Chapter 28 EXCRETION

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review questions

Background from Introductory Biology Courses

1. Online Learning Center for Hole's Human Anatomy & Physiology
   1. Chapter 20 Excretion
   2. check out the other resources such as the study outline, flash cards, animations, etc.
2. On-Line Biology Book by M. J. Farabee 
   1.  Excretory System
3. Kimball's Biology Pages
   1. Excretion in Mammals, the Kidney from Kimball's Biology Pages
4. The Kidney from Wikipedia

1. The Mammalian Excretory System consists of
   1. The Kidney
   2. ureter
   3. bladder
   4. urethra
2. Vertebrate kidneys have six roles in homeostasis
   1. Ion balance
   2. Osmotic balance
   3. Blood pressure
   4. pH balance
   5. Excretion
   6. Hormone production
3. The mammalian nephron consists of following functional parts
   1. Bowman’s Capsule
   2. Proximal Convoluted Tubule
   3. Loop of Henle
   4. Distal Convoluted Tubule
   5. Surrounded by a specific vasculature
4. Kidney Structure
   1. Cortex
   2. Medulla
5. Terrestrial Animals
   1. Animals that produce more concentrated urine have a longer loop of Henle and a thicker medulla
6. Fundamentals of Excretion
   1. About 20-25% of the total cardiac output goes to the kidneys
7. Urine Production
   1. (Ultra)Filtration
   : hydrostatic pressure-driven flow
   1. primary urine
   2. Reabsorption
   3. Secretion:
   4. Excretion
      1. definitive urine
8. NEPHRON
9. Renal Corpuscle
   1. Blood pressure forces fluid from the blood in the glomerulus into the lumen of Bowman’s capsule
   2. Ultrafiltration is non-selective
10. Tubule Regions
    1. Proximal tubule – reabsorption begins
    2. Loop of Henle – most reabsorption occurs; divided into the descending limb, the loop, and the ascending limb
    3. Distal tubule – reabsorption is completed for most solutes
    4. Collecting duct – drains multiple nephrons

1. Reabsorption and Secretion
   1. Primary urine is isosmotic to blood
   2. Most water and salt is reabsorbed
   3. Secretory products: K⁺, NH₄⁺, H⁺, pharmaceuticals, and water-soluble vitamins
   4. Each zone of the nephron possess specific transporters
2. Proximal Convoluted Tubule
3. Loop of Henle
   1. Descending limb
   2. Ascending Limb
      1. thin
      2. thick
4. Distal Convoluted Tubule
5. Collecting duct
6. Regulation of Urinary Function
   1. Endocrine hormones affect kidney function
   2. Diuretics
   3. Antidiuretics
7. Vertebrate Kidney: Structure and basic function
8. BOX 28.2 How Renal Function is Studied
9. The rate at which the kidney filters blood plasma is called the glomerular filtration rate (GFR).
10. Inulin and Creatine are used to measure GFR
11. V x U = GFR x P
12. Solving for GFR (V_filtrate)
13. Clearance measurements
    1. C = GFR = V_urine* (U / P)
    2. Urine flow: V_urine = 1.2 ml/min
    3. ammonia in urine: = 0.0025 mg/ml
    4. NH₃ in plasma = 0.00002 mg/ml
    5. GFR = 1.2 * 1.25 = 150 ml/min
    6. 0.0005 mg/ml has been secreted
14. Example for Glucose
    1. Normal plasma glucose = 1 mg/ml
    2. Urine flow: V = 1.2 ml/min
    3. glucose in urine: = 0 mg/ml
    4. If glucose in plasma = 3 mg/ml
    5. C = GFR = V * (U / P) = 0 = 100% resorption
    6. Filtration rate is 125 ml/min
    7. 375 mg/min of glucose is resorbed
    8. 125 ml/min * 3 mg/ml
    9. Tubular maximum
15. Alcohol and Caffeine
16. Figure 28.22 The posterior gut and Malpighian tubules of an insect
    1. The Malpighian tubule is the insect equivalent to the vertebrate kidney
    2. Primary urine is formed by secretion, not filtration
17. Figure 28.22 The posterior gut and Malpighian tubules of an insect
    1. Malpighian tubules are unique to terrestrial arthropods
    2. System has up to 200 tubules that open into hindgut (with the other end blind in the hemocoele).
    3. Primary urine is formed by secretion, not filtration
18. Excretion in Insects
19. Excretion in Insects
20. Fig. 28.4 Nitrogen Excretion
    1. Ammonia produced during amino acid breakdown is toxic and must be excreted
    2. Ammonia (ammonioteles)
    3. Urea (ureoteles)
    4. Uric acid (uricoteles)
    5. Form of Nitrogenous waste is related to reproductive strategy and habitat
21. Nitrogen Excretion: General
22. Nitrogen Excretion: Ammonia
23. Nitrogen Excretion: Urea
24. Nitrogen Excretion: Uric Acid
25. role of the cloaca
26. Gout

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