2. Review- Horses

Question 1

What kind of “vore”s are horses

Answer 1

Herbivores (monogastric, hidgut fermenters)

Question 2

What animal is a horse’s GI tract similar to?

Answer 2

pigs

Question 3

In terms of length of large and small intestine, how do horses compare to cats and dogs?

Answer 3

LI: more than 10 times as long
SI: around 6 (dogs)-10 (cats) times as long

Question 4

How do the lengths of the large and small intestine compare in horses

Answer 4

small intestine is 2x longer than large intestine

Question 5

Why do horses have such a long large intestine

Answer 5

Hindgut fermentation in the cecum

Microbes allow amino acids to be absorbed in the large intestine

Question 6

What part of the large intestine is enlarged in horses

Answer 6

cecum

Question 7

What macronutrient is best suited for horses?

Answer 7

fiber, hindgut fermentation allows for digestion, still less efficient than ruminants

Question 8

What are the 6 causes of colic in horses

Answer 8

Gas (spasmodic)
Obstruction
Strangulation
Infarction (no bloodflow)
Inflammation
Ulcuration

Question 9

How much do horses chew compared to cats and dogs? Why?

Answer 9

Much more (90 chews/minute)

Saliva secretion is stimulated by chewing and contains a small amount of bicarbonate

This provides a buffer against stomach acid and allows for some microbial fermentation in the stomach

Question 10

How are horses adapted for more intense chewing

Answer 10

Many large, long molars

Question 11

How many teeth do horses have?

Answer 11

36, 12 incisors, 12 premolars, 12 molars (+/- canines and wolf teeth)

Question 12

How are teeth distinct in a horse that is
-2.5 years
-5 years
-10 years
-20 years

Answer 12

-Has all permanent incisors
-All permanent incisors are occluding, cups appear on bottom. All molars present
-all teeth have cups, Galvaynes groove appears
-galvaynes groove reaches the bottom of 03s, incisors are angular

Question 13

What are the 3 regions of the stomach, what tissues are there, and what (if anything) do they secrete?

Answer 13

Esophageal region-
-Squamous epithelium

Fundic region-
-Glandular epithelium
Parietal cells: HCl
Zymogen cells: pepsin

Pyloric region-
-Glandular epithelium: gastrin

Question 14

Where in the stomach can microbial fermentation occur

Answer 14

Esophageal and fundic regions

Question 15

Can horses vomit? Why?

Answer 15

No. Their cardiac sphincter is too strong, so food doesnt come up when running

Question 16

Where is gastrin secreted?

Answer 16

The stomach-> pyloric region-> glandular epithelium

Question 17

Where is HCl secreted?

Answer 17

Stomach -> fundic region
-> glandular epithelium -> parietal cells

Question 18

Where is pepsin secreted?

Answer 18

Stomach -> fundic region
-> glandular epithelium -> Zymogen cells

Question 19

What are the 2 types of endothelial cells in the stomach and what do they secrete?

Answer 19

Squamous- nothing

Glandular- HCl, pepsin, gastrin

Question 20

What is the relative emptying time of a horses stomach? How does that compare to dogs and cats?

Answer 20

120 minutes, its much shorter

Question 21

What is the consequence of horses having a relatively short emptying time?

Answer 21

The flow of food into the SI ends shortly after feeding since there is no protein to digest. The stomach does not act as a reservoir in horses, this encourages constant grazing

Question 22

What are the 3 sections of the small intestine? What is the transit time in horses?

Answer 22

Duodenum -> jejunum -> ileum

~60 minutes

Question 23

What is digested and absorbed in the small intestine?

Answer 23

Protien, starch, fat

Question 24

What are the endocrine roles of the pancreas?

Answer 24

Insulin- promotes sugar uptake into fat stores when blood sugar is high

Glucagon- promotes fat stores releasing sugar when blood sugar is low

Question 25

What are the exocrine roles of the pancreas?

Answer 25

Secretes: enzymes (inactive proteases, lipases, and amylases) and bicarbonate salts

Question 26

What is the role of the liver? What is unique about horses?

Answer 26

Produces bile. Horses have no gallbladder, it is constanly draining into the SI (because horses do not eat much fat, no reservoir needed. horses are also constantly eating)

Question 26

What does bile do?

Answer 26

Emulsifies dietary fat, activates lipases

Question 26

What is the first section of the large intestine, why is it unique in horses? What is synthesized there?

Answer 26

Cecum It is very large (25-35L), contains a microbial population similar to ruminants that breaks down fiber Microbial synthesis of SCFA and protein

Question 26

What is the second part of the large intestine, what are the 4 compartments and 3 flexures?

Answer 26

The large colon Flexures: 1. Sternal flexure 2. Pelvic flexure 3. Diaphragmatic flexure Compartments: 1. right ventral colon (sternal flexure) 2. Left vetral colon (pelvic flexure) 3. Left dorsal colon (diaphragmatic flexure) 4. Right dorsal colon

Question 27

What is the third section of the large intestine? What are the 2 segments?

Answer 27

Small colon 1. small transverse colon 2. distal dorsal colon

Question 28

Where does the large intestine end and connect to?

Answer 28

rectum

Question 29

What are the surface area increasing features of the small and large intestines respectively?

Answer 29

SI: Villus & crypt LI: no villi, but deeper crypts than SI Also increase surface area by having coils and folds

Question 30

What cells in the intestinal lumen allow nutrient transport?

Answer 30

Epithelial cells, transported into capillary bed

Question 31

What different characterisrics do amino acids have? Why is that relevant?

Answer 31

Polarity, pH, charge. May cause competition for what gets absorbed< requires different kinds of transporters.

Question 32

What are the stomach protein enzymes?

Answer 32

Pepsin: bonds within aromatic AAs at N terminus

Question 33

What are the pancreas protein enzymes?

Answer 33

Trypsin: bonds joining basic AAs Chymotrypsin: bonds containing neutral AAs Elastase: bonds beside small AAs Carboxypeptidase: carboxy-terminal peptides (liberates a single AA)

Question 34

What are the intestinal protein enzymes?

Answer 34

Aminopeptidase: N-terminal of oligopeptides (liberates a singe AA or 3-6 peptides) Dipeptidase: dipeptides (liberates free AA) Tripeptidase: tripeptides (liberates free AA and dipeptide)

Question 35

Why can the intestinal lumen absorb both single AAs and small peptides?

Answer 35

Energy conservation, absorbing a single dipeptide takes half the energy of 2 single AAs

Question 36

When can the brush border transport protien and polypeptides?

Answer 36

Early life

Question 37

What are many small peptides transported into? What is the main protien thing entering the blood?

Answer 37

Enterocytes Free AAs

Question 38

Why is brush border transport of proteins not limited in some species?

Answer 38

Transport of colostrum

Question 39

What type of transport is most AA transport? What is required?

Answer 39

Active, energy

Question 40

What are the pancreas carbohydrate enzymes?

Answer 40

alpha amylase: hydrolyzes starch to alpha-limit dextrins

Question 41

What are the intestinal carbohydrate enzymes?

Answer 41

Glucoamylase: hydrolyzes alpha-limit dextrins to singlue glucose units Maltase: cleaves maltose into single glucose units Isomaltase: hydrolyzes short chain glucose units into single glucose units Sucrase: cleaves sucrose into fructose and glucose

Question 42

What is the general name of cells that produce incretins?

Answer 42

enteroendocrine cells

Question 43

What are the pancreatic fat enzymes?

Answer 43

Lipase: breaks down triglyceridrs into FFAs and monoglycerides

Question 44

How do fats get absorbed? Where do they drain first? What about those produced by fermentation?

Answer 44

LCFAs: By bile salts binding, emulsifying and forming micelles (allows nonpolar molecule to pass through the polar endothelium) Absorbed in small intestine. Drains into the lymphatic system rather than the portal vein as a chylomicron (fat = protein) SCFA (microbial fermentation): Can be absorbed in the large intestine

Question 45

Where are SCFAs produced? How much of a horses energy do these provide?

Answer 45

The large intestine 50-70% Microbiome is very sensitive to dietary change

Question 46

How are SCFAs absorbed?

Answer 46

Passively, facilitated, or with symporter

Question 47

How well can horses adapt to dietary changes?

Answer 47

Not very well since they are herbivores (not omnivores)