Osmoregulation - Part 2 (11/14)

What does the kidney do in osmoregulation?

Performs filtration and absorption in mammals

How does the kidney use filtration and reabsorption in osmoregulation?

1. Filters the blood by separating the water-based part of the blood (blood plasma) from the blood

2. Reabsorbs most of the water, electrolytes, and non-waste molecules into the blood

What is the renal artery?

Supplies oxygen-rich blood to the kidneys

What is the renal vein?

Carries deoxygenated blood back to the heart

What is the ureter?

Carries urine from the kidney to the urinary bladder

What is the urinary bladder?

Stores urine

What are the three major regions of the kidney and what happens in each?

1. Renal Cortex

Area where the majority of the filtering units, called nephrons, can be found

2. Renal medulla

Area where filtered blood plasma is concentrated into its final form (urine)

3. Renal Pelvis

Catches urine as it is produced in the renal medulla and funnels it into the ureter

What is a nephron and how does it function?

Windy, tube-shaped filtering units called nephrons

What is the medullary gradient and how does it function?

An osmotic gradient of electrolytes that allows the nephron to use active transport, diffusion, and osmosis to reabsorb filtered plasma back into the blood.

What are the five major sections of the nephron in order that pre-urine flows through them?

1. Renal corpuscle

2. Proximal tubule

3. Loop of Henle

4. Distal tubule

5. Collecting duct

What does the renal corpuscle do and how does it do it?

The renal corpuscle is where plasmids are filtered out by the blood (called filtrate or pre-urine)

What is the glomerulus and what force “pushes” filtration in the glomerulus?

A network of tiny blood vessels inside the corpuscle

• Allows the blood plasmid + small molecules in it to leave

How can the imbalances of blood pressure cause kidney problems?

1. Long term high blood pressure (hypertension) damages the corpuscle and causes kidney failure

2. Short term low blood pressure (hypotension) stops the filtration process and allows toxic waste products to build up in the body

What is obligatory reabsorption and where in the nephron does it happen?

Obligatory reabsorption is the process that automatically reabsorbs 90% of pre-urine

Happens in:

1. Proximal tubule

2. Loop of Henle

What does the proximal tubule do during obligatory reabsorption? How does it happen?

1. Proximal tubule

Uses active transport, diffusion, and osmosis to selectively reabsorb 2/3 of all materials in the pre-urine

• Reabsorbs some of the water and electrolytes

• Reabsorbs all of the nutrients and vitamins

Pre-urine that exits the Proximal tubule contains water, electrolytes, and waste products

What does the Loop of Henle do during obligatory reabsorption? How does it happen?

2. Loop of Henle

Uses only diffusion and osmosis to reabsorb water and electrolytes

• Uses the medullary gradient instead of using any energy

What are the descending limb and ascending limb and how is reabsorption different in each limb?

Descending limb is only permeable to water

Ascending limb is only permeable to electrolytes

What is regulated reabsorption and where in the nephron does it happen?

The remaining 15-18 liters of pre-urine is regulated by homeostasis

Happens in the:

1. Distal tubule

2. Collecting duct

What does the distal tubule do in regulated reabsorption and how is it regulated by aldosterone levels?

The distal tubule reabsorbs sodium and chloride by active transport, how much is reabsorbed is regulated by aldosterone

If sodium levels in the body are low:

• A large amount of aldosterone is released

• Distal tubule reabsorbs more sodium and chloride

If sodium levels in the body are high:

• A small amount of aldosterone is released

• Distal tubule reabsorbs less sodium and chloride

What does the collecting duct do in regulated reabsorption and how is it regulated by ADH levels?

The collecting dust only reabsorbs water, how much is absorbed is regulated by the hormone anti-diuretic hormone (ADH)

If there is a low level of water in the body:

• Large amount of ADH is released

• Collecting duct reabsorbs more water

If there is a high level of water in the body:

• Low amount of ADH is released

• Collecting duct reabsorbs less water