1. Urine Formation
Is a result of three processes which help to regulate the blood composition and volume
Filtration
Reabsorption
Secretion
Function of Nephron Video

2. Filtration Non-selective, passive process
Forcing of fluids and dissolved substances smaller than a certain size through a membrane by pressure
Filtrate - (no blood cells or most proteins are part of the filtrate)
Begins at the glomerulus

4. Structure of Nephrons are advantageous in 3 ways
Glomerular capsule contains glomerular capillaries with lots of SA for filtration
Filtering membrane is very thin and selectively permeable (water, glucose, vitamins, amino acids, nitrogenous wastes can pass)
Efferent arteriole is smaller in diameter than afferent arteriolehigh resistance to the outflow of blood from glomerulus. (flows from high concentration gradient to low)

6. Tubular Reabsorption
99% of filtrate is reabsorbed back into the blood of the peritubular capillaries
Some water, glucose, a.a. and ions such as Na+, K+, Cl-, HCO3-
carried out by epithelial cells mostly in the proximal convoluted tubules
Osmosis, diffusion
active transport especially plays a role with sodium and chloride ions

8. Water content of the blood
Regulated mainly by ADH (antidiuretic hormone from posterior pituitary gland) via negative feedback loops
In the absence of ADH, portions of the nephron are impermeable to water urine contains a large volume of water
In the presence of ADH nephrons are permeable

9. When water conc. in blood is lowADH is released into bloodcells become more permeable to water and they release water into the blood
As more water is reabsorbed, the blood’s water conc. increases

11. Tubular Secretion Two functions: Help control blood pH
Adds material to the filtrate into the blood for excretion
Secreted materials include:
Potassium (K+)
Hydrogen (H+)
Ammonium (NH4+)
Creatinine, urea and certain drugs
occurs in renal tubule and collecting duct