L40 - Regulation Of The Fluid Compartments And The Lympathic System

Question 1

What are the 2 major fluid compartments?

Answer 1

• extracellular = 14L // plasma 3, intersitial 14
• intracellular = 28L

Question 2

How are the volumes in the 3 compartments maintained?

Answer 2

• intracellular to interstitium - osmosis
• interstitium to plasma - colloid osmotic pressure (absorption)
• plasma to interstitium - hydrostatic pressure (filtration)

Question 3

What is the definition for osmosis?

Answer 3

Net diffusion of water across a selectively permeable membrane from a region of high water conc to one that has lower water conc (low particle to high particle conc)

Question 4

What is an osmole?

Answer 4

• how the total number of particles in a solution is measured in terms of
• 1 osm = 1 mole of solute particles in 1L

Question 5

What is osmolarity independent of?

Answer 5

MW

Question 6

What are cellular membranes like in selectively permeable membranes?

Answer 6

• permeable to water
• impermeable to solutes (ions)
• osmosis determines distribution of water (size of intracellular and extracellular compartments)

Question 7

What is the osmotic pressure?

Answer 7

Pressure required to prevent osmosis
(Directly proportional to the conc. osmotically active particles in solution)

Question 8

What is the balance of ions maintained by between intracellular and extracellular compartments?

Answer 8

Active transport

Question 9

What are the different effects of changing extracellular media upon cell size: establishment of osmotic eq?

Answer 9

• isotonic - no change (intra = extra)
• hypotonic - cell swells (intra>extra)
• hypertonic - cell shrinks (intra<extra)

Question 10

What is capillary membrane like? What does it allow?

Answer 10

• as capillary membrane is semi-permeable
• permits diffusion of ions, water, oxygen, nutrients and waste
• not proteins

Question 11

What causes colloid osmotic pressure?

Answer 11

• pressure exerted by the higher levels of protein in the plasma compared with interstitial fluid
• draws water back to plasma by osmosis (absorption)

Question 12

What is hydrostatic pressure, what does it drive?

Answer 12

• the force exerted by the blood upon the capillary walls
• drives blood from plasma into interstitial space
• pressure drops as the blood moves through the capillaries

Question 13

What is the overall movement across capillary membrane determined by?

Answer 13

Capillary net filtration pressure (NFP)

Question 14

What is the eqn for NFP?

Answer 14

NFP = (Pc + pi.if) - (P.if + pi.c)
P - hydrostatic pressure
Pi - colloid osmotic pressure
Pc - capillary hp
pi.c - osmotic force due to plasma protein conc = 28mmHg
P.if - interstitial fluid hp = 0
Pi.if - osmotic force due to interstitial fluid protein conc = 3mmHg

Question 15

What is NFP like in arterial and venous end of the capillaries?

Answer 15

• varies
• arterial end - net outward filtration, P dominates
• venous end - net inward filtration, pi dominates

Question 16

What is bulk flow of fluid from the plasma?

Answer 16

• 8L/day net movement of fluid from plasma
• lymphatics pick up spare liquid
• transport back into blood

Question 17

What is the lymp system parallel to? What are the 2 major functions?

Answer 17

• vascular system
• draining fluid from tissue and returning to cardiovascular system
• maintenance of immune response

Question 18

What is the drainage like in the lympathic system?

Answer 18

• fluid passes from blood to interstitial area
• excess passes into lymph capillaries through lymph nodes (detec infection) before passing to blood stream at neck
• collects fats from intestines/liver and deposits into veins

Question 19

What do lymp vessels contain?

Answer 19

Valves - fluid forced along by action of muscles and breathing (respiration)

Question 20

What do larger lymph vessels have?

Answer 20

Surrounded by smooth muscle - contract spontaneously and driven by pacemaker cells

Question 21

What is immunity like in the lymphatic system?

Answer 21

• lymph fluid contains white immune bc (lymphocytes, macrophages, dendritic cells)
• collects antigens - recognised by Blymphocytes in lymph nodes = activation of immunity
• Bcell proliferate = a/bods

Question 22

What can lead to oedemas?

Answer 22

• increased capillary hydrostatic pressure (both ends) - greater net movement out
• decrease in colloid osmotic pressure // reduction in plasma proteins (urine, denuded skin areas, malnutrition)
• blockage of lymph nodes // cancer, infections, surgery

Question 23

What is an intracellular oedema?

Answer 23

• reduction of metabolic system of tissues
• lack of adequate nutrient to the cells // ischaemia