Download Digestive and Urinary

Digestive System (c 136)
Digestive System Overview
• Alimentary canal
o Oral cavity (mouth), Pharynx (throat), Esophagus
o Bolus: food after swallowed
• Gastro-intestinal tract
o Stomach (digestive juices, pepsin, chyme), Small intestines (duodenum, jejunum, ileum), Large intestines (cecum,
appendix, transverse colon, rectum, anal canal)
o Sphincter muscles
• Accessory Organs
o Teeth, Tongue, Salivary glands (saliva, amylase)
o Liver (lobes, lobules, portal vein, hepatic artery, bile ducts)
o Gall bladder (cystic duct, bile storage)
o Pancreas (Endocrine & Exocrine functions, pancreatic juices)
o Spleen (Recycling and lymphatic functions)
Digestive System Terms
• Ingestion—entry of food through mouth.
• Mastication—physical (mechanical) manipulation of solid food by teeth, mixing by tongue.
• Digestion—chemical breakdown of food into small molecules.
• Secretion—release of water, acids, enzymes, buffers from lining of tract and accessory organs, aid in digestion.
• Absorption—movement of small organic molecules, electrolytes, vitamins, water, across epithelium into capillaries and
lymphatic vessels.
• Peristalsis —muscular action that moves material through small and large intestines.
• Excretion—elimination of waste after compaction.
Oral Cavity
• Food tasted, masticated, partially digested here.
• Structures
o Hard and soft palates
o Tongue—Muscular structure, manipulates food; senses temperature, taste; base extends into pharynx (throat)
o Salivary glands—Produce almost half a gallon (1.5 L) of saliva each day; saliva is 99% water, 1% ions, buffers, waste
products, antibodies, and digestive enzymes; pH=6.8-7.1
Pharynx and Esophagus
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Pharynx (throat)
o Transmits solid food and liquids to esophagus and air to larynx (windpipe).
o Muscular contractions in pharyngeal muscles initiate swallowing.
Esophagus—Muscular tube, about 0.8 in. diameter; begins at the pharynx, pierces the diaphragm, ends at the stomach.
Stomach
• Dimensions—Accordion-like folds in muscle wall (rugae) allow expansion to almost 0.5 gallon.
• Functions
o Temporary storage of ingested food; Mixing of ingested food
o Secretion of gastric juices—HCl reduces pH to level suitable for protein-degrading activity of pepsin (1.5)
o Secretes mucus, which coats inner lining of stomach and protects it from corrosion.
o Absorption of some substances (e.g., alcohol).
Small Intestine
• Almost 10 ft long, 1.6 to 1 inch wide
• 80% of absorption occurs here
• Three sections
o Duodenum--receives enzymes from pancreas and liver
o Jejunum--most absorption here
o Ileum
Liver
• Largest organ (excluding skin)
• Functions
o Regulates body metabolism
o Extracts nutrients absorbed into bloodstream; Monitors and adjusts levels of key nutrients in blood
o Removes and destroys some toxins (e.g., alcohol)
o Large reservoir of blood; phagocytes here constantly remove cell debris, pathogens
o Produces bile, which aids in digestion of fats
• Receives blood from digestive organs via hepatic portal vein, filtering this blood before it enters the body
Pancreas
• Exocrine activity—Secretes digestive enzymes (lipases, carbohydrases, proteases) and buffers through pancreatic duct.
• Endocrine activity in about 1% of cells; produce
o Insulin—causes cells to take up sugars from bloodstream.
o Glucagon—releases glucose from storage in skeletal muscles, liver.
Gall Bladder
• Muscular sac that stores bile produced by liver.
• Bile produced in liver may flow directly into small intestine through common hepatic duct (as during mealtimes).
• May back up through cystic duct to be stored in gallbladder.
Large Intestine
• Holds and compacts undigested material.
• Absorbs water and vitamins produced by intestinal bacteria.
• Sections: Cecum, Appendix, Ascending Colon, Transverse Colon, Descending Colon, Sigmoid Colon, Rectum, Anal canal
Carbohydrate Digestion
• Digestion
o Mouth: begins here; salivary amylases break complex carbohydrates down to 2- or 3-carbon sugars.
o Duodenum: pancreatic carbohydrases digest 2- or 3-carbon sugars to single-carbon sugars.
• Absorption: Sugars pass into interstitial fluid of microvilli, enter intestinal capillaries, and are then carried to liver.
Protein Digestion
• Digestion
o Stomach: begins here; low pH, activity of pepsin split proteins into small fragments.
o Duodenum: pancreatic proteases break protein fragments into amino acids
• Absorption: amino acids are absorbed by microvilli and carried to liver.
Lipid Digestion
• Digestion
o Duodenum: emulsified by bile to form small droplets suitable for enzyme action.
o Duodenum: pancreatic lipases break lipids into fatty acids.
• Absorption: Fatty acids enter intestinal cells, bind to lipid-transport proteins, then enter lymphatic vessels that underlie microvilli;
fatty acids eventually enter venous circulation.
Water and Vitamin Digestion
• Water
o 2 L to 2.5 L of water enters body as food and drink.
o Secretions of tract contribute 6–7 L more.
o Most reabsorbed; only about 150 ml leaves in fecal waste.
• Vitamins
o Fat-soluble vitamins (A, D, E, K) are stored in body; excessive intake leads to toxic effects, liver damage.
o Water-soluble vitamins (C, B) not readily toxic; excess excreted.
• Minerals
o Iron, Calcium, Magnesium, Potassium, Selenium, Zinc, Manganese, Copper, Chromium, Iodine, Silicon, Vanadium,
Trace Minerals
o Critical for optimum health; severely lacking in American diet and food supply; best acquired via glacial water and
ocean food sources.
Effects of Tobacco: Gastrointestinal Reflux Disease (from paralyzed sphincter), Peptic Ulcer Disease, Cancers (esophagus, stomach,
colon, 2x pancreas), Periodontal Disease, Halitosis, decreased micronutrient absorption (particularly of antioxidants)
The Urinary System (c 146)
Overview
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One part of the excretory system: waste material is removed through excretory organs (skin, lungs, large intestine, kidneys/bladder)
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Not just for waste excretion: maintain homeostasis and conserve bodily resources by:
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Gathering and discharging waste
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Regulating blood volume
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Controlling ion concentrations and pH of blood
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Structures
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2 Kidneys
 Cortex and Medulla
 Nephron (Glomerulus, Bowman’s capsule, proximal tubule, Loop of Henle, distal tubule, collecting duct)
 Calyces and Pelvis
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2 Ureters
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1 Bladder
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1 Urethra
Kidneys
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Blood flows into the hilum of the kidney through the renal artery and leaves via the renal vein.
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Kidney acts as filter that captures some substances from arteries and channels it into ureter.
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Also acts as an endocrine gland by secreting erythropoietin (EPO) & renin
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Approximately 1/4th (1200 ml) of systemic cardiac output flows through the kidneys each minute
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Structure
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Outer Renal Cortex
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Inner Renal Medulla (triangular)
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Renal Pelvis—Inner chamber that collects fluids from calyces and channels them into ureter
The Nephron: Working Unit of the Kidney
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Glomerulus--ball of intertwined capillaries that filter water, sugar, salts, and nitrogenous waste products (urea, creatinine, uric acid), but not
proteins and blood cells, into Bowman’s capsule. Filtration occurs here.
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Bowman’s Capsule--C-shape cup surrounding glomerulus passing glomerular filtrate into renal tubule
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Renal Tubule. Tubular Reabsorption and Tubular Secretion
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Proximal Tubule --first part of tubule; in renal cortex
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Loop of Henle --tubule extends into medulla; water and ions may pass back into
surrounding peritubular capillaries (reabsorption)
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Distal Tubule --water passes back into blood supply via peritubular capillaries if
ADH is present; water left in tubule if ADH not present
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Collecting Tubule--located in medulla. Carries urine from renal cortex to renal pelvis.
1% of original filtrate from glomerulus becomes urine.
Hormones Control Water Retention
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When blood volume falls, solute concentration rises.
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Hypothalamus detects and directs release of ADH from pituitary.
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ADH (Antidiuretic Hormone)
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Increases permeability of distal tubule and collecting duct to water.
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More water moves out of tubule and makes it back to circulation; urine becomes
more concentrated.
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Alcohol suppresses ADH production, leads to increased urine volume.
Urine Transport, Storage, and Excretion
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Ureter—Peristaltic waves squeeze urine from renal pelvis. 12 inches long.
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Urinary Bladder
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Hollow, muscular organ—Stores urine (< 800 ml).
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Internal sphincter exerts involuntary control of urine flow into urethra.
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Urethra
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External sphincter—Provides voluntary (adult) control of urine release to exterior.
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In males, urethra is about 7 inches long, upper part surrounded by prostate gland.
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Transports urine and sperm cells and other secretions from reproductive organs.
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Opens to outside at urinary meatus.
Urine Excretion (Micturition)
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Urge to urinate occurs when bladder contains about 200 ml of urine.
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Stretch receptors in bladder send nerve impulse to brain.
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Voluntary relaxation of external sphincter produces relaxation of internal sphincter.
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Buildup of pressure forces internal sphincter to relax involuntarily if urine exceeds about 500 ml.
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About 1.8 L of urine is excreted daily. Less than 10 ml remains in bladder after urination.
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Normal Urine: clear, no glucose, no ketones, low protein, sterile
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pH=4.5 to 8.5. More acidic in nonvegetarians. More acidic in morning due to decreased pulmonary
ventilation while sleeping. Citrus, vegetables, and legumes make urine more alkaline. Meat and cranberries make urine more acidic.
Effects of Tobacco: increased BP damages kidney. #1 cause of bladder cancer