Kidneys Ureters Bladder Utrethra

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5 Excretion Homeostasis Osmoregulation Regulation of salts in the body Regulation of pH Production of a hormone (EPO)

7  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 composition Electrolytes Blood pH Blood pressure

8  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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10  Ureters connect kidneys to urinary bladder  Urethra leads from bladder outside the body

 Filtration  Reabsorption  Secretion

 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)

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15 Functional unit of the kidney  Filtration,  tubular reabsorption,  tubular secretion

16  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+

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Blood Flow Bowman’s Capsule Glomerulus Water

 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).

 Reabsorption of Water to capillaries & salts to interstitial tissues in medulla.

21  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 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.

 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) Copyright © 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

 Polyuria  Anuria  Oliguria  Polydipsia  Micturation  Cystitis  Glomerular nephritis  Renal