White blood cells, also called leukocytes, are one of the cells that are involved in the body's immune system. They protect the body against various infections diseases and other invaders. Leukocytes are produced in the bone marrow (hematopoietic stem cells). They are not the only cells that are important for the defense of the body but are important.
The two main types of exocrine secretory cells of the stomach are parietal cells and chief cells. Parietal cells secrete hydrochloric acid and chief cells secrete digestive enzymes such as pepsin
