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The Renal System

The Renal System. Components: kidneys, urinary bladder, ureters, urethra renal artery, renal vein. 25.1. The Renal System. Functions: excretion- elimination of metabolic wastes, toxins, excess ions regulation of blood volume and composition production of erythropoetin

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The Renal System

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  1. The Renal System • Components: • kidneys, urinary bladder, ureters, urethra • renal artery, renal vein 25.1

  2. The Renal System • Functions: • excretion-elimination of metabolic wastes, toxins, excess ions • regulation of blood volume and composition • production of erythropoetin • metabolism of vitamin D to active form • production of renin

  3. Kidneys-Basic Anatomy & Physiology • cortex-outer layer of the kidney; contains the bulk of the nephrons , giving it a granular appearance • medulla-layer deep to the cortex arranged in cone-shaped sections; contains the collecting ducts, giving it a striped appearance Fig. 25.4a

  4. Kidneys-Basic Anatomy & Physiology • kidney lobes-~8 per kidney, include a section of cortex, medulla and associated blood vesssels • fibrous capsule– outer, protective covering of the kidney; prevents infection from other organs Fibrous capsule Fig. 25.4a

  5. Microscopic Structures of the Kidney • Nephron-microscopic filtering units of the kidney • Site of blood filtration into the renal tubule end (Bowman’s capsule) 25.5a

  6. Nephron • Comprised of two parts: • Glomerulus-specialized capillary beds of then kidney where blood gets filtered (filtrate enters renal tubule) • Renal tubule- microscopic tube that collects the filtrate of the blood and processes it (via tubular reabsorption and secretion) to become urine

  7. Glomerulus

  8. Figure 25.11 Efferent arteriole

  9. Parts of the renal tubule • Bowman’s capsule- end of the renal tubule where the filtrate enters (also called Glomerular capsule) • Proximal convoluted tubule- part of the renal tubule between the Bowman’s capsule and the loop of Henle; • much reabsorption of water and nutrients takes place here • Loop of Henle-hairpin loop of the renal tubule that dips down into the medulla; important site of Na+ and K+ transport into and out of the tubule • Distal convoluted tubule-part of the renal tubule between the loop of Henle and the collecting duct

  10. Glomerulus • Bowman’s capsule of renal tubule distal.conv. tubule prox. conv. tubule loop of Henle

  11. Filtration membrane-barrier between the blood in the glomerulus and the renal tubule (Bowman’s capsule), that filters the blood; • allows small solutes and fluid to pass through, and retains blood cells and large solutes (proteins); • part of nephron

  12. Filtration Membrane • Comprised of: • Endothelium of the glomerular capillaries (fenestrated) • Basement membrane • Podocytes of the Bowman’s capsule cells

  13. Filtration Membrane Not required

  14. Structures Associated with the Nephron • Afferent arterioles- lead into the glomerulus • (blood originates from the renal artery) • Efferent arterioles- lead out of the glomerulus • (from here, blood flows into the peritubular capillaries, then ultimately to the renal vein)

  15. Structures Associated with the Nephron • Peritubular capillaries-capillary bed formed after blood leaves the glomerulus through the efferent arteriole, that intertwines around the renal tubule, allowing exchange of substances (tubular reabsorption and secretion, also gas exchange of O2/CO2) • Collecting ducts-small tubular structures that receive filtrate (now urine-like)from the nephron and deliver it to the renal pelvis

  16. Glomerulus • Bowman’s capsule of renal tubule Efferent arteriole Afferent arteriole prox. conv. tubule peritubular capillaries Collecting duct

  17. Mechanisms of Urine Formation • Filtration- filtration of the blood by the filtration membrane • Tubular reabsorption- selective reuptake of fluid and solutes present in the tubules back into the blood (of the peritubular capillaries) • Secretion- selective movement of molecules in the peritubular capillary blood that did not enter the tubules at the Bowman’s capsule →into the renal tubules (and eliminated from the body).

  18. Mechanisms of Urine Formation • After the filtrate containing wastes leaves the renal tubule(now urine-like)

  19. Mechanisms of Urine Formation • After the filtrate containing wastes leaves the renal tubule(now urine-like)enters collecting ducts

  20. Renal Clearance • Volume of plasma that is cleared of a particular substance in a given time (ml/min)

  21. Renal Clearance • If a drug has a high renal clearance:(eliminated from the body rapidly) • Is reabsorbed poorly and/or secreted extensively. • If a drug has a low renal clearance: (eliminated from the body slowly) • Reabsorbed extensively and/or secreted poorly.

  22. Glomerulus • Bowman’s capsule of renal tubule Efferent arteriole Afferent arteriole Renal tubule Collecting ducts Peritubular capillaries

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