Flashcards in Digestive System Deck (50):
Function of Digestive System
the organ system that processes food, extracts nutrients from it, and eliminates the residue
Five stages of digestive
Ingestion, Digestion, Absorption, Compaction and Defecation
selective intake of food
mechanical and chemical breakdown of food into a form usable by the body
uptake of nutrient molecules into the epithelial cells of the digestive tract and then into the blood and lymph
absorbing water and consolidating the indigestible residue into feces
elimination of feces
is the beginning of the digestive tract;
receives food from your mouth when you swallow. the esophagus delivers food to your stomach.
-food storage organ
-mechanically breaks up food particles, liquefies the food, and begins chemical digestion of protein and fat
-most digestion occurs after the chyme passes on to the small intestine
-stomach to small intestine
Made up of three segments — the duodenum, jejunum, and ileum — the small intestine breaks down food using enzymes released by the pancreas and bile from the liver. Peristalsis also is at work in this organ, moving food through and mixing it with digestive secretions from the pancreas and liver. The duodenum is largely responsible for the continuous breaking-down process, with the jejunum and ileum mainly responsible for absorption of nutrients into the bloodstream.
The pancreas secretes digestive enzymes into the duodenum, the first segment of the small intestine. These enzymes break down protein, fats, and carbohydrates. The pancreas also makes insulin, secreting it directly into the bloodstream. Insulin is the chief hormone for metabolizing sugar.
The liver has multiple functions, but its main function within the digestive system is to process the nutrients absorbed from the small intestine. Bile from the liver secreted into the small intestine also plays an important role in digesting fat. In addition, the liver is the body’s chemical "factory." It takes the raw materials absorbed by the intestine and makes all the various chemicals the body needs to function. The liver also detoxifies potentially harmful chemicals. It breaks down and secretes many drugs.
The gallbladder stores and concentrates bile, and then releases it into the duodenum to help absorb and digest fats.
Colon (Large Intestine)
The large intestine is a highly specialized organ that is responsible for processing waste so that emptying the bowels is easy and convenient.
It is the rectum's job to receive stool from the colon, to let the person know that there is stool to be evacuated, and to hold the stool until evacuation happens.
The lining of the upper anus is specialized to detect rectal contents. It lets you know whether the contents are liquid, gas, or solid.
Saliva + Food in a ball
Protease enzyme is secreted by?
Stomach, Pancrease, and small intestine
Function of protease
Proteins are long chains of amino acids, and protease enzymes break them into peptides (smaller chains of amino acids molecules) and eventually into individual amino acids, which are small and easily absorbed in the small intestine.
proteins-------> amino acids
Carbohydrase Enzyme is secreted by?
Salivary glands, pancreas, and small intestine
Function of Carbohydrase enzyme
STARCH ----(amylase)---> MALTOSE -----(maltase)----> GLUCOSE
soupy or pasty mixture of semi-digested food in the stomach
Lipase Enzyme is secreted by?
Pancreas and small intestine
Function of Lipase
Lipase is secreted by the pancreas and the walls of the small intestine. It digests complex fat (or lipid) molecules into simple, soluble fatty acid and glycerol molecules.
Lipids ----(lipase)-----> fatty acids + glycerol
Contractions of small intestine serve three functions:
1. to mix chyme with intestinal juice, bile, and pancreatic juice to neutralize acid
2 .to churn chyme and bring it in contact with the mucosa for contact digestion and nutrient absorption
3. to move residue toward large intestine
- the movement in which stationary ring-like constrictions appear in several places along the intestine
-they relax and new constrictions form elsewhere
-most common kind of intestinal contraction
-Doesn’t move food forward, just mixes it in place
-gradual movement of contents towards colon
-peristaltic wave begins in the duodenum,
-milk chyme toward colon over a period of two hours
-ileocecal valve usually closed
-as cecum fills with residue, pressure pinches the valve shut
-prevents reflux of cecal contents into the ileum
-occurs every 30 mins.
Haustral churning is contraction of the colon resulting in mixing & more importantly dividing the contents into smaller pieces in the haustra.
Regulation of the digestive tracts are:
neural control, hormonal, and paracrine mechanisms
Name the two types of reflexes of neural control and define them.
1. Short reflexes –stimulates peristaltic contractions of swallowing
2. Long reflexes - parasympathetic stimulation of digestive motility and secretion
chemical messengers secreted into bloodstream, and stimulate distant parts of the digestive tract
-gastrin and secretin
chemical messengers that diffuse through the tissue fluids to stimulate nearby target cells
What are the two functions of pancreas? (glands)
Endocrine and Exocrine
secretes insulin and glucagons
-secretes pancreatic juice into small intestine which breaks down all categories of foodstuff
-acini (clusters of secretory cells) contain zymogen granules with digestive enzymes
alkaline mixture of water, enzymes, zymogens, sodium bicarbonate, and other electrolytes
inactive enzymes in the pancreas
What are the 3 inactive enzymes in the pancreatic zymogens?
secreted into intestinal lumen
converted to trypsin by enterokinase- an enzyme secreted by mucosa of small intestine
trypsinogen -----> trypsin
converted to chymotrypsin by trypsin
converted to carboxypeptidase by trypsin
ribonuclease and deoxyribonuclease (pancreas)
digests RNA and DNA respectively.
Three stimuli are responsible for the release of pancreatic juice and bile
2. cholecystokinin (CCK)
-from vagus and enteric nerves
-stimulates acini to secrete their enzymes during the cephalic phase of gastric control even before food is swallowed
-secreted by mucosa of duodenum in response to arrival of fats in small intestine
-stimulate pancreatic acini to secrete enzymes
-strongly stimulates gall bladder
-induces contractions of the gallbladder and relaxation of hepatopancreatic sphincter causing discharge of bile into the duodenum
-released from duodenum in response to acidic chyme arriving from the stomach
-stimulates ducts of both liver and pancreas to secrete more sodium bicarbonate
-raising pH to level pancreatic and intestinal digestive enzymes require