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164 Cards in this Set

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What do the bile ducts drain into?
What is the main phospholipid in bile?
Lecithin
What is the main bile pigment?
Bilirubin - a breakdown product of red blood cells. Yellow in color.
What is the cause of jaundice?
The circulation of bilirubin in the blood.
What gives urine its yellow color?
Bilirubin
What gives feces the brown color?
Bilirubin
In what part of the small intestine is bilirubin reabsorbed?
Ileum
What percentage of the bilirubin is excreted in the feces?
5%
What signals the secretion of CCK?
The presence of fatty acids in the duodenum signal the release of this molecule.
What is the funciton of CCK?
1) Relaxation of the sphincter of Oddi2) Gallbladder contraction which causes the bile to flow into common bile duct and into the duodenum
What is secreted by the small intestine?
1) Lubrication2) Chloride, sodium, and bicarbonate ions3) Hypertonic chyme - causing water to secrete into the small intestine.
Absorption in the small intestine is driven by what?
This is due to the transport of sodium
What is segmentation?
Certain areas of contraction move along the small intestine causing a mixing of the chyme, enzymes, bile salts, and other components.
What is the rate of contraction in the duodenum?
12 contractions/min
What is the rate of contraciton in the Ileum?
9 contraction/min
What is the result of the difference in contration rates in the small intestine?
This causes the chyme to flow from one end of the small intestine to the other.
What is the migrating myoelectric complex?
This is initiated by motilin upon eating. This will begin in the stomach and squeeze the existing contents in the duodenum for about a couple of feet. This is mainly material that will not be absorbed.
How does the migrating myoelectric complex effect the large intestine?
This will keep the bacteria of the large intestine in the large intestine.
What is the gastroileal reflex?
This is the increase in segmentation intensity in the ileum by food passing through the pyloric sphincter.
What is the intestino-intestinal reflex?
This is the cessation of intesitnal motility due to ...
what is the function of the large intestine?
The function of this organ is storage of fecal matter prior to defecation.
What are the longitudinal muscles in the large intestine responsible for?
These 3 flat bands of this muscle (tenia coli) propel contents.
What does the L. intestine secrete?
Mucus and fluids containing potassium and bicarbonate.
What is absorbed in the L. intestine?
sodium and water
What is flatus?
This is swallowed air consisting mainly of nitrogen, carbon dioxide, hydrogen, methane, and hydrogen sulfide.
Segmentation in L. intestine occurs at what rate?
2 contractions/hr
What is the mass movement in the L. intestine?
This is the clearing of the contents of the transverse colon during ingestion of a meal.
What is the internal anal sphincter composed of?
Smooth muscle makes up this sphincter.
What is the external anal sphincter composed of?
Skeletal muscle makes up this sphincter.
What is the defecation reflex?
1) distention of rectum signaled by mechanoreceptors - urge to def.2) contraction of rectum3) Relaxation of internal anal sphincter4) Contraction of external anal sphincter5) Increased peristaltic activity in sigmoid colon
What is the valsalve maneuver?
This is a deep breath and closure of the glottis - contraction of the abdominal and thoracic muscles.
What are ulcers?
This is an erosion of the gastric, esophageal, or duodenal surface.
What natural protectants are present against ulcers?
1) Alkaline mucus - prevents acid from eating throught the initial layer of cells.2) Tight Junctions - prevent movement of compounds through cells.3) Rapid Epithelial Replacement - Rapid turnover and replacement of the cells in dangerous locations.
What is the danger in having ulcers?
GI bleeding
What is helicobactor pylori?
This is a bacteria that causes the breakdown of the surfaces, causing ulcers.
What is the net effect of histimine blockers?
by blocking histamine secondary transport they effect the amount of H+ concentration.
Where is the complex reflex coordinated?
vomiting center in the medulla oblongata
What are the effects of severe vomiting?
1) Dehydration and circulatory problems2) Metabolic alkalosis
What is metabolic alkalosis?
Due to the loss of material due to vomiting, this drives the flow of acid into the lumen to replace it. Therefore, more bicarbonate is transfered to the blood thus raising the pH of the blood.
What is a hypochalimic condition?
This is a decrease in the extracellular potassium concentration causing membrane potentials to hyperpolarize.
What are gallstones?
These are crystallized cholesterol or precipitated bile pigments.
What occurs if the gallstone lodges in teh common bile duct?
1) Steatorrhea - due to fat not being metabolized the fat wil leave in the feces (can casue diarrhea)2) Jaundice
What is Lactose intolerance?
This is the inability to digest lactose to glucose and galactose becasue of a decline in the enzyme lactase in the luminal plasma membranes of hte small intestine.
What can a lactose intolerance cause?
this can cause diarrhea
What is constipation?
This is infrequent bowel movements.
What is the toxicity of retained fecal matter?
This matter is not toxic.
What is a laxative?
This is any agent that increases frequency or ease of bowel movements.
What is cholera?
This is a bacterium - secretion leading to diarrhea
What is traveler's bacteria?
This bacterium secretes causing diarrhea
What are the effects of diarrhea?
1) Dehydration and circulatory problems2) Due to loss of bicarbinate ions in large intestine, acid is sent out the basolateral side to cause the blood to acidify - acidosis
What organs have excretory functions in the GI system?
Pancreas and Liver
What do parietal cells secrete?
HCl and Intrinsic Factor
What do pancreatic cells secrete?
Enzymes and bicarbonate (HCO3-) stimulated by CCK and secretin.
ECL cells secrete what?
Histamine
What do the cheif cells secrete?
Pepsinogen
What is digestion?
Breakdown of food into small molecules.
What is secretion?
The insertion of digesting agents into the GI tract.
What is absorption?
The transfer into blood or lymph for transport hroughout the body.
What is motility?
The mixing and moving casued by smooth muscle.
What do the mouth/pharynx excrete and what are their functions?
No excretions - Chewing and initiation of the swallowing reflex.
What do the salivary glands excrete and what is its functions?
1) Salt and water - Moisten food2) Mucus - Lubrication3) Amylase - Polysaccharide-digesting enzyme
What does the esophagus excrete and what is its function?
1) Mucus - Lubrication2) Moves food to stomach by peristaltic waves
What is the function of the stomach?
Store, mix, dissolve, and continue digestion of food; regulate emptying of dissolved food into small intestine.
What does the stomach excrete?
1) HCl - Solubilization of food particles; kills microbes; activation of pepsinogens to pepsin.2) Pepsin - Protein digesting enzyme3) Mucus - Lubrication and protect epithelial cell surface
What is the function (GI) of the pancreas?
Secretion of enzymes and bicarbonate.
What does the pancreas secrete?
1) Digestive enzymes - digests fats, proteins, carbohydrates, and nucleic acids.2) Bicarbonate - neutralize HCl entering the small intestine from the stomach.
What does the liver secrete?
1) Bile - emulsification of fats2) Bicarbonate - neutralize HCl entering small intestine from stomach3) Organic wastes - Elimination in the feces.
What is the function of the gallbladder?
Storage of bile salts.
What does the small intestine secrete?
1) Enzymes - Food digestion2) Salt and water - Maintain fluidity of luminal contents3) Mucus - Lubrication
What does the large intestine secrete?
1) Mucus - lubrication
What is the function of saliva?
1) Moisten and lubricate food.2) Digestion of polysaccharides by amylase.3) Dissolve food.4) Antibacterial actions.
What is chyme?
A solution of proteins, polysaccharides, fat droplets, salt and water, which is produced by the digestive and secretory actions in the stomach.
Which part of the stomach is the shortest?
Longest?
What is bile?
bicarbonate ions, cholesterol, phospholipids, bile pigments, organic wastes and bile salts.
What does the gallbladder drain into?
cystic duct then into the common bile duct.
What drains into the common bile duct?
Cystic duct and common hepatic duct
What are the resluts of motility?
1) Mixes luminal contents with secretions2) Promotes contact with epithelial surfaces and thereby effects absorption3) Advances chyme toward large intestine
What is the average amount of water (mL/day) and solids (g/day) ingested per day?
Water - 1200 mL/day
How much saliva is excreted per day?
1500 mL/day
How much gastric secretions are released per day?
2000 mL/day
How much bile is excreted per day?
500 mL/day
How much pancreatic secretions are released per day?
1500 mL/day
How much intestinal secretions are released per day?
1500 mL/day (primarily small intestine)
How much water and solids are excreted per day?
Water - 100 mL/day
How much fluid is absorbed into the blood from the small intestines?
6700 mL/day
How much fluid is absorbed by the large intestines per day?
1400 mL/day
What makes up the mucosa in the GI wall?
Epithelium, lamina propria, and muscularis mucosa.
Where are endocrine cells found in the GI wall?
Epithelial layer
Where are mucous cells found in the GI wall?
Epithelial layer
What constitutes the submucosa layer?
Submucosal nerve plexus, major blood and lymphatic vessels
What constitutes the muscularis externa?
Circular muscle, myenteric nerve plexus, and longitudinal muscle
What constitutes the serosa layer?
This is a thin layer of connective tissue.
What are Peyer's patches?
Found in the small intestine, secrete inflammatory mediators which alter motility. This helps fight infectious organisms that are not destroyed by the stomach acidity.
What makes-up sucrose, lactose, and maltose?
1) Sucrose - Glucose & Fructose2) Lactose - Glucose & Galactose3) Maltose - Glucose & Glucose
What is fiber?
Complex polysaccharides (ie cellulose) that are non-absorbable
What does amylase accomplish?
The breakdown of polysaccharides to the disaccharide maltose and short branched chains of glucose molecules.
What do the enzymes on brush border membranes (microvilli) accomplish?
Breakdown short glucose chains and disaccharides to monosaccharids.
How is fructose absorbed?
Facilitated diffusion
How is glucose and galactose absorbed?
Secondary active transport using the Na+ gradient.
What substances will break down proteins into peptide fragments and where are they synthesized?
1) Pepsin - the active form of pepsinogen which is synthesized in the stomach.2) Trypsin and Chymotrypsin - synthesized in the pancreas
What substances will break down peptide fragments into free amino acids and where are they synthesized?
1) Carboxypeptidase - synthesized in the pancreas2) Aminopeptidase - Located on the luminal membranes of the small intestine epithelial cells.
How do amino acids enter the epithelial cells?
1) Secondary active transport for which Na+ provides the electrochemical gradient. There are multiple transporters for the 20 amino acids.2) Short amino acid chains are absorbed by secondary active transport where H+ provides the electrochemical gradient. These are then further hydrolyzed within the cells to amino acids.
How do amino acids cross the basolateral membrane?
Facilitated diffusion
What is the major enzyme involved in fat digestion?
Pancreatic lipase - breaks up a triglyceride into 2 fatty acids and a monoglyceride
Where does most all of fat digestions take place?
Small intestine
How large are the emulsion droplets?
1 μm in diameter
What is colipase?
This is an amphipathic molecule that lodges on the lipid droplet surface. It binds the lipase and holds it on the surface of the droplet.
What are chylomicrons?
Triglyceride resynthesis in the endoplastic reticulum of the intestinal epithelial cells froms these fat droplets.
Which vitamins are fat soluable and therefore follow the pathway for fat absorption?
A, D, E, and K
How are water soluble vitamins absorbed?
Diffusion or mediated transport.
What is special regarding the absorption of vitamin B12?
This must first bind to the protein called intrinsic factor. The bound compound is then absorbed in the ileum by endocytosis.
How is water absorbed?
1) Through tight junctions down its concentration gradient2) Aquaporins
What vitamin is needed in order for calcium to be absorbed?
Vit. D
How is the absorption of iron typical to that of most trace metals?
1) Cellular storage proteins and plasma carrier proteins are involved2) The control of absorption, rather than urinary excretion, is the major mechanism for the homeostatic control of the body's content of the trace metal.
If the body's storage of iron is low what results?
The production of intestinal ferritin decreases allowing for the greater amounts of free iron to enter the blood stream.
What is the function of ferritin?
This binds to iron in the intestinal epithelial cells thus preventing the absorption of the iron into the blood.
What initiates the GI reflexes?
Luminal stimuli acting on receptors in the wall of the GI tract.
What are the effectors of the reflexes initiated by luminal stimuli?
Smooth muscle layers and exocrine glands
What is the enteric nervous system?
This is the GI's own local nervous system consisting of two nerve networks.
Which nerve network is responsible mainly for the smooth muscle activity of the GI tract?
Myenteric plexus
Which nerve network is responsible for the secretory activity of the GI tract?
Submucosal plexus
Axons in each plexus run where?
Between plexuses, to CNS, and further down the GI tract within the same plexus.
What are short reflexes?
Receptor - plexus - effector
What are long reflexes?
receptor - CNS via afferent nerves - plexuses and effectors via autonomic neurons
What stimulates the release of gastrin?
Amino acids, peptides in stomach; parasympathetic nerves
What inhibits the release of gastrin?
Acid in stomach; somatostatin
What is CCK?
A peptide formed in the small intestine.
What stimulates the release of CCK?
Amino acids, fatty acids in small intestine
What is secretin?
A peptide formed in the small intestine.
What stimulates the release of secretin?
acid in the small intestine.
What is GIP?
A peptide formed in the small intestine.
What stimulates the release of GIP?
glucose, fat in the small intestine.
What does gastrin stimulate?
1) Acid secretion in the stomach2) Motility of the stomach3) Growth in the stomach4) Growth of exocrine pancreas5) Motility of the ileum6) Growth of the small intestine7) Mass movement in large intestine
What does CCK stimulate?
1) Potentiates secretin's stimulation of bicarbonate secretion in pancreas2) Pancreas enzyme secretion3) Growth of exocrine pancreas4) Potentiates secretin's stimulation of the liver to secrete bicarbonate5) Gallbladder contraction6) Relaxation of the sphincter of Oddi
What does CCK inhibit?
1) Stomach acid secretion2) Stomach motility
What does secretin stimulate?
1) pancreas bicarbonate secretion2) Potentiates CCK's stimulation of pancreas enzyme secretion3) Growth of exocrine pancreas4) Liver bicarbonate secretion
What does secretin inhibit?
1) Stomach acid secretion2) Stomach motility
What does GIP stimulate?
1) Pancreas insulin secretion
What are the three phases of GI control?
1) Cephalic - Receptors in brain are stimulated by sight, smell, taste, chewing, and emotional states causing the vagus to fire2) Gastric - Responses to distention, acidity, a.a., & peptides formed during digestion are mediated by short and long reflexes and by release of gastrin.3) Intestinal - Responses to distention, acidity, osmolarity and various digestive products are mediated by long and short reflexes and by the secretion of secretin, CCK, and GIP.
Does chewing alter the rate of digestion and absorption?
No.
What are the receptors in salivary glands that stimulate salivary secretion?
Alpha 1
What effect do parasympathetics have on salivary glands?
Increases blood flow to salivary glands which in turn increases the saliva output.
What initiates the salivary reflex?
Chemoreceptors and pressure receptors
What is Sjogren's syndrome?
immune disorder - nonfunctioning exocrine glands including salivary glands - frequent sips of water and oral flouride treatments are prescribed
What occurs if the bolus does not reach the stomach during as a result of the primary peristaltic wave?
The distension of the esophagus stimulates a secondary peristaltic wave.
What can cause the lower esophageal sphincter to enter the diaphragm?
Pregnancy
What are the regions of the stomach?
Body and Antrum
What cells secrete acid and intrinsic factor?
parietal cells
What cells secrete pepsinogen?
Chief cells
What cells secrete the paracrine agent histamine?
Enterochromafin-like (ECL) cells
Where are the cells that secrete the peptide messenger somatostatin located?
Tubular glands in the stomach where parietal, chief, and ECL cells are also found.
How does HCl get secreted into the stomach lumen by parietal cells?
H+/K+-ATPase
What stimulates/inhibits the release of HCl into the stomach lumen?
What activates pepsinogen to pepsin?
HCl
What is receptive relaxation?
Prior to food entering the stomach, the walls of the fundus and body relax alowing for the volume of the stomach to increase to as much as 1.5L.
What stimulates receptive relaxation?
Parasympathetic nerves and the swallowing center in the brain.
What are the chemical signals cause the stomach smooth muscle to relax in receptive relaxation?
Nitric oxide and serotonin released by the enteric neurons.
What is the basic elcetrical rhythm of the stomach?
Pacemaker cells in the longitudinal smooth muscle of the stomach undergo spontaneous depoarization-repolarization cycles at a rate on average of 3 per minute.
What determines the strength of contraction of the peristaltic waves in the stomach?
Neural and hormonal input to the antral smooth muscle further depolarize the smooth muscle, bringing it closer to threshold.
What are the effects of parasympathetics and sympathetics on gastric motility?
Parasympathetics stimulate gastric motility
In the pancreas, what secretes digestive enzymes?
Exocrine cells
In the pancreas, what secretes bicarbonate?
Duct cells
What hormone stimulates the release of pancreatic enzymes?
CCK
What hormone stimulates the release of pancreatic bicarbonate?
Secretin