Final Exam Review,Summer 2010 Chapters 16, 25, and 26,Kidney Functions,Removal of toxins, metabolic wastes, and excess ions from the blood Regulation of blood volume, chemical composition, and pH,Kidney Functions,Gluconeogenesis during prolonged fasting Endocrine functions Renin: regulation of blood pressure and kidney function Erythropoietin: regulation of RBC production Activation of vitamin D,Urine Movement,glomerulus proximal convoluted tubule loop of Henle distal convoluted tubule collecting duct minor calyx major calyx pelvis ureter bladder urethra,Figure 25.5,Nephron,Functional unit of kidney Units of nephron Renal corpuscle Bowmans (glomerular) capsule Glomerulus Tubules PCT Loop of Henle DCT Collecting duct,Figure 25.3,Renal cortex,Renal medulla,Major calyx,Papilla of pyramid,Renal pelvis,Ureter,Minor calyx,Renal column,Renal pyramid in renal medulla,Fibrous capsule,Renal hilum,(a) Photograph of right kidney, frontal section,(b) Diagrammatic view,Filtration Membrane,Porous membrane between the blood and the capsular space Consists of Fenestrated endothelium of the glomerular capillaries Visceral membrane of the glomerular capsule (podocytes with foot processes and filtration slits) Gel-like basement membrane (fused basal laminae of the two other layers),Figure 25.9a,Glomerular capillary covered by podocyte- containing visceral layer of glomerular capsule,Glomerular capillary endothelium (podocyte covering and basement membrane removed),Proximal convoluted tubule,Parietal layer of glomerular capsule,Afferent arteriole,Glomerular capsular space,Fenestrations (pores),Efferent arteriole,Podocyte cell body,Foot processes of podocyte,Filtration slits,Cytoplasmic extensions of podocytes,(a) Glomerular capillaries and the visceral layer of the glomerular capsule,Figure 25.5,Fenestrated endothelium of the glomerulus,Podocyte,Basement membrane,Glomerular capsule: visceral layer,Filtration Membrane,Allows passage of water and solutes smaller than most plasma proteins Fenestrations prevent filtration of blood cells Negatively charged basement membrane repels large anions such as plasma proteins Slit diaphragms also help to repel macromolecules,Figure 25.9c,(c) Three parts of the filtration membrane,Fenestration (pore),Filtrate in capsular space,Foot processes of podocyte,Filtration slit,Slit diaphragm,Capillary,Filtration membrane Capillary endothelium Basement membrane Foot processes of podocyte of glomerular capsule,Plasma,Kidney Physiology: Mechanisms of Urine Formation,Filtrate Blood plasma minus proteins Urine 1% of total filtrate Contains metabolic wastes and unneeded substances,Juxtaglomerular Apparatus (JGA),One per nephron Important in regulation of filtrate formation and blood pressure Involves modified portions of the Distal portion of the ascending limb of the loop of Henle Afferent (sometimes efferent) arteriole,Juxtaglomerular Apparatus (JGA),Granular cells (juxtaglomerular, or JG cells) Enlarged, smooth muscle cells of arteriole Secretory granules contain renin Act as mechanoreceptors that sense blood pressure decrease in BP stimulates renin secretion Renin activates angiotensinogen then converted to angiotensin II Angiotensin II stimulates aldosterone secretion and vasoconstriction,Juxtaglomerular Apparatus (JGA),Macula densa Tall, closely packed cells of the ascending limb Act as chemoreceptors that sense NaCl content of filtrate,Figure 25.12,Stretch of smooth muscle in walls of afferent arterioles,Blood pressure in afferent arterioles; GFR,Vasodilation of afferent arterioles,GFR,Myogenic mechanism of autoregulation,Release of vasoactive chemical inhibited,Intrinsic mechanisms directly regulate GFR despite moderate changes in blood pressure (between 80 and 180 mm Hg mean arterial pressure).,Extrinsic mechanisms indirectly regulate GFR by maintaining systemic blood pressure, which drives filtration in the kidneys.,Tubuloglomerular mechanism of autoregulation,Hormonal (renin-angiotensin) mechanism,Neural controls,SYSTEMIC BLOOD PRESSURE,GFR,Macula densa cells of JG apparatus of kidney,Filtrate flow and NaCl in ascending limb of Henles loop,Targets,Granular cells of juxtaglomerular apparatus of kidney,Angiotensinogen,Angiotensin II,Adrenal cortex,Systemic arterioles,(+),Renin,Release,Catalyzes cascade resulting in conversion,(+),(+),(+),Kidney tubules,Aldosterone,Releases,Targets,Vasoconstriction; peripheral resistance,Blood volume,Na+ reabsorption; water follows,Systemic blood pressure,(+),(+),(),Increase,Decrease,Stimulates,Inhibits,Baroreceptors in blood vessels of systemic circulation,Sympathetic nervous system,(+),(),Vasodilation of afferent arterioles,Mechanisms of Urine Formation,Glomerular filtration Tubular reabsorption Returns all glucose and amino acids, 99% of water, salt, and other components to the blood Tubular secretion Reverse of reabsorption: selective addition to ur