Chapter 19: Binge Drinking – The Digestive and Urinary Systems Study Guide

Introduction to Binge Drinking and Systemic Interaction

• Binge Drinking Statistics and Concerns: Binge drinking on college campuses is a significant health concern. In a single year, over $30,000$ students required medical treatment specifically for alcohol poisoning.
• Chapter Objectives:     - Describe the structures and functions of the digestive system.     - List accessory organs and their roles in digestion.     - Explain hormonal control of the digestive system.     - Identify structures of the mammalian urinary system.     - Describe the steps of urine excretion.     - Identify safer ways to engage with alcohol consumption.
• Central Aim: Understanding how the digestive and urinary systems relate to each other in the context of processing nutrients and toxins like alcohol.

The Digestive System: Structure and Primary Functions

• Definition: The digestive system metabolizes (breaks down) food so it can be used for energy by the body. Energy is stored in the chemical bonds of food.
• The Digestive Tract: A long, continuous tube with openings at the mouth and the anus. It exposes food to the actions and secretions of various organs and glands.
• Methods of Digestion:     - Mechanical Digestion: The physical breakdown of food (e.g., chewing).     - Chemical Digestion: The use of chemical agents and enzymes to break food into smaller units.
• The Mouth and Throat:     - Teeth: Incisors, canines, premolars, and molars grind food to increase the surface area available for enzyme exposure.     - Salivary Glands: Secrete saliva containing enzymes that begin the breakdown of sugars/carbohydrates.     - Tongue: A muscular structure that forms food into a bolus (a ball of food) and pushes it to the back of the mouth.     - Pharynx: The back of the throat that branches into the trachea (leading to lungs) and the esophagus (leading to the stomach).     - Epiglottis: A thin flap of cartilage below the tongue that prevents swallowed food from entering the trachea.
• Pathway to the Stomach:     - Esophagus: The pathway for food to reach the stomach.     - Peristalsis: Rhythmic waves of involuntary smooth muscle contractions that push food down the esophagus.     - Lower Esophageal Sphincter: A ring of contracting muscles at the base of the esophagus that prevents the backflow of stomach contents.
• The Stomach:     - Food is degraded further by digestive enzymes and acids (gastric juices).     - Pepsin: An enzyme in the stomach that specifically breaks down proteins.     - Mucus: Coats the stomach lining to prevent gastric juices from breaking down the organ itself.     - Chyme: A slurry mixture of food and digestive enzymes formed by stomach peristalsis.     - Pyloric Sphincter: Found at the base of the stomach; it regulates the secretion of chyme into the small intestine.
• The Small and Large Intestines:     - Small Intestine: A tube approximately $20\,\text{feet}$ long in adults. It is the major site of chemical digestion for all nutrient types and the primary site for nutrient and alcohol absorption into the bloodstream via the epithelium.     - Large Intestine (Colon): Holds materials not absorbed by the small intestine. Its primary function is the reabsorption of water. Undigested materials (largely plant fibers) are excreted as feces via the rectum and anus.

Accessory Organs of the Digestive System

• Definition: Organs that lie outside the digestive tract but produce or secrete substances essential for digestion.
• Pancreas: Produces digestive enzymes for carbohydrates, fats, proteins, and nucleic acids. It also produces a buffer (sodium bicarbonate) that neutralizes the acidity of stomach acid entering the small intestine.
• Liver: Produces bile, which helps dissolve and absorb fats in the small intestine. It also metabolizes toxins, including alcohol and drugs.
• Gallbladder: Stores and concentrates bile by removing water ($H_2O$) before releasing it into the small intestine.     - Gallstones: Crystallized bile that results from the removal of too much water.

Alcohol's Impact on the Digestive System

• Mouth and Throat: Alcohol abusers have a higher incidence of oral cancers, tooth decay, gum disease, and tooth loss.
• Esophagus and Stomach:     - Heartburn: Alcohol relaxes the lower esophageal sphincter, allowing acidified stomach contents to move back into the esophagus.     - Diarrhea: Alcohol relaxes muscles used for peristalsis, causing food to remain in the tract longer; however, increased exposure to enzymes can also trigger diarrhea.     - Vomiting: High concentrations of alcohol in chyme irritate the stomach lining, triggering the vomiting reflex.
• Metabolizing Alcohol:     - Only a small percentage of alcohol is metabolized in the stomach.     - Alcohol Dehydrogenases: Enzymes secreted by epithelial cells in the stomach lining to help metabolize alcohol and reduce intoxication.     - Food Interaction: Eating food causes the pyloric sphincter to remain closed longer, slowing the rate at which alcohol enters the small intestine and the bloodstream.
• Accessory Organ Damage:     - Cirrhosis: An irreversible process caused by heavy drinking where healthy liver tissue is replaced by scar tissue, preventing proper blood flow.     - Pancreatitis: Inflammation of the pancreas that prevents the secretion of digestive enzymes, disrupting digestion.

Nutrient Absorption and Surface Area

• Villi: Finger-like, membranous projections of the small intestine that absorb nutrients into the bloodstream. They contain blood capillaries and lymphatic vessels.
• Microvilli: Even smaller projections on the villi that transport nutrients into the blood vessels. Together with villi, they vastly increase the surface area of the small intestine for absorption.
• Alcohol Damage: Chronic alcohol abuse or binge drinking can damage intestinal villi, preventing the absorption of necessary nutrients.

Hormonal Regulation of Digestion

• Gastrin: Produced by the stomach after eating; stimulates the production of acidic gastric juices.
• Secretin and Cholecystokinin (CCK): Produced by the small intestine after the release of gastrin; these hormones signal the pancreas and gallbladder to increase the secretion of digestive juices.
• Alcohol and Hormones: Excessive alcohol can decrease testosterone production if not removed from the blood, potentially leading to erectile dysfunction and lower sperm production.

The Urinary System and Toxin Removal

• Function: Removes wastes while retaining materials that can be reused or recycled. It filters and cleanses circulating blood.
• Major Organs:     - Kidneys: Paired organs located behind the liver and stomach.     - Ureters: Tubes that carry waste from kidneys to the bladder.     - Urinary Bladder: Stores urine until excretion.     - Urethra: The tube through which urine leaves the body.
• Kidney Structure:     - Renal Arteries: Large vessels that bring blood to the kidneys. All blood in the body passes through the kidneys hundreds of times per day.     - Nephrons: The functional unit of the kidney. There are approximately $1,250,000$ tubules per kidney, with a combined length of $145\,\text{km}$ ($85\,\text{miles}$) in an adult.
• Four Phases of Waste Processing:     1. Filtration: Occurs in the Bowman’s capsule; blood pressure forces plasma into the nephron through tiny holes in capillaries.     2. Reabsorption: Sugars, amino acids, and water are reabsorbed into kidney tissue across the nephron loop. Salt is actively removed from the filtrate on the ascending limb, causing water to flow out due to the concentration gradient.     3. Secretion: Wastes in low concentration in the blood are actively secreted into the far end of the nephron and flow into the collecting duct.     4. Excretion: Concentrated urine is excreted into the bladder and then out of the body.

Regulation of Blood and the Effects of Alcohol

• Homeostasis: Kidneys regulate acidity and salt balance by excreting acids and reabsorbing salts.
• Antidiuretic Hormone (ADH):     - Released by the pituitary gland when blood pressure is low to reabsorb more water into the bloodstream.     - When blood pressure is high, ADH is not released, and more water is excreted.
• Alcohol as a Diuretic: Alcohol inhibits ADH secretion. This causes the kidneys to reabsorb less water, producing a higher volume of urine than the liquid consumed, leading to dehydration, headaches, and nausea.
• Other Alcohol Effects:     - Depressant: Slows brain function, altering perception, reflexes, and balance. Note: Energy drinks can mask these effects.     - Physiological effects: Moderate intake ($1$-$2$ drinks/day) may slightly improve glomerular filtration rates and lower cardiovascular disease risk, but larger consumption increases blood pressure to remove toxins and raises the risk of heart disease and stroke.

Blood Alcohol Concentration (BAC)

• Breathalyzers: Alcohol in the circulatory system evaporates from the lungs. The amount in the breath is proportional to the amount in the blood.
• Metabolic Rate: The liver can only metabolize approximately $1$ standard drink per hour.
• Standard Drink Definition: $14\,\text{g}$ of pure alcohol, which equals:     - $12\,\text{oz}$ of beer     - $5\,\text{oz}$ of wine     - $1.5\,\text{oz}$ of hard liquor ($80\,\text{proof}$ like Vodka, gin, or whiskey)
• BAC Thresholds and Symptoms:     - $0.03$-$0.04$: Relaxation, mild euphoria, slight concentration impairment.     - $0.05$: Impaired reasoning and motor skills (driving is unsafe).     - $0.08$: Legal intoxication; illegal to drive.     - Above $0.1$: Uncontrolled emotions, boisterous behavior, impaired reflexes and speech.     - $0.2$: Possible unconsciousness and blackouts.     - $0.3$ or higher: Central nervous system depression, impaired breathing/heart rate, potential death.

Safer Engagement with Alcohol

Questions & Discussion

• Q: In which organ does the majority of chemical digestion for all nutrient types occur?     - A: The small intestine.
• Q: Men and women with similar body sizes will metabolize alcohol at the same rate. (True/False)     - A: False. Women typically produce less alcohol dehydrogenase and have less enzyme per pound of body weight, leading to higher intoxication from less alcohol.
• Q: What is ALDH1?     - A: A variant of the alcohol dehydrogenase enzyme (common in East Asian descent) that metabolizes acetaldehyde slowly. High acetaldehyde causes face flushing, dizziness, and nausea.
• Q: What hormone stimulates the production of acidic juices by the stomach?     - A: Gastrin.
• Q: What organ filters and cleanses circulating blood by creating urine to be excreted?     - A: The kidney.
• Q: Because alcohol affects ADH secretion, you may urinate a higher volume of liquid than you consume when drinking. (True/False)     - A: True.