Over view of the digestive system
Two groups of organs compose the digestive system:
-The gastrointestinal tract and the acessory igestive organbs
the gi tract is a continous tube that extends form the mouth to the anus,
the gi tract contains food from the mouth to the anus
the gi tract contains food from the time it is eaten until it is digested and abosrbed or eliminated from the body
orangs in this tract: mouth pharynx asophogus stomach small intestine and large intestine.
Acessory digestive system: the teeth tongue, salivary glands, liver, gallbladder and pancreas
teeth: brerak down food
tongue: chewing and swallowing
6 basic processes of the digestive systemL
ingestiuon- the process involves taking foods and liquids into the mouth
secretion: each day cells within the walls of the gi tract and acessory organs secrete a total of 7 liters of water, acid, buffers and enzymes into the lumen of the tract.
Mixing and propulsion: alternating contraction and relaxation of smooth muscle in the walls of the gi tract mix food and secretiion and propel them toward the anus.
Mobility: the aBILITY OF THE GI TRACT TO MIX AND move material along its length
digestioin: mechanical digestion- the teeth cut and grind foof before it is swallowed and then smooth muscles of the stomach and small intenstine churn the food.
Chemical digestion- the large carbohydrate, lipid, protein and nucleic acid molecules in food are broken down into smaller molewcules by digestive enzymes.
Absorbtion: the entrance of ingested and secreted fluids, ions and small molecules that are products of digestion into the epithelial cells lining the lumen of the gi tract is called absorbtion. The absorbed substances pass into interstitial fluid and then into blood or lymph and circulate to cells throughtout the body.
Defecation: wastes, indigestible substances, bacteria, cells cshed from the lining of the gi tract and digested materibals that were not absorbed leave the body.