Urinary System Organs Kidney Filters blood, allowing toxins, metabolic wastes, and excess ions to leave the body in urine Urinary bladder provides a temporary storage reservoir for urine Paired ureters transport urine from the kidneys to the bladder Urethra transports urine from the bladder out of the body 1
Figure 25.1 The urinary system. Hepatic veins (cut) Esophagus (cut) Inferior vena cava Adrenal gland Aorta Iliac crest Renal arte Renal hilu Renal vein Kidney Ureter Rectum (cut) Uterus (part of female reproductive system) Urinary bladder Urethra MDufilho 10/20/13 2
Kidneys -Overview Blood passes through kidney filtration occurs at capillaries 20% of plasma becomes filtrate Filtrate passes through nephrons water and electrolytes are reabsorbed Some electrolytes, drugs and toxins may be secreted into filtrate by tubular secretion = Urine 3
Figure 25.9 A schematic, uncoiled nephron showing the three major renal processes that adjust plasma composition. Afferent Glomerular capillaries Cortical radiate artery 1 Glomerular capsule Renal tubule and collecting duct containing filtrate 2 3 Peritubular capillary To cortical radiate vein MDufilho Three major renal processes: Urine 1 2 Glomerular filtration Tubular reabsorption 3 Tubular secretion 10/20/13 4
Figure 25.8 Juxtaglomerular complex (JGC) of a nephron. Glomerular capsule Afferent Glomerulus Parietal layer of glomerular capsule Capsular space Foot processes of podocytes Podocyte cell body (visceral layer) Red blood cell Proximal tubule cell Juxtaglomerular complex Macula densa cells of the ascending limb of nephron loop Extraglomerular mesangial cells Granular cells Afferent Juxtaglomerular complex Glomerular mesangial cells Renal corpuscle Lumens of glomerular capillaries Endothelial cell of glomerular capillary MDufilho 10/20/13 5
Figure 25.10 The filtration membrane. Glomerular capsular space Cytoplasmic extensions of podocytes Filtration slits Afferent Podocyte cell body Glomerular capillary covered by podocytes that form the visceral layer of glomerular capsule Parietal layer of glomerular capsule Glomerular capillaries and the visceral layer of the glomerular capsule Filtration slits Proximal convoluted tubule Fenestrations (pores) Glomerular capillary endothelium (podocyte covering and basement membrane removed) Foot processes of podocyte Podocyte cell body Capillary Filtration membrane Capillary endothelium Basement membrane Foot processes of podocyte of glomerular capsule Foot processes Filtration slit Plasma Filtrate in capsular space Slit diaphragm MDufilho Filtration slits between the podocyte foot processes 10/20/13 Fenestration (pore) Foot processes of podocyte Three layers of the filtration membrane 6
Figure 25.5 Location and structure of nephrons. Renal cortex Renal medulla Renal pelvis Kidney Renal corpuscle Glomerular capsule Glomerulus Ureter Distal convoluted tubule Glomerular capsule: parietal layer Basement membrane Podocyte Fenestrated endothelium of the glomerulus Glomerular capsule: visceral layer Apical microvilli Mitochondria Cortex Proximal convoluted tubule Highly infolded basolateral membrane Proximal convoluted tubule cells Apical side Medulla Thin segment Nephron loop Descending limb Ascending limb Thick segment Collecting duct Basolateral side Distal convoluted tubule cells Nephron loop (thin-segment) cells Principal cell Intercalated cell MDufilho 10/20/13 Collecting duct cells 7
Renal Tubule Proximal convoluted tubule (PCT) composed of cuboidal cells with numerous microvilli and mitochondria Reabsorbs water and solutes from filtrate and secretes substances into it Reabsorbs 100% of glucose, amino acids, escaped proteins, some vitamins, 60-70% of Na+, K+, Cl-, Ca++ and water Secretes H+, NH3 (ammonia), drugs, toxins, uric acid and histamine 8
Renal Tubule Loop of Henle a hairpin-shaped loop of the renal tubule Descending Limb Impermeable to electrolytes, permeable to water 80% Water is absorbed, filtrate becomes hypertonic Ascending Limb Permeable to Na+ and Cl- but not water Filtrate becomes hypotonic 9
Renal Tubule Distal convoluted tubule (DCT) Reabsorbs: Na+ directed by aldosterone Water directed by ADH Ca++ directed by PTH Some HCO3-, depending on ph of blood Secretes: NH3, K+, drugs, toxins, and creatinine Some H+, depending on ph of blood 10
Collecting Tubule Reabsorbs Na+ directed by aldosterone HCO3- depending on blood ph Urea to maintain hypertonic interstitial fluid around nephron tubules Water directed by ADH 11
Capillary Beds of the Nephron Every nephron has two capillary beds Glomerulus Peritubular capillaries Each glomerulus is: Fed by an afferent - larger Drained by an efferent - smaller 12
Figure 25.8 Juxtaglomerular complex (JGC) of a nephron. Glomerular capsule Afferent Glomerulus Parietal layer of glomerular capsule Capsular space Foot processes of podocytes Podocyte cell body (visceral layer) Red blood cell Proximal tubule cell Juxtaglomerular complex Macula densa cells of the ascending limb of nephron loop Extraglomerular mesangial cells Granular cells Afferent Juxtaglomerular complex Glomerular mesangial cells Renal corpuscle Lumens of glomerular capillaries Endothelial cell of glomerular capillary MDufilho 10/20/13 13
Figure 25.7 Blood vessels of cortical and juxtamedullary nephrons. Cortical nephron Short nephron loop Glomerulus further from the cortex-medulla junction supplies peritubular capillaries Juxtamedullary nephron Long nephron loop Glomerulus closer to the cortex-medulla junction supplies vasa recta Renal corpuscle Glomerulus (capillaries) Glomerular capsule Proximal convoluted tubule Cortical radiate vein Cortical radiate artery Afferent Collecting duct Distal convoluted tubule Afferent Peritubular capillaries Ascending limb of nephron loop Arcuate vein Cortexmedulla junction Kidney Arcuate artery Vasa recta Nephron loop Descending limb of nephron loop Peritubular capillary bed Glomerulus Afferent MDufilho 10/20/13 14
Hemodialysis Diffusion of solutes through semipermeable membrane Dialysis machine- group of tubules that act like a nephron Membrane allows free passage of glucose, electrolytes and nitrogenous wastes Filtration and production of filtrate is not required 15