Blood / Tissue Fluid Flashcards
What are the components of the blood?
Blood plasma, erythrocytes, white blood cells, platelets
What is the blood plasma and what does it contain?
A watery solution containing dissolved substances (glucose, amino acids, mineral ions). It also contains dissolved oxygen and plasma proteins.
What is blood responsible for transporting?
- O2 to / CO2 from respiring cells
- digested food from small intestine
- nitrogenous waste products to excretory organs
- cells / antibodies involved in immune response
- platelets to damaged areas
- food molecules
What happens to the blood in the capillaries?
Fluid passes out of the blood and bathes the tissue cells - known as tissue fluid.
How does tissue fluid leave and return to the blood?
It leaves the blood at the arterial end to transfer dissolved substances to cells.
Waste molecules pass into the tissue fluid which returns to the bloodstream at the venous end of the capillaries.
Why is fluid forced out at the arterial end of capillaries?
Blood is under relatively high pressure - hydrostatic pressure. This forces the fluid out of the blood.
Why does tissue fluid return to the blood at the venous end of capillaries?
Plasma proteins are hydrophilic, and stay in the bloodstream. Their presence lowers the water potential, meaning fluid has a tendency to move back into the blood by osmosis.
This is known as oncotic pressure.
Explain the differences in hydrostatic and oncotic pressure at each end of the capillary.
Arterial end:
hydrostatic > oncontic - fluid forced out of the blood
Venous end:
oncotic > hydrostatic - fluid drains back in due to presence of hydrophilic plasma proteins
What is the draining of fluid out of the blood known as?
Ultrafiltration
How much tissue fluid is re-absorbed into the blood?
Around 90%
What happens to tissue fluid that does not drain back into the blood?
The remaining 10% that is not re-absorbed drains into lymph capillaries and into the lymphatic system.
What is tissue fluid known as after it drains into the lymphatic system?
Lymph fluid
How is lymph fluid transported?
It is transported through the lymph vessels by the squeezing of skeletal muscles. One way valves prevent the backflow of lymph.
Lymph returns to the bloodstream via subclavian veins under the collarbone.
What are lymph nodes?
Nodes along lymph vessels where lymphocytes build up and produce antibodies.
What are the adaptations of erythrocytes?
- biconcave disc - large SA for exchange
- no nucleus or organelles associated with protein synthesis (ribosomes, rough ER, golgi)
- no mitochondria in mature cells
- contains haemoglobin
- approx 7 micrometers diameter - roughly same as capillaries - shorter exchange pathway
What happens to oxygen when it binds to haemolglobin?
It is taken out of solution, meaning a steep concentration gradient is maintained.
