CHAPTER 30: HEMATOLOGIC SYSTEM
STRUCTURES AND FUNCTIONS
Hematology is the study of blood and blood-forming tissues. This includes the bone marrow,
blood, spleen, and lymph system.
Blood cell production (hematopoiesis) occurs within the bone marrow. Bone marrow is the soft
material that fills the central core of bones.
Blood is a type of connective tissue that performs three major functions: transportation,
regulation, and protection. There are two major components to blood: plasma and blood cells.
Plasma is composed primarily of water, but it also contains proteins, electrolytes, gases,
nutrients, and waste.
There are three types of blood cells: erythrocytes (RBCs), leukocytes (WBCs), and thrombocytes
Erythrocytes are primarily composed of a large molecule called hemoglobin. Hemoglobin, a
complex protein-iron compound composed of heme (an iron compound) and globin (a simple
protein), functions to bind with oxygen and carbon dioxide.
Leukocytes (WBCs) appear white when separated from blood. There are five different types of
leukocytes, each of which has a different function.
o Granulocytes (neutrophils, eosinophils, basophils): the primary function of the
granulocytes is phagocytosis, a process by which WBCs ingest or engulf any unwanted
organism and then digest and kill it. The neutrophil is the most common type of
o Lymphocytes: the main function of lymphocytes is related to the immune response.
Lymphocytes form the basis of the cellular and humoral immune responses.
o Monocytes: monocytes are phagocytic cells. They can ingest small or large masses of
matter, such as bacteria, dead cells, tissue debris, and old or defective RBCs.
The primary function of thrombocytes, or platelets, is to initiate the clotting process by
producing an initial platelet plug in the early phases of the clotting process.
Hemostasis is a term used to describe the blood clotting process. This process is important in
minimizing blood loss when various body structures are injured. Four components contribute to normal hemostasis: vascular response, platelet plug formation,