Bone Marrow: Structure, Functions & Disorders

Bone marrow definition can be stated that it is the soft blood-forming tissue that fills the bone cavities. This tissue contains fat and immature blood cells and is responsible for producing mature blood cells, white blood cells, that helps fight diseases and build immunity, helps to form red blood cells and platelets. And any diseases or drugs that affect the human body and the human bone marrow also affects the total counts of these cells and in turn, may lead to fatal consequences and life-threatening diseases. 

What is Bone Marrow and What is Marrow?

Bone marrow is pronounced as bone MAYR-oh and marrow is basically the soft and spongy tissue that has many blood vessels and cell producing tissues and it is found in the centre of most bones in the human body. The human bone marrow produces approximately 500 billion blood cells per day, which functions in the joining of the systemic blood circulation via the permeable vasculature sinusoids or capillaries within the medullary cavity which is the innermost part of the central cavity of the bone shafts. 

Now that we have understood what is bone marrow and marrow are, let us learn about where is bone marrow located, bone marrow structure, types of bone marrow, bone marrow function, bone marrow disorders that cause bone marrow diseases and the remedies.    

Structure of Bone Marrow

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• Bone marrow in the bone is a soft, flexible connective tissue that is also highly vascular and therefore serves as the primary site of production of new blood cells.

• It is composed of both the cellular and the non-cellular components that aid in the fulfilment of functions of the bone marrow.

• Structurally, the bone marrow can be divided into vascular and non-vascular regions.

Where is Bone Marrow Located?

The location of the bone marrow in the human body is of vital importance as it plays a major role in blood cells production. The bone marrow approximately comprises 5 percent of the total body mass in a healthy adult human. For instance, if a man weighs 73 kg then the body contains around 3.65kg of the marrow in the bone.  In adult humans, the bone marrow is primarily located in 

• The ribs, 

• Vertebrae of the spine where there is the active marrow which functions in cell production, 

• The sternum, in the thigh bone that is the femur and the ends of the tibia and humerus (long bone of the upper limb or arms). 

• And it is also located in the bones of the pelvis that is the hips 

Types of Bone Marrow 

The types of bone marrow are depending on the location of it on the bone. The red bone marrow contains the hematopoietic tissue, which are the stem cells that form blood cells and are primarily found in the medullary cavity located towards the outer surface of the bone. And the yellow bone marrow is in the medullary cavity in the shaft of long bones and is often surrounded by a layer of red bone marrow.

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Difference Between Red Bone Marrow and Yellow Bone Marrow

Bone Marrow Function

• The T cells and B cells that are important to the immune system are produced and migrated through the bone marrow.  

• The bone marrow produces all of the lymphoid cells that migrate to the thymus to mature into T cells, which are important for adaptive immune responses. 

• The B cells mature in the bone marrow and they are primarily responsible for mediating the production of antibodies that are antigen-specific immunoglobulin (Ig) and undergo selection for non-self before making their way to the peripheral lymphoid tissues.

• The bone marrow which constitutes the hemopoietic cells that are derived from the multipotential stem cells gives rise to all of the lymphoid cells found in the lymphoid tissue, along with all of the cells found in the blood.

• The red bone marrow cells produce platelets, which are crucial for the blood clotting process that stops the loss of blood in case of cuts and injuries.  

• This fat stored in the yellow bone marrow can be used as a source of energy as needed.

Bone Marrow Disorders and Related Bone Marrow Diseases

The functions of the bone marrow clearly signify its important role in the human body. And its lack of proper function due to any reason will cause many disorders. Most of it is blood-related and immunity-related conditions.

• When there is a lack of healthy white blood cells in the body, it leads to fever.

• One experiences weakness and gets easily tired and the body is faced with fatigue even when one performs milder activities due to the lack of oxygen-carrying haemoglobin in the red blood cells when there is improper maturity of the red blood cells. 

• Lack of oxygen in the blood circulation, due to the absence of haemoglobin or underdeveloped pigment that is haemoglobin in the red blood cells leads to shortness of breath. 

• A lesser number of white blood cells or a low total count of white blood cells leads to one getting infected more frequently.

• Less number of platelets leads to easy bleeding when bruised and if the cut is deeper there will be a huge loss of blood. 

• The other diseases that are caused due to a weaker bone marrow are- leukaemia, a type of cancer that affects the lymphatic system, aplastic anaemia, which occurs from damage to the stem cells that leads to less to no production of new blood cells. 

• Myeloproliferative disorders when there is an abnormal growth in the bone marrow leads to Primary myelofibrosis, Polycythemia vera, Essential thrombocythemia, Hypereosinophilic syndrome and Systemic mastocytosis.

Bone Marrow Transplant

In all of these cases, when the body is severely affected due to damage in the bone marrow the treatment is a bone marrow transplant. The bone marrow transplant is only done when an expert or a professional recommends it since it is a medical procedure that involves risk both to the donor and the recipient. 

A bone marrow transplant can involve complications depending on the age, overall health, the disease one is being treated for and the type of transplant one receives. In milder cases, the symptoms after the transplant are acute and short-lived like a drop in blood pressure, headache, nausea, pain, shortness of, breath, chills and fever. In severe cases, one experiences damage to vital organs, early menopause, nausea, diarrhoea, internal bleeding in the lungs, brain, and other parts of the body, when transplanted cells don’t begin producing new cells as planned lead to graft failure, in some instances, the donor cells starts attacking the host’s body that results in graft-versus-host disease (GVHD) which can be fatal. The degree of the risk can be hindered with a doctor’s help. 

Types of Bone Marrow Transplant

Anybody with no history of cancer aged between 18 and 45, who is in good health can donate bone marrow. The match for red blood cells and white blood cells is difficult to find. A bone marrow transplant can be categorized into two types- 

1. Autologous Bone Marrow Transplant - The term auto means self, so here, a person’s own stem cells are used In this procedure. When one is going through or likely to go through radiation treatment or are given high-dose chemotherapy in case of cancer treatment and prior to such treatments the stem cells are taken from the body and froze to preserve it. After the treatment since the body is fighting to regain its strength the preserved stem cells are placed back into the body to help retain the proper function of blood cell formation. This procedure is also called a rescue transplant.

2. Allogeneic Bone Marrow Transplant -  The term “allo” means other that is other than the self or a donor. Here, stem cells are removed from another person, and many times, it is a prerequisite that the donor's genes must at least partly match the recipient’s genes. Many special tests are performed prior to the transplant in order to screen if a donor is a good match. In this procedure, a family member is a donor due to genetic similarities and most likely a sibling is to be the best match. And the probability of a good match can also be relatives, parents and children.

• Umbilical Cord Blood Transplant - This is a type of allogeneic transplant and in this procedure, the stem cells from a newborn baby's umbilical cord are detached just after the birth. After which the stem cells are frozen for preservation. They are stored until they are required for a transplant which takes a long time because stem cells from the umbilical cord are not mature enough to start producing new blood cells at the required pace. 

Ways to Healthy Bone Marrow

• For the bone marrow to be healthy, it is essential that the bone is healthy so one must find ways to keep the bones stronger. The methods are simple and effective and one must be consistent with them.

• Having vegetables with a high level of vitamin C’s antioxidant property stimulates the production of bone-forming cells and thus increases bone mineral density that keeps it from damaging easily.

• Performing weight-bearing exercises and strength training exercises.

• Having protein-rich foods like lean meats, poultry, fish and seafood, eggs and dairy products like milk, yoghurt (especially Greek yoghurt), and cheese like cottage cheese. 

• Having high calcium food is also crucial to maintain a good bone mineral density.

• Having Vitamin D and Vitamin K rich food rather than supplements.

• Foods with high magnesium and zinc must also be an important addition to the diet plan.

• At all costs, one must avoid low-calorie diet intake contrary to popular opinion. 

• Maintaining stable health and an active lifestyle consistently is very important especially for women which will help in the post menopause phase and bones will not become brittle.

• Consume Food with high omega-3 fats for their anti-inflammatory properties, like fish and other seafood such as salmon, mackerel, tuna, herring, and sardines, nuts and seeds such as flaxseed, chia seeds, and walnuts, plant oils like flaxseed oil, soybean oil, and canola oil. 

Conclusion

Bones are the entire skeletal system of the body that is constantly providing us support and the marrow has an important role in the circulation of blood and the blood health along with our immune system. Especially after the age of 30, the strength of the bone starts to weaken and if proper care is not taken then with weakening bones the bone marrow also fails to function properly and support the body. One must take care and stay healthy and bone health is as important as any other part of the body.