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Oral cavity functions
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intital digestion of proteins and lipids
small intestine functions
chemical and mechanical digestion
large intestine functions
compaction of feces
What is ingestion?
taking food and drinks into oral cavity
what is digestion?
breaking down foods into usable forms
What is the difference between chemical and mechanical digestion?
chemical: use of enzymes to break down polymers into monomers for absorption
mechanical: alters consistency of food to ease transport
What is the movement of materials into digestive tract epithelium → interstitial fluid→ blood/lymph?
What is compaction?
absorbing all usable material and consolidating the ingestible and nonabsorbable materials as feces
What is the function of protection of the digestive system( (epithelium and lymphoid tissue)
epithelia protect against abrasion, chemical damage, pathogens
lymphoid tissue protects against pathogens that enter interstitial fluid
What structures are included in the digestive tract (alimentary canal)?
mouth, esophagus, stomach, small intestine, large intestine
What are the accessory organs?
teeth, tongue, salivary glands, liver, gallbladder, pancreas
What are the functions of the accessory organs?
many produce secretions that are released into the lumen of digestive tract through ducts
What are the 4 digestive tract layers? list from innermost to outermost.
What is the function of mucosa?
absorb monosaccharides, amino acids, lipids
protect from abrasion
What are the functions of submucosa?
contains blood vessels and lymphatic vessels
What are the functions of muscularis externa?
inner circular/outer longitudinal smooth muscle
stomach contains a third oblique layer
churns and propels waste
What are the functions of serosa?
secrete serous fluid
Which membrane maintains spatial relationships between organs?
What is the function of mesentery?
supply blood vessels, nerves, lymphatic vessels, lymph nodes
What are the two posterior mesenteries?
mesocolon and mesentery proper
What are the two anterior mesenteries?
lesser omentum and greater omentum
What is peritonitis?
acute inflammation of the peritoneum caused my infection microbes, GI tract rupture, perforated ulcer, trauma, appendicitis
which cranial nerve controls the tongue?
CN XII (hypoglossal)
What is the function of the tongue?
mechanically break up food
manipulate food into a bolus
glands secrete saliva and ligual lipase
ducts of salivary glands open near lingual frenulum
What are the functions of saliva?
mucus for lubrication
enzymes that initiate the digestion of carbs and lipids
IgA antibodies and lysozyme
solvent for dissolving food molecules
bicarbonate that neutralizes bacterial acids
What is the function of the upper esophageal sphincter?
prevents air from entering esophagus when contracted
How many layers of muscularis externa is in the stomach? what is the function of the extra layer?
prevents over-stretching and helps churn food
What is the function of the mucus neck cell?
secrete acidic fluid containing mucin
What do parietal cells secrete?
Hydrochloric acid (HCl)
intrinsic factor (IF)
What is ghrelin?
appetite stimulating hormone
What is the importance of IF and B12?
essential for Hb synthesis
both get taken up via receptor mediated endocytosis
What do the chief cells secrete?
What activates pepsinogen to pepsin?
initiates chemical digestion of protein
what do enteroendocrine cells secrete
gastrin from G cells
What is the function of gastrin?
stimulates parietal and chief cell secretion
increases stomach motility, relaxes pyloric sphincter, constricts cardiac sphincter
stem cells that replace lost pit and gland cells
Parietal cells generate __ from __ , then pump into lumen while exchanging __.
what is bicarbonate exchanged for in gastric hydrochoric acid?
plasma chloride ions
CO2 is converted to carbonic acid, carbonic acid dissociates into _____ ,__ , , then , _ moves in and __moves out.
K+, H+, HCO3-
chloride moves in
bicarbonate moves out
What pump facilitates the gastric hydrochloric acid formula
protein H+ K+ ATPase pump
What is the function of gastric hydrochloric acid
kills microbes, denatures food enzymes, breaks down plant cell walls, meat CTs
activates pepsinogen and lingual lipase
Where does the initial digestion of lipids take place, and by what?
in the mouth/stomach by lingual lipase and gastric lipase
How is pepsin autocatalytic?
catalyzes own reaction by splitting amino acids to activate pepsinogen, that activates more pepsin
why is there little absorption in the stomach?
lack of transport proteins
Mucus cells contain ___________ which converts ethanol to acetaldehyde
Function of duodenum
recieves chyme from stomach and secretions from accessory organs
neutralizes stomach acid
site of pancreatic enzyme function
majority of chemical digestion and absorption occur here
lymphoid nodules protect against bacteria
Small intestine villi
absorb nutrients and deliver to liver
each contains a lacteal
What is a lacteal?
lymphatic capillary that absorbs lipids
small intestine microvilli
form brush border enzymes (BBEs)
increase surface area for absorption
carry out final stage of digestion
peptidases and enteropeptidase
Small intestine - intestinal crypts
what does upper portion contain?
what does lower portion contain?
what cell secretes lysozyme?
upper: enterocytes, goblet cells
lower: stem cells
What is the function of the duodenal glands?
produce mucus to protect epithelium
contains bicarbonate ions
__ of foodstuffs are used to make __ for biosynthesis
What is a hydrolysis reaction?
use water to break polymers into monomers
What initiates digestion of carbohydrates?
What initiates digestion of lipids?
lingual and gastric lipase
what initiates digestion of proteins?
Maltase, sucrase, lactase:
brush border of small intestine
maltose, sucrose, lactose
oligosacchardies, trisaccharides, maltose
oligosaccharides, trisaccharides, maltose
What bond does pepsin break?
tyrosine and phenylalanine bond
Pepsinogen (pepsin) --- stomach
chief cells of gastric glands
proteins and polypeptides
pepsinogen (pepsin) remarks (3)?
activated by HCl
breaks bonds between tyrosine and phenylalanine
enteropeptidase --- sm intestine
brush border and lumen of sm intestine
trypsinogen --- sm intestine
procarboxypeptidase (carboxypeptidase) --- sm intestine
activated by trypsin
proelastase (elastase) --- sm intestine
dipeptidases and peptidases --- sm intestine
dipeptides and tripeptides
Which two factors break lipid globules into smaller globules?
stomach churning and segmentation
and ___ from bile coat surface of small globules
what is the purpose of coating the small globules?
prevent them from coming back together
increase SA for lipase enzymes
Lipase breaks ____ into ____ and a ____
glands of tongue
FFAs and monoglycerides
What 2 nucleases are contained in pancreatic juice?
what is the function of deoxyribonuclease and ribonuclease?
break polymers into nucleotides
Brush border contains nucleosidases and phosphatases that result in which 3 things?
sugar (deoxyribose or ribose)