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Urinary System

Urinary System. The Urinary System. Kidney. Every vertebrate has a pair of kidneys Three major parts of the kidney are: 1. Cortex - outer part of kidney - contains the glomerulus, Bowman’s capsule, and blood supply to the nephron unit 2. Medulla - middle of the kidney

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Urinary System

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  1. Urinary System

  2. The Urinary System

  3. Kidney • Every vertebrate has a pair of kidneys • Three major parts of the kidney are: 1. Cortex - outer part of kidney - contains the glomerulus, Bowman’s capsule, and blood supply to the nephron unit 2. Medulla - middle of the kidney - contains the Hoop of Henle and collecting duct of the nephron unit 3. Renal Pelvis - inner cavity of the kidney - area where the collecting ducts of all the nephron units terminate

  4. Nephrons • Functional units of the kidneys are called nephrons – collect fluid from filtered blood • More than 1 million nephrons in each kidney • Part of nephron unit are found in both the cortex and medulla of the kidney • Nephrons consist of: • Bowman’s capsule • Glomerulus • Proximal convoluted tubule • Loop of Henle • Distal convoluted tubule • Collecting tubule/duct

  5. Nephrons Afferent arterioles • Supply nephrons with blood, branching into a structure called a glomerulus (capillary bed) • From the renal artery Efferent arterioles • Takes blood away from the glomerulus and to peritubular capillaries (capillary bed) • Located in cortex of kidney

  6. The Kidney Anatomyhttp://trc.ucdavis.edu/biosci10v/bis10v/media/ch24/kidney_anatomy_v2.html

  7. Renal Artery • Blood from aorta goes to the kidney by the renal artery • Kidney is only 0.5 kg and yet can hold as much as 25% of the body’s blood at once time (1.25 L in a 70 kg person) • Wastes are filtered from the blood and conducted to the bladder • Kidney filters 1600 L of blood per day, producing 1 L of urine.

  8. Kidney Function • Fluids to be processed into urine enter the Bowman’s Capsule from the blood • Capsule tapers into thin tubule called Proximal Tubule • Urine is carried from proximal tubule to the Loop of Henle, which descends into the medulla of the kidney • Urine moves through the Distal Tubule (last segment of the nephron) and into the Collecting Ducts • Urine is collected from many nephrons and merges into pelvis of kidney (Renal Pelvis)

  9. http://www.youtube.com/watch?v=glu0dzK4dbU&safety_mode=true&persist_safety_mode=1&safe=activehttp://www.youtube.com/watch?v=glu0dzK4dbU&safety_mode=true&persist_safety_mode=1&safe=active

  10. The Functions of the Kidneys: • Regulation of water levels, salt and ion concentration levels, waste levels in the blood through filtration, reabsorption and secretion processes. • Regulates osmotic pressure and pH of blood.

  11. Formation of Urine Three process are involved: • Filtration • Reabsorption all three processes occur in the nephron • Secretion Step 1: Filtration • Each nephron has an independent blood supply, glomerulus, which is a high pressure filter (8 kPa) • Dissolved solutes are forced through the walls of the glomerulus and into the Bowman’s Capsule • Water, NaCl, glucose, amino acids, urea, and drugs pass through • Plasma protein, blood cells, and platelets do not pass through – they are too large – exit glomerulus through efferent arteriole

  12. Step 2: Reabsorption • Only 1 mL of urine is formed for every 120 mL that is filtered, the remaining 119 mL is reabsorbed • As the fluid flows through the nephron, selective reabsorption of desirable things (water, Na, glucose etc) occurs by active and passive transport • Mitochondria supply the energy for active transport but it is not limitless – if you have too much glucose or NaCl in blood, it will be excreted with the urine

  13. Different parts of nephron vary in their permeabilities to substances: • Descending limb – permeable to water • Ascending limb – permeable to salt • As substances are actively transported out, high concentrations of water follow – creates an osmotic gradient and water is drawn out of the nephron and into the tissues of the kidney • Urine becomes more and more concentrated as it reaches the collecting ducts

  14. Reabsorption and Secretion Reabsorption • passive diffusion • facilitated diffusion • osmosis • active transport Secretion • active transport

  15. Active and Passive Transport Step 3: Secretion • The movement of wastes from the blood into the nephron • Nitrogen containing wastes, drugs and other toxins

  16. Parts of Nephron Proximal Tubule • Reabsorption of nutrients from filtrate by active and passive transport (salt, K+, H+,NH3, glucose, amino acids, vitamins, urea) and 85% water • H+ is secreted (from blood into nephron) and HCO3- is reabsorbed, pH control Descending Loop • Permeable to water but not salt or urea– therefore water pass out by osmosis and salt becomes concentrated in the nephron

  17. Ascending Loop • Thin part – permeable to salt and less permeable to water – salt leaves passively • Thick part – salt is actively transported out – impermeable to water • Tissue around loop becomes very concentrated with salt and creates a high osmotic pressure – water diffuses out of nephron Distal Tubule • K+, H+ secreted into nephron by active transport and HCO3- to regulate these concentrations in the body (pH) • Collecting Duct (bottom) – urea diffuses out • Concentrated urine produced and excreted

  18. Vasopressin or ADH • Antidiruretic hormone causes the kidney to increase water absorption, producing more concentrated urine • ADH produced in the hypothalamus and moves to the pituitary gland which stores and releases it when needed Example Decreased water intake – or loss through exercise or illness • Blood becomes more concentrated, increase in osmotic pressure and water moves into the blood • Causes cells in hypothalamus to shrink – signals release of ADH which travels to the kidney (causes thirst) • ADH makes the upper part of the distal tubule and the upper collecting duct permeable to water and more water is reabsorbed – urine becomes more concentrated

  19. Filtration: Osmosis, Diffusion, Non-Selective • Driven hydrostatic pressure (fluid pressure gradient) from the glomerular capillaries and the glomerular capsule. • Glomerular Hydrostatic Pressure:  Pressure pushing out of the glomerular capillaries • Colloid Osmotic Pressure: Pressure pushing into the glomerular capillaries because of differences in protein concentrations • Capsular Hydrostatic Pressure:  Pressure pushing into the glomerular capillaries from fluid already in Bowman's capsule.

  20. Water and Ion Balance • Excretory Systems (kidneys, liver, lungs, and skin) regulate the chemical composition of body fluids by removing metabolic wastes and retaining the proper amounts of water, salts, and nutrients. • Cells produce water and carbon dioxide as by-products of metabolic breakdown of sugars, fats, and proteins. • Feces are the solid waste products of digestible and indigestible material. • Ammonia (NH3), urea (a compound the body can tolerate at higher concentrations than ammonia), uric acid, and creatinine are the waste products of protein metabolism.

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