Transcript Chapter 19a
Chapter 19a The Kidneys About this Chapter • Anatomy of the urinary system • Overview of kidney function • Homeostasis • pH • Electrolytes • fluid • Filtration • Reabsorption • Secretion • Excretion • Micturition Functions of the Kidneys • Regulation of extracellular fluid volume and blood pressure • Regulation of osmolarity • Maintenance of ion balance • Homeostatic regulation of pH • Excretion of wastes • Production of hormones Anatomy: The Urinary System THE URINARY SYSTEM Kidney Ureter Urinary bladder Urethra (a) The urinary system Figure 19-1a Anatomy: The Urinary System Diaphragm Left adrenal gland Inferior vena cava Left kidney Right kidney Renal artery Ureter Aorta Renal vein Peritoneum (cut) Urinary bladder Rectum (cut) (b) The kidneys are located retroperitoneally at the level of the lower ribs. Figure 19-1b Anatomy: The Urinary System Nephrons Cortex Polycystic kidney Medulla Renal pelvis Ureter Capsule (c) The kidney, in cross section. Figure 19-1c Anatomy: The Urinary System Arterioles Nephrons Cortex Medulla (i) Some nephrons dip deep into the medulla. Figure 19-1i Anatomy: The Urinary System Efferent arteriole Juxtaglomerular apparatus Peritubular capillaries Peritubular capillaries Glomerulus Afferent arteriole Glomerulus (capillaries) Vasa recta Collecting duct Loop of Henle (g) One nephron has two arterioles and two sets of capillaries. (h) Juxtamedullary nephron with vasa recta Figure 19-1g–h Anatomy: The Urinary System Figure 19-1d–e Anatomy: The Urinary System STRUCTURE OF THE NEPHRON Glomerulus Cut edge of nephron tubule (f) The capillaries of the glomerulus form a ball-like mass. Figure 19-1f Anatomy: The Urinary System Bowman’s capsule Proximal tubule Descending limb of loop begins Distal tubule Ascending limb of loop ends Collecting duct Descending limb (j) Parts of a nephron Ascending limb Loop of Henle To bladder Figure 19-1j Kidney Function • Filtration, reabsorption, secretion, and excretion Distal tubule Peritubular capillaries Efferent arteriole Glomerulus Afferent arteriole Bowman’s capsule Proximal tubule KEY = Filtration: blood to lumen = Reabsorption: lumen to blood Loop of Henle Collecting duct To renal vein = Secretion: blood to lumen = Excretion: lumen to external environment To bladder and external environment Figure 19-2 Kidney Function Table 19-1 Kidney Function • The urinary excretion of substance depends on its filtration, reabsorption, and secretion Glomerulus Efferent arteriole Peritubular capillaries To renal vein Tubule Afferent arteriole Bowman’s capsule Amount Amount – reabsorbed filtered To bladder and external environment + Amount secreted = amount of solute excreted Figure 19-3 The Filtration Fraction Efferent arteriole 80% Afferent arteriole 1 Plasma volume entering afferent arteriole = 100% Peritubular capillaries 2 20% of volume filters. Bowman’s capsule 4 >99% of plasma entering kidney returns to systemic circulation. 3 >19% of fluid is reabsorbed. 5 <1% of volume is excreted to external environment. Remainder of nephron Glomerulus Figure 19-4 The Renal Corpuscle Thick ascending limb of loop of Henle Efferent arteriole Bowman’s capsule Capsular epithelium Podocyte Proximal tubule Glomerular capillary Afferent arteriole Lumen of Bowman’s capsule (a) The epithelium around glomerular capillaries is modified into podocytes. Figure 19-5a The Renal Corpuscle Foot process of podocyte Filtration slit Pores in endothelium Basal lamina Capillary lumen Filtered material Lumen of Bowman’s capsule (d) Filtered substances pass through endothelial pores and filtration slits. Figure 19-5d The Renal Corpuscle Podocyte Lumen of Bowman’s capsule Glomerular capillary Podocyte foot processes Capillary endothelium Mesangial cell (c) Podocyte foot processes surround each capillary, leaving slits through which filtration takes place. Figure 19-5c Forces that Influence Filtration • Hydrostatic pressure (blood pressure) • Colloid osmotic pressure • Fluid pressure created by fluid in Bowman’s capsule Filtration • Filtration pressure in the renal corpuscle depends on hydrostatic pressure, and is opposed by colloid osmotic pressure and capsule fluid pressure Efferent arteriole 15 mm Hg Pfluid 30 mm Hg Net filtration pressure = 10 mm Hg PH 55 mm Hg Afferent arteriole Glomerulus Bowman’s capsule PH – – Pfluid 55 – 30 – 15 = net filtration pressure = 10mm Hg KEY PH = Hydrostatic pressure (blood pressure) = Colloid osmotic pressure gradient due to proteins in plasma but not in Bowman’s capsule Pfluid = Fluid pressure created by fluid in Bowman’s capsule Figure 19-6 Filtration • Autoregulation of glomerular filtration rate takes place over a wide range of blood pressures Figure 19-7 Filtration • Resistance changes in renal arterioles alter renal blood flow and GFR Figure 19-8a Filtration Figure 19-8b Filtration Figure 19-8c GFR Regulation • Myogenic response • Similar to autoregulation in other systemic arterioles • Tubuloglomerular feedback • Paracrine control by macula densa • Hormones and autonomic neurons • By changing resistance in arterioles • By altering the filtration coefficient • Surface area Juxtaglomerular Apparatus Bowman’s capsule Efferent arteriole Ascending limb of loop of Henle Glomerulus Macula densa cells Proximal tubule Granular cells Afferent arteriole (a) Endothelium (b) Figure 19-9 Tubuloglomerular Feedback 1 Glomerulus Distal tubule GFR increases. Efferent arteriole 2 Flow through tubule increases. Bowman’s capsule 3 Flow past macula densa increases. Macula densa 4 1 5 Granular cells 4 Paracrine from macula densa to afferent arteriole Afferent arteriole 2 3 Proximal tubule 5 Afferent arteriole constricts. Resistance in afferent arteriole increases. Collecting duct Hydrostatic pressure in glomerulus decreases. GFR decreases. Loop of Henle Figure 19-10, steps 1–5 (4 of 4)