1. Homeostasis in the urinary system

2. Function-maintenance of homeostasis
a. Regulation of water content in the blood
In the case of dehydration, sensors in the brain stimulate the release of the hormone ADH (antidiuretic hormone also called vasopressin)
ADH is released from the pituitary
It passes through the blood to the kidneys where it stimulates the release of water back into the blood from the distal tubule and the collecting duct.
When water balance is normal, the ADH secretion is stopped.
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4. Penicillin, salicylates (aspirin) excreted
b. Regulation of levels of molecules in the blood
Penicillin, salicylates (aspirin) excreted
glucose, proteins, and amino acids are all reabsorbed.
phosphate, sulfate, lactate, vit. C all reabsorbed.
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5. Most important buffer system is bicarbonate ion (HCO3- )
c. Maintenance of blood pH
Most important buffer system is bicarbonate ion (HCO3- )
buffers maintain constant pH
kidney reabsorbs bicarbonate when blood is acidic and produces bicarbonate to further buffer the blood.
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6. d. Regulation of blood pressure and oxygen content
when blood pressure falls, kidneys release renin into the blood. This causes formation of angiotensin.
angiotensin causes arterioles to constrict increasing blood pressure. Constriction also causes less blood to be filtered, maintaining water balance and further increasing blood pressure.
for low oxygen levels, kidneys release erythropoietin, stimulating red blood cell growth
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7. Cross Section of a Kidney
Biology: Life on Earth (Audesirk)
Renal Pelvis
Renal Cortex
Cross Section of a Kidney
Renal Artery
Nephron
Renal Medulla
Renal Vein
Renal Pelvis
The cross section shows the blood supply and internal structure of a kidney. The renal artery, which brings blood to the kidney, and the renal vein, which carries the filtered blood away, branch extensively within the kidney. The two are joined by a highly permeable capillary network through which substances are exchanged between the blood and the nephrons. A nephron, considerably enlarged, is drawn to show its orientation in the kidney. The renal pelvis is the branched collecting chamber that funnels urine out of the kidney.
Ureter
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8. Regulation of Water in Blood
Biology: Life on Earth (Audesirk)
Regulation of Water in Blood
Sensors in hypothalamus gauge osmotic concentration
Deviations cause posterior pituitary to turn ADH release on or off
ADH restores blood osmotic concentration
Red = increased osmotic concentration
Green = decreased osmotic concentration 1 5 2
The water content of the blood is regulated in part by a negative feedback mechanism. Sensors in the hypothalamus gauge the concentration of solutes in the blood; deviations from a set point cause the anterior pituitary gland to turn on or turn off a release of the hormone ADH. Any perturbation of the system (for example, by dehydration) triggers a change that will restore blood solute concentration to the appropriate level (red arrows indicate increased osmotic concentration; green arrows indicate decreased concentration). 3 4
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9. Chapter 30
The End