Red blood cells are round, with thick edges and thin center. When they are first formed, they have a nucleus, but it is absorbed before they begin their function in circulation. There is an average of 5-10 thousand per milliliter of blood. There are several types, formed in bone marrow and lymph glands. The white blood cell types are monocytes, lymphocytes, neutrophils, eosinophils, and basophils.
Lymphocytes attack foreign cells directly or secrete an enzyme that immobilizes foreign substances.
In the course of defending the body, many white blood cells die. They are the primary component of pus. These are third constituent of blood. You have a built-in system that works like telephone wires, containing millions of specialized cells called neurons. A neuron is a nerve cell which transmits messages from one part of the body to another.