The Urinary System Objectives Function Evolution (Smith, role of the jaw) Anatomy Kidney structure Composition of nephrons Identification of nephron components Excretory components One objective is to be able to identify these cells Urinary System - Function in Homeostasis Rid body of waste (urea, uric acid, creatinine,salts) Preserves constancy of extracellular fluid in composition, volume, and pH Endocrine function a) Secrete erythropoietin - red blood cell production b) Produces renin - aldosterone release Role of the jaw Fresh water Salt water PORTAL ARTERIOLE Arterial Portal System Function of Capillary Portal portal system? Arteriole Capillary = 1st afferent arteriole Local change efferent ARTERIOLE, and PERITUBULAR in blood CAPILLARIES composition where first 2nd capillary modifies blood and second allows the 1st 2nd change in composition to affect local cells near it. hilum hilum Efferent Arteriole, Afferent Arteriole, and Peritubular Capillaries Kidney Function Based on Combination of: • Filtration • Active Secretion • Passive Diffusion • Selective Absorption http://www.youtube.com/watch?v=glu0dz Glomerular Features for Extreme Filtration Very Large Surface Area (1.5 m2) Large resistance afforded by reduced diameter of the efferent arteriole Thin Filter (0.1 µm) Thus, 25 times more permeable than regular capillaries Cells of the Glomerulus Parietal epithelium Podocyte Mesangial cell Endothelial cell Cells of the Glomerulus and Capsule Parietal epithelium Podocyte Mesangial cell Endothelial cell Parietal Epithelium Podocyte Mesangial Cell Endothelial Cell Mesangial cells secrete erythropoietin - red blood cell production Filtrate Blood ? Blood Filtrate Filtrate Blood Glomerulus - Passive Ultrafiltration Endothelial cell >600,000 MW Basal lamina >160,000 MW Filtration slits >70,000 MW Proximal Convoluted Tubules Brush border Acidophilic cytoplasm Nuclei far apart Indistinct lateral cell boundaries fenestrated capillary Distal Convoluted Tubules No brush border Less acidophilic cytoplasm Nuclei relatively close Larger lumen Juxtaglomerular apparatus Juxtaglomerular apparatus 258 Renin granules in JG cells of Kidney (PAS) Angiotensinogen (Plasma Globulin) Renin (Enzyme from JG Cells) Angiotensin I (Plasma Enzyme) Angiotensin II (Most Potent Vasoconstrictor) Increased Blood Pressure Angiotensin II Vasoconstriction Aldosterone release from Adrenals Increased Blood Pressure Increased Sodium (Water Reabsorption by Distal Tubule) Increased Blood Volume Adrenal Function Aldosterone stimulates Na+ resorption in: • Distal tubule of kidney • Gastric mucosa • Salivary glands • Sweat glands peritubular fenestrated endothelium Cortical nephrons Loop increases temperature over straight tube with same amount of heat Juxtamedullay nephrons Arterial Portal System Capillary Portal Arteriole Capillary = Afferent arteriole, Efferent Arteriole, and Peritubular Capillaries Peritubular Capillaries Absorbs - 180 liters/day from interstitial spaces; thus, ~4 Peritubular Capillaries times reabsorption of venous end of all other capillaries of body Endothelial cells - extremely porous Colloidal osmotic pressure of plasma proteins Low capillary pressure Proximity to uriniferous tubules Parathyroid Glands Parathyroid hormone (PTH) acts on Bones (osteocytes / osteoclasts), kidneys (increase reabsorption of distal tubules), and intestines (increase calcium absorption) to maintain tight control of calcium concentrations in the extracellular fluid ( 8.5 – 10.5 mg/100 mL) Calcium necessary for muscle contractions, glandular secretions, blood coagulation, and key enzymes of intermediary metabolism Removal of gland results in violent spasm of skeletal muscle (tetany) and ultimately death Flow rate Minor and major calyces are lined with transitional epithelium Epithelia of the Urinary System Simple Squamous Parietal, Thin Segment Simple Cuboidal Proximal, Distal Tubule Simple Columnar Proximal Tubule, Collection Ducts Pseudostratified Columnar Urethra Stratified Squamous Urethra Stratified Columnar Urethra Transitional Kidney, Ureters, Bladder, Urethra Membranes Cortical nephrons Juxtamedullay nephrons .