2a Digestive Physiology - Dog and Cat Flashcards
What are some functions of the GI tract?
- digestion
- nutrient and water absorption
- immune function
- secretion
- excretion
- vitamin and mineral balance
What is the main difference between the gastrointestinal tract of a dog and cat?
length
What is the body length, SI and LI length of a dog?
- body length: 0.75m
- SI: 3.9m
- LI: 0.6m
What is the body length, SI and LI length of a cat?
- body length: 0.5m
- SI: 1.7m
- LI: 0.4m
What are the 4 structures used to increase gut capacity relative to body weight?
- villi
- microvilli
- coils
- folds
What does intestinal length influence?
- retention time of food in the gut
What kind of diet does the dog have?
omnivorous
What kind of diet does the cat have?
carnivorous
For what macronutrients does the lowest capacity exist to digest?
fiber
What is the consequence for fermentation?
- digestion of finer
- VFA production
- microbial protein
What does the smell and presence of food stimulate?
the salivary glands to produce saliva
What are the 4 pairs of salivary glands?
- parotid
- mandibular
- sublingual
- zygomatic
What affects the saliva amount and composition?
type of food ingested and its moisture content
What do dog and cat saliva lack?
salivary amylase to digest starch
Why is the function of saliva important?
- aids in mixing of food and lubrication as many dogs and cats swallow with minimal chewing
What is another important function of saliva for dogs?
- evaporative cooling
What kind of teeth do dogs have?
- cutting canine teeth for ripping and tearing
- large molars and premolars can grind and chew large or tough pieces of food
What kind of teeth do cats have?
- teeth suited for holding and killing small prey animals
- less efficient in chewing and grinding
What is the esophagus?
- short hollow muscular tube
- uses peristalsis to move food
How does the cell lining of the esophagus help?
- produces mucus
What is at the base of the stomach?
- cardiac sphincter
- prevents reflux of food from stomach to lower esophagus
What is the stomach and its function?
- a food reservoir that mixes food, regulates flow of digesta to the SI and initiates chemical digestion of protein
What is the point of chemical digestion in the stomach?
disrupt 3D structure of food (proteins)
- no digestion of carbs and fats
What 2 sections is the stomach divided into?
- proximal and distal sections
What is one function of the proximal stomach in dogs?
- proximal expands during temporary food storage allowing dog to eat discrete meals
What is gastric secretion influenced by?
- the amount of protein in the meal, the meal volume and hormones
What does gastric pH depend on?
- varies depending on the type of meal consumed (buffering capacity of the food)
What 4 things is gastric emptying rate controlled by?
- stomach volume
- body weight
- water intake
- diet type
Do high density or smaller particles empty more slowly?
high density
What is hormonal control of gastric emptying based on?
- maconutrient composition and characteristics
What is the average half emptying times for dogs?
72-240 min
What is the average half emptying time for cats?
22-449 min
What is the role of soluble fibre?
- increases viscosity which slows flow of digesta from stomach to small intestine
How is a cat stomach different from a dog stomach?
- cat stomach less important as storage reservoir
- cat stomach simpler and smaller with smaller glandular funds
What is the function of the small intestine?
- chemical digestion and absorption of fat, starch, sugar and protein
- acidic chyme stimulates secretion of pancreatic juice which increases pH of digesta
- chyme missed with enzymes from duodenal mucosa and pancreas
- mechanical digestion through peristalsis
- villi increase surface area
What are the functions of the pancreas?
- exocrine: secretes inactive enzymes and bicarbonate salts into gut
- endocrine: secrete hormones into the blood
What is the function of the liver?
- production of bile which is stored in gall bladder
- bile released when chyme enters SI (gall bladder contracts)
- emulsifies dietary fat and activate enzymes to aid in fat digestion
- portal vein runs from gut to liver
Describe the small intestinal microbiology.
- dog has a simple microbial population
- cats may have a greater amount of bacteria
- role in preventing pathogenic microbes from colonizing
How can transit time of digesta be measured?
- indigestible markers such as chromic oxide
How do sugar transport systems in the dog and cat differ?
- cat: sugar transport systems not adaptive to varying levels of dietary carbohydrate
- cat amylase about 5% of that in dogs
- amino acid transporters in cat are highly adaptable
- dog sugar transport systems are highly adaptive to dietary carbohydrates
What are the functions of the large intestine?
- absorption of water and electrolytes
- fermentation of dietary fibre and undigested nutrients from the SI
Does the large intestine contain villi?
- no
What are the 3 parts of the large intestine?
- cecum, colon, rectum
What is excreted cecal matter made up of?
- undigested food, sloughed cells, bacteria and endogenous losses
- can change depending on type of diet
What does bacterial fermentation produce?
- SCFA, lactate, CO2 and hydrogen gas
How is the GI tract controlled?
- nutrient flow from intestine to portal vein functions to control enzymes, nutrient transporters, persitalsis
What are the 3 mechanisms of GI control?
- incretins
- pancreas (enzymes, hormones, bicarbonate)
- nervous system
What are incretins?
- gastrointestinal hormones
What is GIP’s cell type?
K
What is GIP’s location of action?
duodenum, jejunum and ileum
What is GIP’s primary stimulatory and inhibitory action?
- stimulates: insulin secretion and synthesis
- inhibits: gastric acid secretion, gastric and small intestine mobility
What is GIP’s stimulus for secretion?
- glucose, AAs and FAs in small intestine
- somatostatin regulates release
What is CCK’s cell type?
I
What is CCK’s location of action?
duodenum and jejunum
What is CCK’s primary stimulatory and inhibitory action?
- stimulates: pancreatic enzyme secretion and gall bladder contraction
- inhibits: gastric emptying and secretion and relaxes sphincter of Oddi
What is CCK’s stimulus for secretion?
- peptides, AAs and FAs in duodenum
What is the function of taste and nutrient receptors?
control of intake
What is the outcome of control of digested nutrients?
- nutrient utilization and deposition
- satiety
- feed intake and feeding behaviour
