Topic 12: Overview of Kidney, Nephron Anatomy and Function

1. Regulation of Bofy fluid volume -decreased BV = decreased BP -conserve/eliminate water in blood 2. regulation offluid osmolarity and composition -Na+, K+, Cl-, Ca2+, phosphate ions 3. waste removal(metabolism by products) -AA: nitrogeneous wastes (urea from liver) -Fatty acids: acids -removes things from the blood = cleans it 4. endocrine control -renin: cascade for BP: regulates the production of hormones involved in sodium balance and BP homeostasis -Erythropoietin: for RBC production --its a hormone that boosts RBC production from bone marrow --synthesizes RBC 5. territory and sex marking

-(2)kidney: filters blood: site of urine formation -(2)ureters: hollow tube away from the kidney to the bladder -bladder: holds urine -urethra: urine excreted through this from bladder

Know this

Paired -kidney bean shaped -4.5inches long -it lies behind the peritoneal cavity ---aka retroperitoneal position -left kidney is higher

capsule: transparent outer fibrous membrane -tough and rigid structure Renal Cortex: latyer between capsule and medulla -includes cortical column: Each column consists of lines of blood vessels and urinary tubes and a fibrous material -cortical arches -includes the glomeruli, distal/proximal convoluted tubules Renal Medulla: 8-18 renal pyramids --includes the loop of henle, collecting ducts /classes/bios/bios100/lecturesf04am/kidney01a.jpg Renal Pelvis: funnel-like dilated proximal part of the ureter in the kidney. -minor --> major calyce --transfers urine to ureter

-its a functional unit: responsible for the actual purification and filtration of the blood -- regulates concentration of water and sodium salts by filtering the blood, reabsorption and excretion of rest as urine --1-3million per kidney --each 3cm long = 50 miles of tubing -functions: 1. filtration of blood plasma 2. reabsorption of water, AA's, sugar and salts 3. secretion of H, K ions -these functions all urine concentration and acidification types: 1. coritcal nephron: located in the renal cortex --glomerulus and convoluted tubules 2. juxtamedullary nephron: located in the renal medulla --loop of henle/collection duct

Renal corpuscle proximal convoluted tubule loop of henle distal convoluted tubule collection duct

-site of plasma filtration and glomerulus -renal corpuscle = glomerulus + bowmen's capsule -include afferent/efferent arterioles

-fenestrated capillary exchange unit --means the capillary has large pores that allow most components of plasma to filter through the endothelium -glomerulus = filtration function: filter fluid out of blood and into the lumen of the nephron at this location -includes -simple squamous: form parietal layer of capsule -basal lamina: filtration layer/barrier --separate capillary endothelium from lining of Bowmen's Capsule -podocytes: control the filtration of proteins from the capillary lumen into Bowman's space. -mesangial cells: serve as structural supports, may regulate blood flow, are phagocytic and may act as accessory cells, presenting antigen in immune responses.

Afferent: incoming flow into glomerulus -smooth muscle resistant to angiotensin II ---no vasoconstriction = no increase in BP efferent: outgoing flow from the glomerulus -only kidney has capillaries that are drained by arteriole -smooth muscle activated by angiotensin II ---vasoconstriction = increased in BP ---maintains GFR and pressure in kidneys

-surrounds the glomerulus -collects fluid from the glomerulus and into its capsule

Main function = REABSORPTION -85% reabsorption of water, Na+, AA, glucose, electrolytes -glucose coupled with Na+ transport -most important part of the nephron -tubular maximum(Tm) = 375mg/dl men 300mg/dl women --this relates to levels of SUGAR in urine -if less than this number = not diabetic(none in urine) -if more than this number = diabetic(sugar in urine) http://img221.imageshack.us/img221/4852/renaldiuretics9gr.gif

-creates a concentration gradient in the medulla -is a counter current multiplier: production of hyperosmolar urine -becomes more concentrated as it goes down loop and less concentrated going up the loop -thin descending limb: water permeable to medullary space --actively pump salt into tissue so water follows --makes the filtrate more concentrated -thick ascending limb: water impermeable and Na+ permeable --reestablished the hypo/iso state of filtrate Vasa recta: involved in coutercurrent exchange -flow in opposite directions; leads to exchange of concentrations --returns reabsorbed fluid/solute back into vascular system /PPaulev/chapter25/images/25-14.jpg -whereever the salt goes, water follows http://img221.imageshack.us/img221/4852/renaldiuretics9gr.gif

-active secretion of substances into tubular filtrate -functions 1. secretion(K+ withaldosterone) into filtrate -sodium level/absorption mediated by aldosterone 2. acidification -secrete H+ protons into filtrate 3. reabsorption -Na+ reabsorbed into body tissue -aldosterone increases sodium reabsorption -macula densa/J-G apparatus: -macula densa: detect water and ionic volume levels; if low, then promote release of renin by the J-G apparatus --in the end, regulate blood volume and pressure through renin-angiotensin-aldosterone system http://img221.imageshack.us/img221/4852/renaldiuretics9gr.gif

-absorb remaining 15% of fluids -final water reabsorption -allows final urine concentration to occur -permeable to water/urea ---makes it more concentrated -H20 reabsorption from ADH produced by Supraoptic nuclei of hypothalamus -ADH stored/released by posterior pituitary http://img221.imageshack.us/img221/4852/renaldiuretics9gr.gif