Digestion Flashcards
Three segments of the stomach
fundus
body
antrum
alimentary canal
-everything the food touches
the whole passage along which food passes through the body from mouth to anus. It includes the esophagus, stomach, and intestines.
accessory glands
-food does not touch
salivary glands, liver and gall bladder, and the pancreas aid the processes of ingestion, digestion, and absorption
what does the salivary glands do
secrete saliva
what is in saliva
-water
-mucus
-antimicrobial compounds ( IgA, H2O2)
-salivary amylase
-lingual lipase
salivary amylase
encoded by the gene AMY1, is a major component of human saliva that initiates carbohydrate digestion in the mouth
lingual lipase
enerates nonesterified fatty acids (NEFA) from dietary fats during oral processing by lipolysis
what does the stomach connect to?
the SI via the pylorus
how does the stomach carry out some chemical digestion
uses acid hydrolysis and pepsin.
what does the stomach limit
the amount of chyme entering the SI at a time
small intestine
site of additional digestion and absorption
duodenum
digestion, receiving inputs from liver/gall bladder through bile duct and pancreas via pancreatic duct
jejunum
larger and thicker, more mucosal tissue
ileum
most distal, majority of length of s,i
section of the small intestine
-duodenum
-jejunum
-ileum
large instestin
Used for reabsorption of water and absorption of some water soluble materials
four sections of large intestine
ascending
transverse
descending
rectum
layers of Gi tract
-mucosa
-submucosa
-serosa
mucosa
cells that secrete enymes and ions needed for digestion, mucus, hormones
enterocytes ( absorption)
innermost
muscularis mucosae
muscles that wave villi
GALT
gut associated lymphoid tissue
is the largest mass of lymphoid tissue in the body.
submucosa
connective tissue, blood vessels, lymph vessels
-submucosal plexus
Serosa
connective tissue sheet
outermost
continuous with the peritoneum
digestion
chemical and mechanical breakdown of food into absorbable units
absorption
movement of material from GI lumen to ECF
motility
movement of material through the GI tract as a result of muscle contraction
secretion
movement of materail from cells into lumen or ECF
processes of digestive
mechanical breakdown
-chewing, mixing
process of digestion chemical
hydrolysis of covalent bonds in polymers
-acid hydrolysis
-enzyme mediated hydrolysis
processes of secretion
variety of compounds are released by cells that line the GI tract into the lumen
secretion process water
roughly 9L per day move through GI tract
only 2 L are imbibed, the rest are secreted into the lumen
secretion process digestive enzymes
slaivary glands, stomach, SI, pancreas
mainly secreated by proenzymes zymogens
secretion process mucus
forms mucus upon contact with water
physical barrier that protects the GI tract from pathogens and digestive juices
what is mucins secreated by
goblet cells
motility process
Smooth muscle contractions move materials around in the lumen of the alimentary canal
-single unit smooth muscule
-different region s exhibit one of two contraction patterns
where does tonic contraction occur
in smooth muscles sphincters and anterior portion of the stomach
how long is tonic contractions substained
minutes or hours
tonic contraction
keeps bolus from moving backwards
how long does phasic contractions occur
few seconds at a time
two patterns in phasic contaction
peristalsis- moves bolus forward
segmentation-mixes
slow wave potentials
spontaneous cycles of depolarization and repolarization
where does slow wave potentials originate from
interstitial cells of cajal
modified smooth muscle celss
where does chemical and mechanical digestion begin
mouth
saliary secretion is under
autonomic control
salivary secretion does what
softens and lubricates food
saliva also has an protective function
chewing is
mastication
intiation fo long vagal reflex
20% of total gastric secretion
degluttion reflex
tongue pushes bolus against the soft palate
-muscle contraction raise the soft palate and move the larynx
-upper esophageal sphincter opens
-peristaltic contraction push bolus down to stomach
food moves downward into the esophagus, propelled by peristaltic waves and aided by gravity
where does sensory nerve carry signal
medulla via glosspharyngeal nerce (CN9)
when is breathing inbitited
as the bolus passes the closed airway
when is breathing inhibited
as the bolus passes the closed airway
three function of the stomach in gastric phase
storage
secretion
protection
when does digestive activity in the stomach begin?
with the long vagal reflex of the cephalic phase
what is the ned product of gastric phase
acid chyme
acid chyme
ph-2
little to no complex carbohydrate
large fat droplets
most protein broken into shorter chains.
most nucleic acids broken down to short chain.
pyloric sphincter parses acid chyme into
small manageable portions
most digestion occurs in
small intestine
what does bicarbonate do
neutralizes gastric acid (also comes from pancreas)
goblet cells secrete
mucus for protection and lubrication
cholecystoknin(cck) stimulates
the emptying of the gall bladder and pancreas
enteropeptidase converts
zymogens from pancreas into active forms
what do duodenum kick off
the process of intestinal phase, large amount of secretion
bile salts coats what
lipids to make emullsion
where does most absorption occur
in the small intestine via facillitated diffusion or active transport
what are most substance broken down into
component monomers for absorption
where are watar, ions, and several water soluble vitamins absorbed
large intestine
where are many synthesize vitamins, short fatty acids, and complex carbohydrates absorbed
coloncytes
main energy substrate of coloncytes
fatty acids
colon has large population
symbiotic bacteria
what regulates short reflexes
enteric nervous system
isolated gut exhibts
secretion and motility
submucosal plexus regulates
secretion in response to signals from lumen ( pressure chemical)
myenteric plexus causes
slow wave potentials, mixing, and peristalsis
long reflexes integrated by
CNS and endocrines
CCK targets
gallbaldder, pancreas, and stomach
CCK stimulates
fatty acid and some amino acids
CCK effects
stimulates gallbladder contraction and pancreatic enzyme secretion
inhibits gastric emptying and acid secretion
promotes satiety some effect may be due to CCK as a neurotransmitter
secretin target
pancreas, stomach
secretin stimulates
acid in small intestine
secretin effects
stimulates HCO-, secretion
-inhibits gastric emptying and acid secretion
motlin targets
gastric and intestinal smooth muscles
motlin stimulates
fasting periodic release, every 1.5-2 hours
motlin effects
stimulates migrating motor complex
inhibited by eating a meal
GIP targets
beta cells of pancreas
GIP stimules
glucose, fatty acids and amino acids in small intestine
GIP effects
stimulates insulin release, inhbits gastric emptying and acid secretion
GLP-1 targets
endocrine pancreas
GLP-1 stimulus
mixed meal that includes carbohydrates of fats in the lumen
GLP-1 effects
stimulates insulin release
inhbits glucagon release and gastric function
promotes satiety
