Human Anatomy Unit 7 Quiz 2

To produce urine, what do nephrons and collecting ducts do?

Three basic things:

• Glomerular filtration: water & most blood solutes move across glomerular wall into Bowman’s capsule.

• Tubular reabsorption: most water & solutes are moved back into the bloodstream from the tubules.

• Tubular secretion: some materials (water, drugs, wastes) from blood are moved back into the tubules.

What is the glomerular filtration role of nephrons and collecting ducts?

water & most blood solutes move across glomerular wall into Bowman’s capsule

What is the tubular reabsorption role of nephrons and collecting ducts?

most water & solutes are moved back into the bloodstream from the tubules

What is the tubular secretion role of nephrons and collecting ducts?

some materials (water, drugs, wastes) from blood are moved back into the tubules

What is the overall goal / role of nephrons and collecting ducts?

to produce urine

What is the role of nephrons? How does it achieve this role?

By filtering, reabsorbing, & secreting, nephrons help to maintain homeostasis of blood volume & composition.

How many nephrons are there per kidney?

1 million

How much liquid do nephrons filter? Where does this liquid go?

150-180 liters/day, with 99% of it returning to the bloodstream and 1-2 liters being excreted as urine

What are characteristics of the cells that line the glomerular capillaries?

• They’re leaky and form a filtration membrane:

  • Large solutes like large proteins & blood cells can’t pass through.

  • Small molecules do pass through the capillaries & into Bowman’s capsule:

    • Water, glucose, vitamins, amino acids, ammonia, urea, ions & some small proteins.

What can’t pass through the filtration membrane that line the glomerular capillaries?

Large solutes like large proteins & blood cells

What can pass through the filtration membrane that line the glomerular capillaries?

Small molecules (pass into Bowman’s capsule): Water, glucose, vitamins, amino acids, ammonia, urea, ions & some small proteins.

What is involved in filtration?

• the leaky nature / permeability of the cells that line the glomerular capillaries

• glomerular blood pressure

What is the role of glomerular blood pressure?

• The hydrostatic pressure of blood here is high & helps to force fluids & solutes through the filtration membrane like pushing material through a sieve.

• The fluid that collects in Bowman’s capsule is called filtrate.

• Amount of filtrate formed each minute determines the glomerular filtration rate (GFR).

What is filtrate?

the fluid that collects in Bowman’s capsule

What is GFR?

glomerular filtration rate; determined by the amount of filtrate formed each minute

What mechanisms do kidneys have to adjust GFR?

• Renal autoregulation: if blood pressure rises or falls, afferent vessels to the nephrons adjust to keep GFR constant.

• Neural regulation: CNS responds to things like exercise or hemorrhage to decrease GFR (less urine & more blood volume to tissues)

• Hormonal regulation: Angiotensin II constricts vessels to the nephron when blood volume decreases.

What is renal autoregulation?

if blood pressure rises or falls, afferent vessels to the nephrons adjust to keep GFR constant

What is neural regulation?

CNS responds to things like exercise or hemorrhage to decrease GFR (less urine & more blood volume to tissues)

What is hormonal regulation?

Angiotensin II constricts vessels to the nephron when blood volume decreases

What happens to the things that enter the kidney?

Almost everything that enters the kidney is reabsorbed (put back into the bloodstream)

What is the progression of filtered fluid?

• Filtered fluid becomes tubular fluid once it enters the proximal convoluted tubule (PCT).

• Composition of tubular fluid changes as it passes through nephron.

• Fluid that drains from papillary duct at the end is called urine.

What is tubular fluid?

filtered fluid once it enters the proximal convoluted tubule (PCT)

What is urine?

Fluid that drains from the papillary duct at the end

How can substances be reabsorbed?

via active & passive transport or pinocytosis

How does the kidney maintain homeostasis?

By reabsorbing (bringing substances back into the bloodstream) and secreting (putting substances from the blood into the tubular fluid), the kidney is able to maintain constant fluid volume in your body even though your intake can vary

When fluid intake is low, what happens to excretion?

kidney can conserve water & excrete small amounts of concentrated urine

When fluid intake is high, what happens to excretion?

urine is more dilute & in larger quantities