Blood

"The human body contains about 5 liters of blood, and the heart pumps this amount of blood with every beat! " (Sylvia Mader; Human biology 10e)

Blood supplies the tissues with oxygen, supplies nutrients, removes waste, clots when the body is injured, it serves as a messaging system, it regulates the bodies ph and body temperature.

Blood is a tissue therefore it contains cells and cell fragments. These fragments are suspended in plasma. The cells and the cell fragments make what is called formed elements. Formed elements contain red blood cells, white blood cells, and platelets. They are formed in red bone marrow. Blood contains plasma which is the liquid that carries substances in the blood.

Red blood cells transport oxygen. They don't have a nucleus and instead have hemoglobin. Hemoglobin is the pigment that makes red blood cells and blood red. Each hemoglobin molecule can transport 4 molecules of oxygen. Each red blood cell contains approximately 280 million hemoglobin molecules.

Some common disorders associated with red blood cells are anemia, which is when you red blood count is low. Some symptoms of this would be fatigue, lack of energy, etc. A hereditary red blood cell disorder is sickle cell disease. This is when the person's red blood cells are sickle shaped and rupture as they pass through the capillaries.

White blood cells are the ones that helps our body to naturally fight off infection and disease. A lot of times doctors are able to tell there is some sort of infection in your body just due to the white blood cell count. White blood cells are larger than red blood cells and contain a nucleus. There are two classifications for white blood cells. They are granular leukocytes and agranular leukocytes. They are called this because some have noticeable granules and some don't. The granual leukocytes are neutrophils which account for 50 - 70 % of all white blood cells. They are usually the first ones to respond to a bacterial infection. Then there's the eosinophils which contain a bilobed nucleus. They don't quite know the function of this. They do know that if you have a parasite or an allergic reaction they reproduce quickly. The last of the granular leukocytes is the basophils. This cell releases a histamine when you have an allergic reaction. The histamine dilates your blood vessels, but cuts off the air tubes that lead to the lungs.

The agranular leukocytes are lymphocytes and monocytes. Lymphocytes are 25 - 35% of white blood cells. They are responisble for specific immunity to certain pathogens and toxins. Lymphocytes are called T cells and B cells. The AIDS virus attacks the T-cells. Then you have monocytes they are the largest of the white blood cells. They live in the tissue and become dendritic cells which work as a "vacuum cleaner" to clean up cellular debris.

Some disorders associated with white blood cells are sever combined immunodeficency disease which is when the stem cells lack an enzyme therefore the body can not fight of any infections. There is also leukemia which is caused by uncontrollable white blood cell proliferation.