regulators (endogenous):

Answer 27

• Autonomic nervous system
• “hormones”
• Nutritional content of food, esp indigestible fiber

Question 28

What is a motilin, where does it come from, and why did its parents not raise it right

Answer 28

chemical (hormone?) released from endocrine M cells in the mucosa of the duodenum and jejunum.

Question 29

where are motilin receptors found?

Answer 29

All small intestines
Colon and rectum but NOT cecum
CNS

Question 30

What do motilin receptors actually do?

Answer 30

trigger “migrating motor complexes” that push peristaltic waves along. (everywhere but the cecum)

Question 31

What can pretend to be a motilin?

Answer 31

erythromycin or a bunch of crap with no name

NOT any of the commonly used prokinetics - those are mostly dopamine or 5HT receptor agonists

Question 32

Rabbit feces is made during what?

Answer 32

mostly while eating

Question 33

Cecotropes are made when?

Answer 33

usually a few hours later, while resting

Question 34

How fast are cecal contractions, usually; and what do they do?

Answer 34

1-2 per minute; they mix up the fermenty stuff and keep it cooking.

Question 35

What kinds of contractions does the colon undergo? (there are 3 big ones)

Answer 35

1) Shallow, aboral, of haustra (14-16 per minute) - separating fibers
2) Occasional ORAD in single-haustra zone - refluxes usable things to cecum
3) Migrating segmental contractions to push out poop

Question 36

Will high protein in the diet increase or decrease cecotrophy?

Answer 36

Decrease it

Question 37

How does excess protein lead to dysbiosis?

Answer 37

Excess dietary protein elevates plasma urea AND CECAL AMMONIA CONTENT; this raises the pH and allows overgrowth of Clostridia and E. coli among others.

Question 38

Increased dietary carbs are most likely to cause enteritis in which age group?

Answer 38

young rabbits - more starch makes it to the ileum with them, and it will have a higher effect on the intestine. In other age groups, if they eat enough fiber, the carb content matters slightly less. (This is probably why a rabbit who eats a good diet can tolerate fruit more than one fed a shitty diet).

Question 39

fiber & protein differences between first and second cut hay?

Answer 39

First cut - usually higher in fiber, lower protein

Second cut - usually more protein & softer

Question 40

Normal water intake for pet rabbits?

Answer 40

will depend greatly on diet & amt fresh greens, but est 120 ml/kg upper end