Plasma also contains salts, nutrients, hormones and dissolved gases. Involving Red Blood Cells. Centers of accumulation of lymphocytes include the thymus, spleen and lynph nodes scattered throughout the body. Epstein-Barr virus D. Platelets. Platelets are destroyed within about 10 days because they have no nucleus to supply mRNA for synthesis to replaced aged o r depleted proteins.
Platelets play a major role in blood clotting as described in the next section.
This reaction has the effect of closing down the blood vessel and in that way limiting the loss of blood. This is an autonomic system homeostatic reflex lasting only for up to 30 minutes. Exposure of collagen fibers in the injured blood vessel wall causes platelets to become sticky. They adhere to the collagen filaments. The platelet granules break down releasing se veral substances one of which, serotonin , induces the vascular smooth muscle spasms.