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Biology 20

Biology 20. Excretion General, Structure & Function, Four Steps to Urine Formation Hormones, Composition of Urine. Introduction. Humans are 70% water 1/3 of this is in plasma Blood – carries nutrients, picks up waste Wastes need to be removed

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Biology 20

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  1. Biology 20 Excretion General, Structure & Function, Four Steps to Urine Formation Hormones, Composition of Urine

  2. Introduction • Humans are 70% water • 1/3 of this is in plasma • Blood – carries nutrients, picks up waste • Wastes need to be removed • Composition of fluids need to be kept in balance • Excretion: monitor, analyze, select, reject

  3. EXCRETION • Excretion is the process of removing metabolic wastes from the body. • During the metabolic processes of the body, wasteproducts are removed from the site of production by the blood. • As these wastes accumulate, the kidney removes them from the blood and excretes them to the environment. • The excretory product becomes urine.

  4. Excretion • Process of removing cellular waste • Balance pH of blood • Maintain water balance • Happens in Kidney

  5. FUNCTIONS OF THE EXCRETORY SYSTEM • Functions: • To maintain homeostasis • Regulates and stabilise the internal environment by controlling 4 groups of chemicals • Water: • Excretion of metabolic wastes: Elimination of poisonous by-products of chemical reactions: • Osmoregulationfluid and salt regulation: regulation of hydrogen, sodium, potassium, calcium, chloride ions: • Regulation of body fluid composition: Removal of essential nutrients that dangerous in excess:

  6. WASTE PRODUCTS • The principle metabolic wastes in most animals are: • Carbon Dioxide – is excreted through the respiratory surfaces • Water – excreted through respiratory surfaces, skin as sweat as well as kidneys • Nitrogenous Wastes – products of protein and nucleicacid digestion

  7. Waste Products Carbon Dioxide Water Nitrogen Wastes

  8. NITROGENOUS WASTES • Ammonia – The first metabolic product of amino acid deamination – hydrolysis (protein digestion) • highly toxic • cannot accumulate in body • must be converted into less toxic uric acid and urea • Uric Acid – produced from ammonia • not very soluble – can be excreted as a paste with little water loss • non - toxic

  9. Deamination & Urea • Proteins – contain a nitrogen molecule • Amino acid – building blocks of protein • Nitrogenous base • Removal of N and H • Occurs in the liver • Byproduct – ammonia • Toxic substance • Ammonia combines with CO2 to form urea • Urea –less toxic • Uric acid – waste product from the breakdown of nucleic acids (DNA)

  10. NITROGENOUS WASTES • Urea – converted from ammonia • less toxic than ammonia • produced in the liver • can be excreted in concentrated form • requires more water to excrete than uric acid

  11. Urinary System

  12. 1. Vena cava 2.Right Kidney 3. Ureter 4. Bladder 5. Urethra 6. Aorta 7. Left Kidney 8. Renal Vein 9. Renal Artery

  13. Urinary System Adrenal gland Kidney Ureters Bladder Urethra

  14. ORGAN: Function • Kidney: site of blood filtration • Renal artery: brings blood to kidney • Renal vein: brings blood back to heart • Ureter: Brings waste TObladder • Bladder: Temporary urine storage site • Urethra: Brings waste FROM bladder, out of system

  15. Structure Function Cortex Outer layer Where filtration occurs Medulla Inner area Water reabsorption Renal Pelvis Collects waste Joins kidney to ureter The Kidney

  16. STRUCTURE AND FUNCTION OF KIDNEY • Three distinct regions of the kidney • Cortex – outer region • Medulla – just below cortex • Pelvis – a hollow chamber within the medulla • The cortex and medulla of each kidney are made up of a approximately one millionnephrons

  17. Renal Cortex The Kidney Renal Medulla Renal Pelvis Ureter Nephrons Renal Artery Renal Vein

  18. STRUCTURE AND FUNCTION OF KIDNEY • NEPHRON • the structural and functional unit of the kidney

  19. Label the following diagram Bowman’s Capsule Glomerulus Renal artery Distal tubule Proximal tubule Renal vein Collecting duct Capillary bed Loop of Henle

  20. STRUCTURE FUNCTION Afferent arteriole Brings blood to glomerulus Efferent Arteriole Leaves glomerulus, goes to vein Glomerulus Ball of capillaries – site of filtration Bowman’s Capsule Filter Proximal Tubule First tube in nephron. From BC. Reabsorption of Water Distal Tubule Leads to collecting duct Collecting duct Empties waste into renal pelvis Renal pelvis Collecting site for all nephrons – waste out to ureter

  21. NEPHRON the structural and functional unit of the kidney BOWMAN’SCAPSULE a double walled chamber – start of the tubule. STRUCTURE AND FUNCTION OF KIDNEY

  22. The Nephron Bowman's Capsule

  23. GLOMERULUS network of capillaries within the Bowman’s capsule high pressure (4x higher than in capillaries) STRUCTURE AND FUNCTION OF KIDNEY

  24. The Nephron Bowman's Capsule Glomerulus The Nephron

  25. STRUCTURE AND FUNCTION OF KIDNEY • PROXIMAL TUBULE • active transport of many valuable substances back into blood network • glucose • amino acids • sodium

  26. The Nephron Proximal Convoluted Tubule

  27. STRUCTURE AND FUNCTION OF KIDNEY • PROXIMAL TUBULE • What doesn’t get absorbed? • urea • other toxic substances • some salt • much of the water

  28. STRUCTURE AND FUNCTION OF KIDNEY • LOOP OF HENLE • the long hair-pin turn!!

  29. The Nephron Loop of Henle

  30. LOOP OF HENLE the long hair-pin turn!! some of the remaining water and salt will be returned to the blood lies in the medulla which is relatively salty (hypertonic) STRUCTURE AND FUNCTION OF KIDNEY

  31. STRUCTURE AND FUNCTION OF KIDNEY • DISTAL TUBULE and COLLECTING DUCTS

  32. The Nephron Distal Convoluted Tubule

  33. The Nephron Collecting Duct

  34. STRUCTURE AND FUNCTION OF KIDNEY • DISTAL TUBULE and COLLECTING DUCTS • More water reabsorption • This depends on the presence of certain hormones • (ADH) Anti diuretic Hormone • Exact amounts of substances are reclaimed to the blood • very precise

  35. Urine Formation • Depends on three functions: • Filtration • Movement from blood – Bowman’s capsule • Reabsorption • Transfer of needed nutrient back INTO blood • Tubules • Secretion • Movement of material from blood back into nephron

  36. Four Steps to Urine Formation 1)FILTRATION • Occurs at the junction of the glomerulus and the wall of the Bowman’s capsule • Each glomerulus receives blood from an afferent arteriole and discharges its blood into an efferent arteriole (hypertonic). • Fluid and dissolved materials (nutrients, wastes, ions) in the blood plasma pass from the glomerulus into Bowman’s capsule • due to a local increase in blood pressure within the glomerulus

  37. Four Steps to Urine Formation 1) Filtration (con’t) • this material is then called nephric filtrate • blood cells, plasma proteins and platelets are too large to pass through the wall of the capillary and therefore remain within the capillary.

  38. Four Steps to Urine Formation 2) REABSORPTION • in the proximal tubule • returns about 99% of filtrate to the blood • efferent arteriole feeds second capillary network that surrounds the tubule • this network receives reabsorbed substances • eventually leads to renal vein

  39. Four Steps to Urine Formation 2) REABSORPTION (con’t) • Water rushes into the blood because of osmosis Problem • Not enough water is returned this way. Solution • Just actively transport water into the blood right?

  40. Wrong!!! There is no way of ACTIVELY transporting water So how can we transport more water into the blood?

  41. Solution 2) Reabsorption (con’t) • active transport of solutes into the capillary bed • glucose • amino acids • vitamins • inorganic ions (Na+) • water is passively reabsorbed from the proximal tubule as these solutes are actively removed from the filtrate

  42. Four Steps to Urine Formation 2) Reabsorption (con’t) • Reabsorption and the distal tubule. • A more selective, precisely regulated reabsorption occurs in the distal tubules • Additional quantities of salts and water may be reabsorbed • The exact amount of each substance reclaimed occurs in the distal tubules. • excess is excreted in urine • e.g. glucose and diabetes

  43. Four Steps to Urine Formation 3) SECRETION • This is the last chance for anything to leave the blood and enter the urine • Active transport • Occurs in the distal tubule and collecting duct • Hydrogen ion secretion – helps regulate blood pH • Distal tubule • Na+ moves into the blood and H+ moves into the tubule filtrate • blood pH increases (ranges 7.3 - 7.4) • urine pH decreases (ranges 4.5 - 8.5)

  44. Four Steps to Urine Formation • potassium secretion • prevents accumulation of potassium that can create neural and muscular problems • some drugs are removed from the body by secretion • substances eliminated in this manner are • creatine – by product of protein metabolism • potassium • penicillin

  45. Four Steps to Urine Formation 4) Elimination • Pathway • collecting duct • renal pelvis • ureter • urinary bladder • urethra • environment

  46. Nephron Function Summary NH 3 + K Reabsorption CORTEX Amino Acids Na Water Glucose Water Secretion Na Filtration Na Water Na Water Na Water Na ADH Na Water MEDULLA Na Active Transport Water Water Passive Transport

  47. What is in urine? • Excess sugars • Excess salts • Excess H+ ions • Urea and uric acid • Excess H2O

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