Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
273 Cards in this Set
- Front
- Back
|
The fundus and body are sometimes collectively known as what?
|
oxyntic mucosa
|
|
|
The intrinsic factor secreted by the fundus and body of the stomach is necessary for what?
|
for absorption of vitamin B-12 which is required to properly shape RBC
|
|
|
The antrum is sometimes referred to as what area?
|
the pyloric gland area
|
|
|
What do the chief cells lining the glands secrete?
|
pepsinogen (enzyme that digests proteins)
|
|
|
What do the parietal cells lining the glands secrete?
|
HCl and intrinsic factor
|
|
|
What do the g cells in the pyloric gland area secrete?
|
gastrin
|
|
|
What do the d cells in the pyloric gland area produce?
|
somastatin
|
|
|
What do the enterochromaffinlike (ECL) cells in the oxyntic mucosa produce?
|
histamine
|
|
|
Name 5 kinds of cells found in the oxyntic mucosa?
|
1. surface epithelial cells
2. mucous cells 3. chief cells 4. parietal cells 5. ECL cells |
|
|
Where are the glands that secrete digestive juices and how much do they secrete daily?
|
1. secreted by glands at base of gastric pit
2. 2 L secreted daily |
|
|
What type of secretions are the secretion of digestive juices?
|
exocrine
|
|
|
3 Gastric exocrine cells in the oxyntic mucosa?
|
1. mucous cells
2. chief cells 3. parietal cells |
|
|
Describe mucous cells of the oxyntic mucosa?
|
line pits and entrance of glands, secrete thin, watery mucous
|
|
|
Describe chief cells of the oxyntic mucosa?
|
line gastric glands, numerous, secrete pepsinogen
|
|
|
Describe parietal cells of the oxyntic mucosa?
|
line gastric glands, fewer then chief cells; secrete HCl and intrinsic factor
|
|
|
Where are exocrine secretions released?
|
into the gastric lumen
|
|
|
Paracrine vs. endocrine secretions?
|
Paracrine is secreted and acts locally (from endocrine cells), Endocrine is secreted into blood
|
|
|
Endocrine and paracrine secretions are what kind of factors?
|
regulatory
|
|
|
Name the 3 cells involved with endocrine and paracrine secretion?
|
1. ECL cells
2. G cells 3. D cells |
|
|
Describe the ECL cells?
|
1. in oxyntic mucosa
2. secrete paracrine (histamine) |
|
|
histamine is a what?
|
paracrine
|
|
|
Describe G cells?
|
1. in pyloric gland area
2. secrete hormone (gastrin) |
|
|
Describe D cells?
|
1. in pyloric gland area (but even more in duodenum)
2. secrete paracrine (somatostatin) |
|
|
HCl is secreted by what cells?
|
By the parietal cells of the oxyntic mucosa
|
|
|
How low is the pH in the stomach?
|
as low as 2
|
|
|
4 functions of the low pH of the stomach?
|
1. converts inactive pepsinogen into active pepsin, initiating protein digestion
2. Denatures proteins (uncoiling from tertiary structures) 3. Breakdown of connective tissue and muscle fibers 4. Kills most microorganisms |
|
|
Describe the mucus lining on the gastric mucosa surface? (3)
|
PROTECTIVE
1. mechanical injury 2. self-digestion (pepsinogen) 3. alkaline, neutralizing HCl near gastric lining |
|
|
What do parietal cells make?
|
HCl
|
|
|
Bicarbonate and Cl are what kind of transport?
|
secondary active transport
|
|
|
How do hydrogen ions (H+) go into the stomach?
|
primary transport
|
|
|
Describe Carbonic anhydrase?
|
An enzyme found in the parietal cells and RBC
, converts CO2 and H2O to produce carbonic acid which dissociates into H+ ion and bicarbonate ion |
|
|
When H+ is transported into the stomach via primary transport what is being pumped into the cells?
|
K+
|
|
|
Why does the bicarbonate ion go into the stomach?
|
it's a great buffer
|
|
|
How does Cl- get into stomach and for what reason?
|
via Cl channel, to produce HCl in stomach
|
|
|
What do the chief cells secrete?
|
pepsinogen
|
|
|
Pepsinogen is inactive, so what doesn't it do?
|
does not digest cells and proteins
|
|
|
What can pepsinogen do?
|
autocatalyze itself to active pepsin which aids in protein digestion.
|
|
|
Pepsinogen can autocatalyze but what is needed initially to start the process?
|
HCl
|
|
|
For Mucous Cells:
1. Product secreted 2. Stimuli for secretion 3. Function of Product |
1. Alkaline mucus
2. Mechanical stimulation 3. protection |
|
|
For Chief cells:
1. Product secreted 2. Stimuli for secretion 3. Function of Product |
1. Pepsinogen
2. ACh, gastrin 3. Active, begins protein digestion |
|
|
For Parietal Cells:
1. Product secreted 2. Stimuli for secretion 3. Function of Product |
1. HCl, intrinsic factor
2. ACh, gastrin, histamine 3. Activates pepsinogen, etc. vit. B-12 |
|
|
For ECL cells:
1. Product secreted 2. Stimuli for secretion 3. Function of Product |
1. Histamine
2. ACh, gastrin 3. Stimulates parietal cells |
|
|
For G cells:
1. Product secreted 2. Stimuli for secretion 3. Function of Product |
1. gastrin
2. protein products, ACh 3. Stimulates parietal, chief, and ECL cells |
|
|
For D cells:
1. Product secreted 2. Stimuli for secretion 3. Function of Product |
1. Somatostatin
2. Acid 3. Inhibits parietal, G, and ECL cells |
|
|
The threes cells with exocrine products?
|
(digestive juices)
1. mucous cells 2. chief cells 3. parietal cells |
|
|
The 3 cells with endocrine/paracrine products?
|
1. ECL cells
2. G cells 3. D cells |
|
|
The 4 chemical messengers (stimuli) that influences secretion of gastric juice?
|
1. ACh
2. Gastrin 3. Histamine 4. Somatostatin |
|
|
ACh is released from what kind of nerve plexuses general?
|
intrinsic nerve plexuses
|
|
|
What does ACh stimulate?
|
parietal and chief cells
|
|
|
What is ACh released in response to?
|
short reflexes and vagal stimulation (vagal is external stimulation, so both intrinsic and external)
|
|
|
Where is Gastrin released from?
|
G cells
|
|
|
What does gastrin stimulate?
|
parietal and chief cells
|
|
|
What is gastrin released in response to?
|
ACh and protein products in the lumen
|
|
|
What cells release histamine?
|
ECL cells
|
|
|
What does histamine stimulate?
|
acts locally on parietal cells to increase HCl release
|
|
|
What is histamine released in response to?
|
Gastrin and ACh
|
|
|
What cells release somatostatin?
|
D cells
|
|
|
What does somatostatin inhibit?
|
locally inhibits secretions from parietal, G, and ECL cells
|
|
|
What is gastrin released in response to?
|
Acid
|
|
|
Where are D cells located?
|
some in antrum but even more in duodenum
|
|
|
3 phases involved in the control of gastric secretion?
|
1. Cephalic phase
2. Gastric phase 3. Intestinal phase |
|
|
Describe the Cephalic phase of gastric secretion control?
|
stimuli from head (seeing, smelling, etc) increases secretion of HCl and pepsinogen via vagal (extrinsic) nerve activity
|
|
|
Describe the Gastric phase of gastric secretion control?
|
Stimuli in stomach (eg, proteins) initiate gastric secretions via intrinsic nerve plexuses and extrinsic vagal pathway
|
|
|
Describe the Intestinal phase of the control of gastric secretion?
|
INHIBITORY, shuts off flow of gastric juices via factors in duodenum (eg, fat, acid, etc)
|
|
|
Where does Carbohydrate digestion begin and continue? why?
|
Begins in mouth and continues in the stomach, there is actually not a lot of digestion in the stomach
-food is not mixed with gastric secretions in the stomach -the salivary amylase continues to work in the internal mass of food |
|
|
Where does salivary amylase come from?
|
the mouth
|
|
|
Where does protein digestion begin? Why?
|
in the antrum, this is where food is mixed with HCl and pepsin
|
|
|
What 2 things does the stomach absorb? What does it not absorb?
|
1. absorbs alcohol (lipid soluble)
2. absorbs Aspirin (weak acid, lipid soluble here) 3. not food |
|
|
How is the stomach lining protected from gastric secretions?
|
by gastric mucosal barrier
-mucosal membrane is almost impermeable to hydrogen ions |
|
|
What does drinking coffee do to the gastric juices?
|
increases them
|
|
|
What does drinking alcohol do to the gastric juices?
|
increases them
|
|
|
The mucus coating in the stomach lining is impermeable to what?
|
HCl
|
|
|
Where is the pancreas located relative to the stomach?
|
behind it
|
|
|
The pancreas contains what types of cells?
|
exocrine and endocrine
|
|
|
Hormones, insulin, glucagon and islets of langerhans are associated with what?
|
Endocrine pancreas
|
|
|
Acinar and duct cells are associated with what?
|
Exocrine pancreas
|
|
|
Acinar cells produce what?
|
digestive enzymes
|
|
|
Duct cells are responsible for what?
|
aqueous alkaline fluid (NaHCO3, sodium bicarbonate)
|
|
|
3 enzymes released by the Acinar cells of the exocrine pancreas?
|
1. Proteolytic enzymes
2. Pancreatic enzymes 3. Pancreatic lipase |
|
|
Name 3 proteolytic enzymes?
|
1. trypsin (from trypsinogen)
2. chymotrypsin 3. carboxypeptidase |
|
|
What does pancreatic amylase do?
|
converts starch to disaccharides
|
|
|
What does pancreatic lipase do?
|
hydrolyzes dietary lipids
|
|
|
The enzymes trypsin and chymotrypsin act on what substrate to produce what action?
|
substrate = proteins
action = proteins to peptides |
|
|
What substrate does carboxypeptidase act on? What is the action?
|
substrate = proteins
Action = removes last AA from carboxy end of peptide |
|
|
What substrate does the enzyme lipase act on? What is the action produced?
|
substrate = fat
action = converts triglycerides into fatty acids and monoglycerides |
|
|
What substrate does the enzyme pancreatic amylase act on? What action is produced?
|
Substrate = polysaccharide
Action = converts polysaccharides into glucose and maltose |
|
|
What substrate does the enzyme RNAse and DNAse act on? What action is produced?
|
substrate = nucleic acid
action = converts nucleic acids into nucleotides |
|
|
Digestive enzymes secreted by which cells in pancreas?
|
acinar cells
|
|
|
What cells secrete aqueous NaHCO3 solution?
|
Duct cells
|
|
|
The endocrine portion of the pancreas is AKA?
|
islets of langerhahn
|
|
|
Exocrine portion of pancreas?
|
acinar and duct cells
|
|
|
Hormones seen in pancreas?
|
insulin, glucagon
|
|
|
4 part process triggered by Acid in the duodenal lumen?
|
1. increases secretin release from duodenal mucosa
2. Secretin (hormone) is carried by blood and stimulates the pancreatic duct 3. this increases the secretion of aqueous NaHCO3 into the duodenal lumen 4. This increase in NaHCO3 feedsback to the acid in the duodenal system and neutralizes it |
|
|
4 part process triggered by Fat and protein products in duodenal lumen?
|
1. Increases CCK release from duodenal mucosa
2. CCK is carried in the blood and stimulates the pancreatic acinar cells 3. the increases the secretion of pancreatic digestive enzymes into duodenal lumen 4. These digetive enzymes then feedback and digests the fat and protein products that began the process |
|
|
2 components that are not actually part of the GI tract? What is their importance?
|
1. Liver and Gallbladder
2. integral to processing food |
|
|
Liver does more than just what?
|
digestion
|
|
|
What secretion from the liver is involved in digestion?
|
bile secretion
|
|
|
Liver is involved in the metabolic processing of what?
|
nutrients
|
|
|
Liver does what to body wastes?
|
detoxifies or degrades it
|
|
|
Liver synthesizes what?
|
plasma proteins
|
|
|
What does the liver store? (5)
|
1. glycogen
2. fats 3. iron 4. copper 5. vitamins |
|
|
What does the liver activate?
|
vitamin D
|
|
|
What does the liver remove? (what cells involved in process)
|
removes bacteria and worn-out RBCs (Kupffer cells: resident macrophages)
|
|
|
What does the liver secrete?
|
cholesterol and bilirubin
|
|
|
What kind of system is the liver?
|
portal (2 capillary beds connected by a vessel)
|
|
|
The liver is what kind of portal system? explain.
|
hepatic portal system. blood enters liver from the digestive tract via hepatic portal system. Portal vein breaks into capillary network, the liver sinusoids.
|
|
|
The functional units of the liver are known as?
|
the liver lobules
|
|
|
Describe the liver lobules (3).
|
1. hexagonal arrangements of tissue surrounding central vein
2. lobules delineated by vascular and bile channels (hepatocytes continuously secrete bile into these channels) 3. Bile ducts from lobules converge to form common bile duct (duct transports bile from liver to duodenum) |
|
|
What is stored in the gallbladder between meals?
|
bile
|
|
|
After a meal what happens to bile?
|
liver and gallbladder secrete bile into small intestine for fat digestion
|
|
|
Liver has it's own supply of what?
|
has it's own blood supply
(hepatic portal vein) |
|
|
What 2 structures bring blood into the liver?
|
1. hepatic artery
2. hepatic portal vein |
|
|
Thru what structure does the blood exit the liver?
|
central vein (which leaves via the hepatic vein)
|
|
|
Hepatocytes are what?
|
liver cells
|
|
|
Each hepatocyte is in contact with what 2 things?
|
sinusoid on one side and bile duct on the other
|
|
|
Bile could be described as what kind of fluid?
|
aqeous alkaline fluid
|
|
|
The components of bile: such as bile salts, cholesterol, and lecithin do what?
|
Stabilize fat, aid in fat digestion and absorption
|
|
|
The component of bile, bicarbonate ion, does what?
|
neutralizes acid in the duodenum
|
|
|
Give an example of a bile waste product? How is it excreted?
|
ex. bilirubin
-excreted via GI tract |
|
|
Bile salts are derivatives of what?
|
cholesterol
|
|
|
Bile salts (cholesterol derivatives) are recycled through what?
|
thru enterohepatic circulation
|
|
|
What is the common bile duct?
|
a connection from the liver to the small intestine (gall bladder is also attached)
|
|
|
Where is bile stored?
|
gall bladder till needed by small intestine
|
|
|
What does bile do to fats?
|
emulsifies them
|
|
|
Describe 3 aspects of bile's emulsification of fats?
|
1. fat globules broken into smaller droplets
2. increases surface area, facilitates enzymatic attack 3. pancreatic lipase anchored to fat droplets by polypeptide colipase |
|
|
Bile salts are adsorbed to the surface of what? Why?
|
small fat droplets, to prevent the droplets from recoalescing
|
|
|
Most potent stimulus for increased bile secretion?
|
bile itself
|
|
|
When bile is adsorbed to the surface of small fat droplets to prevent the droplets from recoalescing what are they forming?
|
micelles
|
|
|
The core of the micelle vs the outer shell?
|
the core is hydrophobic (fats)
the outer shell is hydrophilic (water soluble head of bile salts) |
|
|
What else is involved in the micelles of bile and fats?
|
lecithin (has water soluble TAIL and hydrophobic HEAD)
|
|
|
What is bilirubin?
|
waste product excreted in the bile
|
|
|
What kinds of mechanisms cause bile secretion?
|
1. chemical
2. hormonal 3. neural |
|
|
What is a choleretic?
|
any mechanism that increases bile secretion
|
|
|
Give a chemical mechanism that increases bile secretion?
|
bile salts
|
|
|
Give a hormonal mechanism that increases bile secretion?
|
secretin (from duodenum)
|
|
|
Give a neural mechanism that increases bile secretion?
|
vagus nerve (shows there is external and intrinsic stim. throughout entire tract)
|
|
|
If there is nothing in the GI tract what happens to bile?
|
it is stored in the gall bladder
|
|
|
What is the gall bladders main function?
|
stores and secretes bile
|
|
|
When is bile stored?
|
between meals
|
|
|
When is bile emptied?
|
during meals
|
|
|
What is possible in the gall bladder?
|
gallstones
|
|
|
Can the gall bladder be removed?
|
yes, but not very common
|
|
|
What does the secretion of CCK do to the gall bladder?
|
stimulates contraction, relaxes sphincter of Oddi, releases bile into duodenum
|
|
|
What is CCK release triggered by? What is an especially potent trigger?
|
Chyme reaching small intestine
-fat is esp. potent |
|
|
Where does most digestion and absorption occur?
|
the small intestine
|
|
|
Three segments of the small intestine?
|
1. Duodenum
2. Jejunum 3. Ileum |
|
|
Motility in the small intestine occurs via what?
|
segmentation
|
|
|
Describe the motility (segmentation) of the small intestine?
|
1. it mixes and slowly propels chime
2. segmentation contraction is intitiated by BER cells 3. Circular smooth muscle responsiveness is influenced by the distension of the intestine, gastrin, and extrinsic nerve activity |
|
|
The motility (via segmentation) of the small intestine is under what control?
|
parasympathetic
|
|
|
What would the an SNS response do to motility?
|
stop it because you would be in fight or flight mode
|
|
|
What is a BER cell?
|
involved in segmentation contractions
-basic electric rhythm (pacesetter cells that increase to threshold to have APs) |
|
|
Travel time during motility of small intestine?
|
3-4 hours
|
|
|
What pushes the food down through the small intestine?
|
the way that the frequency of segmentation decreases as you move out of the duodenum to the jejumen to the Ileum.
|
|
|
What causes stomach growling?
|
the migrating motility complex
|
|
|
Describe 3 aspects of the migrating motility complex?
|
1. Weak, repetitive, peristaltic waves (moves a short distance then dies out, occurs between meals when segmentation ceases)
2. "internal housekeeper": sweeps intestine clean between meals 3. motilin : hormone secreted by endocrine cells of small intestine regulates migrating motility complex |
|
|
Describe the iliocecal juncture of the small intestine?
|
1. sphincter
2. between the small and the large intestine 3. prevents contamination of small intestine by colonic bacteria |
|
|
What 2 things enhances the relaxation of the iliocecal sphincter?
|
1. hormones (gastrin)
2. local intrinsic neural plexuses that register distension and relax to open sphincter |
|
|
The small intestine does not secrete what into the lumen?
|
digestive enzymes
|
|
|
What does secrete enzymes into the small intestine lumen?
|
pancreas
|
|
|
What is completely digested in the small intestine due to enzymes from the pancreas?
|
fats
|
|
|
What are fats digested to in the small intestine?
|
free fatty acids and monoglycerides
|
|
|
What two things need further digestion even after the pancreas has released enzymes into the lumen of the small intestine?
|
proteins and carbohydrates
|
|
|
What do exocrine cells in the small intestine secrete?
|
Aqueous salt and mucus solution (aka succus entericus)
|
|
|
What does the succus entericus from the exocrine cells provide?
|
1. protection and lubrication
2. lots of H2O for hydrolysis, a key part of digestion |
|
|
Although the small intestine does not secrete digestive enzymes what does it produce?
|
it produces enzymes
|
|
|
Where do the enzymes produced by the small intestine act?
|
they act intracellularly at the brush border to complete digestion
|
|
|
What does the lumen take care of?
|
fat
|
|
|
What does the brush border take care of?
|
proteins and carbs
|
|
|
Describe the structure of the brush border?
|
special, hairlike projections on epithelial cells of small intestine
|
|
|
The plasma membrane of the brush border of the small intestine contains what 3 categories of membrane bound enzymes?
|
1. Enterokinase
2. Dissacharidases (maltase, sucrase, lactase) 3. Aminopeptidases |
|
|
Describe enterokinase (membrane-bound enzyme of brush border of small intestine)?
|
activates pancreatic enzyme, trypsinogen
|
|
|
Describe the dissacharidases (maltase, sucrase, lactase) found in the brush border of the small intestine?
|
complete carbohydrate digestion
(membrane bound enzyme) |
|
|
Describe aminopeptidases of the brush border of the small intestine?
|
(membrane bound enzyme)
hydrolyzes small peptide fragments into AA components |
|
|
Of all the electrolytes which one's are the only ones with controlled absorption?
|
Calcium and Fe
|
|
|
What is lacking or nonfunctional in lactose intolerant people?
|
lactase
|
|
|
What does the villi increase?
|
surface area on the brush border
|
|
|
The central lacteal is what kind of vessel?
|
lymph vessel
|
|
|
What in the brush border is a source of new epithelial cells (contains stem cells)?
|
The crypt of Lieberkuhn
|
|
|
Where are the transport mechanisms of the small intestine observed?
|
In the epithelial cells in the inner lining of the small intestine (there are a variety of transport mechanisms)
|
|
|
2 types of transport mechanisms seen in epithelial cells in small intestine?
|
1. Energy dependent Na+ transport absorption drives passive water absorption
2. Carbohydrate and protein: both absorbed by 2ndary active transport (except fructose) and enter blood |
|
|
What in the small intestine drives passive water absorption?
|
energy dependent Na+ transport absorption
|
|
|
How does energy dependent Na+ transport absorption drive passive water absorption?
|
1. Na+ is pumped from the lumen into the interstitial fluid, then it enters the capillaries by diffusion
2. Na+ transport creates osmotic pressure, water follows the sodium |
|
|
How are proteins and carbodhydrates absorbed? What do they enter?
|
absorbed by 2ndary active transport and enter blood
|
|
|
What is the exception to the fact that carbs are absorbed by 2ndary active transport? Explain.
|
Fructose is the exception. it has passive facilitated diffusion
|
|
|
Describe transport of the carbohdrates glucose and galactose?
|
2ndary active transport, co-transported by Na+
|
|
|
Amino acids and peptides transport is what type?
|
2ndary active
|
|
|
What enzymes involved in carbohydrate digestion?
|
lactase, maltase, and sucrase, salivary amylase, pancreatic enzymes
|
|
|
What does carbohydrate digestion leave us with?
|
monosaccharides
|
|
|
Energy is needed for what transport during carbohydrate digestion? What goes along for the ride?
|
energy needed from Na+ transport, glucose and galactose go along for the ride
|
|
|
Proteins can get in our body how?
|
exogenous or endogenous
|
|
|
What enzymes are involved in the digestion of protein?
|
pepsin, pancreatic proteolytic enzymes
|
|
|
Carbohydrate digestion and protein digestion ultimately end up being released into the what?
|
blood
|
|
|
Digestion of fat ultimately ends up being released where?
|
into lymph system thru central lacteal
|
|
|
There are no enzymes where?
|
in brush border of small intestine
|
|
|
Why don't lipids need transport molecules?
|
passive diffusion because lipophilic
|
|
|
The absorption of vitamins is mainly what?
|
passive
|
|
|
Water-soluble vitamins are absorbed with what?
|
water
|
|
|
Fat-soluble vitamins are absorbed in what?
|
micelles
|
|
|
Iron and Ca+ absorption is what?
|
regulated
|
|
|
Only part of ingested iron can be what?
|
absorbed
|
|
|
Some absorbed iron is immediately transported where?
|
to the blood
|
|
|
What carries some iron to the bone marrow? For what reason?
|
Transferrin, for RBCs
|
|
|
Where is excess iron stored?
|
in ferritin pool
|
|
|
Where is unused iron lost?
|
in the feces
|
|
|
Fe is used in the production of what?
|
RBC
|
|
|
Most calcium is absorbed by what?
|
active transport
|
|
|
Approx. how much of ingested calcium is absorbed and how much is eliminated?
|
about 2/3 absorbed and 1/3 is eliminated
|
|
|
What needs to be present for the active transport of calcium?
|
vitamin D (parathyroid is also involved)
|
|
|
Most absorbed nutrients immediately pass through what?
|
immediately pass thru the liver for processing (except fats)
|
|
|
Why don't fats pass thru the liver for processing?
|
because they are in the lymph
|
|
|
Venules leave the small intestine via what? Where do they empty?
|
leave via villi and empty into the hepatic portal vein
|
|
|
What does the hepatic portal vein carry?
|
blood and all absorbed contents to the liver
|
|
|
Products of digestion are subject to what?
|
metabolic processing in the liver
|
|
|
Once in the liver any absorbed toxic substances are what?
|
Detoxified
|
|
|
3 major categories of nutrients?
|
1. carbohydrates
2. proteins 3. fats |
|
|
Enzymes for digesting carbohydrates.
|
1. amylase
2. Disaccharidases (maltase, sucrase, lactase) |
|
|
What are the 2 different sources for amylase?
|
1. salivary glands
2. exocrine pancreas |
|
|
What is the site of action for amylase secreted by the salivary glands?
|
mouth and body of stomach
|
|
|
What is the site of action for amylase secreted by the exocrine pancreas?
|
small intestine lumen
|
|
|
What is the action of amylase secreted by the salivary glands?
|
hydrolyzes polysaccharides to disaccharides
|
|
|
What is the action of amylase secreted by the exocrine pancreas?
|
Hydrolyzes disaccharides to monosaccharides
|
|
|
The end product, absorbable units of nutrients, produced by amylase?
|
monosaccharides, especially glucose
|
|
|
Enzymes responsible for digesting proteins? (3)
|
1. Pepsin
2. Trypsin, chymotrypsin carboxypeptidase 3. aminopeptidases |
|
|
Source of pepsin?
|
stomach chief cells
|
|
|
Site of action of pepsin?
|
stomach antrum
|
|
|
Action of pepsin?
|
hydrolyzes proteins to peptide fragments
|
|
|
Source of trypsin etc?
|
exocrine pancreas
|
|
|
Site of action for trypsin etc.
|
small intestine lumen
|
|
|
Action of trypsin etc.
|
attack different peptide fragments
|
|
|
Source of aminopeptidases?
|
small intestine epithelial cells
|
|
|
Site of action for aminopeptidases?
|
small intestine brush border
|
|
|
Action of aminopeptidases?
|
hydrolyzes peptide fragments to AAs
|
|
|
Absorbable units of nutrients derived from proteins?
|
AAs and a few small peptides
|
|
|
2 enzymes responsible for digesting fat?
|
1. lipase
2. bile salts (NOT AN ENZYME) |
|
|
Source of lipase?
|
exocrine pancreas
|
|
|
Source of bile salts?
|
liver
|
|
|
Site of action for both lipase and bile salts?
|
small intestine lumen
|
|
|
Action of lipase?
|
hydrolyzes triglycerides to fatty acids and monoglycerides
|
|
|
Absorbable nutrients that are the end result of fat?
|
fatty acids and monoglycerides
|
|
|
Action of bile salts?
|
emulsify large fat globules for attack by pancreas lipase
|
|
|
The large intestine is mainly what?
|
a drying and storage organ
|
|
|
Where is most digestion and absorption accomplished?
|
small intestine
|
|
|
What does the colon receive?
|
indigestible food, unabsorbed biliary components, and any remaining fluid
|
|
|
What does the colon extract and what does it eliminate?
|
extracts water and salt...eliminates feces
|
|
|
What does the colon have that helps fight diseases?
|
lymphocytes
|
|
|
Describe the smooth muscle of the anal sphincter?
|
internal...relaxes under ANS control...you do not have voluntary control over it
|
|
|
Describe the skeletal muscle of the anal sphincter?
|
external...voluntary control
|
|
|
What kind of contractions slowly shuffle colonic contents back and forth?
|
Haustral contractions
|
|
|
Are haustral contractions propulsive?
|
no, they are simply for mixing purposes
|
|
|
How are haustral contractions initiated?
|
By autonomous rhythmic contractions of smooth muscle in wall of large intestine
|
|
|
Which contractions are more frequent, those in the large intestine or in the small intestine?
|
The ones in the smaller intestine...the ones in the large intestine are about 1/2 hour apart.
|
|
|
What kind of contraction propels colonic contents long distances along the large intestine?
|
Mass movements
|
|
|
How often do mass movements occur in the large intestine?
|
3-4 times daily
|
|
|
Where do mass movements drive feces?
|
into distal part of large intestine
|
|
|
Mass movements propel colonic contents long distances primarily via what?
|
Gastrocolic reflex
|
|
|
How is the gastrocolic reflex caused?
|
Caused by food entering the stomach...gastrin is the mediator
|
|
|
What reflex eliminates feces?
|
Defecation reflex
|
|
|
How many species of bacteria are present in flora?
|
500
|
|
|
During the defecation reflex fecal material entering the rectum stimulates what?
|
stimulates stretch receptors of rectal wall
|
|
|
The Defecation reflex causes what to relax?
|
the internal anal sphincter smooth muscle (autonomic control)
|
|
|
What does the defecation reflex cause to contract vigorously?
|
the rectal and sigmoid colon
|
|
|
Once the fecal reflex has cause the internal smooth anal sphincter to relax, and caused the rectal and sigmoid colon to contract what else has to happen to make defecation occur?
|
the external anal sphincter (skeletal muscle, voluntary control) also has to relax
|
|
|
How can one prevent defecation?
|
by voluntarily contracting the skeletal external sphincter
|
|
|
If you prevent defecation by contracting the external sphincter what continues to happen to the feces?
|
continues to dry...can cause constipation
|
|
|
When one contracts the skeletal external anal sphincter what is delayed defecation?
|
it causes the rectal wall to relax, and it removes the defecation urge until the next mass movement
|
|
|
What is gastrin stimulated by?
|
chyme in the stomach (esp. if it contains proteins)
|
|
|
3 effects of gastrin?
|
1. increases secretion of HCl and pepsinogen
2. enhances gastric motility 3. trophic to small intestine |
|
|
What is secretin stimulated by?
|
the presence of acid in the duodenum
|
|
|
3 effects of secretin?
|
1. Inhibits gastric emptying and gastric secretion
2. stimulates pancreas to produce sodium bicarbonate 3. stimulates liver to produce bile |
|
|
What is CCK stimulated by?
|
by the presence of fat and other nutrients in the duodenum
|
|
|
3 effects of CCK?
|
1. inhibits gastric motility and secretion
2. stimulates pancreatic enzymes 3. signals gallbladder to secrete bile |
|
|
What is GIP?
|
"glucose-dependent insulinotrophic peptide"
|
|
|
Effect of GIP?
|
promotes metabolic processing of nutrients once they are absorbed via stimulation of insulin release from the pancreas
|
