Bone marrow

Bone marrow is a soft, pliable and spongy substance that can be seen in the center of the bones. It helps in the production of bone marrow stem cells and other substances, which eventually produce blood cells. Bone marrow is of two types.  

• Red bone marrow comprises blood stem cells, which help in the production of red blood cells, white blood cells or platelets.
• Yellow bone marrow aids in storing fat and contains stem cells that can become cartilage, fat, or bone cells.

In this article, we have discussed various functions of red and yellow bone marrow and the conditions that can affect the bone marrow.

Important function of red bone marrow

Red bone marrow involves the production of blood cells called Hematopoiesis. Hematopoietic stem cells are seen in the red bone marrow that can develop into different blood cells, including:

• Red blood cells – Red blood cells help carry oxygen-rich blood to different cells of the body and transport carbon dioxide to the lungs.
• Platelets – Platelets play a major role in blood clotting. This helps in the prevention of uncontrolled bleeding.
• White blood cells – White blood cells protect and safeguard our bodies from infections.

New blood cells enter your bloodstream and form a new cell called Sinusoids.

During the process of ageing, your red bone marrow will be replaced by the yellow bone marrow. In the phase of adulthood, red bone marrow can be visible in bones, including the:

• skull
• vertebrae
• sternum
• ribs
• upper arm bone
• pelvis
• thigh bone

Important functions of yellow bone marrow

As mentioned earlier, yellow bone marrow helps in the storage of fats. These yellow bone marrow fats are deposited in cells called Adipocytes. These fats are used to boost energy in critical situations.  

Yellow bone marrow contains stem cells called mesenchymal stem cells. These cells develop into bone, fat, cartilage or muscle cells.

Over a period of time, the yellow bone marrow will be replaced by the red bone marrow. Most of the adult bones in our body contain yellow bone marrow.

Condition that causes bone marrow

Bone marrow is imperative for the production of blood cells. Therefore, blood-related conditions can risk the formation of bone marrow.

These blood-related problems disrupt the number of blood cells produced in the bone marrow and cause symptoms including:

Fever  

Fever can be due to the absence of enough white blood cells.

Fatigue

Lack of haemoglobin causes fatigue.

Increased infections

These infections might be due to insufficient white blood cells that help fight infections.

Shortness of breath

This is due to a low red blood cell count that disrupts the flow of oxygen being delivered to tissues in the body.

Easy bleeding

This is due to the absence of healthy platelets, vital for blood clotting.

Diseases affecting bone marrow

Leukemia 

Leukemia is cancer that affects both your bone marrow and lymphatic system of the body. This happens due to DNA mutations in the blood cells. This causes them to grow more rapidly than healthy blood cells. Over a period of time, these cells get condensed near the healthy cells in your bone marrow.

Leukemia is of two types based on how fast leukemia progresses:

• Acute leukemia  
• Chronic leukemia

The next classification is based on the type of white blood cell it involves:

• Lymphocytic leukemia – Affects the lymphoid cells (lymphocytes), which form lymphoid or lymphatic tissue. Lymphatic tissue makes up the immune system.  
• Myeloid leukemia, also known as myelogenous leukemia – Affects all the red blood cells, white blood cells and platelets.  

Some of the important leukemia types are:

• Acute Myeloid Leukemia (AML)
• Chronic Myeloid Leukemia (CML)
• Acute Lymphocytic Leukemia (ALL)
• Chronic Lymphocytic Leukemia (CLL)

Myeloproliferative disorders

Myeloproliferative disorders are due to the abnormal growth of stem cells in the bone marrow. This is due to a sudden rise in blood cell count levels.

Different types of myeloproliferative disorders are Primary Myelofibrosis, Polycythemia vera, Essential Thrombocythemia, Hypereosinophilic syndrome and Systemic mastocytosis.

Bone marrow transplants

Bone marrow transplants are done when people are affected by autoimmune diseases or cancers. These are also known as stem cell transplants.

During a bone marrow transplant, stem cells are harvested from a donor and transplanted to a person affected with stem cell defects. These stem cells work on eradicating cancer and unhealthy cells.

Types of bone marrow transplants

There are three varieties of bone marrow transplants.  

• Autologous bone marrow transplant. An autologous stem cell transplant replaces diseased or damaged bone marrow with healthy blood stem cells from your own body.
• Allogeneic bone marrow transplant. A donor whose genetic type is the same as the patient’s can donate their stem cells. For example, siblings, parents or unrelated donors.
• Umbilical cord blood transplant. This transplant involves harvesting stem cells from the umbilical cord promptly after a baby’s birth. Then, they are tested and preserved until they are needed.

Bone marrow transplants can cause side effects and complications to people who are already affected by a disease. The success rate of the bone marrow transplant depends on the following factors:

• Strength of the person
• Mode of transplant
• Type of disease

Summing up

Bone marrow is found in all your bone. Red bone marrow involves the production of blood cells, whereas yellow marrow plays a vital role in fat storage.  

Bone marrow transplant replenishes healthy bone marrow tissues for people who have cancer and stem cell defects.