A large group of single-cell microorganisms. Some cause infections and disease in animals and humans. Usually reproduce asexually by binary fission. The singular of bacteria is bacterium.
Small, round cells found in the lower part (or base) of the epidermis, the outer layer of the skin.
A type of granulocyte found in the blood and resembling the tissue mast cell.
Lymphocyte which develops in the bone marrow in adults and produce antibodies.
The fatty network of connective tissue that fills the cavities of bones