Bone marrow

Bone marrow is a semi-solid <a href="/facts/Biological_tissue/H7CpML7A">tissue</a> found within the <a href="/facts/Spongy_bone/pCU37jBe">spongy</a> (also known as cancellous) portions of <a href="/facts/Bone/kwJaR6IQ">bones</a>. In birds and mammals, bone marrow is the primary site of new <a href="/facts/Blood_cell/lf9GA0Dj">blood cell</a> production (or <a href="/facts/Haematopoiesis/VRDwMymd">haematopoiesis</a>). It is composed of <a href="/facts/Blood_cell/lf9GA0Dj">hematopoietic cells</a>, <a href="/facts/Marrow_adipose_tissue/0gBIlMr6">marrow adipose tissue</a>, and supportive <a href="/facts/Stromal_cell/31AA691H">stromal cells</a>. In adult humans, bone marrow is primarily located in the <a href="/facts/Rib_cage/KzXLlujq">ribs</a>, <a href="/facts/Vertebra/qAdLhD5H">vertebrae</a>, <a href="/facts/Sternum/qIPMpyIz">sternum</a>, and <a href="/facts/Pelvis/8Fq9z3TY">bones of the pelvis</a>. Bone marrow comprises approximately 5% of total body mass in healthy adult humans, such that a person weighing 73 kg (161 lbs) will have around 3.7 kg (8 lbs) of bone marrow.
Human marrow produces approximately 500 billion blood cells per day, which join the <a href="/facts/Circulatory_system/WXwudzzc">systemic circulation</a> via permeable <a href="/facts/Vasculature/WXwudzzc">vasculature</a> <a href="/facts/Sinusoids/4BIzKJAe">sinusoids</a> within the <a href="/facts/Medullary_cavity/s9Mva8Vb">medullary cavity</a>. All types of <a href="/facts/Hematopoietic_cell/lf9GA0Dj">hematopoietic cells</a>, including both <a href="/facts/Myeloid_tissue/TLtqRWRx">myeloid</a> and <a href="/facts/Lymphocyte/pS2pv2Ma">lymphoid lineages</a>, are created in bone marrow; however, lymphoid cells must migrate to other <a href="/facts/Lymphatic_system/yw5QLgMT">lymphoid organs</a> (e.g. <a href="/facts/Thymus/YYEJu7KA">thymus</a>) in order to complete maturation.
<a href="/facts/Hematopoietic_stem_cell_transplantation/rGYRsATD">Bone marrow transplants</a> can be conducted to treat severe diseases of the bone marrow, including certain forms of <a href="/facts/Cancer/PVW6n1D0">cancer</a> such as <a href="/facts/Leukemia/WpEfW0Qh">leukemia</a>. Several types of stem cells are related to bone marrow. <a href="/facts/Hematopoietic_stem_cell/RQNE9IRu">Hematopoietic stem cells</a> in the bone marrow can give rise to hematopoietic lineage cells, and <a href="/facts/Mesenchymal_stem_cell/W0jeK2a3">mesenchymal stem cells</a>, which can be isolated from the primary culture of bone marrow stroma, can give rise to bone, <a href="/facts/Adipose_tissue/PxxedB6e">adipose</a>, and <a href="/facts/Cartilage/vxy2qzKN">cartilage</a> tissue.

Bone marrow open-in-new

Bone marrow