MCB 10: Assembly of Cells into Tissues I (Part II: Tissue Fluids)

Question 1

What percentage of fluid is inside the cells and in the extracellular space?

Answer 1

• 55% inside cells
• 45% in the extracellular space

Question 2

What is the composition of extracellular fluid?

Answer 2

• interstitial fluid: 35%
• blood plasma: 7%
• transcellular fluid: 2%

Question 3

Where are extracellular fluid compartments typically found/arranged in tissues?

Answer 3

Question 4

How are extracellular fluids compartmentalised?

Answer 4

• by barriers such as:
• the plasma membrane
• layers of cells that form junctions with each other e.g:
• epithelial cell layers separate various tissues spaces
• endothelial cells line blood vessels, and are the main barrier separating the fluid of the blood (the plasma) and the interstitial fluids

Question 5

Observe the composition of body fluids and their solute concentrations

Answer 5

Question 6

What are the major cations of tissue fluids?

Answer 6

Question 7

What are the major anions of tissue fluids?

Answer 7

Question 8

Why is calcium such an important ion even though it has low concentrations in tissues?

Answer 8

Question 9

Describe the concentration of soluble proteins in tissue fluids

Answer 9

Question 10

What is the definition of osmosis?

Answer 10

• movement of water down its own concentration gradient
• Osmosis moves water toward the area of higher osmolarity and can change cell volume.

Question 11

Definition of osmolarity

Answer 11

• a measure of the concentration of all solute particles in a solution

Question 12

What happens when you have a higher concentration of an impermeant solute on one side?

e.g. higher concentration of protein inside the cell

Answer 12

• as proteins are impermeable, there will be an osmotic difference between the two sides
• water would enter the cell down the osmotic gradient, causing the cell to swell
• this evens out the osmotic balance

Question 13

Why does the cell not burst if water moves into the cell due to a high concentration of impermeant solute in the cell?

Answer 13

• Na ions are being pumped out of the cells constantly
• so that concentration inside is low and high concentration outside
• it is said to act as an impermeant solute
• this is because even though it will diffuse back into the cell, it is being constantly pumped out, so effectively it is impermeant
• in the end you have an impermeant solute both inside and outside the cell, so there is no osmotic imbalance

Question 14

What is hypertonic?

Answer 14

Question 15

What is hypotonic?

Answer 15

Question 16

What is isotonic?

Answer 16

Question 17

Why are vessels (both blood and lymph) a key part of what makes a tissue?

Answer 17

Question 18

How much plasma leaks out of blood vessels each day?

Answer 18

Question 19

Describe the fluid and solute movement across a blood vessel

Answer 19

Question 20

What is the definition of hydrostatic pressure?

Answer 20

• the pressure exerted by an aqueous fluid in a confined space

Question 21

Definition of colloidal osmotic pressure (COP or oncotic pressure)

Answer 21

• a form of osmotic pressure exerted by proteins in a blood vessel’s plasma that tends to pull water into the circulatory system.
• It is the opposing force to hydrostatic pressure

Question 22

If fluid is constantly leaking out of blood vessels, how does it get returned to the blood?

Answer 22

• Lymphatic capillaries collect interstitial fluid that is destined for return to the blood circulation.
• In tissues, these small lymph vessels are “blind-ending”, in other words, their ends are not directly connected to other vessels, unlike blood vessels.
• Fluid has to enter from the interstitial space, across their walls.

Question 23

Describe the lymphatic system

Answer 23

Question 24

What is oedema?

Answer 24