The Urinary System

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Human urinary tract diagram

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Regulation of the Chemical Environment Animals = avg. 70% water by weight; 2/3 within cells & 1/3

extracellular fluid (similar to marine environment surrounding earliest cells)

Water Compartments Plasma- 7% Interstitial fluid/lymph- 28% Intracellular fluid- 65%

Blood Plasma Composition Must be regulated constantly (homeostatic environment); very

selective process Monitoring/ analysis/ selection/ rejection Blood Composition is the responsibility of the EXCRETORY organs Nephridia: mollusks, annelids Malpighian tubules: insects Kidneys: vertebrates

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SUBSTANCES REGULATED BY SUBSTANCES REGULATED BY THE KIDNEYSTHE KIDNEYS

Regulation needed: Excretion of metabolic wastes Regulation of the concentrations of ions and other chemicals Maintenance of water balance Metabolic Wastes CO2

Nitrogenous compounds: (NH3) ammonia= highly toxic, must convert into nontoxic forms

Mammals convert N-wastes to UREA (carried to kidneys to mix with water for excretion)

Uric acid salts (crystalline) birds, reptiles, insects waste = whitish paste (dropping)

Ion concentrations are regulated: Na+, Cl-, H+, Mg2+, Ca2+, HCO-

3 Also excess blood sugar (glucose) Concentrations depend on amount of water in body (hydrated?

dehydrated?) 4

Some examples of strategies: Freshwater- vs.- saltwater fish

Osmosis in /out? Hypertonic / hypotonic environment? "Which must gulp water to maintain itself?" (salt glands for excretion of solutes)

Paramecium- contractile vacuoles = "bailing device" Sharks: Isotonicity with surrounding water = (high urea

tolerance)Sources of Water Loss and Gain in Terrestrial Animals Gain: drinking, eating water-containing foods, Water also gained as by-product of glucose-oxidation (0.6g

water/g glucose), protein oxidation (0.3 g water/g protein), fat oxidation (1.1 g water/g fat)

Loss: sweat glands, urine, breathing (water vapor), feces Evolutionary adaptations: kangaroo rat = nocturnal,

highly conc. urine, no sweat glands5

kidney animation

The Kidneys (2) = 10 cm long, dark red, bean- shaped

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Renal tubule- composed of a proximal (near) and a distal (far) tubule(s), connected by a loop of Henle

Nephron ends in Collecting Duct Bowman’s Capsule   Glomerulus

•Afferent arteriole- leads in to the glomerulus •Efferent arteriole- leads out

"Peritubular" capillaries = surround the nephron tubes          Venules, CapillariesLoop of HenleRenal pelvisCollecting ductDistal tubule Proximal tubule

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As blood flows though the nephrons, materials are removed from the blood, enter the nephron.

Along the way, some materials are re-absorbed back into the bloodstream (osmoregulation and selection happen to maintain blood concentrations) 

Filtration and removal of metabolic wastes from the blood Urea (nitrogen waste from proteins) Excess Salts Excess Water Excess Glucose (sugar) Excess Minerals (Na+, K+, Ca2+)

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Filtration: materials from the blood are forced out of the glomerulus into the Bowman’s capsule (“filtrate”).

Reabsorption: some of the substances that left the blood need to be returned, for homeostasis purposes, and so are selectively diffused or actively transported out of the proximal convoluted tubule back into the capillaries

Secretion: final “tweak”. Some more wastes and H+ ions are secreted from the blood into the distal convoluted tubule

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diagram of the "what" and "where"  HERE10

Human urinary tract diagram

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kidney animation Human urinary tract diagram

ADH (antidiuretic hormone)- formed by hypothalamus, released by pituitary gland Increase permeability of the Collecting ducts (of the nephrons) to

water—more water moves back into blood (decreases water excretion)

ADH release is triggered by BP sensors in walls of blood vessels (especially dehydration, hemorrhage…)

Alcohol inhibits ADH secretion; symptoms Aldosterone - produced by adrenal cortex; causes

reabsorption of NaCl into blood and secretion of K+ into nephron

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