A&P II URINARY SYSTEM
Urinary Anatomy Kidney Ureter Bladder Urethra The urinary system consists of two kidneys that filter the blood, two ureters, a urinary bladder, and a urethra to convey waste substances to the outside Kidney Ureter Bladder Urethra
Functions of Urinary System The kidneys are positioned retroperitoneally on either side of the vertebral column between the twelfth thoracic and third lumbar vertebrae Clears blood of waste products of metabolism Uremia accumulation of toxic levels of wastes in blood maintain normal H2O and electrolyte balance fluid volumes blood pressure body pH
Kidneys Excretory Organ Excretes Intestine, Skin, Lungs N2 wastes Toxins H20 Electrolytes
Kidney Kidney Functions The kidneys function to regulate the volume, composition, and pH of body fluids and remove metabolic wastes from the blood in the process. The kidneys also help control the rate of red blood cell formation by secreting erythropoietin, and regulate blood pressure by secreting renin.
Microscopic Structure Nephron unit of function 1.25 million / kidney Highly vascular 20% of blood pumped / min
Functions 1) maintain fluid balance 2) maintain electrolyte balance 3) maintain acid-base balance 4) remove N2 wastes urea 5) synthesize prostaglandin's 6) influence rate of secretion of hormones ADH / Aldosterone
Nephron Anatomy 1) Glomerulus 2) Tubule Arterioles Bowman’s Capsule Proximal Loop of Henle Ascending Descending Distal Collecting
Urine Formation Actions in forming urine 1) filtration 2) reabsorption 3) secretion
Fluid is squeezed out of the glomerular capillary bed Resorption Most nutrients, water ad essential ions are returned to the blood of the peritubular capillaries Secretion c. Moves additional undesirable molecules into tubule from blood of peritubular capillaries
Glomerular Filtration blood flows through glomerular capillaries H2O and solutes filter out into Bowman’s Capsule
Glomerular Filtration blood flows through glomerular capillaries H2O and solutes filter out into Bowman’s Capsule
Glomerular Filtration pressure gradient causes filtration some kidney diseases permeability of glomerulus increases allows blood proteins to filter out into the capsule
Glomerular Filtration High blood pressure in the glomerulus forces small molecules from blood into the Bowman’s capsule
Glomerular Filtration Stress can lead to constriction of afferent arterioles causes filtration rate to lower and renal suppression “kidney shutdown”
Glomerular Filtration glomerular filtration rate directly related to systemic blood pressure ↓ BP = ↓ glomerular filtration ↑ BP = ↑ glomerular filtration (slight)
Tubular Reabsorption Glucose, amino acids, ions and other useful substances are actively transported from the tubule into blood
Glucose Reabsorption if blood glucose levels exceed threshold amount (150mg/100ml) not all glucose is reabsorbed
Reabsorption from Loop of Henle Descending Loop Water diffuses out of the tubule by osmosis
Reabsorption from Loop of Henle Ascending Loop Salts are actively transported out of the tubule, but water cannot follow because the walls of the tubule are impermeable to water
Reabsorption from Loop of Henle NaCl is trapped in interstitial fluid of kidney medulla
Reabsorption from Distal Tubules proximal tubules reabsorb 2/3 of Na+ distal tubules reabsorb 1/10 of Na+
Reabsorption from Distal Tubules distal tubules reabsorb H2O if antidiuretic hormone (ADH) is present
Distal Tubule K+, H+ and other ions, and certain large molecules are actively transported from the blood into the tubule, regulating the pH and ionic concentration of the blood
Collecting Duct As the urine passes down the duct, water moves by osmosis from the duct into the blood
Collecting Duct As the urine passes down the duct, water moves by osmosis from the duct into the blood
ADH cause distal tubules to become permeable to H2O
Regulation of Urine Volume 1) ADH 2) Aldosterone 3) Extracellular fluid volume 4) Urine solute concentration
Regulation of Urine Volume 1) ADH Presence decrease Urine Volume Absence increase Urine Volume
Regulation of Urine Volume 2) Aldosterone increases Na+ reabsorption in distal tubule with H2O following
Regulation of Urine Volume 3) urine volume relates directly to extracellular fluid volume (ECF) ECF ↓ urine volume ↓ ECF ↑ urine volume ↑ rapid ingestion of large amount of fluid and resulting increased ECF leads to increased urinary output
Regulation of Urine Volume 4) high solute concentration in urine increases urine volume by osmotic pressure untreated diabetes void large amounts of urine because excess glucose in blood “spilling over”
Influence of Kidney on Blood Pressure Renal Hypertension decreased blood flow to kidney constriction of arterioles increased BP
Ureters Tubes leading from kidney to bladder Urine moves by peristaltic movement
Ureters Renal Calculi distend ureter walls stones develop in kidney, washed out by urine into ureter distend ureter walls pain
Bladder collapsible, elastic bag Ureters 2 Bladder Urethra 1
Functions of Bladder 1) reservoir for urine 2) expels urine distended causes sensation and desire to void
Urethra passageway for eliminating urine
Urethra passageway for eliminating urine Smooth muscle with inner mucosa changes from transitional through stages to stratified squamous near end Drains urine out of the bladder and body Male: about 20 cm (8”) long Female: 3-4 cm (1.5”) long Short length is why females have more urinary tract infections than males - ascending bacteria from stool contamination
Urine H2O 95% N2 wastes Electrolytes Toxins Pigments Hormones