-reabsorption of ions including sodium, organic substances, and water

-cells have mircovilli and apical border

-99% of glucose, amino acids, and other organic nuterients are reabsorbed by the PCT. Involves carrier-mediated transport

-60 to 70% of sodium and chloride ions in the orginal filtrate is reabsorbed by the PCT

-also 60-70% of water is reabsorbed from the tubular fluid into the peritubular fluid

-secretes waste products, toxic substances, and ions brought from peritubular into tubular to be excreted into urine.

-after it passes through PCT, it decreases volume and concentration is isotonic

-transported using carrier-mediated transport and osmosis

Loop of Henle

Most Important fucntion is to establish a concentration gradient.

Ascending and Descending limbs have two very different membrane properties.

-descending limb: this portion is inactive, it is impermeable to salts, it is only permeable to water ONLY. No solutes are organic leave. as water leaves it becomes extremely concentrated. (hypertonic, and it has lost volume 25% of water is reabsorbed) 300 mOsm/L to 1200

-Ascending limb: cell membrane is does NOT allow osmosis. Only sodium chloride (Na+Cl-) co-transport carriers are present, the move this from the filtrate to peritubular fluids. 20 to 25% of Na and Cl ions are reabsorbed.  Filtrate is becomes less concentrated causing a solution that ranges between isotonic and hypotonic compared to original filtrate, but the volume remains the same.1200 to 100

-counter multiplication of the loop of Henle: made possible by how close the parallel tubes are to one another. Fluid movement in opp. directions of one another  (descending is from cortex to medulla)(Ascending is from medulla to cortex)

-this is an efficient way to reabsorb solutes and water before the tubular fluid reaches the distal convoluted tubule and collecting system.

-establish a concentration gradient that will permit the passive reabsorption of water from the tubular fluid in the collecting system.

-aldosterone plays an important role in regulation the reabsorption of sodium in the DCT, it its produced by the adrenal cortex and stiumulates the synthesis and incoporation of sodium/K+ counter-transport carriers and sodium channels in cell membranes along the DCT. the net result is the reabsorption of sodium ions form the filtrate.

-reabsorption of a variable amount of water (about 5%) and some sodium ion, under aldosterone

-carrier-mediated transport and osmosis

-secrete ions, acids, and other materials

-Stimulated by anti-diuretuc hormone (ADH) produced by pituitary gland (When ADH rises so does amount of water reabsorbed)

-When there is no ADH osmosis is not permitted , diluted urine with a large volume

-With ADH low volume that is very concentrated.

-9 % of water

-carrier, and osomosis

-maintain what loop created

-networks around juxtamedullary nephrons (responsible for creating salt gradient)

-uses osmosis and diffusion

-redistribution of water and solutes reabsorbed in the cortex

-uses osmosis and diffusion