Ch:21 Digestive System Flashcards
What type of cells are important in secretion and absorption in the digestive system?
Epithelial cells
What do secretions in the digestive system include?
Digestive enzymes, stomach acid, base to neutralize acid, and waste products.
What are the three phases of digestion?
- Cephalic phase (Mouth and esophagus)
- Gastric phase (Stomach)
- Intestinal phase (Small intestine)
What stimulates the cephalic phase?
- The anticipation of food
2. Food in the mouth
What 2 digestive enzymes are in saliva?
What are their functions?
Amylase- Breaks down starch
Lysozyme- Attacks bacteria
What are the 3 functions of the stomach?
- Storage
- Digestion
- Protection against bacteria & other pathogens
What does the stomach secrete?
- HCl (parietal cells)
- Pepsinogen & Gastric lipase (chief cells)
- Mucus & Bicarbonate (surface mucous cells)
- Gastrin (G cells)
- Histamine (ECL cells)
What is digested in the stomach?
Mainly proteins but also minimal fats
What is absorbed in the stomach?
Lipid-soluble substances such as alcohol and aspirin
What type of motility is used in the stomach?
Peristaltic mixing & propulsion
What is digested in the mouth?
Carbohydrates
What is absorbed in the mouth?
Nothing
What type of motility is used in the mouth?
Chewing & Swallowing
What is secreted into the small intestine?
- Enzymes (enterocytes)
- Mucus (globlet cells)
- Hormones (CCK, secretin, GIP)
- Enzymes and Bicarbonate (exocrine pancreas)
- Bile (liver, stored in gallbladder)
What is digested in the small intestine?
Polypeptides, carbs, fats & nucleic acids
What is absorbed in the small intestine?
-Amino Acids & small peptides
-Monosaccharides, Fatty acids, monoglycerides,
& cholesterol
-Nitrogenous bases, water, ions, minerals & vitamins
What type of motility is used in the small intestine?
Mixing & propulsion primarily by sedimentation
and some peristalsis
The small intestine receives secretions from the ______ & ________.
Liver & Pancreas
What does the liver secrete to the small intestine?
Bile
What does the pancreas secrete to the small intestine?
Bicarbonate to neutralize stomach acid
What is secreted into the Large intestine?
Mucus (goblet cells)
What is digested in the Large intestine?
Nothing (except by bacteria)
What is absorbed in the Large intestine?
ions, minerals, vitamins, water and small organic molecules made by gut bacteria
What type of motility is used in the Large intestine?
Segmental mixing & mass movement for propulsion
What is responsible for most of the digestion taking place in the Large intestine?
Gut bacteria
Where does absorption in the intestinal phase continue?
Large intestine
What are the 2 layers of the GI Tract Wall?
- Lumen of the digestive tract
2. Abdominal cavity
What are the 4 layers of the lumen in the digestive tract?
- Mucosa
- Submucosa
- Muscularis externa
- Serosa
What type of tissue doe the Mucosa contain?
Epithelium, Lamina propria, & Muscularis mucosae (smooth muscle)
What does the Submucosa contain?
- Blood & lymph vessels
- Submucosal plexus (enteric nervous system)
What does the muscularis externa contain?
- Circular & Longitudinal smooth muscle
- Myenteric plexus (enteric nervous system)
What are epithelia cells in the digestive system involved in?
Absorption & Secretion
Where is the leaky epithelia of the digestive system located and what type of pathway does it use?
Small intestine & paracellular pathway
Where is tight epithelial of the digestive system located?
Stomach & Colon
What is secreted from salivary glands?
Saliva (amylase, lipase)
What is secreted by the stomach?
HCl (parietal cells) & Pepsinogen (chief cells)
What does the pancreas secrete?
sodium bicarbonate (duct cells) & digestive enzymes
(acinar cells)What does the liver secrete?
Bile (bile salts, bile pigments, cholesterol)
What does the small intestine secrete?
NaCl (crypt cells) & digestive enzymes (brush border)
Where are parietal cells located?
gastric gland
What membrane of the parietal cell is the H+/K+ ATPase located on?
Apical membrane
Which membrane of the intestinal crypt cell is the NKCC symporter located?
Basolateral membrane on the serosal side (interstitial fluid)
Which membrane of the intestinal crypt cell is the CFTR Cl- channel located on?
Apical membrane on the lumenal side
How is water and Na+ transported through intestinal crypt cells into the lumen?
Paracellular & water leak
What is Cystic Fibrosis?
A hereditary disease affecting exocrine cells resulting in THICK MUCUS
What causes Cystic Fibrosis?
a defective CFTR anion channel in airway epithelia
What are the consequence of Cystic Fibrosis?
persistant lung infections, lung damage and ultimately respiratory failure
What membrane of pancreatic duct cells is the Cl-/HCO3 antiporter & CFTR Cl- channel located on?
Apical membrane
What is the job of carbonic anhydrase in pancreatic duct cells?
To conver H2O & CO2 into HCO3 (bicarbonate)
How is Na+ transported across pancreatic duct cells into the lumen?
Paracellular Na+ leak
What does Acinar cells in the pancreas secrete?
digestive enzymes
What do duct cells in the pancreas secrete that enters the digestive tract?
NaHCO3
What do pancreatic islet cells secrete that enters the blood?
hormones
What portion of the pancreas does the pancreatic acini form?
the exocrine portion
What does the Common Hepatic Duct do?
transports bile from the liver to the gallbladder
What is the function of the gallbladder?
Bile storage
What does the Hepatic Artery do?
transports oxygenated blood containing metabolites from peripheral tissues to the liver
What does the Hepatic Portal Vein contain and what does it transport?
- rich in nutrients from the GI tract & hemoglobin byproducts from the spleen.
- transports blood from the liver the liver
What is the function of the Sphincter of Oddi?
controls release of bile & pancreatic secretions into the duodenum
What is the function of the Common Bile Duct?
transports bile from gallbladder to the lumen of the small intestine
Bile is secreted from the liver by the ___________.
bile duct
Bile is secreted from the liver to the _________ for storage.
gallbladder
What are the 3 Endopeptidases and what organs secrete them?
- Pepsin (pepsinogen)
What is the function of Endopeptidases?
digests INTERNAL peptide bonds into 2 smaller peptides
What is the function of Exopeptidases?
digests TERMINAL peptide bonds to release amino acids
What are the 2 Exopeptidases and what secretes them?
- Aminopeptidase
2. Carboxypeptidase
What activates pepsidases?
Proteolysis
What enzyme breaks down glycogen & starch into disaccharides?
Amylase
What enzyme breaks down disaccharides into monosaccharides?
Disaccharidase
What enzyme breaks down maltose into 2 glucoses?
Maltase
What enzyme breaks down sucrose into 1 glucose & 1 fructose?
Sucrase
What enzyme breaks down lactose into 1 glucose & 1 galactose?
Lactase
What are Triglycerides broken down into?
monoglycerides & free fatty acids
What breaks down Triglycerides into monoglycerides?
Lipase
What breaks down Triglycerides into free fatty acids?
Colipase
What activates Trypsinogen and converts it to Trypsin?
Enteropeptidases in the brush border of the intestinal mucosa
What activates Zymogens into activated enzymes?
Trypsin
What are Zymogens?
Inactivated pancreatic secretions
What are the 4 zymogens?
- Chymotrypsinogen
- Procarboxypeptidase
- Procolipase
4 Prophospholipase
What are the 4 activated enzymes produced from zymogens?
- Chymotrypsin
- Carboxypeptidase
- Colipase
- Phospholipase
What is the role of villi in the intestine?
increase surface area
What is the role of microvilli in the intestine?
to further increase surface area
What do crypt cells secrete?
ions and water
What is the function of enterocytes?
transport ions and nutrients
What is the function of Goblet cells?
Secrete mucus
What is the function of Lateals?
transport fats to lymph
What is the function of stem cells?
to divide and replace damaged cells
How is glucose absorbed in the small intestine?
glucose enters with Na+ on SGLT and exits on GLUT2
How is fructose absorbed in the small intestine?
Fructose enters on GLUT5 and exits on GLUT2 (same as glucose)
Where does glucose reabsorption take place?
Proximal tubule
In the proximal tubule, glucose uses ________ transport on the _________ side & _________ transport on the __________ side.
Na+ linked transport—-> lumenal side
Facilitated transport—–> interstitial side
What is the function of bile salts?
to emulsify lipids on the intestine
What does fat + cholesterol form in the intestinal epithelium?
chylomicrons
In the secretion of NaCl and water by the intestine _________________________________________.
Cl- is transported by the transcellular pathway
Na+ & water are transported by the paracellular pathway
Bicarbonate is transported by ___________ cells.
duct cells in the pancreas
Monoglycerides & fatty acids are absorbed in the intestine by ______________.
Simple diffusion
What synthesizes pepsinogen and where is it synthesized?
Chief cells in the stomach
Where does secretion and absorption occur?
Epithelia cells
The stomach secretes HCl from ________cells.
Parietal cells
The small intestine secretes NaCl from _____cells.
Crypt
The pancreas secretes sodium bicarbonate from ________cells.
duct cells
The liver produces ___________ which solubilize fats.
bile salts
Endopeptidases, activated by ________, are secreted by the ________ (pepsin) and ________ (trypsin & chymotripsin)
Proteolysis
Stomach
Pancreas
Fats are taken up and incorporated into _________ in the intestine.
chylomicrons
What type of motility is used during and after a meal?
Peristalsis & Segmental contractions
What is the difference between peristalsis and segmental contractions?
peristalsis moves a bolus of food in a forward direction
segmental contractions mixes the food with no net forward movement
What type of motility is used in between meals?
Migrating motor complex
What is the migrating motor complex?
contractions move slowly from the stomach to the large intestine taking about 90 min
What mediates short reflexes?
Enteric nervous system
What mediates long reflexes?
the Brain
What hormones are in the Gastrin family?
Gastrin and CCK
What does the hormone gastrin stimulate?
gastric acid (HCl)
What does the hormone CCK stimulate?
pancreatic and bile secretion
What hormones are apart of the Secretin family?
Secretin, gastric inhibitory peptide (GIP), and glucagon-like peptide (GLP)
What does the hormone secretin do?
Stimulates bicarbonate release and inhibits gastric acid
What does the hormone GIP do?
stimulates insulin release
What does the hormone GLP do?
stimulates insulin release but also inhibits glucagon
What does the hormone motilin do?
stimulates the migrating motor complex
What organs does the cephalic phase include?
mouth (oral cavity) and esophagus
What organ(s) does the gastric phase include?
stomach
What organ initiates autonomic stimulation of the salivary glands and enteric nervous system of the cephalic phase?
Medulla
Gastric function (secretion and motility) are under what type of control?
Reflex
What stimulates gastric function?
parasympathetic system
Which cells secrete gastric acid and intrinsic factor?
Parietal cells
Which cells secrete histamine and what secretions does it promote?
ECL (enterochromaffin-like cells) and it promotes acid secretion
What do Histamine H2 blockers inhibit and why?
HCl secretion to relieve stomach hyperacidity
What hormone do G cells secrete?
gastrin
What hormone do D cells secrete?
somatostatin
What hormones do chief cells secrete?
Pepsin(ogen) & Gastric lipase
What hormones are secreted from the gastric gland?
- mucus (mucous surface cell)
- bicarbonate (mucous neck cell)
- HCl & intrinsic factor (parietal cell)
- Histamine (ECL cells)
- Pepsin & gastric lipase (chief cells)
- Somatostatin (D cells)
- Gastrin (G cells)
What do mucous neck cells secrete and why?
mucus and bicarbonate to protect the stomach from self digestion
What is the pH of the epithelial surface & lumen of the stomach?
epithelial surface=pH 7
lumen=pH 2
What is the function of bicarbonate?
to neutralize acid
Where does the short & long reflex of gastric function occur?
short- stomach (enteric nervous system)
long- central nervous system
What initiates the short reflexes?
distension or peptides and amino acids in the stomach
Which reflex is involved in stimulation of the medulla oblongata—> preganglionic parasympathetic neuron in vagus nerve—————->Enteric Plexus?
Long reflex
Which reflex is involved in Enteric Plexus—-> postganglionic parasympathetic and intrinsic enteric neurons?
Short reflex
Where do parasympathetic neurons project from and what are the parasympathetic ganglia closer to?
brains stem & bottom of spinal cord. ganglia is closer to the target
Where do sympathetic neurons project from and what are the sympathetic ganglia closer to?
the middle of the spinal cord and ganglia is closer to the spinal cord
What hormone does somatostatin inhibit?
growth hormone released by the anterior pit.
Acetylcholine stimulates _____ secretion directly and indirectly by stimulating _______ & _________.
- HCl
2 & 3. gastrin and histamine
Acetylcholine also stimulates _________ secretion by chief cells.
pepsinogen
Intestinal signals stimulate __________ and inhibit __________.
stimulate pancreatic stimulation
inhibits stomach function
What is absorbed in the large intestine?
water
What is in the large intestine that digests complex carbohydrates & proteins and produces vitamin K?
Colonic bacteria
What is the function of the Hepatic portal vein?
conducts newly absorbed material to the liver for metabolism, storage or detoxification
