1: Digestive physiology of dogs and cats Flashcards
The role of the digestive system is to…
break down large food molecules into simple forms that can be absorbed by the body for use
Also barrier function
What is a clinical sign if the GI tract is not working well
Diarrhea (secretory or malabsorptive)
Vomiting
Length of the GI tract of the dog vs the cat
What does intestinal length influence?
Dog
Body length = 0.75m
SI =3.9m
LI =0.6m
Cat
Body length = 0.5m
SI = 1.7m
LI = 0.4m
Length influences retention time of food in the gut
What are the structures used to increase capacity of the GI tract relative to body weight?
Coils, folds, villi, microvilli
Describe the GI tract of the dog
- Monogastric GI system
- Adapted to an omnivorous diet containing a high proportion of animal tissues
Starch digestion in cats vs dogs
Domestic dog has more capacity to digest starch (have amylase)
Cats have trouble digesting starch
Describe the cat GI tract
- Monogastric GI system
- Adapted to a carnivorous diet
- Eat protein and fat, with some CHO found in animal tissues
Where is CHO found in animal tissues?
Glycogen is in muscle and liver, can be mobilized into glucose
What affects production of saliva by salivary glands? 4 pairs of glands:
Smell and presence of food stimulates the salivary gland to product saliva
- type of food ingested and its moisture content affect saliva amount and composition
glands: parotid, mandibular, sublingual and zygomatic
What is the role of saliva? What do dogs and cats lack in salivary glands that humans have?
Saliva aids with the mixing/chewing of food and lubrication before swallowing
Dogs and cats lack alpha-amylase (starch digestion is not initiated in the oral cavity)
Important function of saliva in dogs
Evaporative cooling
Describe teeth in dogs
- cutting canine teeth for ripping and tearing
- large molars and premolars can grind and chew large or tough pieces of food (more omnivorous = more chewing)
Describe teeth in cats
- teeth are suited for holding and killing small prey animals
- less efficient in chewing and grinding food
What is the esophagus? its role?
- short, hollow, muscular tube
- cell-lining produces mucus to help food passage
- uses peristalsis to move the food
What is found at the base of the esophagus? Role?
The cardiac sphincter
- relaxation causes food to enter the stomach
- immediately closes again (prevents reflux of food from the stomach to the lower esophagus)
What is the stomach? Its roles?
A food reservoir
- mixes food
- regulates flow of digesta into the SI via a sphincter
- initiates chemical digestion of protein (secretion of HCl and pepsinogen = protein unravels)
NO digestion of CHO and fats
Sections of the stomach
Proximal and distal
Proximal expands during temporary food storage (allows dogs to eat discrete meals)
What affects gastric secretions?
- influenced by the amount of protein in the meal, the meal volume and hormones
- gastric pH varies depending on the type of meal consumed (buffering capacity of the food)
What controls the rate of gastric emptying? What is the role of soluble fibre in gastric emptying?
- stomach volume, body weight, water intake and diet type
- high density particles empty slower than smaller sized particles
- hormonal control via macronutrient composition and characteristics
Soluble fiber decreases rate of gastric emptying
Differences in the stomach of cats vs dogs
Stomach as storage reservoir is less important for cats than dogs
- Average half emptying times are 22 to 449 mins for cats vs. 72 to 240 mins for dogs
- stomach is simpler for cat than dog (smaller with smaller glandular fundus)
What is the SI the primary site of? What happens to chyme
Site of chemical digestion and absorption of fat, starch, sugar, and protein
Acidic chyme moves from stomach into small intestine which stimulates secretion of pancreatic juice which increases the pH of the digesta.
Chyme is mixed with enzymes in the duodenum (which come from duodenal mucosa and pancreas)
Functions of the pancreas
Exocrine: secretes enzymes and bicarbonate salts into the gut to establish optimal pH
- enzymes: inactive proteases, lipases and amylases
Endocrine: secrete hormones into the blood
What do pancreatic juices of dogs have?
Antibacterial properties
Which hormones are released by the pancreas and when?
Insulin released after a meal in dogs
Glucagon stimulates release of aa from muscle
