0-1 Chapter 25 - digestive system Flashcards
(193 cards)
gastroenterology
the study of the digestive tract and the diagnosis and treatment of its disorders
digestive system
the organ system that processes food, extracts nutrients from it, and eliminates the residue
five stages of digestion
ingestion digestion absorption- compaction defecation
ingestion
selective intake of food
digestion
mechanical and chemical breakdown of food into a form usable by the body
absorption-
uptake of nutrient molecules into the epithelial cells of the digestive tract and then into the blood and lymph
compaction
absorbing water and consolidating the indigestible residue into feces
defecation
elimination of feces
mechanical digestion
the physical breakdown of food into smaller particles
–cutting and grinding action of the teeth
–churning action of stomach and small intestines
–exposes more food surface to the action of digestive enzymes
chemical digestion
aseries of hydrolysis reactions that breaks dietary macromolecules into their monomers (residues)
–carried out by digestive enzymes produced by salivary glands, stomach, pancreas and small intestine
results:
- polysaccharides into monosaccharides
- proteins into amino acids
- fats into monoglycerides and fatty acids
- nucleic acids into nucleotides
some nutrients are present in a usable form in ingested food
–absorbed without being digested
–vitamins, free amino acids, minerals, cholesterol, and water
digestive system has two anatomical subdivisions
digestive tract
gastrointestinal
digestive tract
(alimentary canal)
–30 foot long muscular tube extending from mouth to anus
–mouth, pharynx, esophagus, stomach, small intestine, and large intestine
gastrointestinal (GI) tract
is the stomach and intestines
accessory organs
teeth, tongue, salivary glands, liver, gallbladder, and pancreas
General Anatomy
•digestive tract is open to the environment at both ends
•most material in it has not entered the body tissues
–is considered to be external to the body until it is absorbed by the epithelial cells of the alimentary canal
•in a strict sense, defecated food residue was never in the body
basis structural plan
most of the digestive tract follows the basis structural plan with digestive tract wall consisting of the following tissue layers, in order from inner to outer surface
basis structural plan
order
•mucosa –epithelium –lamina propria –muscularis mucosae •submucosa •muscularis externa –inner circular layer –outer longitudinal layer •serosa –areolar tissue –mesothelium
mucosa
(mucous membrane) –lines the lumen and consists of:
–inner epithelium
–lamina propria –
–muscularis mucosa
–mucosa-associated lymphatic tissue (MALT) –
inner epithelium
- simple columnar in most of digestive tract
* stratified squamous from mouth through esophagus, and in lower anal canal
lamina propria
loose connective tissue layer
muscularis mucosa
thin layer of smooth muscle
•tenses mucosa creating grooves and ridges that enhance surface area and contact with food
•improves efficiency of digestion and nutrient absorption
mucosa-associated lymphatic tissue (MALT)
the mucosa exhibits an abundance of lymphocytes and lymphatic nodules