Histology: Urinary System PDF

Histology: Urinary System By: Dr. Mark Henry C Booc Chapter 19: Junqueira’s Basic Histology  Components Kidneys (Right and Left) Ureters Urinary Bladder Urethra Main Role: Ensure optimal properties of the blood, which the kidney monitors.  Re...

Histology: Urinary System By: Dr. Mark Henry C Booc Chapter 19: Junqueira’s Basic Histology  Components Kidneys (Right and Left) Ureters Urinary Bladder Urethra Main Role: Ensure optimal properties of the blood, which the kidney monitors.  Renal Functions Balance of water, electrolytes and acid-base balance Excretion of metabolic wates, excess water, and electrolytes Excretion of bioactive substances (drugs) Secretion of Renin, Erythropoietin Conversion of sterioid prohormone vitamin D to active calcitriol Gluconeogenesis durig starvation The Kidney  Blood Supply Abdominal aorta -> Renal Arteries -> Segmental Arteries -> Interlobar Arteries -> Arcuate Arteries -> Cortical Radial Arteries -> Afferent Arterioles -> Glomerulus Glomerulus -> Efferent Arterioles -> Peritubular Capillaries or may form Vasa Recta if near Juxtaglomerular corpuscles Vas Recta or Peritubular Capillaries (depending on location) -> Cortical Radial Veins, Arcuate Veins, Interlobar Vein, -> Segmental Vein, - >Renal Vein, Inferior Vena Cava  Filtration, Secretion, and Absorption Filtration: water and solutes in blood leave vascular space and enter lumen of nephron. Tubular Secretion: Substances move from epithelial cells of tubules into lumens usually after uptake from interstitial area and capillaries Tubular Reabsorption: Substances move from the tubular lumen into the Epithelium and into interstium and surrounding capillaries. Renal Corpuscles & Blood Filtration  Filtration Must Pass Fenestrations of capillary endothelium Glomerular basement membrane Filtration slit diaphragms between pedicels of podocytes  Functions of the Mesangium Physical support of capillaries Adjust contractions in response to blood pressure Phagocytosis if protein aggregates Secretion of cytokines and other immune defense factors.  Proximal Convoluted Tubule  Other Roles of Proximal Convoluted Tubule Hydroxylation of vitamin D and release to capillaries Production of erythropoietin by interstitial cells near proximal convoluted tubules  Summary of Functions Reabsorption of all organic nutrients, protein, most of the water and electrolytes Secretion of organic anions and cations, hydrogen and ammonium. Production of Erythropoietin Hydroxylation of Vit D The Loop of Henle Distal Convoluted Tubule and Juxtaglomerular Apparatus  Accessing limb of henle is straight as it enters cortex and forms macula densa and then becomes distal convoluted tubule Simple cuboidal cells smaller, no brush border may be slightly flatter and smaller and less mitochondria Sodium absorption in this area is regulated by aldosterone  Macula Densa This is part of sensory structure called Juxtaglomerular Apparatus The JGA uses feedback mechanisms to regulate glomerular blood flow and keep glomerular filtration constant. The muscular layer of the afferent arteriole is modified to form juxtaglomerular granular cells which contain enzyme renin  If Elevated Arterial Pressure Elevated arterial pressure-> increase in glomerular filtration rate -> higher sodium in thick ascending limb of henle. Macula densa sense high sodium levels MD will secrete ATP, adenosine and other vasoactive compounds that case contraction of afferent arteriole. This will decrease glomerular pressure and lower GFR Lower GFR results in lower sodium sensed by MD causing the MD to turn off.  If low arterial pressure Low arterial pressure-> autonomic stimulation to JGA as result of baroreceptor function -> release of renin from jg cells. Renin cleaves angiotensinogen to angiotensin I Angiotensin I goes to lungs and is converted to Angiotensin II by angiotensin converting enzyme. Angiotensin II has many effects (vasoconstriction, stimulates adrenals to secrete aldosterone) Aldosterone promotes sodium and water reabsorption in distal and collecting tubules Collecting Ducts Quick Summary Ureters, Bladder, and Urethra