GI2 Flashcards
What are the three levels of surface infoldings in the small intestines?
Plicae circulares
Villi
Microvilli
What are the gland like structures at the base of the villi in the small intestine?
Crypts of Leiberkuhn
What are the 4 cell types of the small intestine and what do they secrete ?
Mature enterocytes
Goblet cells- mucus
Paneth cells - antimicrobial enzymes and peptides
Enteroendocrine cells- CCK, secretin, and. GIP
What tubulo alveolar glands are located in the small intestine ?
Brunner gland
Brunners glands secrete what? And what is function of these secretions?
Glycoproteins and bicarbonate ion.
Protection of small intestine mucosa by neutralizing the acid-containing chyme delivered to it from the stomach
What immune system components are present in the small intestine?
M fold cells phagocytose bacteria
Antigen presentation in peyers patches and mesenteric lymph nodes.
Production of IgA antibodies that are secreted in the mucus
____________ cells of the small intestine arise from stem cells and differentiate into the cells of the small intestine
Progenitor
When food is hyperosmotic what is the direction of water movement?
Alll water secretion mediated by osmosis
Hyperosmotic draws water from the lateral spaces into intestinal lumen
Where are nutrients absorbed from the intestine directed?
Hepatic portal vein passes through the liver
Lymphatic drainage enters blood stream through thoracic duct
What are the functions of the liver?
Metabolism of carbohydrates, amino acids, proteins, and lipids
Storage of glycogen, lipid, vitamins, copper, and iron
Synthesis of bile, hormones, and immune system components
Biotransformation of medications, xenobiotics, and byproduct metabolism
What proteins are synthesized in the liver?
Albumins Lipoproteins Glycoproteins Prothrombin and fibrinogen Nonimmune a- and b- globulins
What hormones are synthesized in the liver?
Angiotensin gen -> prohomrone
Thrombopoetin -> hormone (growth factor)
IGF -> IGF 1 and 2
Hepcidin ->small peptide hormone
What is biotransformation?
Conversion of toxic molecules into non-toxic, water soluble and excretable substances
(Increase polarity of drugs)
What are the two phases of biotransformation?
Phase 1: oxidation adds a OH group (hydroxylation) or a COOH groups (carboxylation) in smooth ER and mitochondria
Phase 2: conjugation with glucuonic acid, glycine, or taurine
The ____________ produces bile and it is stored and concentrated in the _____________
Hepatocytes of liver; and gallbladder
What is bile synthesized from and what important property does bile have?
Cholesterol conjugated to amino acids
Amphipathic
What stimulates the secretion of bile acids?
Increase amino acids and fatty acids in duodenum -> CCK release -> contraction of smooth muscle of the ducts and relaxation of Oddi’s sphincter
Reflectory -> ACh -> contraction of smooth muscle
What is the enterohepatic circulation of bile acids?
Bile acids secreted into the duodenum and reabsorbed in the ileum, transported back to the liver, to be used again (95%)
Only 5% of bile acids are synthesized de novo in the liver
Pancreatic juice contains what molecules? And what transporters are involved?
HCO3-, Na+, and K+
Paracellular - Na and K
Cl- apical channel
Na/K/Cl cotransporter (basolateral)
The pancreas produces _________ which must be activated to __________
Zymogens; proteases
What are the digestive enzymes produced in the pancreas?
Peptidases
Nucleases
Amylases
Lipase
Pancreatic cells have receptors for ?
ACh, CCK, and secretin
Pancreatic secretions adjust to food composition. Food with high starch stimulates ____________ enzyme production. High fat and protein foods stimulates increase __________ and __________ production
Amylase
Lipase and petidase
A low pH in the intestine stimulates the release of _____________ hormone to stimulate _____________ rich pancreatic secretions
Secretin; bicarbonate
What condition has insufficient production of digestive enzymes by exocrine pancreas?
Pancreatic insufficiency
What condition, common in dogs, has pancreatic acini destroyed and replaced by CT
Pancreatitis
An __________ pathway degrades energy rich molecules to capture energy
Catabolic
An ______________ pathway uses energy to combine small molecules to form more complex molecules
Anabolic
What are the functions of carbohydrates?
Energy source
Storage of energy
Cell membrane component
Structural
Digestion of carbohydrates requires ___________ from the pancreas
Amylase
What enzymes synthesized by the intestinal mucosa are required for digestion of carbohydrates?
Lactase
Isomaltase
Maltase
Saccharase
Carbohydrates are absorbed apically by _____ and _______transporters, -pp32wppqand basolaterally by _____ transporters
SGLT and GLUT5- apically (Na dependent)
GLUT 2- basolaterally
________ pathway uses a glucose molecule to form 2pyruvate, 2NADH, and 2 ATP
Glycolysis
In anaerobic glycolysis, pyruvate is converted to _____
Lactate
In aerobic glycolysis, pyruvate enters the _______ cycle within the mitochondria
Krebs cycle
Glycolysis is regulated by?
Phosphorylation /dephosphorylation of rate-limiting enzymes (short term)
Hormonal influences on the proteins/enzymes synthesized (long term)
What are the important biochemical events that allow the production of energy in the cell?
Pyruvate converted to Acetyl-CoA TCA Respiratory (electron transport) chain ATP synthesis by oxidative phosphorylation B-oxidation
What is the production of glucose from non-sugar molecules and where does this process occur?
Gluconeogenesis
Liver and kidney
What are the important substrates for gluconeogenesis
Glycerol -> glycerol phosphate
Lactate -> pyruvate
Amino acids -> TCA -> oxaloacetate
What mechanism is used to store glucose in skeletal muscle and the liver?
Glycogenesis -> glucose to glycogen (glucose linked by 2-glycosidic bonds)
The pentose phosphate pathway produces what two important molecules
NADPH
Ribose-5-phosphate
What is the function of NADPH ?
Electron source
- > reductase
- > electron transport chain
- > cytochrome P450 (reduce)
- > respiratory burst -> NO synthesis
