Blood + blood vessels and tissue fluid formation Flashcards
How are blood vessels comprised?
Elastic fibres –> elastin = stretch + recoil –> flexible
Smooth muscle –> contract/relax = changes size of lumen
Collagen –> structural support .: maintain shape + volume of vessel
What is an artery?
Carries 🩸 AWAY from🫀.
Stretch + recoil to maintain high blood pressure.
Thick muscle layer = contract/relax to control blood flow.
Thick wall to prevent bursting from high pressures.
What is an arteriole?
Link artery to capillary
Low pressure
Thicker smooth muscle = contract to reduce blood flow into capillary.
What is a capillary?
Link arterioles to venules
Very small lumen.
Substances exchanged through capillary walls.
What are the adaptations of capillaries?
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 materials to occur.
What are veins?
Carry 🩸 TOWARDS 🫀.
Low pressure.
Valves to prevent back flow of blood
Lots of collagen
Little elastic fibre
Wide lumen = easy blood flow
What are venules?
Links capillaries with veins.
Little smooth muscle
Thin walls
Describe composition of blood?
Main transport medium.
Consists of plasma —> carries dissolved glucose, mineral ions, albumin (maintains osmotic potential of blood)
Platelets –> fragments of cells = clotting mechanism
What are the main functions of blood?
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
What is tissue fluid?
Fluid cells soaked in to facilitate substance exchange between cells and blood.
Same composition of plasma without RBC and plasma proteins.
Diffusion takes place between blood and cells through tissue fluid.
What is oncotic pressure?
Tendancy of H2O moving into blood by osmosis. due to presence of proteins.
Plasma proteins in blood cause difference in WP between blood and tissue fluid
.: osmosis can occur. (osmotic effect)
Always -3.3 kPa
~~> plasma proteins too big to leave blood.
What is hydrostatic pressure?
Pressure generated by heart contractions.
Changes according to location.
~arterial end: + 4.6 kPa
~venous end: + 2.3 kPa
What do the - / + mean?
Positive pressure = move out of blood
Negative pressure = move into blood
What happens at the arterial end?
Hydrostatic pressure> oncotic pressure
Ultrafiltration
Net movement = out fenestrations
Fluid fills space = tissue fluid.
What happens at venous end?
Hydrostatic pressure < oncotic pressure
Net movement = in
Reabsorption
Water moves back in capillaries
Describe lymph?
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.
What are lymph nodes?
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.
