Excretory System

Question 1

What are the functions of the kidneys?

Answer 1

1. TO rid the body of wastes especially nitrogenous wastes such as urea.
2. To regulate the balance of fluid, pH, and salt.

Question 1

How does it perform these functions?

Answer 1

• These outcomes are achieved by filtering the blood as it passes through the kidneys.
• Waste products are removed through the process of filtration and tubular secretion.
• Useful products are returned to the body through the process of selective reabsorption.

Question 2

What is the structure of the urinary system?

Answer 2

• 2x Kidneys
• 2 Ureters
• 1 Urinary Bladder
• 1 Urethra

Question 3

What is the nephron?

Answer 3

The nephron is the functional unit of the kidneys, which consists of the bowmans capsule, and the renal tubule and their associated blood supply. Each kidney contains approximately 1 million nephrons.

Question 4

What is the renal corpuscle?

Answer 4

This is where filtration takes places.
The renal corpuscle consists of the Bowmans capsule, and a mass of blood capillaries called the glomerulus.

Question 5

What are the filtrates resulting from the renal corpuscle?

Answer 5

Water (Passive) , Urea, Glucose, Amino Acids, Vitamins, salts, especially sodium and chloride (passive)

Question 6

Describe the flow of waste products in the glomerulus.

Answer 6

Afferent Arteriole -> Glomerulus -> Smaller molecules such as amino acids or glucose or ions are able to move through the endothelial cells, which are very fenestrated, allowing small molecules to pass through the walls of the vessel -> The smaller molecules are able to pass through the Basement membrane, while larger molecules such as RBC or proteins are unable to even if they pass through the Endothelial cells -> Epithelial Cells which alos enhance the filtration -> Efferent Arteriole -> Proximal Convolute Tubule.

Question 7

Describe the Proximal Convolute Tubule.

Answer 7

This is the tube closest to the Bowman’s Capsule.
- Microvilli line the proximal tubule creating a brush lining which greatly increases the surface area for reabsorption.

Question 8

What substances are reabsorbed?

Answer 8

PCT: Water (60-70%), Salts (60-70%), Glucose (100%), Amino Acids (100%), Vitamins (100%).
Loop of Henle: Water (25%), Salts (25%).
DCT: Water (5%), Salts (5%).
Common Collecting Duct: Water (5%)

Question 9

What substances are secreted through tubular secretion?

Answer 9

1. Hydrogen Ions.
2. Ammonia
3. Creatinine.
4. Toxins.
5. Drugs.
6. Neurotransmitters.

Question 10

What is Urine?

Answer 10

Urine is a clear transparent fluid which is usually amber in colour.
it is stored in the urinary bladder and eliminated through the urethra.

Question 11

What is the composition of Urine?

Answer 11

Water - 95%
Other Solutes (5%) - Organic molecules such as urea, uric acid, and creatinine, ions, and other metabolic wastes.