digestion

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Hormones affect appetite and metabolism CCK hormone increases with age and can suppress the appetite. Digestive System

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Do not post to Internet Before and after gastric bypass surgery Surgery such as ‘stomach stapling’ reduces ghrelin secretion. Leptin hormone rises when we are full, and reduces appetite. Ghrelin hormone rises when the stomach is empty. This makes us feel hungry.

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Once formed, fat-storing cells (adipose) stay forever Exercise or weight loss may reduce fat in these cells

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Mouth (oral cavity) Food is pulverized by teeth (physical break-up) Saliva is produced by salivary glands at back of mouth and under tongue salivary glands

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Saliva includes Amylase enzyme ( chemical breakup) Bicarbonate (buffers strong acids) Mucins (lubricants bind food into bolus) Water

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2. Pharynx (throat) Muscular section in back of mouth Place where swallowing occurs Tongue forces food into pharynx

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epiglottis pharynx esophagus trachea (wind pipe) Last voluntary muscle control until anus Epiglottis and vocal cords close off trachea; breathing temporarily ceases

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Esophagus (long tube) Transports the bolus to the stomach Mucosa lining mostly only one layer thick produces mucus Controlled by involuntary smooth muscles

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2 sphincters– one-way “valve” ring of muscles that control digestive back flow. Food moves into esophagus, then through the lower esophageal sphincter into the stomach. Esophageal sphincter

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Peristalsis-- wave-like contractions of involuntary muscles forces nutrients through entire GI tract

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GERD Gastroesophageal Reflux Disease The esophageal sphincter does not close properly Esophageal sphincter 5 to 7% of Americans Avoid spicy, acidic, stimulating foods Take medication that inhibits acid formation

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Bitter, sour tasting fluid rises up through the stomach and into the esophagus and into the mouth Heartburn like discomfort

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Stomach Stores and mixes food with gastric fluids Breaks proteins into fragments mucosa sphincters muscle serosa

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Pyloric sphincter Smooth muscles control contractions

Stomach Secretions : 

Stomach Secretions Gastric fluid chemically breaks up food. Hydrochloric acid (HCl) pH = 2 Mucus (protective) Pepsinogen (converts to digestive enzyme, pepsin)

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Gastric fluid + food = Chyme (milky substance) Kills most food borne pathogens and can cause heartburn

Rate of stomach emptying : 

Rate of stomach emptying Stomach distention triggers receptors in the stomach lining to “call” for more gastric fluid and hence increase digestion. Fat contents, depression, and fear slows the rate of peristalsis and hence stomach emptying.

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GI Disorders 1. Peptic Ulcer Forms when digestive enzymes and gastric fluid erode the lining of the stomach Most ulcers start after an infection from the bacterium Heliobacter pylori and can be treated with antibiotics

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Other factors may include stress and swallowing saliva on an empty stomach.

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Positive feedback loop Mucosa injury triggers the release of histamine. This causes increased release of acidic gastric fluid which causes further damage.

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Injury to mucosa Increased gastric fluid production Histamine released Positive feedback loop

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Bulimia Psychological disorder that begins with binging and purging Purging through induced vomiting or laxative consumption

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Acidic chyme erodes tooth enamel, tooth mass decreases, gums recedes Lowering of the immune system Ulceration of the esophagus lining of the mouth

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3. Anorexia Nervosa Self-induced starvation Usually begins as a psychological disorder Medical Problems: Anemia Loss of muscle mass Extreme protein digestion in body tissue, eventually enzyme osteoporosis

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4. Kwashiorkor Protein deficient diet results in reduced muscle mass, depressed immune system, and retarded growth.

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Digestion is completed and most nutrients are absorbed. Three regions Duodenum Jejunum Ileum 5. Small Intestine

Walls of Small Intestine : 

Walls of Small Intestine Projections of villi into the intestinal lumen increases the surface area available for absorption one villus lumen

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villi connective tissue vesicles artery vein lymph vessel Villi on one of the folds, longitudinal section One villus epithelium blood capillaries lymph vessel microvilli Viewing only

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1. absorption 2. mucus secretion (goblet cell) 3. hormone secretion (goblet cell) 4. phagocytosis lysozyme secretion Microvilli Increase surface area Four specialized cells making up the epithilium of a villus

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serosa mucosa (inner lining) Thick- walled viewing

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Duodenum Receives chyme from stomach Lots of goblet cells

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Intestinal and pancreatic enzymes break down carbs, fats, and proteins Receives secretions from liver, gallbladder, and pancreas through ducts

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Pancreas produces digestive enzymes, such as trypsin, which are carried through a duct to the duodenum. Liver produces bile. Bile salts attach to fats and cause the physical break up of fat globules. Associated Organs and Glands

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Gallbladder Stores and concentrates bile

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Gallbladder Surgery “Stones” of cholesterol (gallstones) form in the gallbladder and migrate out to block the duct so bile can’t make it into the small intestine. This interferes with digestion.

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Absorption of nutrients occurs mainly in the jejunum and ileum of the small intestine. Segmentation mixes the lumen contents against the wall and enhances absorption. B. Jejunum and Ileum

Absorption Mechanisms : 

Absorption Mechanisms Monosaccharides & amino acids are actively transported across plasma membrane. INTESTINAL LUMEN carbohydrates monosaccharides EPITHELIAL CELL INTERNAL ENVIRONMENT proteins amino acids

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bile salts + fat globules (triglycerides) fatty acids, monoglycerides emulsification droplets micelles chylomicrons triglycerides + proteins bile salts EPITHELIAL CELL INTERNAL ENVIRONMENT Lipase is a fat splitting enzyme which brings about further break up of fats. Lipase inhibitors (diet drugs) decrease absorption of fat.

6. Large Intestine (Colon) : 

6. Large Intestine (Colon) Place where water is reabsorbed Concentrates and stores feces

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Lining secretes mucus and bicarbonate Resident population of E. Coli bacteria makes vitamin K

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Appendicitis The appendix is a little tube attached to the large intestine. Symptoms: sudden abdominal pain, slight fever, loss of appetite, vomiting

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Secretions can become blocked and infection sets in. If it bursts, it can cause peritonitis, a life -threatening condition.

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Constipation impaired movement of feces through the colon Causes: some medications dehydration

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inactivity Ignoring defecation reflex Common treatment: Laxatives --- can lead to a physiological dependence

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7. Rectum Thick , muscular tube below the large intestine. Anus 2 sphincters, one controlled by voluntary, skeletal muscle. This is where some people get hemorrhoids and fissures.

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1. Kidneys Function: -Filter water, mineral ions, wastes from the blood -Returns most of the filtrate to the blood -Remaining water and solutes in filtrate is called urine

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renal vein renal artery kidney cortex kidney medulla ureter renal pelvis viewing

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Structure: Cortex (outer) Medulla (middle) Renal pelvis collects urine and funnels it to ureter Nephrons located

Nephron : 

Nephron Functional unit of the kidney Each consists of a renal tubule and associated capillaries Bowman’s capsule (red) proximal tubule distal tubule loop of Henle collecting duct cortex

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How it works: a. Blood enters glomerular capillaries in the Bowman’s capsule of a nephron. -Glomerular capillaries have large pores Bowman’s capsule nephron

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b. Fluid leaks from glomerular capillaries into kidney tubules Bowman’s capsule Glomerular capillaries tubule

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Interstitial fluid blood c. Most of the filtrate moves through Interstitial fluid that lies between cells and other tissues.

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d. Peritubular capillaries pick up the water and ions from the interstitial fluid and return them to the circulatory system. peritubular capillaries

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peritubular capillaries e. Hydrogen ions, wastes, and toxins flow from peritubular capillaries into tubule collecting duct. -this filtrate flows into a collecting duct and into ureters.

Summary : 

Summary filtration tubular reabsorption tubular secretion hormone action excretion Filtrate water, salts, H+, urea , metabolites ADH water salts nutrients H+ wastes toxins

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Losing a lot of water lowers the blood volume. Sensory receptors in the hypothalamus detect the deviation from the set point. The hypothalamus signals pituitary gland to secrete more ADH. ADH circulates to kidneys, makes cells of nephron distal tubules and collecting ducts more permeable to water. Kidneys reabsorb more water, so less water leaves in urine. The blood volume rises. Sensory receptors in hypothalamus detect the increase in blood volume. Signals calling for ADH secretion stop. viewing

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Ureters Ureters are long tubes that deliver urine to the bladder

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Urethra Skeletal muscle surrounds the urethra and allows voluntary control of urination. urethra bladder

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Muscle contraction: Sacromeres (basic units of muscle contraction) with actin & myosin protein fibers. -Store creatine phosphate as a source of P (phosphates). This provides energy for contractions (ADP + P = ATP)

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- Steps: a. Myosin ‘head’ attaches to actin binding site, tilts toward the center of the sarcomere, and slides the actin filament. Myosin head Actin binding site head tilts, sliding the actin filament Myosin filament Actin filament + Calcium

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- Steps: b. ATP binds to myosin head, causing myosin to release its grip on actin. Myosin head head tilts, sliding the actin filament Myosin filament Actin filament ATP

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c. Calcium released into the sarcomere causes myosin head to bind again to actin. Filament slides (contraction of muscle). - Myosin head Actin binding site head tilts, sliding the actin filament Myosin filament Actin filament + Calcium

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- Myosin head Myosin filament Actin filament + Calcium Z-band (Z-disk) Myosin and actin are anchored to Z-bands of the sarcomere, which keep the filaments aligned with each other.

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Bladder Elastic storage tank Contraction of the smooth muscle of the bladder forces urine out of the body into the urethra. Bladder infections urethra bladder Are often caused by bacteria from outside the body that travel up the urethra.

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HCO3– bicarbonate H2CO3 carbonic acid H2O + CO2 H+ + Only the urinary system can rid the body of excess H+ Kidneys work in concert with buffering systems to keep the extra-cellular fluid at the proper pH

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Drug Testing by Urine Analysis Don’t be surprised if you are served with a one hours notice to give a urine sample. Most masking agents don’t work, especially taken after short notice. Testing for drugs and metabolites Check: pH, temp., creatinine levels

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Kidney Stones Deposits from the formation of urine that collect in the renal pelvis. Sometimes they will get lodged in the ureter or urethra and have to be surgically removed. Blood and Urine analysis determine treatment . Drinking lots of water is recommended.

Renal Failure : 

Renal Failure Both kidneys are damaged to the point where they are nonfunctional Dialysis is used to restore normal solute balances temporarily Transplant is the only way to fully restore function Causes: diabetes, severe bleeding or dehydration, toxins, blockage of tubule