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Excretory System

Excretory System. Main parts/functions. Made up of the urinary system (bladder, urethra), kidneys, liver and uses the circulatory system to rid the body of wastes Water and solute balance. Human urinary system. How is your blood filtered?. Starts at the liver

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Excretory System

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  1. Excretory System

  2. Main parts/functions • Made up of the urinary system (bladder, urethra), kidneys, liver and uses the circulatory system to rid the body of wastes • Water and solute balance

  3. Human urinary system

  4. How is your blood filtered? • Starts at the liver • Liver breaks down amino acids (proteins) from blood by removing an amino group (-NH2)  called deamination • This NH2 forms ammonia (NH3) – VERY TOXIC! • So what happen is 2–NH3 molecules + CO2 to form urea – less toxic to body • Uric acid is also produced, but from the breakdown of nucleic acids

  5. Liver also helps to transform injected toxins (heavy metals and alcohol) into less toxic forms within the body

  6. Functions of the Kidneys • Removal of wastes • Balancing blood pH • **Maintenance of water balance** • Human kidney

  7. Kidneys • **must maintain water balance • 1% water loss = thirst • 5% water loss = collapse and dehydration • 10% water loss= death • Need to intake 2L per day because we lose ~2L through perspiration, exhalation, urination

  8. In the kidneys…. 3 main regions • Renal Cortex • Outer layer of kidneys • Renal medulla • Inner layer of kidney under cortex • Renal pelvis • Where ureter connects to the kidney

  9. In the kidneys…. • Renal artery • Carries blood from aorta to kidneys • Renal vein • Drains blood from the kidney • Returns solutes and water reabsorbed by kidneys to bloodstream

  10. In the cortex/medulla….

  11. Nephron • Filtration unit found in the kidneys • Filters and absorbs substances • Produces urine • Millions of nephrons make up each kidney • Is partially in renal cortex and partially in renal medulla

  12. Inside nephron • Efferent arteriole • Carries blood from glomerulus and joins renal vein • Afferent arteriole • Carries blood from renal artery to glomerulus

  13. Inside Nephron • 1.Glomerulus • Network of capillaries • Impermeable to RBC and proteins (stay in blood) • Allows water, ions and urea to pass through capillary walls • Filtrate heads into Bowman’s capsule. • Blood enters through the afferent arteriole and leaves glomerulus through the efferent arteriole filtration

  14. Structure of the glomerulus

  15. Within the nephron • 2.Bowman’s capsule (C) • Surrounds the glomerulus • Receives Na+, Cl-, H+, glucose, amino acids and urea from glomerulus

  16. Inside the nephron • 3.Proximal tubule (Reabsorption) • Joins Bowman’s capsule to loop of Henle • Lined with many mitochondria that are used to make ATP for active transport

  17. Proximal tubule (Reabsorption) • Glucose and Na+ are actively transported back into bloodstream • Water follows due to osmosis • Cl- follows the positive ion

  18. Inside the nephron • 4.Loop of Henle (descending) [M] • Plunges into medulla region (very salty environment) • This part of the loop is permeable to water, so water flows out back into capillaries • H20 leaving the loop causes the Na+ concentration inside the loop to reach maximum concentration • Loop at this point is impermeable to solutes

  19. Inside the nephron • 5.Loop of Henle (ascending) [M] • Loop is now impermeable to water and permeable to solute • Na+ is actively transport from loop to nearby blood vessels • Cl- passively flows out as well • Allows the medulla to remain salty • Is dependent upon the need for salt (if body has lots, less is reabsorbed into bloodstream

  20. Inside the nephron • 6.Distal Tubule (re-absorption & secretion) [C] • K+ and H+ ions from bloodstream are actively transported here • Drugs taken are also reabsorbed from bloodstream here • Continues to actively transport out Na+ and osmosis of water to bloodstream

  21. Secretion • Movement of wastes from blood to nephron • K+ H+ ions, drugs like penicillin

  22. Inside the nephron • 7.Collecting duct [M] (water reabsorption) • Reclaims water back to bloodstream from filtrate to reduce water loss • Based on water levels: If a person is dehydrated, the permeability of duct increases so more water may return to the bloodstream. • At this point, the filtrate is called “urine” [1% of original filtrate]

  23. Tubular reabsorption Urine formation

  24. pH Balance • The kidney also functions to balance pH • When the pH of blood lowers (due to excess H+ ions) HCO3- (bicarbonate) can react with it to maintain pH levels • Excess H+ ions are excreted in urine

  25. pH Balance in kidney

  26. 12.2 – Kidney Disfunctions

  27. What controls the Urinary system? • Osmotic pressure –The amount of pressure exerted on water to travel out of the blood vessel • The greater the osmotic pressure the more water is reabsorbed back into the bloodstream from the distal tubule and the collecting duct • Osmoreceptors (hypothalamus) detect the difference in osmotic pressure to signal the release of the hormone ADH • ADH causes less urine to be produced by making the upper part of distal tubule and collecting duct permeable to water. • Produced in Hypothalamus gland and stored in the Pituatary gland

  28. Aldosterone • A hormone that increases the reabsorption of Na+ in the distal tubule and the collecting duct. • This increases the osmotic gradient and more water is reeabsorbed.

  29. Excretory Disorders • Urinary Tract Infection – is painful urination due to bacteria from bowels to enter urethra • More common in females due to their anatomy • If untreated may cause kidney infections

  30. Excretory Disorders • Kidney Stones – the formation of calcium crystallization in the urinary system • Can be urinated out or may require surgery

  31. Diabetes Mellitus – when the body does not release enough insulin to reduce glucose levels in the blood; will excrete large amounts of urine due to a lack of water reabsorption in the kidney • Diabetes Insipidus – defect in the ADH that does not allow for as much water reabsorption. • These people produce large amounts of urine.

  32. Nephritis • A range of diseases that cause the inflammation of the nephron. • E.g. – toxins from invading microbes can cause the glomerulus to become more permaeble to large molecules like proteins. • Since proteins can not be reabsorbed they change the osmotic gradient and more water leaves the body as urine. • Can lead to kidney damage or complete failure.

  33. Dialysis • Dialysis is the exchange of materials across a semi-permeable membrane • Hemodialysis – machine is connected to a vein and is cleaned of wastes (acts like a kidney); is external of the body • Peritoneal dialysis – a catheter is placed in abdominal cavity where dialysate is pumped through, drained and replaced every 6 hours. • Kidney dialysis

  34. Kidney Transplants 85% success rate today Preferred form of treatment Although dialysis is good, nothing can replace the workings of a real kidney

  35. The main disadvantage as with any organ transplant… • Immune system sees the new kidney as a foreign invader and acts against it. • Often patients are given immunosuppressant drugs to help with this issue. • Xenotransplants!!!!! Page 391 • Islet cell transplants • Quirks and Quarks Islet cell transplant

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