Seven to eight percent of an adult's weight is made up of blood that flows through the body's arteries and veins. Blood, which is pumped from the heart into the arteries, passes through each cell of the body delivering them nutrients and oxygen. Blood is made up of a set of living cells that are immersed in plasma or serum, which is an amber yellow liquid. You will read next:


Blood components

Where and how is hematopoiesis done in our body?

Erythrocyte disorders and diseases

White blood cells disorders and diseases

Platelet disorders

Coagulopathic disorders (blood coagulation diseases)

Disorders of the myeloid cells



Blood components:

Fifty-five percent of total blood volume is Fluid fraction (serum plasma). Coagulation factors, hormones, and most of the nutrients needed by cells are present in this part. Globulins (which help the body defend itself against infections) are also present in plasma. Plasma contains a protein called albumin, which prevents too much serum from leaving the arteries.

the remaining part of the blood volume is Cellular part of the blood (living part of the blood) which includes the following cells:

  • Red Blood Cells (RBC)
  • White blood cells
  • Platelets

Red Blood Cells (RBC)

They contain a protein called hemoglobin, which is responsible for delivering oxygen to cells. In fact, they are not real cells because they do not have a cell nucleus and are short-lived.

White blood cells

These are the body's main soldiers in the immune system and are divided into two general categories:

  • Granular white blood cells
  • Agranular white blood cells

These cells are called Granular white blood cells because of their small spherical granules under microscopes. They are usually categorized in several types such as:

  • Neutrophils (the largest percentage of all white blood cells and play a major role in the immune system and immune responses)
  • Eosinophils
  • Basophils

One the other side we have the Agranular white blood cells which has the following types:

  • Monocytes
  • Lymphocytes
  • Lymphocytes B
  • Plasma
  • T lymphocytes
  • Cytotoxic
  • Helper
  • Regulatory

Where and how is hematopoiesis done in our body?

It is interesting to know that in every small blood droplet of a healthy adult, there are approximately five million red blood cells, seven thousand five hundred white blood cells, and about three hundred thousand platelets.

In the human fetus, hematopoiesis begins in the fetal corpus luteum (embryonic yolk sac) around the fifth week of pregnancy. Over time, the spleen is added to the hematopoietic sites of the fetus, and eventually the hematopoiesis is transferred to its definitive and permanent place, the bone marrow. The sternum, ribs, and upper extremities of the femurs and arms will be the site of hematopoiesis.

In general, it is assumed that all blood cells originate from a small group of cells called multivalent stem cells. A number of stem cells become myeloid progenitor cells under the influence of certain substances called interleukins and special enzymes, and under the influence of a series of other specific substances they become lymphoid progenitors.

Myeloid precursors will later make red blood cells, platelets, granular white blood cells, and macrophages throughout our lives. One the other hand, Lymphoid class precursors make B and T lymphocytes for the rest of our lives. Any disturbance in the differentiation of these progenitor cells can cause a disease.

Erythrocyte disorders and diseases:

These disorders have different categories depending on the cause of the disease, some of the most important of which we will discuss below. Note that some diseases fall into different categories and the purpose of this classification is to understand the nature of the disease. The most important of these divisions are:

  • Reduction in the number of blood cells
  • Increased degradation of RBCs (hemolytic anemias)
  • Decreased production (hypoproliferative anemia)
  • Hemoglobinopathies
  • Classification of erythrocyte disorders in terms of cell size
  • Hemolysis
  • Erythropoiesis (increase in the number of RBCs)

Decreased number of blood cells can be due to the following reasons:

  • Decrease in cell production
  • Aplastic anemia
  • Folic acid deficiency
  • Vitamin B12 deficiency
  • Leukemia
  • HIV infection
  • Leishmaniasis
  • Tuberculosis
  • Toxins: (alcohol and ...)
  • Myelodysplastic syndrome
  • Primary myelofibrosis
  • Acute leukemia

Increased degradation of RBCs (hemolytic anemias):

This increase in red blood cell destruction can be due to intracellular disorders or due to extracellular problems and diseases. Extracellular disorders may include:

  • Hemolytic anemias
  • autoimmune hemolytic anemias
  • infections 
  • drugs
  • toxins and chemical agents

The increase in red blood cell destruction can also be due to deficiencies and defects that are inside the RBC cell like:

  • RBC membrane disorders
  • Intra RBC enzyme deficiencies
  • Favism

Decreased production (hypoproliferative anemia):

The decrease in blood cell production may be due to multiple reasons like:

  • Iron deficiency anemia
  • Megaloblastic Anemia 
  • Chronic bone marrow infiltration: myelophthisic anemia
  •  Aplastic anemia that can be congenital or acquired.


Impaired quality and structure of hemoglobin chains:

  • Anemia Cycle Cell
  • Hemoglobin S.
  • Hemoglobin E.
  • My hemoglobin
  • Hemoglobin C.
  • And etc.

Disorder in the number of hemoglobin chains:

  • Thalassemias
  • Beta thalassemia
  • Alpha thalassemia


Classification of erythrocyte disorders by cell size:

Erythrocyte disorders can be classified into three categories based on the cell size. These classes are: 

1- Normocytic anemia that includes:

  • Acute phase of blood las
  • Renal failure
  • Infections
  • Liver disease
  • Early stages of iron deficiency

2- Macrocytic like:

  • Infants
  • After splenectomy
  • Hypothyroidism
  • Megaloblastic anemia
  • Liver diseases
  • diamond blackfan anemia
  • Down syndrome
  • Paroxysmal nocturnal hemoglobinuria
  • Aplastic anemia
  • Drugs
  • Methotrexate
  • Phenytoin
  • Mercaptopurine

3- Microcytic hypochromic anemias such as:

  • Iron deficiency anemia
  • Thalassemia alpha
  • Beta thalassemia
  • Sideroblastic anemia
  • Infections
  • Lead poisoning
  • Cancers
  • Inflammations
  • Copper deficiency anemia
  • Severe malnutrition


Hemolysis may happen in any of these cases:

  • Due to lack of internal enzymes
  • Due to defects in the membrane members
  • Hypersplinism
  • Disseminated malignancies

Erythropoiesis (increase in the number of arrhythmias):

Disorders in which we have an increase in RBCs are divided into two important categories:

1- Primary causes of erythropoiesis:

  • Polycythemia vera

2- Secondary causes of erythropoiesis:

  • Chronic hypoxia such as congenital heart disease and Chronic lung disease
  • When the binding of hemoglobin to oxygen is less than other gases
  • Decreased production of erythropoietin
  • Living at the heights
  • smoking

White blood cells disorders and diseases:

White blood cells are also produced by hematopoietic stem cells called stem cells. The main disorders and diseases of this group of cells include the following:

  • Leukocytosis (an increase in the number of non-cancerous white blood cells)
  • Lymphoproliferative disorders that mainly involve cancers


Leukocytosis (an increase in the number of non-cancerous white blood cells) is divided into the following categories depending on the cell involved:

  • Neutrophilia
  • Lymphocytosis
  • Monoclonal Bell lymphocytosis
  • Eosinophilia
  • Basophilia (increase in the number of basophils)
  • Monocytosis
  • neutrophilia (increase in the number of neutrophils):
    • Acute phase of infections
    • Pregnancy
    • Inflammation phase
    • Long-term treatment with corticosteroids Polycythemia vera
    • Sepsis and etc.
  • Lymphocytosis (increase in the number of lymphocytes):
    • Infections
    • Allergic reactions
    • Autoimmune diseases
    • Post splenectomy
    • Smokers
  • Eosinophils
    • Acute eosinophilic leukemia
    • Chronic eosinophilic leukemia
    • Allergic disorders:
    • Drug reactions
    • Atopic dermatitis
    • Asthma
    • Allergic rhinitis
    • Immune Deficiency Disorders:
    • Job Syndrome (Hyper IGA)
    • Autoimmune lymphoproliferative syndrome
    • Rheumatic diseases
    • Connective tissue diseases
  • Basophilia (increase in the number of basophils):
    • Myeloproliferative neoplasms
    • CML
    • Allergies
    • Infection
    • Other malignancies

Lymphoproliferative disorders

  • Thrombocytosis (increased platelet count):
    • infectious diseases
    • Inflammatory diseases
    • Hypersplenism
    • Malignancies
    • Blood loss
  • Monocytosis: (increase in the number of monocytes):
    • Infections
    • Rickettsia
    • Malaria
    • Salmonella

Platelet disorders:

Platelet disorders are often caused by autoimmune problems. Pure platelet malignancy is not very common.

Coagulopathic disorders (blood coagulation diseases):

Hypercoagulability diseases (hypercoagulopathies, thrombotic diseases, thrombophilia):

  • Inheritance (primary):
    • Hereditary thrombophilia
    • Antithrombin deficiency three
    • Protein C deficiency
    • Protein S deficiency
    • Fifth coagulation factor mutation (Leiden factor five)
    • Prothrombin gene mutation
  • Acquired:
    • Antiphospholipid syndrome
    • Increasing the level of factors eight, nine and eleven
    • Increased fibrinogen
    • Defects in fibrinolysis

Decreased coagulation diseases (bleeding diseases):

  • Inheritance:
    • Von Wilbrand's disease
    • Hemophilia:
      • Hemophilia A
      • Hemophilia B
      • Hemophilia C
    • Deficiency of coagulation factor five
    • Deficiency of coagulation factor
    • Deficiency of coagulation factor seven
    • Deficiency of coagulation factor thirteen
    • Prothrombin deficiency
    • Lack of fibrinogen (afibrinogenemia)


  • Excessive consumption of coagulation factors
  • DIC
  • Microangiopathies

Hemolytic anemias

  • Inheritance:
    • Von Wilbrand's disease
    • Hemophilia:
      • Hemophilia A
      • Hemophilia B
      • Hemophilia C
    • Deficiency of coagulation factor five
    • Deficiency of coagulation factor
    • Deficiency of coagulation factor seven
    • Deficiency of coagulation factor thirteen
    • Prothrombin deficiency
    • Lack of fibrinogen (afibrinogenemia)
  • Acquired:
    • Excessive consumption of coagulation factors
    • DIC
    • Microangiopathies
    • Hemolytic anemias

Disorders of the myeloid cells:

In addition to the three blood cells i.e. red and white blood cells and platelets, which have been described, hematopoietic stem cells can also be affected, often causing leukemia and malignant diseases. Here we just briefly mention the most important of them.

Disorders of the myeloid line:

  • Myeloid proliferative neoplasm:
  • Polycythemia vera
  • Systemic mastocytosis
  • Essential thrombocythemia
  • Hyper eosinophilic syndrome
  • Chronic myeloid Leukemia
  • Myelomonocytic Leukemia
  • Myelofibrosis
  • Acute lymphocytic pre-B cell T-cell leukemia




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