The Urinary System Copyright 2004 Pearson Education Inc

• The Urinary System Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Functions of the urinary system • Excretion • The removal of organic waste products from body fluids • Elimination • The discharge of waste products into the environment • Homeostatic regulation of blood plasma • Regulating blood volume and pressure • Regulating plasma ion concentrations • Stabilizing blood p. H • Conserving nutrients Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Figure 26. 1 An introduction to the Urinary System Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 26. 1

Figure 26. 2 The Position of the Kidneys Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 26. 2 a, b

Figure 26. 3 The Urinary System in Gross Dissection Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 26. 3

Sectional anatomy of the kidneys • Superficial outer cortex and inner medulla • The medulla consists of 618 renal pyramids • The cortex is composed of roughly 1. 25 million nephrons • Major and minor calyces along with the pelvis drain urine to the ureters Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Figure 26. 4 The Structure of the Kidney Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 26. 4 a, b

URINARY SYSTEM THE NEPHRON & COLLECTING DUCTS HISTOLOGICAL STRUCTURE AND FUNCTION 1) THE NEPHRON - distributed throughout cortex and various zones of medulla a) RENAL CORPUSCLE BOWMAN’S CAPSULE + GLOMERULUS b) PROXIMAL TUBULE CONVOLUTED AND STRAIGHT PORTIONS c) HENLE’S LOOP THICK AND THIN PORTIONS d) DISTAL TUBULE STRAIGHT AND CONVOLUTED PORTIONS 2) COLLECTING DUCTS Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

URINARY SYSTEM THE NEPHRON & COLLECTING DUCTS HISTOLOGICAL STRUCTURE AND FUNCTION 1) THE NEPHRON - distributed throughout cortex and various zones of medulla a) RENAL CORPUSCLE BOWMAN’S CAPSULE + GLOMERULUS b) PROXIMAL TUBULE CONVOLUTED AND STRAIGHT PORTIONS c) HENLE’S LOOP THICK AND THIN PORTIONS d) DISTAL TUBULE STRAIGHT AND CONVOLUTED PORTIONS 2) COLLECTING DUCTS Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

URINARY SYSTEM RENAL CORPUSCLE BOWMAN’S CAPSULE + GLOMERULUS FILTRATION APPARATUS OF KIDNEY 1. BOWMAN’S CAPSULE: - the beginning of the nephron that consists of a blind sac lined with simple squamous epithelium that is continuous with the PCT - parietal layer & visceral layer (specialized) 2. GLOMERULUS: - specialized tuft of capillaries which housed in the capsular space (10 -20 capillary loops) - blood flowing through glomerulus capillaries undergoes a filtration process to produce the initial urine filtrate Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

URINARY SYSTEM RENAL BOWMAN’S CAPSULE + CORPUSCLE GLOMERULUS FILTRATION APPARATUS OF KIDNEY VASCULAR POLE URINARY POLE GLOMERULUS (FILTRATION MEMBRANE): 1 - fenestrated capillaries; discontinuous endothelium; fenestrae have a diameter of 500 -1000Å and lack a diaphragm 2 - continuous basal lamina 3 - podocytes of visceral layer; processes contact basal lamina and are separated by slits measuring approximately 250ÅInc. , publishing as Benjamin Cummings Copyright © 2004 Pearson Education,

URINARY SYSTEM RENAL BOWMAN’S CAPSULE + CORPUSCLE GLOMERULUS FILTRATION APPARATUS OF KIDNEY GLOMERULUS (FILTRATION MEMBRANE): prevents RBC’s and large MW proteins from leaving circulation, while most other blood constituents pass easily into the capsular space MESANGIAL CELLS - phagocytic cells with a surrounding matrix that lend structural support to the glomerulus Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

URINARY SYSTEM RENAL BOWMAN’S CAPSULE + CORPUSCLE GLOMERULUS FILTRATION APPARATUS OF KIDNEY GLOMERULUS (FILTRATION MEMBRANE): 1 - fenestrated capillaries 2 - continuous basal lamina 3 - podocytes Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Figure 26. 5 The Blood Supply to the Kidneys Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 26. 5 c, d

URINARY SYSTEM BLOOD FLOW (KIDNEY) AORTA RENAL ARTERY INTERLOBAR ARTERIES - run between lobes in medulla ARCUATE ARTERIES - run parallel to bases of pyramids at the corticomedullary junction INTERLOBULAR ARTERIES - delineate lateral limits of renal lobules AFFERENT ARTERIOLES - supply blood to glomerulus GLOMERULAR CAPILLARY BED EFFERENT ARTERIOLES - drain blood from glomerulus and form either peritubular capillary vasaas recta Copyright © plexus 2004 Pearson(cortex) Education, Inc. , or publishing Benjamin Cummings RENAL LOBULE

URINARY SYSTEM BLOOD FLOW (KIDNEY) VENA CAVA RENAL VEIN INTERLOBAR VEINS - run between lobes in medulla ARCUATE VEINS - run parallel to bases of pyramids at the corticomedullary junction INTERLOBULAR VEINS - delineate lateral limits of renal lobules PERITUBULAR CAPILLARY PLEXUS VASA RECTA SYSTEM Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings RENAL LOBULE

Figure 26. 5 The Blood Supply to the Kidneys Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 26. 5 a, b

Figure 26. 6 A Representative Nephron Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 26. 6

Nephron functions include: • Production of filtrate • Reabsorption of organic nutrients • Reabsorption of water and ions • Secretion of waste products into tubular fluid Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Two types of nephron • Cortical nephrons • ~85% of all nephrons • Located in the cortex • Juxtamedullary nephrons • Closer to renal medulla • Loops of Henle extend deep into renal pyramids Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Figure 26. 7 Cortical and Juxtamedullary Nephrons Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 26. 7 a

Figure 26. 7 Cortical and Juxtamedullary Nephrons Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 26. 7 b, c

Figure 26. 8 The Renal Corpuscle Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 26. 8 a, b

Figure 26. 8 The Renal Corpuscle Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings Figure 26. 8 c, d

Functional anatomy of the nephron • Proximal convoluted tubule (PCT) • Actively reabsorbs nutrients, plasma proteins and ions from filtrate • Released into peritubular fluid • Loop of Henle • Descending limb • Ascending limb • Each limb has a thick and thin section PLAY Animation: Urinary System Anatomy Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Functional anatomy of the nephron • Distal convoluted tubule (DCT) • Actively secretes ions, toxins, drugs • Reabsorbs sodium ions from tubular fluid PLAY Animation: Urinary System Dissection and Flythrough Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

SECTION 26 -3 Principles of Renal Physiology Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Urine production maintains homeostasis • Regulating blood volume and composition • Excreting waste products • Urea • Creatinine • Uric acid Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Basic processes of urine formation • Filtration • Blood pressure • Water and solutes across glomerular capillaries • Reabsorption • The removal of water and solutes from the filtrate • Secretion • Transport of solutes from the peritubular fluid into the tubular fluid Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Carrier Mediated Transport • Filtration in the kidneys modified by carrier mediated transport • Facilitated diffusion • Active transport • Countertransport • Carrier proteins have a transport maximum (Tm) • Determines renal threshold Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings

Reabsorption and secretion • Accomplished via diffusion, osmosis, and carriermediated transport • Tm determines renal threshold for reabsorption of substances in tubular fluid Copyright © 2004 Pearson Education, Inc. , publishing as Benjamin Cummings