Chapter 10: Urinary System & Excretion
Organs of Urinary System Kidneys (2) form urine Ureters (2) Carry urine from kidneys to bladder Bladder Stores urine Urethra Carries urine from bladder to outside of body
Functions *Excretion of metabolic wastes - not including feces (digestive waste) *Elimination - Forms urine - eliminate from body
Functions *Homeostatic Regulation: Maintenance of water/salt balance Maintenance of acid/base balance Blood volume RBC concentration Hormone secretion Renin - secreted by kidneys - allows kidneys to regulate water/salt balance Erythropoietin - secreted by kidneys - stimulates red blood cell production
Kidney Renal Cortex Renal Medulla Renal Pyramids Renal Pelvis
Kidney - Nephron Nephrons Functional unit Produces urine Over 1 million per kidney
Nephron Structure 2 Main Parts: Glomerulus Collection of capillaries Tubules: Proximal Convoluted Tubule Loop of Nephron Distal Convoluted Tubule Collecting Ducts
Nephron Glomerulus Collection of capillaries Filters blood plasma (blood in, filtrate out)
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Nephron Tubules: Proximal Convoluted Tubule Reabsorption of filtrate (~90 occurs here) Filtrate contains things body can use! Loop of Nephron Gets rid of water, pushes out salt Distal Convoluted Tubule Movement of molecules from blood into tubule Collecting Ducts Absorbs water, concentrates urine
Steps of Urine Formation 1. Glomerular Filtration - Water, salt, nutrients move into capsular space to form filtrate 2. Tubular Reabsorption - Useful substances are reabsorbed into bloodstream 3. Tubular Secretion - Removes toxins, etc., adds to filtrate (certain drugs, creatinine) 4. Water Conservation - Collecting Ducts reabsorb water to concentrate urine
Glomerular Filtration Water, blood cells, small solutes pass through capillary membrane into intracapsular space How? Osmotic pressure Hydrostatic pressure Membrane permeability
Tubular Reabsorption Useful substances reabsorbed back into bloodstream (99% of filtrate reabsorbed) (PCT) Tubular Secretion Removal of toxins, etc from blood into tubular fluid
Water Conservation Collecting Ducts Reabsorbs water the body can use Concentrates urine
Review Step Location Function Glomerular Filtration Tubular Reabsorption Tubular Secretion Water Conservation Glomerulus Proximal Convoluted Tubule Loop of Nephron Distal Convoluted Tubule Collecting Ducts Nutrients move inside capsule to form filtrate Useful substances are reabsorbed into bloodstream Removes substances from bloodstream - added to filtrate Reabsorbs water, concentrates urine
Urinary System Organs Ureters (2) Carry urine from kidneys to bladder Bladder Stores urine Urethra (1) Carry urine from bladder to outside of body
Kidney Blood Supply *Kidneys receive ~25% of CO *Kidneys 0.4% of body weight *1200ml/min. of blood flow (~40.5oz)
Nephron Blood Supply Peritubular Capillaries Afferent/Efferent Arteriole
Putting it all Together Filtration Blood Blood Filtrate Urine to Ureters & Bladder
Urine Formation Review Good things Move from tubules back into bloodstream Waste products Move from bloodstream back into tubules for excretion
In the End Filtration -Filtrate is fully filtered becomes urine - flows into ureters for removal -Blood flow from peritubular capillaries -Collected reusable products -Has excreted waste products -Returns to venous circulation
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Regulatory Functions of Kidney Maintain water/salt balance of blood Reabsorption of salt & water in tubules If dehydrated, kidneys reabsorb salt and water If overhydrated, kidneys reabsorb salt and water Plays a role in blood pressure - remember effect of fluid volume on blood vessels This process is regulated by hormones
Regulatory Functions of Kidney Maintains acid/base balance Reabsorption of Hydrogen ions (H+) in tubules H + = acidic H + = alkaline If blood is too acidic, kidneys reabsorb H +, and therefore eliminate more in urine If blood is too alkaline, kidneys reabsorb H +, and therefore keep more H + in bloodstream
Alcohol inhibits hormone secretion (atrial natriuretic, ANH) Less water is absorbed ( urine amount) dehydration
Kidney Disorders Urethritis infection of urethra Cystitis infection in bladder Kidney Stones formation of hard granules in renal pelvis
Kidney Stones 23-28
Treatment Dialysis (Hemodialysis, Peritoneal) Replaces function of dysfunctioning kidney Blood is passed through membranous tube (outside of body) Waste is removed from blood Substances added to blood 3-6 hour treatment needed only 2 times /week
Composition of Urine Appearance Colorless - yellow Normally clear Odor Distinctive but not repellent Specific Gravity Ratio of urine density compared to density of water Urine 1.020 1.028 1.010 is isosthenuric ph 4.5-8.2 (usually 6) Chemical Composition Water (95%) Solutes (5%)
Chemical Composition: Water (95%) Solutes (5%) Urea (end product of protein breakdown) NaCl K+ Phosphate Sulfate Creatinine Uric acid 23-31
Urine Volume23-32 Normal volume - 1 to 2 L/day Polyuria > 2L/day Oliguria < 500 ml/day Anuria - 0 to 100 ml/day
Abnormal specific gravity values may indicative of Reduced specific gravity diabetes insipidus certain renal diseases excess fluid intake diabetes mellitus Raised specific gravity dehydration adrenal insufficiency nephrosis congestive cardiac-failure liver disease Constant specific gravity chronic renal disorder
Diabetes Insipidus Inability of kidney to concentrate urine Sx: PU/PD- polyuria:excessive urination & excessive thirst (polydipsia) Cause: Deficiency of ADH normally functions to aid kidneys in water reabsorption Rx: Desmopressin (replaces ADH)