Blood

Introduction Blood is a collection of cells that have been specialized to perform a set of tasks within an organism. For this reason, doctors and scientists consider blood a tissue and not a fluid. Blood consists of two distinct elements: 1.Plasma, the fluid portion of the blood (55% of blood) 2.Cells, the solid portion of blood (45% of blood)

Red Blood Cells (Erythrocytes) Make up 44% of blood. These are specialized cells for oxygen transport. Without them plasma could only carry 2% of the oxygen that normally travels through our bodies. Red blood cells are in the shape of a biconcave disk with no nucleus. They are packed with 280 million molecules of hemoglobin, an iron- containing molecule that binds with oxygen. Hemoglobin is able to bind with four oxygen molecules, however it commonly binds with two, due to space issues.

White Blood Cells (Leukocytes and Lymphocytes) Make up about 1% of blood's volume. All white blood cells contain nuclei and appear colourless. They play many roles in fighting off infection and protecting the body from pathogens. Two of the most important disease fighting white blood cells are leukocytes and lymphocytes. Leukocytes engulf and digest pathogens. They are part of the body's innate immune response (generalized response of the body to infection). Lymphocytes are part of the body's acquired immune response. They recognize and remember specific pathogens and fend them off if they attack again.

Macrophage (Leukocyte)

Neutrophil (Leukocyte)

B Cell (Lymphocyte)

Platelets They are not cells. They are fragments of larger cells that broke apart in the bone marrow. They contain no nucleus and break down relatively quickly. They help the blood to clot and protect the body from excessive blood loss after an injury.

Steps in Blood Clotting 1.A blood vessel is ruptured. (first step triggered by an injury) 2.Substances released by the broken vessel attract platelets to the site. 3.As the platelets collect, they rupture and release certain chemicals. 4.These chemicals combine with clotting agents in the blood plasma creating thromboplastin, an enzyme. 5.Thromboplastin reacts with calcium in the blood and prothrombin, a protein produced by the liver to produce thrombin. 6.Thrombin reacts with fibrinogen to produce fibrin. 7.Fibrin, an insoluble material, forms a mesh of strands around the injury that traps escaping blood cells and forms the clot.

Plasma Carries numerous proteins that are important to many body processes. 1.Fibrinogen is used in blood clotting. 2.Serum Albumin in maintaining blood pressure and blood volume. 3.Serum Globulin contains antibodies that fight against infection and disease. Plasma also plays a role in the removal of carbon dioxide from the body

The Rhesus Factor All blood also contains the Rhesus factor. If you have the protein then you are Rh +. If you don't have the protein then you are Rh -.

The Rhesus Factor Rh-factor problems occur when an Rh- negative person comes in contact with Rh- positive blood for the second time. The first time there is contact the Rh-negative person will create antibodies against the Rh-positive blood. The second time there is contact, the blood will agglutinate and block blood vessels which could be fatal.

The Rhesus Factor Rh-negative mothers with a second Rh- positive baby already have the antibodies to destroy the fetus' blood, so they are put on medication to prevent her antibodies from crossing over into the placenta and attacking the fetal blood.