The kidneys filter 180 liters of blood daily, regulating water, electrolyte, acid-base balance and excreting wastes. Each kidney contains about 1 million nephrons, each with a renal corpuscle that filters blood and renal tubule that modifies the filtrate into urine. The nephron is composed of a glomerulus for blood filtration, Bowman's capsule, proximal tubule, loop of Henle, distal tubule and collecting duct. Specialized cells in different nephron segments reabsorb essential molecules while selectively excreting wastes to produce urine, which travels through the urinary tract for excretion from the body.

1. Kidney’s Function Filter 180 liters of blood daily, allowing excretion of metabolic wastes, foreign chemicals and excess ions to leave the body in urine Regulation of water and electrolyte balances Regulation of arterial pressure Regulation of acid-base balance Secretion, metabolism, and excretion of hormones Gluconeogenesis

3. Urine is produced in the kidneys

4. Paired ureters – transport urine from the kidneys to the bladder

5. Urinary bladder – provides a temporary storage reservoir for urine

6. Urethra – transports urine from the bladder out of the bodyPhysiologic anatomy of the kidneys

8. Adrenal gland lying on top of each kidneyPhysiologic anatomy of the kidneys

10. The medulla divided into multiple cone-shaped masses of tissue called renal pyramids

11. The pyramid terminates in the papilla, which projects into the space of renel pelvis, a funnel shaped continuation of the upper end of the ureterPhysiologic anatomy of the kidneys

12. Renal blood supply Aorta Inferior vena cava Renal a. Renal v. Segmental a. Interlobar a. Interlobar v. Arcuate a. Arcuate v. Interlobular a. Interlobular v. Afferent arteriole Peritubular Capillaries Vasa recta Section of the human kidney showing the major vessels that supply the blood flow to the kidney and schematic of the microcirculation of each nephron. Glomerulus Efferent arteriole

14. The Nephron Is the Functional Unit of the Kidney Each kidney in the human contains about 1 million nephrons, each capable of forming urine. The kidney cannot regenerate new nephrons. Each nephron contains (1) Renal corpuscle which blood plasma is filtered and (2) a long renal tubule in which the filtered fluid is converted into urine on its way to the pelvis of the kidney

16. Renal tubule divided into the proximal tubule, loop of Henle, distal tubule and collecting ducts

17. Descending segment of the loop of Henle and the ascending limb

18. The wall in the descending and lower end of the ascending limb called thin segment of loop of Henle

19. At the end of the thick ascending limb is a short segment called macula densa

20. Then fluid enters distal tubule, followed by cortical collecting tubule, which lead to cortical collecting duct, medullary collecting ducts

22. Capillary Beds of the Nephron Every nephron has two capillary beds Glomerulus Peritubular capillaries Each glomerulus is: Fed by an afferent arteriole Drained by an efferent arteriole

23. Cellular features of renal corpuscle Wrapped around the capillaries of the glomerulus is cells called podocytes Capsular space: is the region within the glomerular capsule that collect the filtrate being force out of the blood The endothelial contain fenestration, which allows passage of water and ions and small molecules Basement membrane encloses the capillaries endothelium Surrounding the basement membrane is long footlike processes podocyte The foot processes are separated by gaps called slit pores through which glomerular filtrate moves

24. Filtration Membrane

25. The fenestrated capillary endothelium, basement membrane, and podocyte makes up the filtration membrane The filtration membrane permits the escape of small molecules while preventing large molecules (proteins) from leaving the bloodstream and passing through into the capsular space

26. The cuboidal epithelial cells of proximal tubule have extensive microvilli in their luminal surfaces The cells contain mitochondria that provide ATP for active transport CELLS OF THE Proximal Tubule

27. Cells in the thin segment of loop of Henle The cells in the thin descending segment of the loop of Henle are simple squamous epithelial cells Lack of brush borders Permeable to water not to solute The thin ascending limb is permeable to solute not to water

28. Cells of the thick ascending loop of Henle and distal tubule Compose of cuboidal epithelium cells Fewer and smaller microvilli compared to proximal tubule Ascending limb highly permeable to solute, highly permeable to solute not to water Distal tubule more permeable to water than ascending limb Distal tubule is the end of the nephron

29. Where the cells of afferent arterioles and the ascending thick loop of Henle are in contact with each other they form juxtaglomerular apparatus Macula densa, specialized cells. They are part of the juxtaglomerular apparatus and appear to be sensitive to the content and rate of the flow of the filtrate Juxtaglomerular cells, smooth muscle cells of the afferent arteriole. Play role in GFR and blood pressure regulation by producing renin The Juxtaglomerular Apparatus

30. Cells of the cortical collecting ducts Two types of cells: Principal cells: Fewer microvilli. They are respond to aldosterone and ADH hormone that regulate their permeability to water and solute Principal cells permeability to water and solutes is regulated by hormones Intercalated cells: Involve in acid base balance Secretion of H+ for acid base balance

31. Cells of the medullary collecting ducts Composed mainly of principal cells Permeability of water and urea is hormonally regulated

32. Flow of fluid from the glomerular filtrate to the urine Glomerular capsule proximal tubule Loop of Henle distal tubule collecting duct papillary duct minor calyx major calyx renal pelvis ureter urinary bladder urethra