Tissue fluid and lymphatic system

• blood is composed of plasma, red blood cells, white blood cells, platelets, dissolved gases, ions, monomers (glucose and amino acids), hormones and plasma proteins.
• blood is used to transport nutrients, oxygen, and waste products around the body, carry lymphocytes for defence, thermoregulation and maintaining ph levels.
• specialized features of an erythrocyte

  No nucleus or organelles - more haemoglobin, biconcave - large surface area to volume ratio for gas exchange, 7 micrometers - larger than capillary thus slows down blood flow for diffusion of substances.
• Tissue fluid is made at the arteriole end of the capillary, where there is a high hydrostatic pressure which forces molecules that are small enough to pass through the pores in the endothelium out of the capillary. These molecules include the monomers (amino acids and glucose), water, oxygen, carbon dioxide and ions.
• hydrostatic pressure: pressure exerted by the fluid on the walls of the blood vessels, forcing out blood plasma onto the body’s cells.
• there is lower hydrostatic pressure at the venule side of the capillary, this is because water is lost.
• oncotic pressure: the removal of blood plasma causes there to be a lower water potential of the blood, thus water moves back into the capillaries by osmosis on the venule end.
• Some tissue fluid does not return to the blood and is instead drained into the lymphatic system where it becomes lymph.
• lymph is a colourless/pale yellow fluid containing more lipids than tissue fluid. this flows through valves and nodes transporting materials, lymphocytes and antibodies to the blood For immune response.
• the lymphatic system is comprised of: lymph nodes, lymphatic vessels, lymphatic capillaries and lymphatic tissue.
• lymph nodes contain high levels of lymphocytes and macrophages, and trap foreign substances/pathogens.
• Erythrocytes cannot undergo mitosis because they do not have DNA.