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URINARY SYSTEM
KidneysUretersBladderUtrethra
fao.org
naxcel.com
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THE KIDNEY
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ROLES OF THE KIDNEY• Excretion• Homeostasis• Osmoregulation• Regulation of salts in
the body• Regulation of pH• Production of a hormone (EPO)
Kidney from a cat
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Kidneys make up 1 % of body mass, but receive about 25% of cardiac output.
Kidney has two major functions:1. Filtration of blood
Removes metabolic wastes from the body, esp. those containing nitrogen
2. Regulation of:Blood volume and compositionElectrolytesBlood pHBlood pressure
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Anatomy Hilus
Renal artery enters and vein & ureter leaves Cortex Medulla
Renal pyramids and renal papillae Major and minor calyces
Renal Pelvis Ureters
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Ureters connect kidneys to urinary bladder
Urethra leads from bladder outside the body
Urine formation
Filtration Reabsorption Secretion
The Nephron.
The Nephron is the smallest functional unit of the kidney.
The number of nephrons will vary with the size of the animal. (million in human sized animals)
The Nephron
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Nephron
Functional unit of the kidney
Filtration, tubular
reabsorption, tubular secretion
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Bowman’s capsule Receives filtrate
Proximal convoluted tubule Reabsorption of glucose, amini acids,
vitamins, proteins, urea and electrolytes.
Secretion of H+ & organic acids & bases
Loop of Henle Regulates concentration of urine Secretion of Cl-, Na+, K+< Ca++, Mg+
+, urea. Reabsorption of Water, Cl- & Na+
Distal convoluted tubule Reabsorption of water and
many electrolytes & Urea Secretion – Ammonium, K+,
H+, Collecting Duct
Secretion Water, Ammonium, K+, H+
http://en.wikipedia.org/wiki/Nephron
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Bowman’s Capsule
Blood Flow
Blood Flow
Bowman’s Capsule
Glomerulus
Water
The Proximal Convoluted Tubule.
The Filtrate composition begins to change immediately.
It contains many substances which are not waste products.
Some substances diffuse passively from the PCT back into the peritubular capillaries.
Others (e.g. Na) are actively transported through the epithelial wall.
65% of all reabsorption occurs in the PCT, including 100% of glucose and amino acids (AA’s).
Loop of Henle Reabsorption of Water to
capillaries & salts to interstitial tissues in medulla.
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Distal convoluted tubule and collecting ducts
Tubular secretion to rid body of substances: K+, H+, urea, ammonia, creatinine and certain drugs
Secretion of H+ helps maintain blood pH(can also reabsorb bicarb and generate new bicarb)
Reabsorption controlled by hormones ADH Aldosterone
The Collecting Duct. The collecting ducts pass through the
medulla and into the renal pelvis.• From here urine is drained into the ureter and into the bladder.• Water permeability is regulated in the collecting duct.• The more permeable to water the more water is reabsorbed.
Reabsorption
Erythropoitin Low Oxygen in blood stimulates kidneys
to release this hormone into blood When it reaches the red marrow of the
bone erythropoitin stimulates the production of more rbcs
Micturition (Voiding)
Slide 15.25Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Both sphincter muscles must open to allow voiding The internal urethral sphincter is relaxed
after stretching of the bladder Activation is from an impulse sent to the
spinal cord and then back via the pelvic splanchnic nerves (reflex arc)
The external urethral sphincter must be voluntarily relaxed
Terms Polyuria Anuria Oliguria Oliguria Polydipsia Micturation Cystitis Glomerular nephritis Renal