Blood cells belong to the connective tissue. Blood cells are cells present in the blood of the body and are found throughout the body. Usually derived from hematopoietic pluripotent stem cells in the bone marrow, blood cells are in the form of biconcave discs and belong to the connective tissue, which mainly includes red blood cells, white blood cells, and platelets. Among them, the main function of red blood cells is to transport oxygen to all parts of the body, white blood cells are mainly involved in the body’s defense reaction, while the main function of platelets is to clot and stop bleeding. Connective tissue is mainly composed of cells and a large number of intercellular matrix, with functions such as connection, support, nutrition and protection. In addition to connective tissue, the human body also includes nerve tissue, muscle tissue, epithelial tissue. Among them, the nerve tissue has a protective, nutritive role, while the muscle tissue function is to contract, diastolic body organs and other activities. Epithelial tissues function in protection, absorption, secretion and so on. If the examination reveals abnormal blood cells, the patient needs to pay attention. Often further tests are needed to clarify the cause of the abnormality and then follow the doctor’s instructions.