5. Bone marrow
• Location
– Gelatinous material found within the cavities of
the bones
– Medullary canals (long bones)
– Cavities of the (cancellous bones)
• Types
– Red (active, hematopoietic cells)
– Yellow (inactive, adipose cells)
6. • Produce all blood cells exclusively, except
lymphocytes
– Erythrocytes-----erythropoiesis
– Granular leukocytes-----granulopoiesis
– Monocytes-----monocytopoiesis
– Platelets-----megakryocytopoiesis
Red bone marrow
7. Red bone marrow
• Structure
– Stroma (a frame work of reticulin and reticular
cells)
– Hematopoietic cords
– Sinusoidal capillaries
• Continuous endothelium type
• Discontinous basement membrane
8. Growth factors
• Affect cell proliferation and differentiation
– Stimulate proliferation
• Progenitor and precursor cells
– Support differentiation of maturing cells
– Enhance the function of mature cells
• Examples
– G-CSF------ macrophage, endothelium, fibroblasts
– GM-CSF---- T lymphocytes, endothelium, fibroblasts
– M-CSF------ macrophage, endothelium, fibroblasts
– IL-3-----T lymphocytes
– EPO----Renal interstitial cells
9. Red bone marrow
• Change to yellow marrow with age
– Conversion Site
• Starts at the distal end of the long bones
• Site
– at puberty
• found in axial skeleton
10. Red bone marrow
• Mass
– 3.5-6.0 % of body weight
• Functions
– Production of blood cells---hematopoietic cells
– Destruction of worn out RBC---- macrophages
– Storage of iron---macrophages
11. The passage of erythrocytes, leukocytes
and platelets across a sinusoidal
capillary in red bone marrow
12. Release of blood cells from the bone
marrow
• Fenestration site arise in the endothelial cells and
provides a passage for the cells entering the venous
sinusoids.
• Mature cells can squeeze through
13. Release of blood cells from the bone
marrow
• Releasing factors
– C3 component of complement
– Hormones (glucocorticoids and androgens)
– Bacterial toxins
14. Yellow bone marrow
• Not seen at birth
• Appearance (3-7 yrs of age)
• Constitutes of adipose tissue
• Site
• Interchangeable
– Severe bleeding
– hypoxia
15. Bone marrow
• Other types of cells
– Fibroblasts (reticular connective tissue, collagen
type I and type II)
– Macrophages
– Osteoblasts
– Osteoclasts
– Adipocytes
– Endothelial cells forming sinusoids
– Mast cells
– Dendritic cells
16. Stem cells
• Red bone marrow
• Procedure
– Collect bone marrow stem cells
– Cultivate them in the medium
– Direct their differentiation to the cell type needed
for transplantation
– Transplant the tissue culture cells in the patient
17. Bone marrow
• Conditions in which bone marrow mass increases
(Bone marrow hyperplasia)
– Hemolytic anaemias
• Conditions in which bone marrow mass decreases
(Bone marrow hypoplasia)
– One type of cells
– All type of cells--- pancytopenia
• Bone marrow aplasia (total stoppage of activity)
22. Take home message
• Types
– Red active
– Yellow inactive
• Site
• Produce all blood cells exclusively, except
lymphocytes
• Yellow marrow retain the potentiality to become red
marrow
• Stem cells
• Extramedullary hematopoiesis
