Quiz 26B

THE DIGESTIVE SYSTEM

Quiz 26B

digestion the breaking of food into smaller substances

assimilation the process by which living cells convert nutrients into cellular structure

Two types of digestion

 

mechanical digestion chemical digestion

mechanical digestion the process of breaking food into smaller pieces and mixing it with the digestive juices

chemical digestion the breaking down of food into substances usable by the cells

GROUPING OF ORGANS OF THE DIGESTION SYSTEM alimentary canal  accessory organs 

alimentary canal the digestive tract: mouth, pharynx, esophagus, stomach, small intestine, large intestine, and anus

FUNCTIONS OF THE DIGESTIVE SYSTEM  the

breakdown of foods both mechanically and chemically  the absorption of foods  the adjusting of concentrations of various foods in the bloodstream  destroying harmful substances that enter the body through the mouth and nose

peristalsis

muscular contractions that move food along the alimentary canal

accessory organs organs that secrete substances that are carried through ducts (tubes) to the alimentary canal

accessory organs    

liver pancreas gallbladder salivary glands

MOUTH

mixed with saliva from the salivary glands (3 pairs of salivary glands) the saliva moistens and lubricates the food for easy swallowing

MOUTH

salivary glands secrete a digestive enzyme--amylase

amylase A digestive enzyme that begins the breakdown of starch to sugar

mastication

The chewing of food

4 different types of teeth are involved in mastication  incisors (8): flat, narrow, bladelike surfaces for cutting and biting food  canines [cuspids] (4): tear food  premolar (8): crush food

 molars (12): grinding food

4 different types of teeth are involved in mastication

ESOPHAGUS the word esophagus means "I will carry down."--its only function

it only requires 3-6 seconds for food to move from the mouth to the stomach

ESOPHAGUS

the esophagus produces no digestive enzymes

cardiac sphincter

Lower Esophageal Sphincter muscular valve that controls food going into the stomach; keeps food in the stomach

STOMACH

the thick, muscular walls of the stomach churn the food and mix it with the acidic gastric juices which contain enzymes for protein digestion

STOMACH

these enzymes would also digest the walls of the stomach if the walls were not protected by the slimy mucous from the mucous membrane lining the stomach

STOMACH the duration of churning may be 4 hours for coarse foods like celery and spinach; foods like oatmeal and pudding move through the stomach quickly

STOMACH chyme: food in a semi-liquid state

STOMACH

although the stomach lining does not absorb many food molecules, it does absorb alcohol, water, and certain drugs

STOMACH pyloric sphincter:

muscles that control the pyloric valve; controls food moving into the small intestine

SMALL INTESTINE

about 23 feet long; about 1 inch in diameter

SMALL INTESTINE

most of digestion and absorption of food occurs here

SMALL INTESTINE

duodenum: first section of the small intestine; about 10 inches

SMALL INTESTINE

as partially digested food from the stomach passes into the duodenum, the acidity of the

SMALL INTESTINE

food stimulates the intestinal lining to secrete hormones

SMALL INTESTINE these hormones stimulate the pancreas, gallbladder, and intestinal lining to secrete

SMALL INTESTINE

enzymes and other materials into the duodenum for digestion,

SMALL INTESTINE

which converts food into small molecules

VILLUS villi: (singular, villus) microscopic, fingerlike structures that line the wall of the small intestine

VILLI

LARGE INTESTINE (COLON)

about 5-6 feet long; 2 1/2 inches in diameter

LARGE INTESTINE (COLON) little or no digestion occurs

LARGE INTESTINE (COLON) functions: 1)removal of waste materials (called feces) 2) absorb water and minerals

LARGE INTESTINE (COLON)

also serves as an ideal site for growth of bacteria and yeasts

LARGE INTESTINE (COLON) there are many beneficial bacteria and yeasts reproducing in the colon

LARGE INTESTINE (COLON) bacteria and yeasts produce vitamins B1, B2, B12, and K

LARGE INTESTINE (COLON) about 25% of the weight of dried feces consists of dried bacteria and yeasts

LIVER

Liver

each liver cell may perform more than 500 separate functions

LIVER called "master chemist of the body"

LIVER Liver receives blood by way of the portal vein

LIVER makes bile, a greenish fluid that breaks up lipids into droplets

LIVER

the liver secretes about 1/2 liter (1 pint) of bile a day

GALLBLADDER

bile is stored in the gallbladder

PANCREAS

pancreas

a soft, pinkishwhite gland about 6-9 inches long; 1 inch wide

PANCREAS

pancreas

about 97% of the pancreas cells produce digestive juices that contain enzymes for digesting carbohydrates, fats, and proteins

PANCREAS most of the remaining pancreas cells produce hormones (insulin) involved in regulating the amount of sugar in the blood