Bone Marrow Flashcards
Bone marrow is the only site of: (4)
- Erythropoiesis,
2.Myelopoiesis - Thrombopoiesis
- Lymphopoiesis
This develops a primitive, undifferentiated cell known as hemocytoblast, or stem cell
Central cavity of bone marrow
1st recognizable precursor in each cell line
Blast
This happens during the first few years of life:
a delicate balance exists between developing bone marrow space (trabecular bone) and the developing infant’s need for blood cells and the liver or spleen remains available because of its hematopoietic capability
This happens during 4th year of life
rate of bone marrow growth exceeds the need for blood cells therefore, active marrow sites are replaced with areas of fatty reserve and fat first develops in the long bones
Bone marrow that is made mostly of fat
Yellow marrow
process of replacing the active marrow by adipocyte
Retrogression
At this age, adipose tissue (adipocytes) becomes more abundant and begin to occupy spaces in the long bones previously dominated by the active bones
Between 5-7 years old
This occurs during the 18th year of life
the only active hematopoietic sites are in the pelvis, vertebrae, ribs, scapulae, sternum, skull and proximal extremities of the long bones
Describe Red Marrow: (3)
1.Site of blood cell development
2. Hematopoietically ACTIVE Bone
3. It comprises approximately 50% of the marrow cavity space
Hematopoietic sites of Red Marrow: (7)
- Sternum
- Skull
- Scapula
- Vertebrae
- ribs
- pelvic bones
- proximal ends of long bones
Describe yellow marrow: (3)
- Hematopoietically INACTIVE Bones
- Made up of adipose tissues → Adipocytes
- The remaining 50% of the space is occupied
PRIMARY LYMPHOID TISSUE
Bone marrow and thymus
SECONDARY LYMPHOID TISSUE
spleen and lymph nodes and gut associated lymphoid tissue
