Digestive System Overview
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Questions and Answers

What is one of the primary functions of saliva?

  • Cleanses the mouth (correct)
  • Heats food for digestion
  • Increases bacteria in the mouth
  • Stimulates digestive enzymes

    • Which component makes up the majority of saliva's composition?

  • Electrolytes
  • Digestive enzymes
  • Mucin
  • Water (correct)

    • What happens during the buccal phase of swallowing?

  • The tongue presses against the hard palate (correct)
  • The upper esophageal sphincter relaxes
  • The uvula rises to block the nasopharynx
  • Food is propelled into the stomach

    • What type of muscle movement is responsible for moving food through the esophagus?

    <p>Peristalsis</p> Signup and view all the answers

    Which of the following is NOT a function of gastric gland cells?

    <p>Absorption of nutrients</p> Signup and view all the answers

    How does the mucosal barrier protect the stomach?

    <p>By separating acid from the epithelial tissue</p> Signup and view all the answers

    What initiates the breakdown of starch in the mouth?

    <p>Salivary amylase</p> Signup and view all the answers

    Which phase of swallowing is controlled by the swallowing center in the brainstem?

    <p>Pharyngeal-esophageal phase</p> Signup and view all the answers

    Which of the following statements about carbohydrates is incorrect?

    <p>Carbohydrates are used mainly for structural functions.</p> Signup and view all the answers

    In which location does glycolysis occur?

    <p>Cytosol</p> Signup and view all the answers

    What is the primary product of the Krebs cycle?

    <p>Carbon Dioxide</p> Signup and view all the answers

    Which of the following best describes gluconeogenesis?

    <p>Formation of glucose from non-carbohydrate sources.</p> Signup and view all the answers

    What is the main function of lipids in the body?

    <p>Store energy as adipose tissue.</p> Signup and view all the answers

    Which of the following dietary sources contains complete proteins?

    <p>Eggs</p> Signup and view all the answers

    During glycolysis, how many ATP molecules are produced?

    <p>2</p> Signup and view all the answers

    Which statement about fatty acids is true?

    <p>Saturated fats are predominantly animal-based.</p> Signup and view all the answers

    What is primarily reabsorbed in the proximal convoluted tubule (PCT)?

    <p>All glucose and amino acids</p> Signup and view all the answers

    What is one of the primary functions of the liver in digestion?

    <p>Production of bile</p> Signup and view all the answers

    In which part of the nephron does osmosis allow water to leave the filtrate?

    <p>Descending limb of the Loop of Henle</p> Signup and view all the answers

    Which component of pancreatic juice is primarily responsible for neutralizing chyme in the duodenum?

    <p>HCO3-</p> Signup and view all the answers

    What triggers the secretion of enzyme-rich pancreatic juice?

    <p>Release of cholecystokinin (CCK)</p> Signup and view all the answers

    What hormone is released in response to dehydration to promote water reabsorption in the collecting ducts?

    <p>Antidiuretic hormone</p> Signup and view all the answers

    Which process is primarily involved in the elimination of excess potassium from the body?

    <p>Tubular secretion driven by aldosterone</p> Signup and view all the answers

    What is the role of bacterial flora in the large intestine?

    <p>Fermentation of undigested food</p> Signup and view all the answers

    How does the liver respond to secretin released into the bloodstream?

    <p>Stimulates bile secretion</p> Signup and view all the answers

    How do the kidneys maintain osmotic concentration around 300 mOsm?

    <p>Through the countercurrent mechanism</p> Signup and view all the answers

    Which of the following statements about the secretion of pancreatic juice is true?

    <p>Secretin primarily stimulates the secretion of bicarbonate-rich pancreatic juice.</p> Signup and view all the answers

    What is the role of the countercurrent multiplier in urine formation?

    <p>Creates an osmotic gradient in the medulla</p> Signup and view all the answers

    What happens to urine concentration when the body is overhydrated?

    <p>It becomes dilute with less concentration</p> Signup and view all the answers

    Which of the following processes does NOT occur during the defecation reflex?

    <p>Secretion of gastric juices</p> Signup and view all the answers

    Which enzyme in pancreatic juice is responsible for breaking down fats?

    <p>Lipase</p> Signup and view all the answers

    What is primarily eliminated through tubular secretion?

    <p>Drugs and metabolites</p> Signup and view all the answers

    What is the primary function of the macula densa cells in the juxtaglomerular complex?

    <p>To act as chemoreceptors monitoring NaCl content of filtrate</p> Signup and view all the answers

    Which process involved in urine formation selectively moves substances from blood to filtrate?

    <p>Tubular secretion</p> Signup and view all the answers

    How do the vasa recta contribute to urine formation?

    <p>By forming bundles of long straight vessels</p> Signup and view all the answers

    What does glomerular filtration produce?

    <p>Cell- and protein-free filtrate</p> Signup and view all the answers

    Which component is responsible for the secretion of renin in the juxtaglomerular complex?

    <p>Granular cells</p> Signup and view all the answers

    In which part of the nephron does tubular reabsorption primarily occur?

    <p>Proximal convoluted tubule</p> Signup and view all the answers

    What is a characteristic of the fenestrated endothelium in the filtration membrane?

    <p>Allows all blood components except blood cells to pass through</p> Signup and view all the answers

    What role do peritubular capillaries serve in the renal system?

    <p>Facilitate the reabsorption of water and solutes</p> Signup and view all the answers

    What role does the vasa recta play in the countercurrent exchanger?

    <p>It helps reabsorb water and solutes while maintaining the osmotic gradient.</p> Signup and view all the answers

    Which condition leads to the formation of a large volume of dilute urine?

    <p>Decreased permeability of collecting duct to water</p> Signup and view all the answers

    What happens when a substance has a renal clearance (C) less than 125 ml/min?

    <p>It is partially reabsorbed back into the plasma.</p> Signup and view all the answers

    What is the primary effect of osmotic diuretics on urine formation?

    <p>They prevent reabsorption of water, keeping it in the urine.</p> Signup and view all the answers

    When maximal ADH is present, what is the expected outcome on urine volume?

    <p>Concentrated urine with a small volume</p> Signup and view all the answers

    What chemical is an example of an ADH inhibitor that can enhance urinary output?

    <p>Alcohol</p> Signup and view all the answers

    If a substance has a renal clearance of 0 ml/min, what does that indicate?

    <p>The substance is completely reabsorbed or not filtered.</p> Signup and view all the answers

    How does the countercurrent exchanger contribute to urine concentration?

    <p>By preventing rapid removal of salts from the interstitial space</p> Signup and view all the answers

    Study Notes

    Digestive System

    • Digestive Processes: Ingestion, Propulsion (swallowing, peristalsis), Mechanical Breakdown (chewing, mixing), Digestion (breaking down complex molecules), Absorption (transporting digested food), and Defecation (removal of waste).

    • Carbohydrate Digestion: Salivary amylase in saliva breaks down starch, pancreatic amylase breaks down starch/glycogen to oligosaccharides/disaccharides. Brush border enzymes further break down to monosaccharides, which are absorbed via secondary active transport and facilitated diffusion.

    • Protein Digestion: Pepsinogen (activated to pepsin in stomach) breaks down proteins into polypeptide chains, pancreatic proteases further break them into smaller chains, brush border enzymes (peptidases) break into amino acids. Amino acids are absorbed via secondary active transport then facilitated diffusion.

    • Lipid Digestion: Triglycerides are the major fat in the diet. The small intestines are primary for lipid digestion. Emulsification (bile salts break large fat globules to small droplets) increases surface area to allow pancreatic lipase to act upon lipids. Pancreatic lipase hydrolyzes triglycerides to monoglycerides and free fatty acids. Micelle formation: These compounds are formed and absorbed as these are associated with bile salts. Diffusion into epithelial cells and chylomicron formation (packaged with proteins and fats), transport extruded from the epithelial cells by exocytosis and enter lacteals and lymph to venous blood in the thoracic duct.

    Peritoneum and Digestive Activity

    • Peritoneum: Serous membrane lining the abdominal cavity. Visceral (covers organs), Parietal (lines body wall). Peritoneal cavity (space between layers) lubricates organs. Mesenteries routes for vessels, lymphatics and nerves; support organs in position, contains fat deposits.

    • Intrinsic Nervous System (Short Reflexes): Submucosal and myenteric nerve plexuses within the gut wall. Linked to CNS with afferent visceral fibers and autonomic nerves.

    • Extrinsic Nervous System (Long Reflexes): Involve CNS centers and autonomic nerves; response to stimuli in or outside the GI tract.

    Saliva, Chewing and Swallowing

    • Saliva Functions: Cleanses mouth, dissolves chemicals for taste, moistens/compacts food, and begins starch breakdown.

    • Saliva Composition: 97-99.5% Water + electrolytes + digestive enzymes (salivary amylase).

    • Chewing (Mastication): Teeth cut, grind, and mix food with saliva.

    • Swallowing (Deglutition): Buccal phase (voluntary), Pharyngeal-esophageal (involuntary), with sphincters, and peristalsis.

    Other Digestive Processes and Functions

    • Gastric Glands and Regulation: Parietal cells secrete HCl (denatures protein, activates pepsin, kills many bacteria) and intrinsic factor (vitamin B12). Chief cells secrete pepsinogen (becomes pepsin). Enteroendocrine cells secrete gastrin (regulates stomach secretions and motility). Phases of gastric secretion: cephalic, gastric, and intestinal.

    • Small Intestine Modifications: Circular folds, villi, and microvilli increase absorption surface area.

    • Liver and Pancreatic Juice Functions in Digestion: Liver produces bile (emulsification), and Pancreas produces pancreatic juice (enzymes, bicarbonate). Enzymes break down proteins, carbs, and fats. Active regulation of pancreatic juice & bile secretion are regulated by CCK & secretin in duodenum

    • Large Intestine Functions: Microbial flora fermentation of otherwise indigestible foods to produce vitamins and energy. Absorption of water, manufacturing vitamins, formation/propulsion of feces to anus, defecation in relation to the defecation reflex.

    Metabolism

    • Carbohydrate Metabolism: Glycolysis (breakdown of glucose), Glycogenesis (glucose to glycogen), Glycogenolysis (glycogen to glucose), Gluconeogenesis (non-carbohydrate sources). Glucose, the primary fuel, stored as glycogen.

    • Lipid Metabolism: Lipolysis (breakdown of fats), lipogenesis (formation of fats). Triglycerides (fats) are stored in adipose tissue and used as energy if carbs are not available.

    • Protein Metabolism: Used for energy or to synthesize new proteins. Excess amino acids are converted into other molecules used as energy or as structural materials.

    Urinary System

    • Kidney Functions: Regulates total water/solute concentration, acid-base balance, removes metabolic waste, produces hormones (renin, erythropoietin), regulates RBC production, converts vitamin D to active form

    • Nephron Structure: Renal corpuscle (glomerulus & Bowman's capsule - filtration) and renal tubule (PCT, nephron loop, DCT, collecting duct-reabsorption/secretion)

    • Glomerular Filtration: Blood pressure forces fluid and small solutes through filtration membrane. Hydrostatic pressure vs opposing forces determining the net filtration pressure.

    • Tubular Reabsorption/Secretion: selective processes that regulate the composition of urine as filtrate flows through the nephrons.

    • Urine Formation (dilute/concentrated): Medullary osmotic gradient, countercurrent multiplier, and countercurrent exchanger mechanisms; control by ADH and Aldosterone

    • Urine Characteristics: Color (urochrome), transparency, composition (nitrogenous waste, electrolytes)

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    Study Guide - Lecture Exam 3 PDF

    Description

    Explore the fundamental processes involved in the digestive system, including ingestion, propulsion, mechanical breakdown, digestion, absorption, and defecation. Delve into carbohydrate, protein, and lipid digestion, focusing on the key enzymes and absorption mechanisms. This quiz will test your knowledge on how our bodies process food.

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