Anatomy and Physiology of Digestive Systems and the Process of Digestion Flashcards
Carnivores
feed on animal tissues
Omnivores
feed on animal tissues and plants (ex. raccoons, humans, pigs, bears)
Herbivores
feed on plants
What is the difference between monogastrics and ruminants?
Monogastrics have one major stomach compartment while ruminants have multiple (usually 4) stomach compartments.
What monogastric did we use to model digestion?
the pig
What are the functions of the mouth?
- Prehension
- Ensalivation
- Mastication
- Bolus formation
What is prehension?
grasping food and bringing it into the mouth
prehension varies by species
ex. humans - hand
dog - tongue
goat - lips
What is ensalivation?
mixing food with saliva
What is mastication?
grinding or pulverizing food
What is bolus formation?
rolling food into balls with the tongue and pushing it to the rear of the mouth
What is the pharynx?
The structure that connects the mouth and throat
What are the two types of swallowing?
voluntary and reflex
What is the esophagus?
a muscular structure connecting the pharynx to the stomach
What are the functions of the stomach?
- stores food material
- secretes substances (like mucous and HCl)
- mixing
- moves chyme from stomach to rest of the digestive system
What is the pylorous and what does it do?
The pylorous is the structure that keeps the stomach closed from the small intestine
What is chyme?
partially digested food
What are the interior lining zones of the stomach?
Esophageal
Cardiac
Fundic
Pyloric
What is the function of the cardiac lining zone of the stomach?
it secretes mucous
What is the function of the fundic lining zone of the stomach?
Secretes acid
What is the function of mucous in the stomach?
It protects the stomach lining from the acid
What is present in the gastric fluid of the stomach?
- Mucous
- HCl
- Lipase (in small amounts)
- Rennin
- Pepsinogen (a zymogen)
What is the function of lipase in the stomach?
Lipase an enzyme that breaks down fats; it is not very active in the stomach due to the low pH
What are zymogens?
an inactive form of an enzyme that needs to be activated
How is the zymogen pepsinogen activated?
Pepsinogen is activated when it is exposed to HCl, turning it into its active form of pepsin.
Pepsinogen –(HCl)–> Pepsin
What is the function of pepsin?
Pepsin is an enzyme that breaks down proteins
What is the function of rennin in the stomach?
It coagulates milk in the stomachs of younger animals
What is gastrin? What are its functions?
Gastrin is a hormone produced by the pyloric region of the stomach.
It targets the stomach to produce more secretions.
It is an endocrine hormone.
Describe the flow regulation of gastric fluid.
- Cephalic phase: nerve impulses prepares stomach for incoming food
- Gastric phase: nerve impulses and hormonal response; food is in the stomach; this is a longer phase and gastrin is heavily involved
- Intestinal phase: hormonal response; food is ready to go to the intestines
What is required for the stomach to be emptied?
- fluidity and acidity of chyme in the stomach must be appropriate
- receptivity of the duodenum (first part of the small intestine)
- Pyloric Pump: contractions of stomach become stronger and push food through the pyloric sphincter (pylorous)
What reduces gastric flow rate?
- enterogastric reflex: nerve reflex that reduces pumping action of the stomach
- enterogastrone: a hormone produced by the small intestine; it slows gastric fluid production and flow rate
These processes are initiated by the duodenum
What is enterogastrone?
a hormone produced by the small intestine that slows the production of gastric fluid and the flow rate
Describe the structure of the small intestine
the small intestine contains a long and muscular tube and villi
What are villi and what is their function
villi increase the surface area to absorb nutrients better
What are the functions of the small intestine
- chemical degradation
- absorb nutrients into bloodstream
What are the sections of the small intestine?
- duodenum
- jejunum
- ileum
Where is the entrance of the ducts from the liver and pancreas located on the small intestine?
at the anterior end
What are the types of digestive fluid?
pacreatic, hepatic, intestinal
Describe pancreatic fluid
produced in the pancreas
alkaline pH
contains enzymes, carbonates, and bicarbonates
hormonal control with secretin and cholecystokinin (CCK) occurs
Enzymes present are trypsin (from the zymogen trypsinogen) and chymotrypsin; amylase and carbohydrase; lipase
What is secretin and what does it do?
Secretin is a hormone produced in the duodenum that causes the pancreas to secrete more pancreatic fluid, carbonates, and bicarbonates
What is cholecystokinin and what does it do?
Cholecystokinin (CCK) is a hormone produced in the duodenum that increases the enzyme output of the pancreas
What are some similarities between trypsin and chymotrypsin?
Both are proteolytic (proteases) and both result from zymogen action that work further to break down proteins into amino acids
What is trypsinogen?
a zymogen that is activated to form trypsin
Trypsinogen —(enterokinase)—> Trypsin
What is amylase?
an enzyme that breaks down amylose and amylopectin into smaller components
Why is more fat broken down in the small intestine than in the stomach?
the pH range in more suitable for lipase
Describe hepatic fluid (bile)
produced in the liver
stored in the gall bladder
alkaline pH
contains waste products of liver metabolism
Functions:
1. emulsifying agent
2. neutralize acids
3. aid in absorption
Hormonal controls include the use of CCK and pancreozymin
How does hepatic fluid act as an emulsifying agent?
it breaks up fat to increase the surface area, which helps lipase break down fats further
How does hepatic fluid neutralize acids?
it increases the alkalinity of the solution
How does cholecystokinin work with hepatic fluid?
it controls the release of hepatic fluid from the gall bladder
Describe intestinal fluid
pH is alkaline
contains all of the enzymes as the other fluids
Describe the structure of the large intestine
this intestine is a large, muscular tube
What are the functions of the large intestine?
- stores residues left from the digestive process
- lubricates residue to exit through anus; forms feces
What are the sections of the large intestine?
- cecum
- colon
- rectum
What does the cecum do?
some fermentation occurs in this structure
the cecum is not part of the long tube portion of the large intestine; food enters and leaves through the same opening
not a major part of the pig’s digestive system
similar to the appendix in humans
Define absorption in the context of digestion
movement of materials from the digestive tract into the bloodstream
What are some mechanisms of absorption?
- diffusion (passive)
- osmosis (passive transport of water)
- active transport - requires energy (moves larger materials like fatty acids)
In monogastrics, where does the majority of absorption occur?
unless its water, most things are absorbed by the small intestine
What does the small intestine absorb?
- amino acids
- simple sugars
- fatty acids and glycerol
- vitamins
- minerals
- some water
What does the large intestine absorb?
- water
- small amounts of other substances
What is the portal vein?
The portal vein carries nutrient rich blood from the gastrointestinal tract to the liver, which metabolizes and detoxifies substances before they circulate to the rest of the body.
Define digestion
breakdown of food in the GI tract
Define gastric digestion
food breakdown under acidic conditions
Define intestinal digestion
food breakdown under alkaline conditions
What are the end products of starch absorption and where are they absorbed?
glucose is the end product, absorbed in the small intestine
What are the end products of sugar digestion and where are they absorbed in the monogastric
glucose; absorbed by small intestine