Tissues - Fluids

Question 1

What are the main fluid compartments?

Answer 1

Intracellular fluid, and extracellular fluid (split into interstitial fluid between cells, blood plasma, and transcellular fluid).

Question 2

What are the types of transcellular fluid?

Answer 2

Cerebrospinal fluid, ocular fluid, and synovial fluid

Question 3

What is the approximate size of the intracellular fluid?

Answer 3

23 litres (55% of body water)

Question 4

What is the approximate size of the extracellular fluid?

Answer 4

19 litres - 45% of body fluid

Question 5

What is the approximate size of the transcellular fluid?

Answer 5

1 litre, 2% of body water

Question 6

What is the approximate size of the blood plasma?

Answer 6

3 litres - 7% of body water

Question 7

What is the approximate size of the interstitial fluid?

Answer 7

15 litres - 36% of body water

Question 8

What are the main extracellular and intracellular cations?

Answer 8

Main extracellular is sodium ions - 150mmol/l compared to 10mmol/l in muscle.
Main intracellular is potassium ions - 150mmol/l compared with 5mmol/l in muscle.

Question 9

What is the relative composition of free calcium ions in the plasma compared to in the muscle?

Answer 9

In the plasma there is 2mmol/l, whereas in the muscle there is 10^-4mmol/l. This is because calcium is an intracellular signalling ion.

Question 10

What are the main extracellular and intracellular anions?

Answer 10

Extracellular is chloride ions, 110mmol/l in plasma and 5mmol/l in muscle. Intracellular is organic phosphates, 130mmol/l in muscle compared with 5mmol/l in plasma.

Question 11

What is the relative composition of proteins inside and outside the muscle?

Answer 11

1mmol/l in the plasma, and 2mmol/l in the muscle. The proteins are in low concentration but have a high charge in the muscle.

Question 12

What is the relative pH in the plasma and in the muscle cell?

Answer 12

7.4 in the plasma and 7.1 in the muscle cell

Question 13

Define osmosis

Answer 13

Movement of water down its own concentration gradient, toward the area of higher osmolarity

Question 14

What is osmolarity?

Answer 14

A measure of the concentration of all solute particles in a solution. (Eg. 150mmol/l NaCl have a concentration in total of 300mmol/l)

Question 15

What is the difference between osmolarity and tonicity?

Answer 15

Tonicity takes into account the permeability of the cell - osmosis does not. Eg. A cell could have a higher osmolarity than the extracellular fluid but there will be no not movement if the cell is permeable to the solute.

Question 16

Define tonicity

Answer 16

The strength of a solution as it affects the final cell volune

Question 17

Can the difference in concentration of permeant solutes result in changes in cell volume?

Answer 17

Yes - if the difference is very large.

Question 18

What are the different terms of tonicity?

Answer 18

• Hypertonic solutions have a higher osmolarity of impermeant solutes outside the cell.
• Hypotonic solutions have a higher osmolarity is impermeant solutes inside the cell.
• Isotonic solutions have an equal osmolarity of impermeant solutes inside and outside the cell

Question 19

How do cells in the human body not explode due to high conc. of proteins inside the cell?

Answer 19

• Permeable to water and impermeable to proteins - making the inside of the cell have a high osmolarity
• To counteract this, sodium ions are pumped out of the cell, making the osmolarity outside the cell increase. The cell becomes essentially impermeable to sodium ions.
• This requires active processes

Question 20

How do tissue preservation solutions work?

Answer 20

• The blood is replaced with cold solutions via the arterial supply. The composition of the solution prevents deterioration.
• Sodium pumps stop working after cooling, so sodium ions may enter the cell alongside water. Potassium ions exit.
• The entry of water causes cells to swell and blebs form causing cell death.
• The solution used to preserve (university of Wisconsin solution) lacks sodium and calcium ions. There are impermeant solutes and starch present to increase osmolarity outside the cell. This reduces cell swelling.

Question 21

Define odema

Answer 21

Swelling of a tissue because of excess interstitial fluid

Question 22

What are the causes of oedema?

Answer 22

• Imbalance in the normal cycle of fluid exchange in the tissues, so tissue fluid accumulates.
• Tissue fluid is not drained by the lymphatic system.
• Occurs in breast cancer patients, elephantitis (where parasitic worms block lymph vessels preventing drainage), when lymph nodes are removed, when there is hypertension, and in the immune response (inflammation).

Question 23

What causes capillaries to become leaky?

Answer 23

High hydrostatic pressure- higher than osmotic pressure, causing fluid los to the interstitial space and increasing pore size.

Question 24

Explain the main types of exchange across the capillary wall

Answer 24

• Plasma proteins can’t cross the cell membranes/pores between cells
• Exchangeable proteins are moved by vesicular transport (exocytosis using encapsulation)
• Small water-soluble substances pass through the pores between cells
• Lipid-soluble substances pass through the endothelial cells by diffusion