excretory system

Question 1

What is the general structure of the Excretory System?

Answer 1

Kidneys
Ureters
Urinary Bladder

Question 2

What is the Kidney’s functional unit and what does it do?

Answer 2

Nephron
Performs the vital function of filtering wastes from the blood.

Question 3

What is the main structure of the Kidney’s functional unit?

Answer 3

Glomerulus
Bowman’s Capsule
Tubules

Question 4

How does the kidney perform excretion?

Answer 4

Filtration - Soluble materials are forced through capillary walls into the nephrons.

Reabsorption - Useful materials are absorbed back into the blood. Waste materials are passed in solution to the bladder and stored until expelled from body.

Question 5

How does the kidney control ion levels and solutes?

Answer 5

Substances dissolved in blood have a kidney threshold. If this threshold is surpassed the kidney ensures that excess is excreted in the urine.

Question 6

How does the kidney maintain water balance?

Answer 6

Water balance of blood and tissue fluids is maintained through balancing solutes and water.
Water is used to dilute waste products and transport them in urine to the bladder. Any water not needed is reabsorbed back from the nephron and into the blood.

Question 7

What is the function of Ureters?

Answer 7

Narrow tubes which carry urine from the kidney to the bladder.
Muscles in the ureter walls tighten and relax forcing urine down this tube, away from the kidneys.

Question 8

What is the function of the Urinary Bladder?

Answer 8

Store and empty Urine.
The bladder’s walls relax and expand to store urine, and contract and flatten to empty urine through the urethra.

Question 9

How is Filtration performed?

Answer 9

Occurs across the glomerulus and the bowman’s capsule.
- high pressure of blood in vessels forces fluid through the glomerulus’ capillary walls into the b. capsule
- primary filtrate is passed through the walls

Question 10

How is Reabsorption performed?

Answer 10

The renal tubules reabsorb most of the primary filtrate (all glucose + amino acids, most water + salts)
something to with the collecting ducts is next.

Glucose + Amino Acids are absorbed actively against a conc. gradient.
Water + Salt are absorbed across osmotic gradient.

Question 11

What is Primary Filtrate?

Answer 11

Contains: water, glucose, salts, amino acids, urea, etc. (small molecules)

Has the same composition as Blood Plasma (except for larger molecules like blood proteins, RBCs, WBCs)