Hematology: The Study of Blood


Blood is a liquid tissue that circulates through the body delivering oxygen and nutrients to cells and picking up waste materials. It is composed of plasma, red blood cells, white blood cells, and platelets. Plasma is the liquid component of blood that carries the blood cells. The three main types of blood cells and their functions are:

Red Blood Cells

Red blood cells, also called erythrocytes, are the most abundant type of blood cell. Their main role is to transport oxygen from the lungs to the tissues and carbon dioxide from the tissues back to the lungs. Red blood cells get their red color from the iron-containing protein hemoglobin inside them. Conditions like anemia can occur when there is a low red blood cell count or low hemoglobin levels.

White Blood Cells

White blood cells, also known as leukocytes, are part of the immune system and help the body fight infections and disease. There are different types of white blood cells including neutrophils, lymphocytes, monocytes, eosinophils, and basophils. Hematology help identify and destroy pathogens inside the body. Diseases like leukemia occur when there are uncontrolled increases in abnormal white blood cells.


Platelets, also called thrombocytes, are cell fragments involved in wound healing and blood clotting. When a blood vessel is damaged, platelets stick together at the wound site to form a clot and stop bleeding. Having too few or non-functioning platelets can lead to excess bleeding disorders like thrombocytopenia or hemophilia.

Components of Blood

In addition to cells, blood contains other components suspended in plasma that help transport substances throughout the body. Some key components include:


Proteins like albumin, globulins, fibrinogen, and clotting factors are important to maintain proper fluid balance and blood pressure. Albumin plays a role in regulating the movement of fluid between blood vessels and tissues. Clotting factors are essential for blood clotting and wound healing.


Essential electrolytes like sodium, potassium, calcium, and magnesium are involved in nerve and muscle function, fluid balance and pH regulation. Electrolyte imbalances can occur from conditions like dehydration.


Blood carries vitamins, minerals, glucose, lipids, amino acids and wastes throughout the body. It delivers nutrients from digestion to cells for energy and tissue maintenance.


Hormones like insulin, thyroid hormone, and cortisol are transported via the bloodstream to target tissues where they have metabolic effects.


Oxygen is delivered from the lungs to tissues via red blood cells. Carbon dioxide is removed from tissues and transported back to the lungs for exhalation.

Clinical Applications of Hematology

Hematology studies blood and blood forming tissues to aid diagnosis and treatment of various diseases. Some key clinical applications include:

Complete Blood Count

A complete blood count (CBC) measures red blood cell, white blood cell, and platelet counts. It can screen for anemia, infection, leukemia or clotting disorders. Abnormal results are further evaluated.

Blood Typing

Determining a person’s blood type (A, B, AB or O) is essential before transfusions. The ABO blood group system and Rh factor must match between donor and recipient.

Coagulation Tests

Tests like prothrombin time and partial thromboplastin time assess the clotting cascade and detect coagulopathies. Prolonged results may indicate clotting factor deficiencies like hemophilia.

Leukemia Screening

Examination of cells under a microscope can detect morphological abnormalities in white blood cells suggestive of leukemia. Immunophenotyping further characterizes abnormal cell populations.

Bone Marrow Biopsy

Removal and examination of bone marrow aspirate and core biopsies helps diagnose blood cancers and marrow failure disorders. It reveals cellularity, types, and maturity of blood cell precursors.

Flow Cytometry

Using antibodies tagged with fluorescent markers to label surface receptors, flow cytometry analyzes cell populations to diagnose different types of leukemia, lymphoma, and myeloproliferative neoplasms.

Molecular Testing

Techniques like fluorescent in situ hybridization, polymerase chain reaction and next-generation gene sequencing investigate DNA and chromosome abnormalities linked to various hematologic malignancies.

Hematology has developed diagnostic tools and therapies that have greatly impacted outcomes of blood disorders. Continued research continues to expand our understanding of hematopoiesis and improve treatment of diseases like anemia, bleeding disorders, blood cancers and marrow failure syndromes. Hematology remains an active field with many opportunities to develop new diagnostics, targeted therapies and potentially gene and cell-based cures.

1.  Source: Coherent Market Insights, Public sources, Desk research
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