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Bone marrow (from Latin medulla ossium) is a tissue that is supplied with blood, it is soft and spongy. It is located mainly inside the marrow cavities of long bones and within the spongy bone. A healthy adult has about 2,5 – 4 kilograms of bone marrow in his body.
Types of bone marrow
There are two types of bone marrow:
- Yellow bone marrow – contains mainly fat cells and is not involved in the process of homeopoiesis (the production and differentiation of blood morphotic elements in the hematopoietic system). The amount of yellow bone marrow increases with age. It does not occur in children. In the case of disorders such as anemia, it can transform into red marrow.
- Red bone marrow – the place where blood morphotic elements such as erythrocytes, leukocytes (mainly granulocytes) and thrombocytes are formed. Only this form of bone marrow is found in children.
Red bone marrow
Bone marrow is formed in utero and appears red until around the age of seven.
In an adult, a person occurs in:
- flat bones: sternum, vertebral bodies, ribs, skull bones, pelvic bones and shoulder blades,
- epiphyses of long bones.
The red bone marrow is a place of constant production and renewal of blood cells. It produces erythrocytes (red blood cells, which are involved in the transport of oxygen to tissues throughout the body), leukocytes (white blood cells, which are a key element of the body’s immune system) and thrombocytes (platelets necessary for blood clotting).
The role of bone marrow
There are stem cells in the bone marrow. Their role is to constantly reproduce and produce blood morphotic elements. The bone marrow constantly produces new erythrocytes and lymphocytes, which are responsible for the immunity of the human body. Damaged and inefficient cells – i.e. incorrect cells – are also utilized. Iron is also recovered and stored in the bone marrow from abnormal cells.
Bone marrow diseases
Bone marrow diseases can be classified into three groups according to their background. There are deficiency, insufficiency or neoplastic disorders.
Bone marrow deficiency disorders:
- anemia – deficiency of vitamin B12, folic acid, iron
Bone marrow failure disorders:
- myelofibrosis,
- thrombocytopenia,
- aplastic anemia,
- granulocyte deficiency.
How is bone marrow harvested?
If bone marrow disease is suspected, a myelogram is required – that is, microscopic examination of a bone marrow smear or cytochemical tests. To test the bone marrow, it must be harvested.
There are two methods of collecting material for testing:
- aspiration biopsy – the study does not differ significantly from other biopsies, with the help of a syringe inserted into the medullary cavity in the bone, a small amount of material is taken. The examination is performed under local anesthesia. The material is taken from the hipbone or sternum;
- trepanobiopsy – this type of collection is used when a fine needle biopsy is impossible. It involves taking a small piece of bone and marrow, also with a needle. The material is taken from the hip bone.