Understanding Blood And Disease


Blood And Disease

Blood delivers the oxygen and nutrients needed to survive, it helps us warm up and cool down, fight off infections and sends carbon dioxide and other waste products to the kidneys, lungs and digestive system to be removed from the body. Blood also carries hormones from the endocrine system to areas of the body which need them.

blood disease

In young children and babies blood cells are formed in the soft tissue inside bones (bone marrow), mainly in the long bones of the upper arm (the humerus) and the thigh (femur).

In older people the blood cells are formed mainly in the bone marrow of the spine (vertebrae), pelvis, ribs, skull, and sternum (breast bone).


Blood Facts

The human body has two types of blood vessels – Arteries and Veins



Arteries carry blood to our bodies which is full of oxygen from the lungs (oxygenated blood)



When the oxygen in the blood has been distributed throughout the body the blood is then returned through the heart and lungs via veins, so it can receive more oxygen to be delivered back to the body via the arteries

The blood transported within the network of veins and arteries is called whole blood

Whole Blood

When blood cells travel through the system they are held within the plasma – a yellowish fluid made up of 90% water containing nutrients, hormones, proteins and waste products.

This mixture of both plasma and blood cells is called whole blood.

  • In a blood transfusion you may receive whole blood or a specific component only, such as platelets, red blood cells or clotting factor. Some of the blood which is donated is separated into different components to be used this way.

Whole blood is made up of three types of blood cells – red blood cells (RBC), white blood cells (WBC) and platelets.


Red Blood Cells

red blood cells

Red blood cells (also known as erythrocytes) look like flattened, slightly indented disks, and contain the iron-rich protein hemoglobin.

The hemoglobin is responsible for picking up oxygen from the lungs and releasing it throughout the body where needed.  

There are more red blood cells in the body than any other cell, and each will live around four months. The body is constantly working to replace those which have died or have been lost from the body.


White Blood Cells

white blood cells

White blood cells (WBC) – also known as leukocytes, are an integral part of the immune system, helping the body to defend itself against infection. These blood cells have the ability to move in and out of the blood stream to the area of infection.

White blood cell may live from a few days to months, and the body can increase white blood cell production to fight infection. New cells are constantly being formed within the bone marrow.


Fighting Infection

There are several parts of blood involved in fighting infections. White blood cells called granulocytes and lymphocytes travel the blood vessel walls defending against germs like viruses and bacteria, and will attempt to destroy any cell that has become infected or has mutated into a cancer cell.

Some white blood cells are responsible for making antibodies (proteins which recognize and neutralize, or destroy foreign material within the body), and after an infection has been defeated lymphocytes remember how to recreate the specific antibodies to fight any returning infection fast.




Platelets (also known as thrombocytes) are tiny oval shaped cells which help with blood clotting.

When a blood vessel breaks (you have a bleed), platelets gather in the area and help plug the leak (they grow little arms which allow them to link together over the problem area forming a plug).

As in other blood cells platelets have a short life span of around nine days so the body must constantly replace them.


Clotting Factors

Proteins called clotting factors are essential to the clotting process. Although platelets can stop or slow small blood vessel leaks a clotting factor is needed to produce a strong, effective blood clot.

Platelets work with clotting factors to seal all forms of leaks such as cuts and scratches; they help prevent bleeding both inside and on the surface of our bodies.

If we have a large wound clotting alone may not be enough to repair the body, for these types of injuries we use different dressings and/or stitches to control the bleeding


Red Blood Cell Diseases – Anemia

Some of the more common blood diseases may involve any or all of the different types of blood cells, and/or affect the body’s ability to clot effectively.

By far, the most common red blood cell condition is anemia (lower than normal number of red cells in the blood, or an inability to utilize the stored oxygen effectively). This can lead to weakness, pale skin, increased heart rate and poor infant growth due to the bloods reduced ability to transport oxygen.

Anemia can be caused by a low red blood cell production rate or an increased red blood cell destruction rate.


Iron Deficiency Anemia

Iron Deficiency Anemia is the most common type affecting people of any age who have a low iron diet or have lost a lot of blood. It is quite common in infants with poor nutrition, premature babies and menstruating females.


Lead poisoning 

When exposed to lead a large proportion is stored in the red blood cells and may harm the production process leading to anemia

Lead poisoning may also affect other body tissues, including the brain and nervous system.


Chronic Disease Anemia

People with chronic diseases such as cancer or human immunodeficiency virus (HIV) often develop anemia complications.


Anemia And Kidney Disease

The production of red blood cells in bone marrow is stimulated by a hormone produced in the kidneys (erythropoietin). Kidney disease may affect the production of this hormone.


Anemia From Increased Red Blood Cell Destruction

When a diseased state destroys red blood cells at an increased rate (hemolysis) and the destruction rate is faster than the body can produce new cells a person will develop anemia.

Conditions that can cause increased RBC destruction include:

G6PD deficiency: common among people of African, South East Asian and Mediterranean descent. It is an enzyme which protects red blood cells from the destructive effects of certain chemicals found in our foods and medications. Without this enzyme for protection it is possible for our red blood cells to sustain serious damage.

Hereditary spherocytosis: an inherited condition where a genetic problem concerning a protein in the red blood cell structure causes the cells to become fragile and misshapen (they appear as spheres instead of disks) and are easily destroyed.

diseases of the blood

Sickle cell disease: a hereditary disease common in people of African descent causing the production of abnormal hemoglobin. The red blood cells become sickle shaped and stick together decreasing their ability to carry oxygen, making them very fragile. In some cases they may block blood vessels causing organ damage and sever pain.

sickle cell disease

White Blood Cell Diseases

  • Neutropenia:  when there is not enough of a specific white blood cell to fight bacterial infections. This can be a side effect for people who take certain chemotherapy drugs.
  • Human immunodeficiency virus (HIV): Attacks lymphocytes which work to fight infection. HIV may lead to acquired immunodeficiency syndrome (AIDS) which makes the body vulnerable to infections and other disease.
  • Leukemias: cancer of the cells that produce white blood cells. These cancers include acute myeloid leukemia (AML), chronic myeloid leukemia (CML), acute lymphocytic leukemia (ALL), and chronic lymphocytic leukemia (CLL).

Diseases of Platelets

Thrombocytopenia: (low platelet count) can be inherited or be the result of a person undergoing chemotherapy, developing a viral infection, having leukemia or producing too few, or using too many platelets. Thrombocytopenia usually presents as abnormal bleeding or bruising

Clotting System Diseases

The human clotting system relies on platelets as well as many other clotting factors and blood components. If any of these components are not functioning properly you may develop a bleeding disorder


Common bleeding disorders include:

Hemophilia: an inherited condition where your blood lacks particular clotting factors and almost always affects the male. This affects the body’s ability to stop bleeding and even minor cuts may become problematic.


Other causes of ineffective clotting include: