Biology 20: Digestive System

function of the mouth

Site of ingestion, Food is chewed here. Enzymes begin to break it up

Ingestion

Intake of food

digestion

The process by which the body breaks down food into small nutrient molecules-proteins, carbs, nucleic acids, lipids

Absorption

The process by which nutrient molecules pass through the wall of the digestive system into the blood stream

where mechanical and chemical occurs in the digestive tract

the stomach (both), mouth(both), small intestine (chemical digestion)

assimilation

moving the nutrients from the bloodstream and storing + using them in tissue

Egestion

The removal of nonsoluble waste materials.

function of saliva

moisten food and forms bolus, starts chemical digestion, inhibits bacteria

function of epiglottis

seal off the windpipe during eating, so that food cannot enter lungs

function of esophagus

to carry food, liquids, and saliva from the mouth to the stomach

Compostion of gastric juice

water, mucus, pepsinogen, hydrochloric acid, gastrin

Gastrin

Digestive hormone that stimulates sustained secretion of gastric juice from the stomach

Secretin

A hormone secreted by the small intestine (duodenum) in response to low pH (e.g., from stomach acid). It promotes the release of bicarbonate from the pancreas to act as a buffer.

enterogastrone

a hormone secreted by the small intestine that decreases gastric secretions and motility, slows peristalsis can help with indigestion and helps digest fats

Cholecystokinin

An intestinal hormone that stimulates the gallbladder to release bile

what the stomach mostly digests

protein

chemical digestion

Process by which enzymes break down food into small molecules that the body can use

mechanical digestion

Physical breakdown of large pieces of food into smaller pieces

function of duodenum

Regulates stomach and gallbladder emptying in response to acidic chyme.

function of pancreas

produces enzymes that digest fats, proteins, carbohydrates and nucleic acid

pancreatic juice contains:

proteases, lipases, nucleases, pancreatic amylases, peptisades

endocrine gland

something is made but it stays within that creation space- glands that produce hormones (insulin and glucagon)

exocrine glands

makes something but it is released to somewhere else- glands that produce enzymes (enzymes in pancreatic juice)

functions of the liver

detox blood, lipid metabolism, carbohydrate metabolism,creates and secrete bile, turn glucose into glycogen

hormone that carries glucose to the bloodstream

insulin

lipid metabolism

stores triglycerides and produces cholesterol

emulsification of fats

breaking fats into small emulsion drops using bile salts

carbohydrate metabolism

changes glucose to glycogen, breaks glycogen down into glucose—glucose released into bloodstream via insulin

function of the gall bladder

stores bile

large intestine composed of:

caecum, appendix, colon, rectum

bile

A substance produced by the liver that breaks up fat particles.

bile salts

compounds in bile that aid in emulsification

Pepsin

Enzyme that breaks down proteins in the stomach

Amylase

Enzyme in saliva that breaks the chemical bonds in starches

Lipase

pancreatic enzyme necessary to digest fats

nuclease

DNA cutting enzyme

villi

Fingerlike extensions of the intestinal mucosa that increase the surface area for absorption

Parts of villi

microvilli, epitheleum, blood capillaries

cardiac sphincter

opening from the esophagus to the stomach

mechanical digestion in the stomach

peristalsis

Peristalsis

Involuntary waves of muscle contraction that keep food moving along in one direction through the digestive system.

Most digestion occurs in the

duodenum, pancreas, gall bladder

2 transport systems of villi

blood vessels- simple sugars, amino acids, vitamins, minerals

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lacteals- lymph fluid

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lacteals

contains lymph: helps absorb fat and fat soluble substances

body cannot not absorb:

cellulose, dead cells, bacteria, undigested food

the _______ __ of _______ in the colon helps trigger the _________ _________ which initiate bowel movement

build up, waste, nerve impulses

what is absorbed in the colon

water, salts, and vitamins

hormonal control

When food passes the cardiac sphincter, gastrin (a hormone) is released from the stomach wall and it travels via bloodstream to the gastric glands causing secretions.

Nervous control

sight, smell, or taste triggers a reflex which causes hormones to start secretions from gastric glands in the stomach.