Lecture 18


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Lecture 18

  1. 1. Lecture 18: Nutrition/Digestion/Urinary Covers Chapters 34 & 35
  2. 2. What nutrients do animals need?* • Nutrients that provide energy: – Carbohydrates – Lipids – Proteins • Other nutrients – Minerals – Vitamins – Water
  3. 3. Carbs provide energy • Carbs broken down into glucose for cellular respiration, makes ATP • Glucose that is not needed at time of ingestion and breakdown is stored as glycogen in liver and muscle • We can only store 1 day’s worth of glycogen, so any excess glucose left after all possible glycogen has been created is stored as fat.
  4. 4. Fats/oils can also provide energy • *Most concentrated energy source • *More than TWICE as many Calories by weight as carbs or proteins (need less of it to get same amount of Calories) • *9 Calories per gram (fats), 4 calories per gram (carbs & proteins) • Fats/oils can be broken down into fatty acids (monomers) which can enter cell respiration and also make ATP
  5. 5. Proteins • Broken down into individual AA’s • AA’s used to make new proteins for the body (structural proteins, enzymes, transport molecules and cell membranes) • If carbs and fats are not available, AA’s from ingested protein can enter cell respiration to make ATP. In extreme starvation, protein from muscle tissue will break itself down into AA’s for cell respiration. (muscle-wasting)
  6. 6. Vitamins • Organic molecules needed in small amounts for normal cell function, growth and development. • Many vitamins are required for proper function of enzymes that control metabolic reactions in the body* – Fat-soluble: A, D, E, K • A used to make light-capturing molecule rhodopsin • D required for normal bone formation • K required for blood clotting – Water-soluble: C, B. Most act as coenzymes, working with enzymes to promote reactions that supply energy or synthesize biological molecules • Vit B-1 is part of a coenzyme that converts pyruvate to acetyl Co-A • Vit B-2 is part of FAD+
  7. 7. Minerals • Elements that play important roles in nutrition • Calcium, magnesium, phosphorus are major constituents of bone and teeth • Sodium, potassium and calcium needed for muscle contraction and conduction of nerve impulses • Iron is a component of hemoglobin • Iodine found in thyroid hormones
  8. 8. Water • All metabolic reactions occur in a “watery” atmosphere (cytoplasm, blood, etc) • Water contributes to blood, saliva, lymph, and cytoplasm, urine • Needed to carry nutrients, eliminate wastes
  9. 9. Evolution • Humans evolved to eat whenever possible because food was not always be readily available • Today, most humans eat more than they need • Store excess carbs and fat as body fat.
  10. 10. Calorie • Amount of energy needed to raise 1 gram of water by 1 degree celsius • Food calorie content is measured in units of 1,000 calories, also known as Calories • Humans burn 70 Calories per hour at rest • Humans burn up to 20 Calories PER MINUTE while working out • People differ in their metabolic rate: speed at which reactions that release energy occur
  11. 11. How does digestion occur?* • Ingestion: food brought in • Mechanical digestion: food is physically broken down (larger surface area) • Chemical digestion: digestive chemicals and enzymes break down food molecules into small subunits (monomers) • Absorption: monomers transported out of digestive tract into the blood • Elimination: indigestible material is eliminated
  12. 12. The Human Digestive Tract Fig. 34-12 Oral cavity, tongue, teeth: Stomach: Breaks down food and begins protein digestion Small intestine: Food is digested and absorbed Rectum: Stores Salivary glands: Secrete lubricating fluid and starch-digesting enzymes Pharynx: Shared digestive and respiratory passage Epiglottis: Directs food down the esophagus Esophagus: Transports food to the stomach Liver: Secretes bile (also has many non-digestive functions) Gallbladder: Stores bile from the liver Pancreas: Secretes pH buffers and several digestive enzymes Large intestine: Absorbs vitamins, minerals, and water; houses bacteria; produces feces
  13. 13. How do humans digest food? mouth to stomach* • Ingestion • Mechanical Digestion: teeth break down food • Chemical Digestion: Three salivary glands produce saliva: • Contains enzymes which begin to breakdown carbs (chemical digestion) • Contain bacteria-killing enzymes and antibodies • Lubricate food • Some molecules dissolved and tongue identifies taste • We swallow food: pharynx >> epiglottis >> esophagus>>stomach (propelled to stomach via peristalsis)
  14. 14. How do humans digest food? Stomach* • Food enters stomach (muscular sac) • Sphincter muscles prevent regurgitation to esophagus and regulates exit of food into small intestine • Mechanical Digestion: Churning contractions • Chemical Digestion: Secretions from gastric glands breakdown proteins • Mucus: coats stomach to protect it from acidic environment • Hydrochloric acid: pH of 1-3, destroys microbes • Pepsinogen: converted to pepsin when in contact with HCL, pepsin breaks proteins down into short chains of AA’s • Other important events: – Hormone gastrin regulates digestion – Food now called CHYME – Peristaltic waves propel chyme to small intestine
  15. 15. How do humans digest food? Small Intestine* • Food enters small intestine • Chemical Digestion: enzymes and other digestive secretions from 3 sources digest/absorb food • Liver: makes bile, which dissolves ingested fats into microscopic particles • Pancreas : secretes pancreatic juice, which contains enzymes: amylase (carbs), lipase (fats), proteases (proteins) • Cells lining small intestine: secrete yet more enzymes • Absorption: Small intestine is 8-10 feet long with numerous folds and projections (villi and microvilli) giving it a surface area 600 times larger than if it was a smooth tube (total 2700 square feet!)
  16. 16. How do humans digest food? Small Intestine* • Absorption: Each villus is provided with rich supply of capillaries and a lymph capillary (lacteal). All of the following are absorbed: – Water (via osmosis) – Monosaccharides – Amino acids and short peptides – Fatty acids: absorbed, flow through lymphatic system to be dumped into blood – Vitamins & minerals
  17. 17. The Structure of the Small Intestine Fig. 34-16 villi capillaries arteriole lymph vessel venule lacteal microvilli intestinal gland fold of the intestinal lining (a) Small intestine (b) A fold of the intestinal lining (c) A villus (d) Cells of a villus
  18. 18. How do humans digest food? Large Intestine • 5 feet long in humans • Colon>>rectum>>anus • Indigestible cellulose from fruits and vegetables, other unabsorbed nutrients and water enter from the small intestine* • Flourishing colonies of bacteria use the waste to thrive and MAKE vitamins B and K • Any remaining material compacted into feces
  19. 19. Hormonal control of digestion • As food enters and moves through system, it stimulates production of: – Gastrin: released INTO BLOODSTREAM in response to digested proteins in the stomach. It stimulates more acid secretion in stomach…gastrin production slows as pH in stomach lowers – Secretin & Cholecystekinin: released by duodenum, and increase bile and pancreatic juice secretion and regulates the speed at which chyme moves through small intestine
  20. 20. Basic functions of human urinary system* • Filtration of blood, removing water and small dissolved substances (including ions and nutrients like AA’s and glucose) and waste • Selective reabsorption of nutrients and water (back into the blood) • Secretion of excess water, drugs, excess ions and dissolved wastes (into the urine) • Concentration of urine • What wastes? A byproduct of protein breakdown is ammonia (NH3). It is toxic to humans. Liver changes it to urea (less toxic) Kidneys remove this from the body.
  21. 21. Urine Formation and Concentration Fig. 35-6 1 Tubular secretion: Additional wastes are actively transported into the proximal and distal tubules from the blood 3 4 Filtration: Water, nutrients, and wastes are filtered from the glomerular capillaries into the Bowman’s capsule of the nephron Tubular reabsorption: In the proximal tubule, most water and nutrients are reabsorbed into the blood 2 Concentration: The loop of Henle produces a salt concentration gradient in the extracellular fluid; in the collecting duct, urine may become more concentrated than the blood as water leaves by osmosis blood leaving the glomerulus loop of Henle blood entering the glomerulus Bowman’s capsule collecting duct distal tubule proximal tubule
  22. 22. Urea Formation and Excretion Fig. 35-2 ammonia NH3 amino acid Proteins in food are digested Amino acids are carried in the blood to body cells The cells convert the amino groups (-NH2) to ammonia, which is carried in the blood to the liver 1 2 3 urea The liver converts ammonia to urea, which is less toxic In kidney nephrons, urea is filtered into the urine Urea is carried in the blood to the kidneys 4 6 5
  23. 23. Urinary System Maintains Homeostasis* • Regulating levels of sodium, potassium, chloride and calcium • Maintaining proper pH of the blood by regulating hydrogen and bicarbonate ion concentrations • Regulating water content in the blood • Retaining important nutrients such as glucose and amino acids • Eliminating cellular waste products like urea • Secreting substances that regulate blood pressure and blood oxygen levels (HORMONES)
  24. 24. Structures of human urinary system* • Kidney: paired organs just above the waist, on either side of spinal column. Blood is filtered and urine is produced • Ureters: carry urine to bladder • Bladder: temporary storage of urine • Urethra: tube carrying urine out of body
  25. 25. Urinary System
  26. 26. Kidney in more detail • Blood supply from Renal Artery: nearly 1 quart per minute • Capillaries bring blood to nephron, then surround nephron, making bloodstream available for more absorption • Three parts to the kidney: – Cortex: outer layer – Medulla: inner layer – Pelvis: branched, funnel-like chamber that collects urine and sends it to bladder
  27. 27. Kidney in Detail
  28. 28. Nephron: Functional unit of kidney* – Bowman’s capsule: blood from renal artery/capillary enters here: filtration – Proximal convoluted tubule: reabsorption of ions, water & nutrients, secretion of more waste and drugs from blood into tubule – Loop of Henle: reabsorption of water and ions • The extracellular fluid concentration in the medulla is high…this forces more water to be absorbed) – Distal convoluted tubule:reabsorption of ions, secretion of drugs and excess ions – Collecting duct and tubule: reabsorption of H20 – final concentrated form of urine moves through ureter to bladder where it is stored until we urinate
  29. 29. collecting duct distal tubule proximal tubule glomerulus Bowman’s capsule arterioles venule branch of the renal vein branch of the renal artery loop of Henle capillaries An Individual Nephron and Its Blood Supply Fig. 35-5
  30. 30. Fig. E35-2 FILTRATION TUBULAR REABSORPTION & TUBULAR SECRETION URINE CONCENTRATION renal cortex renal medulla osmosis diffusion active transport Bowman’s capsule loop of Henle proximal tubule distal tubule 1 2 3 4 5 6 7 8 H2O* H2O H2O* H2O* H2O H2O H2O H2O NaCI urea NaCI NaCI NaCI H+ NH3 some drugs Na+ nutrients HCO3 – Ca2+ Cl– K+ collecting duct H+ K+ some drugs (extracellular fluid) NaCl Ca2+
  31. 31. Hormonal control of kidneys: renin-angiotensin • Kidneys release renin in response to low BP • Renin catalyzes formation of angiotensin in bloodstream • Angiotensin – Stimulates proximal tubules to reabsorb more Na+, and water follows – Stimulates ADH release from pituitary: increases H2O absorption from collecting duct/tubule – Causes artierioles throughout the body to constrict, increasing blood pressure
  32. 32. Hormonal control of kidneys: erythropoetin • Released by kidneys when blood oxygen is low • Stimulates bone marrow to make more RBC’s • More RBC’s can carry more O2 • Blood oxygen level up
  33. 33. Hormonal control of kidneys: Vasopressin/Anti-Diuretic Hormone • Secreted by pituitary gland and carried in bloodstream to kidney • It causes the increased production of aquaporins (channel proteins that reabsorb water) therefore allowing more H20 to be reabsorbed to the blood. • If blood osmolarity (amount of solids/liquids) goes up, more ADH is released and more water reabsorbed to keep blood diluted