Lecture 3 - Secretions Flashcards
What kind of digestion occurs in the large intestine
Microbial digestion
What is digested in the L.I.? Why?
Fiber
Broken down into glucose (can no longer be absorbed) so turn that into volatile f.a.’s which can be utilized by the host as energy
Three volatile f.a. produced by fiber digestion
Acetate (2C)
Propionate (3C)
Butyrate (4C)
Four requirements for microbial digestion
- Fluid environment
- Neutralized environment
- Continuous removal of end-products by absorption
- Long retention time of digesta (breaking down fiber is slow)
What needs to occur for short chain fatty acids to be absorbed
H (from CO2 hydration or Na/H exchange) needs to protonate SCFA to neutralize them, making them lipid soluble
What form are short chain fatty acids in at neutral pH?
Acid form (water soluble; not lipid soluble)
How are short chain f.a. absorbed?
Nonionic diffusion (no E)
or
Apical membrane SCFA-HCO3 exchange (transporter–E required)
Where are SCFA absorbed
Transporters are in small and large intestines
What percent of calf mortality is due to failure of passive transfer?
39%
What is transferred when calves drink colostrum
Antibodies (immunoglobulins; IgG)
What percent of heifer calves have failure passive transfer?
41%
Calves with FPT have…
Lower BW
Lower average daily gain
Higher vet costs
Reduced milk production
“Leaky gut” refers to…
in the first 24h of life when the gut is still able to absorb large proteins
Immunoglobulins are absorbed through…
Pinocytosis (into vesicles)
What happens to pinocytotic capability over time?
It is lost over time
What is butyrate? What does it do to the gut?
Short chain f.a.
Drives gut development (closure) decreasing IgG absorption if given after birth
Pinocytotic capacity is _________. Pinocytosis is ______________ (selective/non-selective).
Limited
Non-selective
Reaction of H2O & CO2 to gut secretions
H2O + CO2 <-> H2CO3 <-> HCO3 + H+
Bicarbonate is part of what secretions? H+?
HCO3 = salivary and pancreatic
H+ = gastric
Important salivary secretory glands?
Zygomatic gland, parotid gland, mandibular gland, sublingual gland
Composition of salivary secretions
Buffer (HCO3)
Na, Cl
Amylase (except ruminants/carnivores)
What is amylase? Where is it made
enzyme, or special protein, that helps you digest carbohydrates
Most made by pancreas and salivary glands
Function of salivary secretions
Moisten food to facilitate deglutition
Neutralize acids from fermentation (ruminants)
How are salivary secretions controlled
Flow increased by cholinergic stimulation
Salivary center (medulla)
Reflex stimulation from mechanoreceptors in mouth/stomach
Acetylcholine activates what salivary glands
Parotid gland and submandibular gland
Roles of the stomach (7)
Storage
Protein denaturation (HCl)
Mixing (mechanical digestion)
Pepsinogen
Digestion (proteins)
Bacteriostatic (prevent pathogens)
B-12 absorption
Four parts of the glandular stomach
Esophageal part
Cardia
Fundus + corpus
Pylorus
Fundus + corpus region of the stomach aka
Proper gastric
What is secreted by the cardia
Mucus
What is secreted by the diff cells of the proper gastric region
Mucus
Parietal cell = HCl, intrinsic factors (B12)
Chief cell = pepsinogen
What do intrinsic factors do
Facilitate B12 absorption into the ileum (binds Vit B12, carries it to end of SI, recognized, B12 absorbed)
What does the pyloric region of the stomach secrete
Mucus and gastrin
What activates pepsinogen into _________
Acidic conditions activate it into pepsin (digests proteins)
Role of HCl in gastric secretions (5)
Breakdown collagen
Protein uncoiling
Bacteriocidal
Activate pepsinogen
Optimum pH
What cells secrete pepsinogen
Chief cells
What molecules stimulate gastric HCl secretion**
- Acetylcholine (stimulates histamine release)
- Gastrin (enters circulation, stimulates parietal cells, histamine release)
- Histamine (stimulates local parietal cells)
What type of cell releases HCl
Parietal
Gastric secretions include…
HCl, pepsin
What molecule inhibits gastric secretion
Somatostatin released when pH is low
What does paracrine mean
Stimulates local cells (neighbours)
What molecules turn parietal cells on
Gastrin, histamine, ACh
In gastric secretion, bicarbonate enters the _______ while HCl enters the ______
Blood, gastric lumen
Why don’t acids and pepsin digest the stomach (epithelial cells)
Protected from acid by mucous layer
Bicarbonate secreted by epithelial cells trapped in mucous layer (buffer)
Epithelial cell mucous secretion is increased by…
Cholinergic stimulation
Mechanical stimulation
What is the main cause of ulcers in humans
Helicobacter pylori
What does helicobacter pylori do to the stomach environment
Increases pH, damages mucous layer to allow acid to reach epithelial wall
Up to what % of growing pigs show lesions of ulcers at slaughter? What % of sows?
60%, 5%
Factors contributing to ulcers in pigs
- Nutritional (low protein, low fiber, high E)
- Physical diet (particle size, moisture)
- Management (irregular feeding, stress, water availability, infections)
- microbial (helicobacter suis)
Clinical signs of ulcers in pigs
Pale animal, breathlessness, vomiting, dark feces, weight loss, death
Is Helicobacter suis zoonotic
It has been found in a veterinarian
What does the pancreas secrete
Proenzymes (e.g. amylase)
Enzymes
Bicarbonate
What cells produced bicarbonate
Duct cells
Pancreatic secretions are adjusted according to…
acid and nutrients entering duodenum
Difference in pancreatic secretion pattern btw horses and ruminants
Ruminants = continuous secretion (4-5L/day)
Horses = constant but increases after eating begins (30-35L/day)
What breeds is exocrine pancreatic insufficiency common in? Symptoms?
German Shepherds, Rough Collies
Weight loss, greasy/foul smelling diarrhea, dry/dandruffy coat
What is exocrine pancreatic insufficiency? Treatment?
Pancreatic acinar atrophy (no digestive enzymes sent to gut)
Treat with pancreatic enzyme replacement therapy (PERT) = oral pancreatic enzymes
Causes of exocrine pancreatic insufficiency
Genetic in dogs
Chronic pancreatitis
Obstruction of pancreatic duct
Where is bicarbonate secreted by the pancreas
Into the duct lumen (gut environment)
Secretory diarrhea can be caused by…
- Prostaglandin E in response to damage or reactive oxygen species
- Serotonin induced by toxins
- Cholera toxin
- Enterotoxigenic E. coli
Slides 42-48**
What cells release somatostatin? Gastrin?
Somato = D cells
Gastrin = G cells
