Quiz, block 2- Digestive system Flashcards
what are the 3 parts of the digestive system?
- gastrointestinal (GI) tract: a long tube that extends from mouth to anus
- mouth: starts at oral (buccal) cavity, pharynx, esophagus, stomach, small intestine, large intestine
- accessory organs include salivary glands, liver, gall bladder, exocrine pancreas.
describe digestion process
breaking down of food into smaller particles and of macrophages in food into smaller, absorbable molecules. accomplished mechanically and by the actions of digestive enzymes, acid and bile.
describe secretion
release from exocrine glands of enzymes, bile, acid, water, ions and mucus into the lumen of the GI tract
describe absorption
movement of the molecules originally in food and drink resulting from digestion from the GI tract lumen across a layer of epithelial cells and into the body’s blood or lymph
describe motility
contractions of the smooth muscles in the GI tract wall that mix the luminal contents and propel them from mouth to anus.
what are the 4 processes in digestive system?
digestion, secretion, absorption, and motility
describe saliva that is secreted by salivary glands.
a. saliva is antibacterial
b. saliva contains mucus for lubricating food particles before swallowing
c. contain AMYLASE, an enzyme that begins polysaccharide digestion
d. dissolve molecules that can then interact with taste buds chemoreceptors that give rise to taste sensations
does GI system absorb everything?
yes, maximum absorption of glucose, water, Na+, etc.
indirectly regulate glucose so it can provide it to others for regulation.
Pharynx and esophagus can:
a. perform digestion
b. provide a pathway from oral cavity to stomach
c. a muscular walls control swallowing
d. b and c
d
upper esophageal sphincter
lower esophageal sphincter (can change in diamete)
stomach functions include:
a. produces the hormone gastrin
b. stores food
c. all of the above
c
what are the exocrine secretions in the stomach?
- hydrochloric acid into the lumen: kill bacteria, dissolves the particulate matter in food, which activate pepsinogen into pepsin.
- pepsin- digest proteins
- mucus- lubricating and protection
- intrinsic factor, for vitamin B12 for absorption in the SI. most vitamin has to be absorbed WHOLE.
what is the only process that the stomach do? not do?
ONLY absorb water, aspirin, and ethanol.
no digestion and absorption of carbs, fats, or proteins in the stomach
what is chyme?
the solution of partially digested protein, polysaccharide fragments, fat droplets, salt, water and other small molecules in the stomach, SI and LI
what are the components of small intestine?
duodenum, jejunum and ileum
what are the general functions of small intestine?
perform most digestion via hydrolytic enzymes and absorption of food molecules
list the 3 functions of small intestine
- small intestine secrete salts, water and mucus into its lumen. Liver/gallbladder secrete bile into its lumen
- beside absorbing monosaccharides, fatty acids, amino acids, it also absorbs vitamin, minerals and water
- SI motility mixes its luminal contents with various secretions, brings the contents into contact with epithelial surface of its wall where things can be absorbed, and slowly propels its contents toward the LI.
everything is absorbed in the SI, especially in the 1/4th of SI.
what are the dual functions of pancreas?
endocrine and exocrine function.
exocrine portion secretes pancreatic juice into the SI, which:
1. contain hco3- for maximally absorbing (necessary to prevent inactivation of pancreatic enzymes)
2. contain enzymes specific for digesting carbs, proteins, fats and nucleic acids
what are the 4 functions of liver?
a. secrete bile salts into the SI
b. secrete bicarbonate in the SI for acid neutralization
c. put some organic waste products and trace metals into the feces via the bile for elimination from the body
d. perform metabolic activities that help body handle carbs, amino acids/proteins, and fatty acids/lipid (including cholesterol).
e. all of the above
e
gallbladder functions:
a. stores and concentrates bile between meals and contract to secrete it into the duodenum
what are two components get dumped from the gallbladder and pancreas?
a. pepsin and gastrin
b. bile and pepsin
c. bile and pancreatic juice
d. hormones and salt
c: bile and pancreatic juice
functions of large intestine:
- secretes mucus into lumen for lubrication by goblet cells
- concentrates and temporarily stores undigested matter
- absorbs water and salt from it
- mixes and propel its contents
- don’t secrete many hormones
what are the 3 layers make up the innermost layer of GI wall?
mucosa.
1. mucosal epithelium- the epithelial layer plus
2. lamina propria: a layer of connective tissue containing blood, lymphatic vessels and nerve fibers, plus
3. muscularis mucosa- a thin layer of smooth muscle
what is the 2nd layer next to mucosa in the GI wall?
submucosa. a connective tissue layer just beneath the mucosa that contains a network of neurons (submucosal plexus), some neurons of which project to the mucosa, plus blood and lymphatic vessels
what’s the 3rd layer in the GI wall?
muscularis externa
composed to smooth muscle (plus a network of neurons between them- myenteric plexus) that contract to provide mixing and propulsion of the GI contents
what are the 2 muscle layers in the muscularis exerna?
- circular muscle: fibers of which encircle the tube and thus narrow its lumen diameter when they contract for mixing
- longitudinal muscle: fibers of which they run along the tube and thus shorten the tube when they contract.
what are the connections between the plexuses in GI wall?
neurons of myenteric plexus are innervated by neurons from the autonomic nervous system, and are connected with neurons of the submucosal plexus.
what is the 4th layer in the GI wall?
serosa.
- the think layer of CT forming outer surface of GI tube
a. outer tunic in the esophagus is called adventitia, rather than serosa.
b. in the abdominal cavity, sheets of CT connect the serosa to the abdominal wall.
what are the projects called that extend from the luminal surface of the SI into its lumen?
villi
what are the smaller projections sticking out of villi? their functions?
microvilli, aka brush border.
they increase the SI surface area.
what is the function of lacteal locating in the center of each villus?
most absorbed fat enters the lymhp via the lacteal
what is the route that the SI, LI, pancreas and part of stomach that drain into instead of the inferior vena cava?
they drain into the hepatic portal vein
what do products of digestion has to undergo before entering the general circulation?
they are absorbed into the SI blood and are processed (metabolized, detoxified, stored, etc.) by liver enzymes before entering the general circulation.