DS Flashcards
WHAT DOES THE DIGESTIVE SYSTEM DOES
the digestive system converts food into small molecules that can de used by th cells of the body.
phases of food processing
ingestion
digestion
absorption
elimination
what is ingestion
process of putting food into your mouth (the opening of the digestive of the tract
ways of breaking down food
mechanical and chemical digestion
mechanical digestion
is the physical breakdown of large pieces of food into smaller pieces. chewing begins the process of mechanical digestion
chemical digestion
is the is when enzymes break down food into small molecules the body can use. chemical digestions begins as digestive enzymes in saliva start the breakdown of complex carbohydrates into smaller molecules
ABSORPTION
once food has broken into small molecules it can be absorbed by cells in the small intestine. from the small intestine, the molecules enter the circulatory system, which transports them throughout the body
ELIMINATION
materials such as cellulose travel through the large intestine and are eliminated from the body as feces
what occurs during digestion
during digestion, food travels through the mouth, esophagus, stomach and small intestine
alimentary canal
one way tube that passes through the body
protection of teeth
coating of mineralized enamel
teeth work
incisors, cuspid and bicuspids cut into and tear foos. molars grind and crush food into a fine paste that can be swallowed.
release of saliva
salivary glands secrete saliva which helps moisten the food and make it easier to chew. the release of saliva is under the control of the nervous system.
SALIVA
begins the process of chemical digestion. saliva contains an enzyme called amylase that begins to break the chemical bonds in starches, forming sugars. saliva also contains lysozyme, an enzyme that fights infection by digesting the cell walls of many bacteria that may enter the mouth with food.
enzymes in saliva
- amylase begins to break the chemical bonds in starches, forming sugars
- lysozyme, an enzyme that fights infection by digesting the cell walls of many bacteria that may enter the mouth with food
what happens when the food is chewed
the combined actors of the tongue and throat muscles push the clump of food, called a bolus, down the throat. when you swallow, the bolus first enters the area at the back of the throat called the pharynx. as this occurs, a flap of connective tissue called the epiglottis closes over the opening of the trachea
the esophagus
from the throat the bolus passes through the esophagus into the stomach.
how you move food through the esophagus toward the stomach
contraction of smooth muscle known as peristalsis provide the force that moves food from the esophagus toward the stomach. muscles in the walls of the esophagus contract in waves.
closing of the esophagus
after food passes into the stomach, a thick ring of muscle called the CARDIAC SPHINCTER closes the esophagus. this prevents the contents of the stomach from flowing back
heartburn
overeating or drinking excess caffeine can cause a back flow of stomach acid into the esophagus. persistent heartburn can cause damage to the esophagus and is a reason to visit a doctor
Pepsin
enzyme that functions best in acidic conditions. breaks down proteins into smaller polypeptide fragments
stomach
is a large muscular sac that continues the process of MECHANICAL AND CHEMICAL digestion the lining of the stomach contains millions of microscopic gastric glands that release many substances into the stomach
Microscopic gastric glands functions
- Some produce hydrochloric acid
- release pepsin (breaks down proteins into smaller polypeptide fragments)
- produce mucus (fluid that lubricates and protects the stomach wall)
MUCUS, ULCERS, STOMACH
A stomach gland produces MUCUS which lubricates and protects the stomach wall. if this layer fail acids may erode the stomach lining and a sore called PEPTIC ULCER. most peptic ulcers are the result of infection with the bacterium called HELICOBACTER PYLORI. peptic ulcer can be cured with antibiotics (extra: scientist thought that peptic ulcers were caused because of too much stomach acid instead of the helicobacter pylori)
Mechanical digestion of the stomach
alternating contraction of the stomach’s three smooth muscle layers thoroughly churn and mix the swallowed food. the churning causes further breakdown of the swallowed food and allows enzymes greater access to the food. gradually a mixture with an oatmeal like consistency called chyme is produced. chyme the goes to the small intestine
what is chyme and how does it goes to the small intestine
CHYME is the result of the churning of the stomach. it has an oatmeal like consistency. after an hour or two of being produced, the PYLORIC VALVE which is located between the stomach and the small intestine opens and chyme begins to spurt into the small intestine.
DIGESTION IN THE SMALL INTESTINE
As CHYME is pushed though the PYLORIC VALVE, in enter the DUODENUM (first part of the small intestine) [most of the CHEMICAL DIGESTION and ABSORPTION occur on the small intestine.] as CHYME enters the the DUODENUM from the STOMACH, it mixes with ENZYMES and DIGESTIVE FLUIDS from the pancreas, liver and the lining of the duodenum.
pancreas
in the digestive system has two main roles
1. produces enzymes that break down carbohydrates, proteins, lipids, and nucleic acids
2. produces sodium bicarbonate (a base that quickly neutralizes the stomach acid when chyme enters the duodenum)
the enzymes produced by the pancreas will be easily destroyed by the stomach acid so this is why we need de sodium bicarbonate to proceed with digestion
The Liver and Gallbladder
the liver assist the pancreas in fat digestion. the liver produces BILE, a fluid loaded with LIPIDS AND SALTS. BILE is tired in the GALLBLADDER. when fat is present in the duodenum, the gallbladder releases bile. FATS tend to glob together with makes the fat digestion by enzymes such as LIPASE difficult. the BILE breaks up the globs of fat into smaller droplets that disperse which make it easier for enzymes to break them down
effects of the digestive system
ACTIVE SITE - ENZYME - EFFECT ON FOOD
1. mouth - salivary amylase - breaks down starches into disaccharides
2. stomach - pepsin - breaks down proteins into polypeptides fragments
3. A) small intestine (pancreas) - PANCREATIC AMYLAS - continues the breakdown of starch
B) small intestine (pancreas) - trypsin - continues the breakdown of protein
C)small intestine (pancreas) - lipase - breaks down fat
4. A) Small intestine - maltase, sucrase and lactase - breaks down remaining disaccharide into monosaccharides
B) small intestine - peptidase - breaks down dipeptides into amino acids
food journey page 879
MOUTH (1 minute) ESOPHAGUS (2 - 3 seconds) STOMACH ( 2 - 4 hrs) SMALL INTESTINE ( 3 - 5 hours) LARGE INTESTINE ( 10 hrs to several days)
how are nutrients absorbed and wastes eliminated
most nutrients from food are absorbed through the walls of the small intestine. the large intestine absorbs water and several vitamins and prepares waste for elimination from the body.
absorption from the small intestine
the small intestine is specially adapted for absorption of nutrients. folded surface and VILLI provide an enormous surface area for absorption of nutrients. VILLI has tiny projections called MICROVILLI which absorbs nutrients when chyme passes by. most of the products of carbohydrates and proteins are absorbed into the capillaries in the villi. most FATS and fatty acid are absorbed by LYMPH VESSELS. by the time chyme is ready to leve the small intestine it is basically nutrient free. complex organic molecules have been digested and absorbe, leaving only WATER, CELLULOSE AN OTHE UNDIGESTIBLE SUBSTANCES behind.
after leaving the small intestine
chyme goes to the APPENDIX. the appendix proccesses CELLULOSE and other materials.
Large intestine absorption
the primary function of the large intestines is to remove water from the undigested material left. water is absorbed across the walls of the large intestine, leaving behind undigested materials. colonies of bacteria in the large intestine produce compounds that the body is able to absorb like vitamin K
ELIMINATION
the waste that remains after most of the water has been removed passes into the rectum and is eliminated from the body through the anus.
where occurs most of the chemical digestión and absorption
small intestine
food journey detailed
- MOUTH: teeth tea and girad food into small pieces. enzymes in saliva kilos some pathogens and start to break down carbohidratos.
- ESOPHAGUS: the bolus través from the mouth to the stomach vía the esophagus. food is squeezed through the peristalsis
- STOMACH: muscle contracciones produce a churning motion that breaks up food and forms a liquidar mixture called chyme.
- SMALL INTESTINE:chyme is slowly released into the small intestine. bile is rehaced and aid in fat digestion. nutrients are absorbed through the small intestine wall
- LARGE INTESTINE: absorbe water as unidgested materials mover through and is eliminaste from the body.
if too much water is absorbed
constipación occurs
if not enough water is absorbed
diarhea occurs
