Renal System

Role of Kidney renal system – referring to the kidney blood filtration waste excretion acid / base balance blood pressure regulation hormone secretion

Kidney Blood Flow Blood enters the kidney through the renal artery. renal arteries stem from the: Filtered blood exits the kidney through the renal vein. renal veins flow into the:

Kidney Blood Flow

Blood and the Nephron Renal artery blood is filtered through nephrons. About a million nephrons make up the kidney. Nephrons collect liquid to be excreted. Fluids are exchanged between the nephron before blood is returned to renal vein.

Blood Flow The renal artery is split into afferent arterioles. blood brought to glomerulus (a capillary bed) blood leaves through the efferent arterioles no veins involved Efferent arterioles are the beginning of a network of peritubular capillaries, that wrap around the nephron.

Glomerulus and Bowman’s Capsule

Nephron

Nephron Nephrons begin surrounding the glomerulus with the Bowman’s capsule structure. What is the pathway taken by the waste solution once it is collected by the Bowman’s capsule?

Kidney Structure renal cortex – outside of kidney; location of Bowman’s capsule renal medulla – middle of kidney; location of loop of Henle renal pelvis – location of the ends of collecting ducts

Urine Flow Urine leaves the renal pelvis through the ureters and travels to the bladder. Fluid leaves the body through the urethra.

Urinary Tract

Nephron Structure proximal tubule efferent arteriole glomerulus distal tubule Bowman’s capsule collucting duct Loop of Henle afferent arteriole

Urinary System aorta renal cortex renal artery renal vein inferior vena cava renal cortex renal artery renal vein renal medulla kidney ureter bladder renal pelvis nephrons urethra ureter

Urine Formation

Three Functions of Urine Formation filtration – reabsorption – secretion –

Filtration Nutrients move from glomerulus into Bowman’s capsule due to high blood pressure (65 mm Hg; normal ~ 25 mm Hg)

Glomerulus  Bowman’s Capsule? Nutrient Flow Solute Glomerulus  Bowman’s Capsule? water yes NaCl H+ ions amino acids glucose plasma proteins no red blood cells (erythrocytes) platelets

Reabsorption Reabsorption saves us from having to continuously replenish our body with fluid. 20% of fluid flowing into kidney is filtered into nephrons less than 1% of nephron fluid is used to make urine

Reabsorption vs. Secretion protein transporters move nutrients molecules from nephron into the blood protein transporters move wastes from blood to nephron

1. Bowman’s Capsule water and dissolved solutes leave glomerulus; enter Bowman’s capsule water Na+ H+ Cl- glucose amino acids vitamins minerals urea uric acid

2. Proximal Tubule HCO3-, K+ Na+, Cl- H2O amino acids glucose vitamins selective reabsorption of nutrients (need transporters) pH determined by HCO3- reabsorption and H+ secretion H+ NH3

3. Loop of Henle – Descending Limb only permeable to H2O (osmosis) impermeable to salt fluids in tube are being concentrated H2O

4. Loop of Henle – Ascending Limb only permeable to salt (need ionic transporters) impermeable to water NaCl

5. Distal Tubule selective reabsorption of nutrients (need transporters) pH determined by HCO3- reabsorption and H+ secretion HCO3- Na+, Cl- H2O H+ NH3 K+

6. Collecting Duct urine formation by concentration nephron fluid any urea and urine that is reabsorbed is less than that was filtered into nephron NaCl urea water

Kidney Stones crystallization of some urine solutes a 2 – 3 mm stone can obstruct flow to the ureter Treatment: increased water consumption surgery