nephron: urinary system

nephron

functional unit of the kidney

filtrate

anything that is small enough to fit through the fenetrations of the blood capillaries (water, glucose, amino acids)

bowmans capsule

cup-shaped strucutre of the nephron of a kidney which encloses the glomerulus and which filtration takes place.

glomerulus

A ball of capillaries surrounded by Bowman's capsule in the nephron and serving as the site of filtration in the vertebrate kidney. (means ball of yarn)

afferent arteriole

The small artery that carries blood toward the capillaries of the glomerulus; still larger than the efferent arteriole to generate pressure so it can filter

efferent arteriole

The small artery that carries blood away from the capillaries of the glomerulus, but continues to wrap around tubules as peritubular capillaries

peritubular capillaries

the network of capillaries from the efferent arteriole that surrounds the tubules at a close proximity to reabsorb substances back into the stream

filtration

substances are forced out through the glomerular fenetrations by pressure created by the decreasing diameter of the arteriole; regulates urine by pressure

blood pressure

drives filtration (positive pressure- 55mmHg)

osmotic pressure

water is attracted by the proteins in the capillaries, so it goes back in (osmosis) (negative pressure-30mmHg)

capsular pressure

the pressure of the filtrate/fluid that is already inside the capsular space; 2 things can't be some place at once (negative pressure-15mmHg)

net filtration pressure (NFP)

NFP= BP-OP-CP (10mmHg)

Golmerular Filtration Rate (GFR)

how fast the pressure happens- measures how much blood passes through glomerulus

stress

increased blood pressure- causes vasoconstriction which increases pressure, meaning you make less urine

starvation

causes decreased osmotic pressure- your body starts to eat the plasma proteins in the blood, so water doesn't go back in which means you pee too much

increased capsule space

creates renal calculi (kidney stones) and blocks filtrate from coming out

reabsorption

process whereby renal tubules return materials necessary to the body back into the bloodstream because filtration filters out even the good stuff

sodium-potassium pump

uses ATP to bring sodium back into the bloodstream, and water follows salt through osmosis, other substances also follow

proximal convoluted tubule (PCT)

drains the filtrate away from capsule. has microvilli which increases surface area allowing for more absorption, has mitochondria to power sodium-potassium pump with ATP (65% of reabsorption)

loop of Henle

the part of a kidney tubule that forms a long loop in the medulla of the kidney, from which water and salts are resorbed into the blood. (15%)

distal convoluted tubule (DCT)

segment of the nephron between the nephron loop and the collecting duct which doesn't have microvilli or a lot of mitochondria so can't absorb as much (with collecting duct absorbs 19%)

collecting duct

the location in the kidney where processed filtrate, called urine, is collected from the renal tubules in the medulla.

secretion

moves large, unfiltered, and reabsorbed toxins back into the renal tubules (essentially the reverse of reabsorption)

secretion purpose:

-eliminates nitrogenous wastes (urea and uric acid)

-rids the body of excess potassium

-controls pH (by secreting more H+)

-allows molecules too big to be filtered to leave the body (ex penicillin)

urine composition

95% water and 5% solutes