Changes

Bone marrow is referred to as [[#Red marrow|red]] or [[#Yellow marrow|yellow]]. Red bone marrow is involved with [[Haemostasis|haemostasis]] while yellow bone marrow is adipose tissue. Bone marrow occupies the cavities in [[Bones and Cartilage - Anatomy & Physiology#Types of Bone|long bones]] and spaces in [[Bones and Cartilage - Anatomy & Physiology#Types of Bone|spongy bones]].

Bone marrow is referred to as [[#Red marrow|red]] or [[#Yellow marrow|yellow]]. Red bone marrow is involved with [[Haemostasis|haemostasis]] while yellow bone marrow is adipose tissue. Bone marrow occupies the cavities in [[Bones and Cartilage - Anatomy & Physiology#Types of Bone|long bones]] and spaces in [[Bones and Cartilage - Anatomy & Physiology#Types of Bone|spongy bones]].

==Development==

==Development==

<p>Pluripotential haematopoietic stem cells (PPSC) migrate into bones from the [[Haematopoiesis#Yolk Sac Phase|embryonic yolk sac]] and the [[Haematopoiesis|foetal liver]] during development, a process called homing. The cells then associate closely with the connective tissues within the bone. The PPSCs continue to constantly divide in the bone marrow with one daughter cell remaining a pluripotential stem cell and the other daughter cells developing into multipotential haematopoietic stem cells. The multipotential stem cells also constantly divide with some daughter cells remaining stem cells and the other daughter cells developing into blood cells ([[Haematopoiesis|haematopoiesis]]).</p>

<p>Pluripotential haematopoietic stem cells (PPSC) migrate into bones from the [[Haematopoiesis - Overview#Yolk Sac Phase|embryonic yolk sac]] and the [[Haematopoiesis - Overview#Foetal Liver|foetal liver]] during development, a process called homing. The cells then associate closely with the connective tissues within the bone. The PPSCs continue to constantly divide in the bone marrow with one daughter cell remaining a pluripotential stem cell and the other daughter cells developing into multipotential haematopoietic stem cells. The multipotential stem cells also constantly divide with some daughter cells remaining stem cells and the other daughter cells developing into blood cells ([[Haematopoiesis - Overview|haematopoiesis]]).</p>

==Red marrow==

==Red marrow==

=== Haematopoietic===

=== Haematopoietic===

[[Image:LH Bone Marrow Erythroblasts Histology.jpg|thumb|75px|'''Developing erythrocytes''' ©RVC 2008]]

[[Image:LH Bone Marrow Erythroblasts Histology.jpg|thumb|75px|'''Developing erythrocytes''' ©RVC 2008]]

<p>The haematopoietic cells produce the vast majority of blood cells in the body ([[Haematopoiesis|haematopoiesis]]). In young animals this occurs in most bones in the body but in mature adults this is limited to membranous bones in the body.</p>

<p>The haematopoietic cells produce the vast majority of blood cells in the body ([[Haematopoiesis - Overview|haematopoiesis]]). In young animals this occurs in most bones in the body but in mature adults this is limited to membranous bones in the body.</p>

<p>To enter circulation newly formed cells press against the sinusoid wall, temporally fusing to it and creating an opening. The cell then passes directly into the circulation and the membrane repairs itself. Mature [[Erythrocytes|erythrocytes]] immediately enter circulation, however the marrow stores [[Leukocytes|leukocytes]] and consequently contains around ten times more [[Leukocytes|leukocytes]] than found in circulation</p>

<p>To enter circulation newly formed cells press against the sinusoid wall, temporally fusing to it and creating an opening. The cell then passes directly into the circulation and the membrane repairs itself. Mature [[Erythrocytes|erythrocytes]] immediately enter circulation, however the marrow stores [[Leukocytes|leukocytes]] and consequently contains around ten times more [[Leukocytes|leukocytes]] than found in circulation</p>

<p>[[Thrombopoiesis#Megakaryocyte|Megakaryocytes]] reside alongside the sinusoid membrane but do not leave the tissue, rather they release their [[Thrombocytes|platelets]] and then withdraw from the membrane.</p>

<p>[[Thrombopoiesis#Megakaryocyte|Megakaryocytes]] reside alongside the sinusoid membrane but do not leave the tissue, rather they release their [[Thrombocytes|platelets]] and then withdraw from the membrane.</p>