Lecture 5- Fluid compartments of the body

Question 1

What are the main fluid compartments of the body and give their approximates sizes

Answer 1

INTRACELLULAR= 23L= 55%
EXTTRACELLULAR = 19L= 45%
    - Interstitial Fluid = 15L = 36%
    - Blood Plasma = 3L = 7%
    - Transcellular fluid = 1L = 2%

Question 2

What is transcellular fluid?

Answer 2

• Cerebrospinal fluid (CSF)
• ocular fluid
• synovial fluid

Question 3

What are the main anions and cations found extra and intra cellularly?

Answer 3

EC: Na+ and Cl-
IC: K+ PO4^3-
Ca2+ found at very low concentrations IC. Used as signalling ion–> adding or removing small amount= big change in conc
Proteins IC>EC

Question 4

What are the pH and osmolarities IC and EC?

Answer 4

pH EC: 7.4 IC: 7.1

osmolarity EC=IC 285mosmol/l

Question 5

Define osmolarity

Answer 5

Conc of all particles in solution e.g. if 1mmol/L of NaCl then it will be 2mmol/L

Question 6

Define osmosis

Answer 6

Movement of water towards the area of higher osmolarity (area of lower water conc) –> change in cell volume

Question 7

Why is osmolarity not a reliable to guess the effects in cell volume?

Answer 7

It does not take into account of cell permeability

Question 8

Define tonicity

Answer 8

The strength of a solution as it affects final cell volume

Question 9

What does tonality depend on?

Answer 9

Cell membrane permeability and solution composition

Question 10

Define hypertonic, hypotonic and isotonic

Answer 10

1) Hypertonic: osm impermeant solutes out> in –> cell shrinks
2) Hypotonic: osm impermant solutes out< in –> cell swells
3) Isotonic: osm impermeant solutes out=in –> no change

Question 11

What are the different ways solutes get across membranes?

Answer 11

PASSIVE

1) Simple diffusion: O2, CO2
2) Channel-mediated: water, ions, urea
3) Transporter-mediated: lactic acid

ACTIVE

4) Transporter mediated:Na+ pumped back out of cell, Na+/ K+ pump
- Secondary active transport: H+/ Na+
5) Endocytosis and exocytosis: peptide hormones from endocrine glands

Question 12

How much plasma leaks out of blood vessels each day?

Answer 12

9L

Question 13

What are the two ways substances exchange across the capillary wall?

Answer 13

1) Lipid soluble- through endothelial cells
2) small water-soluble- through the pores between cells
3) Exchangeable proteins- by vesicular transport

PLASMA PROTEINS REMAIN

Question 14

What causes osmotic pressure in capillaries?

Answer 14

Plasma proteins (Colloid Osmotic pressure)

Question 15

What is oedema?

Answer 15

swelling of a tissue because of excess interstitial fluid

Question 16

What causes oedema?

Answer 16

hydrostatic pressure> osmotic pressure
Caused by imbalance in the normal cycle of fluid exchange in tissues–> fluid builds up in interstitium which would normally be drained by lymphatic vessels

Question 17

What happens during inflammatory oedema? what might cause it?

Answer 17

Vessels become more leaky during inflammation= swelling- leakage> lymphatic drainage

Insect bites

Question 18

What happens during hydrostatic oedema? what might cause it?

Answer 18

Caused by high bp –> Increased hydrostatic pressure in vessels= leakage> lymphatic drainage

Question 19

Name two other causes of oedema

Answer 19

• lymph node removal

- elephantiasis- parasitic worms block lymph vessels