Urinary system- Urine production

Urine production within the glomerulus begins when?

blood enters via an afferent arteriole where blood pressure forces H₂O and small molecules (ultra filtrate), like urea out through pores in the glomerular capillaries into the surrounding Bowman’s capsule

Where does blood leave the glomerulus?

via efferent arteriole

what happens to the ultra-filtrate that is pushed out of the glomeruli?

it collects in Bowman’s capsule and drains into the proximal convoluted tubule-this is foundation of what will become urine

Glomerular Filtration Rate (GFR):

the volume of fluid filtered from the glomerulus into Bowman’s capsule per unit time.

Why is the calculating of GFR important?

for assessment of the excretory function of the kidneys

What occurs in the PCT?

selective reabsorption

Water, glucose, vitamins, important ions and most AAs are reabsorbed from the PCT back into?

adjacent peritubular capillaries via active transport

What happens when the concentration of a substance in the blood reaches a certain level?

the substance is no longer reabsorbed from the PCT; it remains in the urine

What does the PCT no longer reabsorbing substances after a certain level prevent?

the composition of the blood from fluctuating, and it helps regulate the levels of glucose and inorganic ions

What remains in the urine in the PCT?

urea and additional ultra filtrate

How is the Loop of Henle able to conserve H₂O and further concentrate urine?

due to the concentration gradient established in the medulla

The descending loop has low permeability for what?

ions and urea

the descending loop has high permeability for?

H₂O

Why does H₂O move out of the descending loop?

because as water passes through the area of high Na⁺ concentration produced by the ascending loop, water gets pulled toward the high Na

What does this removal of H₂O from the descending loop do?

it concentrates the urine while conserving H₂O for the body

The ascending loop has low permeability for?

H₂O and ions

the ascending loop has high permeability?

Na⁺

What does the result of Na⁺ being actively pumped out of the ascending loop and water not being able to re-enter cause?

it causes a higher concentration of Na⁺ in the medulla, which supports water removal in the descending loop

The distal convoluted tubule is where most of what from the ultra filtrate are re-absorbed?

minerals and salts

What wastes are actively secreted into the urine in the DCT?

H⁺, K⁺, toxic and foreign substances (i.e. drugs, penicillin, uric acid, creatine, creatinine)

DCTs from several nephrons drain into what?

a common collecting duct

What is the final step in the conservation of H₂O and concentration of urine?

when fluid passes through the collecting duct that passes through the concentration gradient, additional H₂O leaves due to osmosis