Blood + blood vessels and tissue fluid formation

Question 1

What are blood vessels comprised of ?

Answer 1

• Elastic fibres –> elastin = stretch + recoil –> flexible
• Smooth muscle –> contract/relax = changes size of lumen
• Collagen –> structural support .: maintain shape + volume of vessel

Question 2

What is an artery?

Answer 2

Carries 🩸 AWAY from🫀.

• Stretch + recoil: maintain high blood pressure.
• Thick muscle layer = contract/relax to control blood flow.
• Thick wall to prevent bursting from high pressures.

Question 3

What is an arteriole?

Answer 3

• Link artery to capillary
• Low pressure
• Thicker smooth muscle = contract to reduce blood flow into capillary.

Question 4

What is a capillary?

Answer 4

• Link arterioles to venules
• Very small lumen.
• Substances exchanged through capillary walls

Question 5

What are the adaptations of capillaries?

Answer 5

• Large SA:V ratio
• Walls single endothelial cell thick = thin layer for diffusion
• Rate of blood flow falls in capillaries = more time for exchange of substances

Question 5

What are veins?

Answer 5

Carry 🩸 TOWARDS 🫀.

• Low pressure.
• Valves to prevent back flow of blood
• Lots of collagen: maintain shape
• Little elastic fibre
• Wide lumen = easy blood flow

Question 6

What are venules?

Answer 6

• Links capillaries with veins.
• Little smooth muscle
• Thin walls

Question 7

Describe composition of blood?

Answer 7

• Main transport medium.
• Consists of plasma —> carries dissolved glucose, mineral ions, albumin (maintains osmotic potential of blood)
• Platelets –> fragments of cells = clotting mechanism

Question 8

What are the main functions of blood?

Answer 8

Transports:

~O2/CO2 to + from respiring cells

~nitrogenous waste to excretory organs

~platelets to damaged areas.

~ antibodies involved immune response

~ hormones

~maintains steady body temp

~acts as buffer –> minimises pH change

Question 9

What is tissue fluid?

Answer 9

• Fluid cells soaked in to facilitate substance exchange between cells and blood.
• Same composition of plasma without RBC + plasma proteins.
• Diffusion takes place between blood and cells through tissue fluid.

Question 10

What is oncotic pressure?

Answer 10

• Tendancy of H2O moving into blood by osmosis
• Plasma proteins in blood cause difference in WP between blood + tissue fluid

.: osmosis can occur. (osmotic effect)

• Always -3.3 kPa
  ~~> plasma proteins too big to leave blood.

Question 11

What is hydrostatic pressure?

Answer 11

• Pressure generated by heart contractions.
• Changes according to location.

~arterial end: + 4.6 kPa

~venous end: + 2.3 kPa

Question 12

What do the - / + mean?

Answer 12

• Positive pressure = move out of blood
• Negative pressure = move into blood

Question 13

What happens at the arterial end?

Answer 13

• Hydrostatic pressure> oncotic pressure
• Net movement = out fenestrations
• Fluid fills space = tissue fluid.

Question 14

What happens at venous end?

Answer 14

• Hydrostatic pressure < oncotic pressure
• Net movement = in
• Water moves back in capillaries

Question 15

Describe lymph?

Answer 15

• Some fluid does not return to capillaries.
• Drained to form lymph
• less oxygen + fewer nutrients + fatty acids
• One-way valves
• Fluid transported through vessels by squeezing of body muscles.

Question 16

What are lymph nodes?

Answer 16

• Where lymphocytes build up to produce antibodies.
• Intercept bacteria + debris from lymph —> ingested by phagocytes found in nodes.
• Lymphatic system play major role in defence mechanism of body.