Homeostasis: Body Fluid

Question 1

What is the compositon of urine?

Answer 1

• 95% water
• 2.8% dissolved salts and other ions
• 2% urea
• 0.2% creatinine, ammonia, and uric acid

Question 2

What are the three kinds of extracellular fluid?

Answer 2

1. interstitial - fluid which bathes the cells;
2. intravascular - fluid found inside blood vessels; and
3. transcellular - fluid found in the ocular and CSF compartments.

Question 3

Define osmotic pressure (2 marks)

Answer 3

the capacity for a solution to take in a solvent via osmosis or the pressure needed to prevent osmosis.

Question 4

List two things that could cause osmotic pressure to increase and two things that could cause it to decrease. (3 marks)

Answer 4

Osmotic pressure can increase by:

• an increase in non-iodised water consumption;
• not-replenishing essential amounts of dissolved salts constantly; and
• sweating (loss of dissolved salts).

Osmotic pressure can decrease by:

• a lack in water consumption (dilution occurs);
• consuming high-salt foods; and
• never exercising.

Question 5

What substances are reabsorbed back into the blood during selective reabsorption?

Answer 5

Glucose, amino acids, K+, Na+, other ions…

Question 6

What substances are secreted back into the DCT via tubular secretion?

Answer 6

K+, creatinine, other ions and drugs.