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 (B)</p> Signup and view all the answers

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

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

How does the mucosal barrier protect the stomach?

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

What initiates the breakdown of starch in the mouth?

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

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

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

Which of the following statements about carbohydrates is incorrect?

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

In which location does glycolysis occur?

<p>Cytosol (C)</p> Signup and view all the answers

What is the primary product of the Krebs cycle?

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

Which of the following best describes gluconeogenesis?

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

What is the main function of lipids in the body?

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

Which of the following dietary sources contains complete proteins?

<p>Eggs (B)</p> Signup and view all the answers

During glycolysis, how many ATP molecules are produced?

<p>2 (B)</p> Signup and view all the answers

Which statement about fatty acids is true?

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

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

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

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

<p>Production of bile (A)</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 (D)</p> Signup and view all the answers

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

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

What triggers the secretion of enzyme-rich pancreatic juice?

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

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

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

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

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

How do the kidneys maintain osmotic concentration around 300 mOsm?

<p>Through the countercurrent mechanism (B)</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. (B)</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 (A)</p> Signup and view all the answers

What happens to urine concentration when the body is overhydrated?

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

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

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

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

<p>Lipase (B)</p> Signup and view all the answers

What is primarily eliminated through tubular secretion?

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

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

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

How do the vasa recta contribute to urine formation?

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

What does glomerular filtration produce?

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

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

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

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

<p>Proximal convoluted tubule (B)</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 (B)</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 (B)</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. (A)</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 (D)</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. (A)</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. (A)</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 (D)</p> Signup and view all the answers

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

<p>Alcohol (B)</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. (A)</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 (C)</p> Signup and view all the answers

Flashcards

Digestive Tract Effectors

Smooth muscle and glands that activate or inhibit digestive glands, and stimulate smooth muscle movement and mixing of lumen contents

Saliva Function

Cleanses the mouth, dissolves food for taste, moistens and compacts food into a bolus, and begins starch breakdown with enzymes.

Saliva Composition

Mostly water (97-99.5%), electrolytes, digestive enzymes (amylase), proteins (mucin, lysozyme, IgA), and metabolic wastes (urea, uric acid).

Chewing (Mastication)

The process of using teeth to cut and grind food in order to mix it with saliva and compact it into a bolus.

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Swallowing Phases

Voluntary Buccal phase in the mouth, and involuntary Pharyngeal-esophageal phase in the pharynx and esophagus controlled by the brain stem; involving muscle contractions and sphincter openings/closings.

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Mucosal Barrier

A protective layer of bicarbonate-rich mucus and tight junctions between stomach epithelial cells that prevents stomach acid from damaging the stomach lining.

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Parietal Cells

Stomach cells that secrete hydrochloric acid (HCl), which helps denatures protein, activates pepsin, breaks down plant cell walls, and kills bacteria. (pH 1.5-3.5)

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Gastric Gland Cell

Cells in the stomach lining responsible for producing secretions necessary for digestion (e.g., hydrochloric acid, and enzymes)

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Carbohydrate Sources

Carbohydrates are found in starches (grains, vegetables), sugars (fruits), and cellulose (fiber).

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Lipid Sources

Lipids come from triglycerides, which can be either saturated fats (animal source) or unsaturated fats (vegetable oils).

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Protein Sources

Proteins are found in eggs, milk, fish, meat, and soybeans (complete proteins). Legumes, nuts, and cereals contain incomplete proteins.

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Glycolysis

Glycolysis is the first step in glucose breakdown, converting glucose into pyruvate, producing ATP and high energy electrons.

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Krebs Cycle

The Krebs Cycle uses pyruvate from glycolysis to produce carbon dioxide, ATP, and more high energy electrons.

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Electron Transport Chain

The Electron Transport Chain uses high energy electrons to create a large amount of ATP and water.

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Glycogenesis

Glycogenesis is when excess glucose is stored as glycogen for later use.

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Glycogenolysis

Glycogenolysis breaks down glycogen to release glucose when blood sugar levels drop.

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Liver function in digestion

The liver processes bloodborne nutrients, stores fat-soluble vitamins, performs detoxification, and produces bile.

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Pancreatic juice composition

Pancreatic juice is a watery alkaline solution containing electrolytes (primarily bicarbonate), enzymes (proteases, amylase, lipases, nucleases), and helps in neutralizing chyme.

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Pancreatic enzyme activation

Pancreatic proteases are initially inactive and activated in the duodenum.

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Regulation of pancreatic juice and bile

Chyme entering the duodenum triggers the release of CCK and secretin, stimulating the secretion of enzyme-rich pancreatic juice and HCO3-rich pancreatic juice, respectively. Bile is also produced and secreted in response to this signalling

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Large intestine function (main)

Propelling feces to the anus, and supporting defecation.

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Gut bacteria role

Fermentation of undigested food extracting energy and synthesis of Vitamin K & B complex.

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Defecation reflex

A coordinated reflex involving distension of the rectum, causing contraction of the rectum and sigmoid colon, and relaxation of the internal anal sphincter, followed by a voluntary relaxation of the external sphincter to allow defecation.

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Portal triad

The liver histological region which includes the hepatic artery, hepatic portal vein, and bile duct.

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Afferent Arteriole

A blood vessel that carries blood to the glomerulus in the kidney, where filtration occurs.

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Efferent Arteriole

A blood vessel that carries blood away from the glomerulus after filtration has occurred.

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Peritubular Capillaries

Tiny blood vessels that surround the renal tubules in the kidney cortex. They play a role in reabsorbing water and solutes from the filtrate.

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Vasa Recta

Long, straight blood vessels that surround the nephron loop in the medulla of the kidney. They play a role in concentrating urine by exchanging water and solutes.

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Juxtaglomerular Complex (JGC)

A specialized structure in the kidney that regulates blood pressure and filtration rate. It includes the macula densa and granular cells.

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Macula Densa

A group of specialized cells in the distal tubule of the nephron that monitor the salt concentration of the filtrate.

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Granular Cells

Specialized smooth muscle cells in the afferent arteriole of the nephron. They secrete renin, a hormone that helps regulate blood pressure.

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Glomerular Filtration

The first step in urine formation where blood plasma is filtered from capillaries into the nephron.

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Tubular Reabsorption

Process where useful substances in the filtrate are returned to the bloodstream from the nephron tubules. It helps maintain the body's internal environment and conserve important nutrients.

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PCT Reabsorption

The proximal convoluted tubule (PCT) is the main site of reabsorption, responsible for reclaiming glucose, amino acids, and the majority of water and electrolytes from the filtrate.

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Loop of Henle Function

The loop of Henle plays a crucial role in concentrating urine. Water diffuses out of the descending limb, while solutes are actively transported out of the ascending limb, establishing an osmotic gradient.

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ADH and Water Reabsorption

Antidiuretic hormone (ADH) increases water reabsorption from the collecting ducts, making the urine more concentrated. This response occurs when the body needs to conserve water.

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Aldosterone and Sodium Reabsorption

Aldosterone promotes sodium reabsorption in the distal convoluted tubule (DCT) and collecting ducts, leading to water retention and increased blood volume.

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Tubular Secretion

Process where unwanted substances, such as drugs, metabolites, and excess potassium ions, are actively transported from the bloodstream into the nephron tubules for excretion.

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Countercurrent Multiplier

Mechanism that establishes a concentration gradient in the medulla of the kidney by creating a loop of fluid flow in opposite directions in the nephron loop.

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Countercurrent Exchanger

Mechanism that preserves the concentration gradient created by the multiplier by exchanging solutes and water between the vasa recta and the nephron loop.

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Dilute Urine Formation

When the body is overhydrated, ADH levels decrease, reducing collecting duct water permeability, leading to less water reabsorption and excretion of a large volume of dilute urine.

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Concentrated Urine Formation

When the body is dehydrated, ADH levels increase, enhancing collecting duct water permeability, leading to more water reabsorption and a small volume of concentrated urine.

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Renal Clearance

The volume of plasma that the kidneys clear of a particular substance in a given time (usually 1 minute). It measures how efficiently the kidneys remove a substance from the blood.

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Freely Filtered Substance

A substance that is completely filtered by the glomerulus, not reabsorbed or secreted, and its renal clearance is equal to the glomerular filtration rate (GFR) of 125 ml/min. Inulin is an example.

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Reabsorbed Substance

A substance that is partially reabsorbed from the filtrate back into the blood, its renal clearance is less than GFR (e.g., urea).

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Secreted Substance

A substance that is actively transported from the blood into the filtrate, increasing its concentration in the urine, and its renal clearance is greater than GFR.

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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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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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