Bone marrow 196130 225204617 2008-07-12T13:15:28Z Robert M. Hunt 2049578 /* References */ Add citation. {{more sources|date=July 2007}} {{for|the [[Dir en grey]] album|The Marrow of a Bone}} [[Image:Gray72.png|thumb|350px|[[Gray's Anatomy]] illustration of cells in bone marrow.]] '''Bone marrow''' is the flexible [[biological tissue|tissue]] found in the hollow interior of [[bone]]s. In adults, marrow in large bones produces new [[blood cell]]s. It constitutes 4%<ref name=T4> Semester 4 medical lectures at Uppsala University 2008 by Leif Jansson</ref> of total body weight, i.e. approximately 2.6 kg (5.7 lbs.) in adults. ==Anatomy== ===Marrow types=== [[Image:Caput femoris cortex medulla.jpg|right|thumb|Section through the [[femur head]], showing the [[cortical bone|cortex]], the ''red bone marrow'' and a spot of ''yellow bone marrow''. The white bar represents 1 centimeter.]] There are two types of bone marrow: '''red marrow''' (consisting mainly of [[myeloid tissue]]) and '''yellow marrow''' (consisting mainly of [[fat cells]]). [[Red blood cell]]s, [[platelet]]s and most [[white blood cell]]s arise in red marrow; some white blood cells develop in yellow marrow. Both types of bone marrow contain numerous blood vessels and capillaries. At birth, all bone marrow is red. With age, more and more of it is converted to the yellow type. About half of the bone marrow is red. <ref name=T4/> Red marrow is found mainly in the [[flat bone]]s, such as the [[pelvis|hip bone]], [[sternum|breast bone]], [[skull]], [[rib]]s, [[vertebra]]e and [[shoulder blade]]s, and in the [[cancellous]] ("spongy") material at the [[anatomical terms of location|proximal]] ends of the [[long bone]]s [[femur]] and [[humerus]]. Yellow marrow is found in the hollow interior of the middle portion of long bones. In cases of severe blood loss, the body can convert yellow marrow back to red marrow in order to increase blood cell production. ===Stroma=== <!--Stroma of bone marrow redirects here--> The ''[[stroma]] of the bone marrow'' is all tissue that isn't directly involved in the primary function of [[hematopoiesis]]. The yellow bone marrow belongs here, and makes the majority of the bone marrow stroma, in addition to stromal cells located in the red bone marrow. Still, the stroma is indirectly involved in hematopoiesis, since it provides the ''hematopoietic microenvironment'' that facilitates hematopoiesis by the [[parenchyma]]l cells. For instance, they generate [[colony stimulating factors]], affecting [[hematopoiesis]]. Cells that constitute the bone marrow stroma are: *[[fibroblasts]] ([[reticular connective tissue]]) *[[macrophages]] *[[adipocytes]] *[[osteoblasts]] *[[blood vessels]] ([[sinusoid blood vessel|sinusoid]]) Macrophages contribute especially to [[red blood cell]] production. They deliver iron for [[hemoglobin]]-production. ====Bone marrow barrier==== The blood vessels constitute a barrier, inhibiting immature blood cells from leaving the bone marrow. Only mature blood cells contain the [[membrane protein]]s required to attach to and pass the blood vessel [[endothelium]]. [[Hematopoietic stem cell]]s may also cross the bone marrow barrier, and may thus be harvested from blood. ====Stem cells==== {{Main|Mesenchymal stem cell}} The bone marrow stroma contain ''mesenchymal stem cells'' (also called ''marrow stromal cells''). These cells are [[multipotent]] [[stem cell]]s that can [[Cellular differentiation|differentiate]] into a variety of cell types. Cell types that MSCs have been shown to differentiate into [[in vitro]] or [[in vivo]] include [[osteoblast]]s, [[chondrocyte]]s, [[myocyte]]s, [[adipocyte]]s, and, as described lately, [[Beta cell|beta-pancreatic islets cells]]. They can also transdifferentiate into [[neuron|neuronal cells]]. ===Compartmentalization=== There is [[biologic compartmentalization]] in the bone marrow, in that certain [[cell types]] tend to aggregate in specific areas. For instance, [[erythrocytes]], [[macrophages]] and their precursors tend to gather around [[blood vessels]], while [[granulocytes]] gather at the borders of the bone marrow. ==Types of stem cells== Bone marrow contains three types of [[stem cell]]s:<ref>{{cite book|title=Rubin's Pathology: Clinicopathologic Foundations of Medicine|author=Raphael Rubin and David S. Strayer|pages=90|date=2007|publisher=Lippincott Williams &amp; Wilkins|id=ISBN 0781795168}}</ref> * [[pluripotential hematopoietic stem cell|Hematopoietic stem cell]]s give rise to the three classes of blood cells that are found in the circulation: [[white blood cell]]s (leukocytes), [[red blood cell]]s (erythrocytes), and [[platelets]] (thrombocytes). * [[Mesenchymal stem cell]]s are found arrayed around the central sinus in the bone marrow. They have the capability to differentiate into [[osteoblasts]], [[chondrocytes]], [[myocytes]], and many other types of cells. They also function as "gatekeeper" cells of the bone marrow. * [[Endothelial stem cell]]s == Diseases involving the bone marrow == The normal bone marrow architecture can be displaced by [[cancer|malignancies]] or infections such as [[tuberculosis]], leading to a decrease in the production of blood cells and blood platelets. In addition, cancers of the hematologic progenitor cells in the bone marrow can arise; these are the [[leukemia]]s. To diagnose diseases involving the bone marrow, a [[bone marrow aspiration]] is sometimes performed. This typically involves using a hollow needle to acquire a sample of red bone marrow from the [[iliac crest|crest of the ilium]] under general or [[local anesthesia]]. The average number of cells in a leg bone is about 440,000,000,000. Exposure to [[ionizing radiation|radiation]] or [[chemotherapy]] will kill many of the rapidly dividing cells of the bone marrow and will therefore result in a depressed [[immune system]]. Many of the symptoms of [[Radiation poisoning|radiation sickness]] are due to damage to the bone marrow cells. ==Examination== {{Main|Bone marrow examination}} [[Image:acute leukemia-ALL.jpg|thumb|left|A [[Wright's stain]]ed bone marrow aspirate smear from a patient with leukemia.]] Bone marrow examination is the [[pathology|pathologic]] analysis of samples of bone marrow obtained by ''bone marrow biopsy'' and ''bone marrow aspiration''. Bone marrow examination is used in the diagnosis of a number of conditions, including [[leukemia]], [[multiple myeloma]], [[anemia]], and [[pancytopenia]]. The bone marrow produces the cellular elements of the [[blood]], including [[platelet]]s, [[red blood cell]]s and [[white blood cell]]s. While much information can be gleaned by testing the blood itself (drawn from a vein by [[phlebotomy]]), it is sometimes necessary to examine the source of the blood cells in the bone marrow to obtain more information on [[hematopoiesis]]; this is the role of bone marrow aspiration and biopsy. == Donation and transplantation of bone marrow == {{main|Hematopoietic stem cell transplantation}} [[Image:Bone marrow biopsy.jpg|thumb|right|300px|Bone marrow harvest]] It is possible to take hematopoietic stem cells from one person and then infuse them into another person (Allogenic) or into the same person at a later time (Autologous). If donor and recipient are compatible, these infused cells will then travel to the bone marrow and initiate blood cell production. Transplantation from one person to another is performed in severe cases of disease of the bone marrow. The patient's marrow is first killed off with drugs or radiation, and then the new stem cells are introduced. Before radiation therapy or chemotherapy in cases of [[cancer]], some of the patient's hematopoietic stem cells are sometimes harvested and later infused back when the therapy is finished to restore the immune system. ===Harvesting=== The stem cells are harvested directly from the red marrow in the [[iliac crest|crest of the ilium]], usually under [[general anesthesia]]. Contrary to popular belief, it is a minimally invasive outpatient procedure with only minor discomfort<sup>reference needed</sup>. Another option is to administer certain drugs that stimulate the release of stem cells from the bone marrow into circulating blood. An IV is inserted into the donor's arm, and the stem cells are filtered out of the blood. The procedure is similar to donating blood or platelets. It may also be taken from the [[sternum]]. The [[tibia]] may seem a good source, since it is very superficial. However, except in children, this bone marrow doesn't contain any substantial amount of red bone marrow, but rather only yellow bone marrow. <ref name=T4> Semester 4 medical lectures at Uppsala University 2008 by Leif Jansson</ref> In newborns, stem cells may be retrieved from the [[umbilical cord]]. == Bone marrow as a food == Though once used in various preparations, including [[pemmican]], bone marrow for human consumption in America has recently fallen out of favor as a food. Now, it is commonly used only as a flavoring for soups and sauces, although dishes with intact bone marrow can still be found in some European restaurants. Bone marrow is a source of [[protein]] and high in [[unsaturated fat|monounsaturated fats]]. These fats are known to decrease [[LDL]] [[cholesterol]] levels resulting in a decreased risk of [[cardiovascular disease]], prompting some to make bone marrow a [[Diet (nutrition)|dietary]] [[staple food|staple]]. The actual health effects of the addition of bone marrow to the diet remain unclear. == References == <references /> *Weiss, Leon (1976) "The hematopoietic microenvironment of the bone marrow: An ultrastructural study of the stroma in rats" ''Anatomical Record'' '''186 (2)''': 161-184 == See also== *[[Leukemia]] *[[Bone marrow transplant]] *[[Bone marrow examination]] *[[Aplastic anemia]] *[[Osso buco]] *[[John Raymond Hobbs (Professor)]] == External links == * {{BiowebUW|APlab/Table_of_Contents/Lab_11/Bone_Marrow_1/bone_marrow_1.html|Microscopic slides of bone marrow, with explanations}} *[http://fooddownunder.com/cgi-bin/recipe.cgi?r=159368 Marrow Balls] *[http://fooddownunder.com/cgi-bin/recipe.cgi?r=264236 Tostadas de tuetano] *[http://www.aadp.org/pages/page.php?pageid=1 Asian American Donor Program] *[http://www.sanjivan.com Organ Donation Blog] {{lymphatic_system}} {{Bone and cartilage}} [[Category:Lymphatic system]] [[ar:نقي]] [[bs:Koštana srž]] [[bg:Костен мозък]] [[ca:Medul·la òssia]] [[cs:Kostní dřeň]] [[da:Knoglemarv]] [[de:Knochenmark]] [[et:Luuüdi]] [[es:Médula ósea]] [[eo:Ostmedolo]] [[fr:Moelle osseuse]] [[ko:골수]] [[hr:Koštana srž]] [[id:Sumsum tulang]] [[it:Midollo osseo]] [[he:מוח עצם]] [[la:Medulla ossium]] [[lt:Raudonieji kaulų čiulpai]] [[mk:Коскена срж]] [[mn:Чөмөг]] [[nl:Beenmerg]] [[ja:骨髄]] [[no:Benmarg]] [[nn:Beinmerg]] [[pl:Szpik kostny]] [[pt:Medula óssea]] [[ru:Костный мозг человека]] [[sk:Kostná dreň]] [[sr:Коштана срж]] [[su:Sungsum tulang]] [[fi:Luuydin]] [[sv:Benmärg]] [[ta:எலும்பு மச்சை]] [[vi:Tủy xương]] [[tr:Kemik iliği]] [[yi:מארך ביין]] [[zh:骨髓]]