Tissue fluid

Question 1

What is tissue fluid?

Answer 1

• fluid that surrounds all cells in body
• contains water, glucose, amino acids, fatty acids, ions & O2

Question 2

Components of blood?

Answer 2

1. 55% plasma (solution)
   - 90% water
   - 10% dissolved substances: nutrients e.g. glucose & amino acids, wastes (e.g. urea), mineral salts, hormones, gases, plasma proteins
2. 45% cells (suspension)
   - RBCs
   - WBCs
   - platelets

Question 3

Hydrostatic pressure?

Answer 3

*outward force (acts on system from outside)
- created by contraction of ventricles of heart (pressure higher inside capillaries than outside)
- blood js passed thru artery & arteriole so - blood under high press aka hydrostatic pressure tends to force fluid out of blood into tissue

Question 4

Osmotic pressure?

Answer 4

inward force as water potential higher outside than inside (due to plasma proteins in blood plasma & not in tissue fluid)
- plasma proteins r hydrophilic so - lower water potential of blood plasma so - tendency for water to move back into blood by osmosis aka osmotic pressure

Question 5

What’s forced out v what remains in capillary?

Answer 5

• water
• dissolved minerals & salts
• glucose
• small proteins & amino acids
• fatty acids
• O2
• RBCs
• platelets
• large proteins

Question 6

At the arteriole end of capillary…

Answer 6

• hydrostatic > osmotic pressure so
• water & dissolved solutes forced out of arteriole end of capillaries thru gaps (fenestra) between endothelial cells aka ultrafiltration - forming tissue fluid
• plasma proteins & cells remain inside as too large
• fluid is cell’s immediate environment & provides cell w what they need & receives waste products from cells e.g CO2

Question 7

Why is hydrostatic pressure less at venule end?

Answer 7

• *loss of liquid (vol of blood decreases as water left arteriole end)
• further from heart
• friction w walls slow blood down

Question 8

At the venule end of capillary…

Answer 8

• hydrostatic pressure much lower as - large amount of water left blood BUT
• osmotic pressure still high - due to plasma proteins (water potential gradient greater as proteins become more conc.)
• hydrostatic pressure < osmotic pressure - causes water to move back into blood by osmosis
• 90% water & dissolved solutes move back into venule end of capillaries down water potential gradient by osmosis
• 110% moves into lymphatic system - eventually drains back into blood

Question 9

Lymph?

Answer 9

not all liquid will be reabsorbed by osmosis - equilibrium reached
- rest of tissue fluid is absorbed into lymphatic system & eventually drains back into bloodstream near heart

Question 10

10% of tissue fluid?

Answer 10

• drains into a series of blind ended vessels aka lymph capillaries…
• connect into larger: lymph vessels, forming lymphatic system
• lymph fluid moves along when lymph vesses r squeezed by nearby skeletal muscles
• valves in vessels help to keep fluid moving forward
• eventually fluid returns to blood via blood vessels under collar bone