The cardiovascular or circulatory system comprises the blood, the heart, and the blood vessels. Blood is a specialized fluid comprising cells in a liquid ...

Approximately 8% of the body mass comprises whole blood, a specialized connective tissue vital for transportation, regulation, and protection. The ...

Whole blood consists of the blood plasma, a fluid extracellular matrix, and formed elements, including cells and cell fragments. Blood plasma, which makes ...

Blood plasma contains approximately 92% water and 8% solutes. Proteins comprise about 7% of blood plasma. Of these, higher molecular weight proteins ...

Hematopoiesis, or hemopoiesis, is the production of the formed elements in blood from common progenitors, called hematopoietic stem cells, or HSCs. During ...

Hemangioblasts, the multipotent stem cells of mesodermal origin, give rise to hematopoietic stem cells or HSCs. The HSCs undergo hematopoiesis to produce ...

Hematopoietic growth factors are a group of regulatory and signaling molecules that influence the differentiation of hematopoietic stem cells, or HSCs. ...

Red blood cells  (RBCs) transport oxygen to all body tissues. These cells survive only for 120 days and then need to be replenished. Erythropoiesis ...

The cardiovascular system regulates erythrocyte numbers for optimal oxygen transport. It also prevents erythrocyte over-proliferation, maintaining blood ...

There are 4.2 to 6 million erythrocytes, or red blood cells, per microliter of blood. These small cells are flattened biconcave discs with depressed ...

Hemoglobin is a tetrameric globular protein consisting of two alpha and two beta polypeptide chains. Each of these chains has an iron-containing heme ...

The circulating erythrocytes frequently squeeze through blood capillaries, damaging their plasma membrane due to constant friction. After about 100 to 120 ...

Erythrocyte disorders are broadly categorized into anemic and polycythemic conditions. Anemia develops due to the low oxygen-carrying capacity of the ...

A healthy individual has about 4,500 to 11,000 leukocytes or white blood cells per microliter of blood, accounting for about 1% of blood volume. Unlike ...

Leukocytes containing cytoplasmic granules are classified as granular, while those with relatively clear cytoplasm are termed agranular. All granulocytes ...

Leukocyte disorders are characterized by either leukopenia, an abnormally low leukocyte count, or leukocytosis, a very high leukocyte number. Bone marrow ...

A microliter of blood contains 150,000 to 400,000 small, disc-shaped cell fragments called platelets or thrombocytes. These fragments originate in the ...

Hemostasis is a series of rapid, defensive reactions triggered to stop excessive bleeding and promote healing after a vascular injury. It is a highly ...

Hemostasis begins with a vascular spasm, also known as the vascular phase. It starts immediately after any damage to a blood vessel, causing a sudden ...

In an injured blood vessel, the platelet phase - which overlaps with the vascular phase - begins about 15-20 seconds after the onset of vascular spasm. As ...

Coagulation or clotting is the last hemostasis phase. It involves a series of chemical reactions to form a blood clot, reinforcing the initial platelet ...

The extrinsic and intrinsic pathways of coagulation involve reaction cascades of clotting factors. They merge into the common pathway, eventually forming ...

The activated platelets in a blood clot extend projections and interact with other platelets and fibrin fibers. Within 30 to 60 minutes, the contractile ...

Thromboembolic disorders and bleeding disorders are two types of disruptions in hemostasis. The thromboembolic disorders are characterized by the ...

The ABO blood group system is based on the presence of specific antigens or agglutinogens on the red blood cells, or RBCs, and antibodies or agglutinins ...

The Rhesus or Rh antigen is a class of agglutinogen on the red blood cells or RBCs. Its presence or absence categorizes a person as Rh-positive or ...

The antigens A, B, and Rh on the surface of red blood cells serve as the foundation for blood grouping. When these antigens come in contact with their ...

A blood transfusion is a medical procedure to replace lost whole blood or its components due to injury, surgery, or treatment for conditions like anemia ...

Bone marrow transplants replace diseased marrow with healthy marrow from a compatible host. It can cure several cancers and genetic disorders like ...