Hematopoiesis & Bone Marrow - Downing Flashcards
What is the function of Hematopoietic Tissue?
Responsible for the formation of red blood cells, white blood cells, and platelets.
What are the two types of hematopoietic tissue?
- Myeloid tissue (bone marrow)
- Lymphatic tissue
What are the five subdivisions of hematopoiesis from myeloid tissue?
- Erythropoiesis - formation of red blood cells
- Granulopoiesis - formation of granular leukocytes
- Lymphopoeisis - formation of lymphocytes
- Monopoiesis - formation of monocytes
- Thrombocytopoiesis - formation of platelets
Where is the first site of prenatal hemopoiesis in the 2nd-3rd week of embryonic life?
Yolk sac
What are the first two cell types formed in prenatal hemopoiesis?
-
Endothelial cells
- line the vascular system
- originate from mesenchymal cells
-
Undifferentiated pluripotential stem cells (colony forming unit = CFU)
- originate from mesenchymal cells
- CFU seeds the liver, spleen, and bone marrow
What organ is the major site of blood formation from week 6 until the middle of fetal life where erythropoiesis dominates and occurs extravascularly?
Liver
In what organ does hemopoiesis begin in about the 3rd month of fetal life?
Spleen
Red cells are still nucleated at 7 weeks, but become non-nucleated by what week?
11th week
In what organ is erythropoiesis and granulopoiesis greatest from the 3rd-5th months and lasts until 7th-8th months of fetal life, but lymphopoiesis lasts throughout life?
Spleen
In what tissue/organ does hemopoiesis begin in the 5th month of fetal life?
Bone
What is the first bone to develop a medullary cavity for myeloid tissue?
Clavicle
What is the name for the pathological condition where hematopoietic tissue develops elsewhere than bone marrow (spleen and/or liver) and produces the kinds of cells that are produced in bone marrow?
Extramedullary myelopoiesis
In what organ does lymphopoiesis occur, which begins in the 5th month of fetal life?
Thymus
(only lymphopoiesis occurs - forms T-lymphocytes)
What occupies much of the diaphysis of the long bones and consists primarily of fat cells with blood vessels coursing through?
Yellow Marrow
What type of myeloid tissue is actively engaged in hemopoietic events, and is located in the dipole of the skull, ribs, sternum, vertebral bodies, cancellous bone, long & short bones, and the iliac crest?
Red Marrow
Red marrow is present in long bones of neonates & children until age 5-7, but by what age is almost all marrow of the limbs converted to yellow marrow?
age 18
What are the three components of myeloid tissue?
- Stroma
- connective tissue network which supports the blood forming cells
- Sinusoids
- wide thin walled vessels which allow newly formed blood cells to gain access to the blood stream
- Developing blood cells
What are the five types of cells in the bone marrow stroma?
- Fibroblasts
- produce collagenous fibers & reticular fibers
- Macrophages
- engulf & destroys imperfect RBCs, pieces of developing RBCs, and platelets
- Fat-storing cells
- predominate in yellow marrow
- Osteogenic cells
- can differentiate into osteoblasts
- Endothelial cells
- form the lining of the sinusoids
What two fibers are found in stroma of myeloid tissue and what is their function?
- Collagenous fibers (Type III)
- support larger blood vessels in medullary cavity
- reinforce tissue as a whole
- Reticular fibers
- form network of fibers that support the blood forming cells
What are the sinusoids of myeloid tissue and what are their function?
- Wide vascular channels usually filled with blood cells
- thin walls of simple squamous endothelium supported by a poorly developed basal lamina and reticular fibers
- Surrounded by developing blood cells
- Connecting the arterial and venous side of the circulation
Red and white blood cells enter circulation by diapedesis, passing through the sinusoidal wall utilizing what two things?
- Intercellular gaps
- Endothelial cell pores
What differentiating and growth regulating factor is produced in the kidney (& other sites), increases the number of hemoglobin-forming cells (erythroblasts) by stimulating the stem cells (CFU-E) to multiply and differentiate into hemoglobin-synthesizing cells, and the formation of it is stimulated by hypoxic conditions?
Erythropoietin
What is the first recognizable cell of the erythrocyte series? What is so recognizable about it?
- Blast cell
- Nucleus = Round
- 1+ nucleoli
- Cytoplasm is basophilic (blue) due to ribosomes & polyribosomes
- Mitotic cell
- Nucleus = Round
What is the second recognizable cell of the erythrocyte maturation series? What is so recognizable about it?
- Basophilic Erythroblast
- Nucleus = Round
- chromatin condensed (checker-board pattern)
- no visible nucleoli
- Cytoplasm is basophilic (blue/purple)
- ribosomes essential for sythesizing more cell substance
- polyribosomes required for hemoglobin synthesis
- Mitotic cell
- Nucleus = Round
