Transcript Digestive System

SI Session
Digestive system
Spring 2010
For Dr. Wright’s Bio 6 Class
Picture from http://www.eregimens.com/regimens/Digestion_Regimen.htm
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What are the organs of the digestive system and what do they do? What are some of the enzymes of the digestve system;
where are they synthesized; where in the digestive system do they actually function, and what food molecules do they break
down?
What substances are secreted by what cells in the stomach?
What food molecules are absorbed by the stomach?
Where in the small intestine do digestion and absorption take place?
What structures in the small intestine facilitate absorption?
What happens in the large intestine? Why are there bacteria in the large intestine and what do they do?
Liver function: what is the purpose of, and how, does the liver
Produce and secrete bile?
Detoxify blood (what does it remove from the blood)
Store and release food molecules
Make plasma proteins (what are they and what do they do)
What is the purpose of the gall bladder?
What is in pancreatic juice and what does it do? What cells in the pancreas are exocrine cells? What stimulates the secretion
of pancreatic juice?
What “arm” of the autonomic nervous system controls digestion?
Digestive system
Responsible for….
-Food intake
-Breaking eaten food down into
its monomer molecules,
 absorbing the monomer
molecules into the body
-Eliminate the undigested
wastes from the body
Picture from: http://www.cartoonstock.com/directory/b/bowel_movement.asp http://www.telegraph.co.uk/science/science-news/3303035/Scientists-find-hormone-to-stop-overeating.html
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Digestion
-Hydrolysis of macromolecules(food molecules:carbohydrates,
protein, fat, nucleic acid) into monomers: Glucose, amino acid, fatty
acids…  ____________
Catabolism
-catalyzed by specific enzymes.
 Digestive enzymes are made mostly by the pancreas and the small
intestine.
-absorbed through the intestinal mucosa
 enter the blood or lymph.
*Only the monomers from the foods are
allowed to pass into the bloodstream.
Picture from http://legacy.owensboro.kctcs.edu/gcaplan/anat2/notes/Notes8%20Digestive%20Physiology.htm
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Oral cavity : Starch(a long chain) is hydrolyzed into shorter
polysaccharide chains.
Stomach : Significant digestion occurs but not fully digested to
monomers.
Small intestine : Most of the digestion and most of the absorption
of water, monomers, and ions.
Duodeum : Receives the acid chyme from stomach and digestive
chemicals(enzymes) from all 3 accessay organs.
Large intestine : The final water and ion absorption from the feces
(Chyme after the small intestine) accurs
Small intestine : Fat globules are emulsified by the detergent
action of bile
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Mouth
-___________(chewing)
of food mixes it with
Mastification
saliva from salivary glands.
-Enzyme: ______________
Salivary amylase
-A formation of a bolus of food
Esophagus
-Wavelike contraction: _________.
Peristalsis
-Esophageal sphincter
Stomach
HCl
-ingested food is churned; mixed with ____.
-pepsinogen converted to pepsin
 __________________
Protein-digesting enzyme
-Store food; initiate the digestion of protein
-Forms and churns chyme
______.
-Rugae
-Pylorus sphincter
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Secretions of the stomach
-mucosal surface forms gastric pits that lead into gastric
glands.
Mucus - goblet cells
HCl - parietal cells
Pepsinogen (pepsin)- chief cells
Gastrin- G cells
Entrochromaffin-like- histamine, serotonin
Somatostatin- D cells
____________
Intrinsic factor - parietal cells
(necessary for absorption of
vitamin B12)
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Small intestine
-Absorption for carbo. Lipids, amino acids Ca2+…
-to increase surface for absorption
______________
Micorvilli & villi
-Contraction
peristalsis & ___________
segmentation
-Enzymes
Disaccharidase, peptidase, Phophtase
-Most food molecules are absorbed in duodenum
__________________
and jejunum
ileum
-Bile salts, water, electrolytes in _____.
Large intestine
-Absorption for water, electrolyte, and minerals
-Little or no digestion
-_________________:
Bacteria (microflora) produce Vit k and folic acid
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Liver
-Largest internal organ
-Functional unit: lobules
-produces and secretes bile (via gall
bladder) which facilitates digestion of fat.
-Modifies the plasma concentrations of
proteins, glucose, triglyceride, and ketone
bodies.
-Detoxifies the blood
Chemical alternation
Phagocytosis
Production of urea or other less toxic molecules
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Liver(Cont’d)
-Carbohydrates of metabolism
glucose –>glycogen or glycogen  glucose
glucogenesis~ produce glucose from amino acid or
lactic acid
-Lipid metabolism
synthesis of triglycerides and cholesterol
excretion of cholesterol in bile
production of ketone bodies from fatty acids
-Protein synthesis
albumins, plasma transport proteins
clotting factors(fibrinogens, prothrombin, etc)
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Gall bladder
-stores and concentrates bile
-release to duodenum via common bile
duct
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Pancreas
-Secrete both exocrine(_____________)
Pancreatic acini and endocrine(______________).
Pancreatic islet
Endocrine into the blood.
Alpha cell – glucagon
Beta cell - insulin
Exocrine: _______________
Pancreatic juice into dudenum: trypsin, amylase, lipase
↑Blood glucose
In Beta cell
↑insulin secretion
In Beta cell
↑insulin secretion
Cells uptake glucose
↓Blood glucose
Insulin
↓Blood glucose by stimulating…
-cellular uptake of glucose
Adipose tissue: Glucose Triglyceride -conversion of glucose to glycogen and fat
Liver/muscle: Glucose  Glycogen
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Pancreatic juice(exocrine)
-Pancreatic acini
-Contains water, bicarbonate, digestive enzyme
Enzyme: trypsin(for protein), amylase(for starch),
lipase(for triglycerides)
-Activation trypsin  triggers activation of other pancreatic enzymes
Secretin and CCK(cholecystokinin)
-Duodenal hormones
-Stimulate the secretion of pancreatic juice
-Secretin
↑HCO3 production in pancreas; ↑HCO3 secretion into bile in liver
secreted in response to below pH < 4.5 in duodenal
chyme is rapidly neutralized by alkaline pancreatic juice  ↓Secretin
-CCK
secreted in response to protein and fat of chyme in duodenum
stimulates the production of pancretic enzymes:trypsin,amylase,lipase
stimulates contraction of gall bladder to eject bile.
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Picture from http://www.bio.miami.edu/~cmallery/150/neuro/neurophysiology.htm
Designed by Pyeongsug Kim, ©2008
Parasympathetic effect in digestive system
-Mouse -Saliva secretion and thin
-Stomach –increase secretion
-Intestine – increase secretion
-GI tract – stimulate motility
-Pancreas – stimulate of exocrine secretions
Table 9.4 in the 8th ed.
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