Lecture 3 - Secretions

Question 1

What does microbial digestion do?

Answer 1

• breaks down CHO fibers to VFAs
• synthesis of microbial protein from non-protein nitrogen such as urea
• synthesis of B vitamins

Question 2

What are the end products of microbial digestion?

Answer 2

• volatile fatty acids = acetate, propionate, butyrate

Question 3

4 requirements for microbial digestion

Answer 3

1. fluid environment
2. neutralized environment
3. continuous removal of the end-products by absorption
4. long retention time of digesta

Question 4

SCFA absorption

Answer 4

• they are in acid form at neutral pH so they are not fat soluble
• protonate SCFA to neutralize them so they can diffuse down the gradient; H from hydration of CO2 or from Na/H exchange
• transporters found in small and large intestine

Question 5

What are the 2 mechanisms for SCFA absorption?

Answer 5

1. nonionic diffusion (majority)
2. apical membrane SCFA-HCO3 exchange

Question 6

What are 4 qualities of calves with failure of passive transfer have?

Answer 6

• lower body wt
• lower average daily gain
• higher vet costs
• reduced milk production

Question 7

Neonatal colostrum absorption

Answer 7

• within 12-24 hrs of life
• leaky gut = when the gut is able to absorb via pinocytosis; this ability is lost over time
• absorbing IgG

Question 8

What 4 things do we know about passive transfer?

Answer 8

1. timing is important
2. pinocytotic capacity is limited
3. many factors affect colostrum quality
4. pinocytosis is non-selective

Question 9

What 4 things do we NOT know about passive transfer?

Answer 9

1. what factors influence absorption timing
2. how much total IgG can be absorbed
3. if molecules other than IgG are absorbed through pinocytosis
4. if molecule size/charge/polarity matters

Question 10

Composition of salivary secretion

Answer 10

1. buffer (HCO3-, H2PO4-_
2. Na, Cl
3. Amylase (except for ruminants and carnivores)

Question 11

Fxn of salivary secretions

Answer 11

1. moisten food to facilitate mastication and deglutition
2. neutralize fermentation acids (ruminant)

Question 12

Where is amylase produced?

Answer 12

acinus

Question 13

How are salivary secretions controlled?

Answer 13

1. flow rate increased by cholinergic stimulation
2. salivary center in medulla; parasympathetic nervous system
3. reflex stimulation from mechanoreceptors in mouth and stomach

Question 14

6 fxns of the stomach

Answer 14

1. store food
2. produce HCl for denaturing proteins and DNA
3. mechanical aspect of digestion for making lipid droplets smaller
4. produce pepsinogen for protein digestion
5. keep bacteria and pathogens out
6. intrinsic factor produced in stomach needed for proper B12 absorption

Question 15

Cheif cells

Answer 15

line stomach lumen and produce pepsinogen

Question 16

Pepsinogen

Answer 16

used for protein digestion

Question 17

Mucin producing cells

Answer 17

line stomach lumen and act as protection

Question 18

Parietal cells

Answer 18

line fundus and corpus and are responsible for pH by producing HCl

Question 19

ECL cell

Answer 19

line stomach lumen and are responsible for histamine

Question 20

4 parts of glandular stomach

Answer 20

1. esophageal part
2. cardia
3. fundus and corpus
4. pylorus

Question 21

Cardia

Answer 21

neutral area of where bacterial fermentation happens in non-glandular stomaches

Question 22

2 gastric secretions

Answer 22

1. HCl
2. Pepsinogen

Question 23

Active form of pepsinogen

Answer 23

pepsin

Question 24

4 regulators of gastric secretions

Answer 24

1. Acetylcholine
2. Gastrin
3. Histamine
4. Somatostatin (-)

Question 25

What protects the stomach from acid and pepsin?

Answer 25

• mucous layer
• mucous secreted by increase in cholinergic and mechanical stimulation
• bicarbonate secreted by epithelial cells gets trapped in mucous gel

Question 26

Helicobacter Pylori

Answer 26

• main cause of ulcers in humans
• requires acid and increases stomach pH
• crosses the mucous layer of stomach and raises pH causing the mucin to de-gel and opens an opportunity for acid to enter epithelial cells and cause damage

Question 27

Multifactorial causes of gastric ulcers in pigs

Answer 27

1. nutritional
2. physical diet
3. management
4. microbial (Helicobacter suis)

Question 28

Pancreatic secretions

Answer 28

1. proenzymes: amylase and trypsinogen
2. bicarbonate (to neutralize small intestine pH)
3. insulin
4. glucagon

Question 29

Mechanism of H2O sections

Answer 29

1. sensory neurons recognize osmolarity, stretch and presence of nutrients
2. Ach released and acts on G protein
3. IP3 activated
4. ER releases calcium
5. calcium binds calmoudin
6. Cl- transporter activated
7. Cl- released and Na+ and water follow

Question 30

Secretory Diarrhea

Answer 30

1. PGE2 bidns receptor in response to damage and triggers cascade
2. serotonin release triggered by toxins; calcium enters cell alonside serotonin triggering last 3 steps of cascade
3. Cholera toxin binds G protein and won’t release = continued water secretion
4. enterotoxigenic E. Coli binds G Protein

Question 31

Viral Diarrhea

Answer 31

• associated with villous damage = reduced absorptive surface