Here is a term paper on ‘Hematopoiesis’. Find paragraphs, long and short term papers on ‘Hematopoiesis’ especially written for college and paramedical students.
Term Paper on Hematopoiesis
Term Paper Contents:
- Term Paper on the Meaning and Sites of Hematopoiesis
- Term Paper on the Structure and Function of Bone Marrow
- Term Paper on the Process of Hematopoiesis
- Term Paper on Erythropoiesis
- Term Paper on Leucopoiesis
- Term Paper on Lymphocytic and Mobocytic Series
- Term Paper on Thrombopoiesis
Term Paper # 1. Meaning and Sites of Hematopoiesis:
Hematopoiesis is the process by which immature precursor cells develop into mature blood cells. The currently accepted theory on how this process works is called the monophyletic theory which simply means that a single type of stem cell gives rise to all the mature blood cells in the body. This stem cell is called the pluripotential (pluripotent) stem cell.
Term Paper # 2. Structure and Function of Bone Marrow:
Bone marrow has a vascular compartment and an extra vascular compartment. The vascular compartment is supplied by a nutrient artery which branches into central longitudinal arteries which send out radial branches that eventually open into sinuses.
These sinuses converge into a central vein that carries the blood out of the bone marrow into the general circulation. Hematopoiesis takes place in the extravascular compartment. The extravascular compartment consists of a stroma of reticular connective tissue and a parenchyma of developing blood cells, plasma cell, macrophages and fat cells.
The high activity of the bone marrow is demonstrated by its daily output of mature blood cells: 2.5 billion erythrocytes, 2.5 billion platelets, 50-100 billion granulocytes. The numbers of lymphocytes and monocytes is also very high.
Bone marrow is the site for other important activities in addition to hematopoiesis. These include the removal of aged and defective erythrocytes and the differentiation of B lymphocytes. It is also the site of numerous plasma cells.
Term Paper # 3. Process of Hematopoiesis:
The monophyletic theory of hematopoiesis states that pluripotent stem cells multiply to produce more pluripotent stem cells, thus ensuring the steady and lasting supply of stem cells. Some of the pluripotent stem cells differentiate into precursor cells that are at least partially committed to become one type of mature blood cell.
Pluripotent stem cells multiply slowly into one of five possible uni-potential stem cells which then multiply rapidly into the precursor of the specific mature blood cell for which they are destined.
Term Paper # 4. Erythropoiesis:
The term erythropoiesis (erythro = RBC) and poiesis = to make) is used to describe the process of RBC formation or production. In humans, erythropoiesis occurs almost exclusively in the red bone marrow. (The yellow bone marrow is primarily composed of fat, but, in response to a greater need for RBC production, the yellow bone marrow can turn to red marrow.)
The red bone marrow of essentially all bones produces RBCs frc3m birth to about five years of age. Between the ages of 5 to 20, the long bones slowly lose their ability to produce RBCs. Above age 20, most RBCs are produced primarily in the marrow of the vertebrae, the sternum, the ribs, and the pelvis
RBC Production Process:
a. Kidneys respond to a lower than normal oxygen concentration in the blood by releasing the hormone erythropoietin.
b. Erythropoietin travels to the red bone marrow and stimulates an increase in the production of red blood cells (RBCs).
c. The red bone marrow manufactures RBCs from stem cells that live inside the marrow.
d. RBCs squeeze through blood vessel membranes to enter the circulation.
e. The heart and lungs work to supply continuous movement and oxygenation of RBCs.
f. Damaged or old RBCs are destroyed primarily by the spleen.
Erythroblast:
Erythroblast is a nucleated red cell. Normoblast implies normal (reaction) erythropoiesis.
Normoblastic maturation involves:
i. Reduction in cell size.
ii. Ripening of cytoplasm, i.e. hemoglobinisation.
Maturation time from pronormoblast to RBC is 7 days. Mitotic division occurs till the intermediate normoblast stage.
Pronormoblast:
12-20 µm, large nucleus surrounded by a rim of deep basophilic cytoplasm and has a perinuclear halo. Nucleus is round and has several nucleoli.
Basophilic Normoblast:
10-16 µm nucleus still large chromatin coarser and deeply staining nucleoli disappear.
Orthochromatic/Intermediate Normoblast:
8-14 µm, nucleus smaller later it becomes pyknotic and essentrically placed ultimately it is lost by extrusion.
Reticulocyte:
Flat, non – nucleated, disc shaped, slightly larger than mature red blood cell. It shows diffuse pale basophilia which appears in the form of a reticulum with supra vital stains (brilliant cresy 1 blue or new ethylene blue). In 1-2 days, it loses its basophilia and become a mature erythrocyte.
Mature RBC:
They are middle sized measuring (6.6-7.7 micron). They have biconcave shape. Protein fraction of RBC is 85%. They don’t have nucleus RBC is. They contain hemoglobin and are the heaviest, of all the solid component of the blood. The shape of erythrocytes is a biconcave disc.
Term Paper # 5. Leucopoiesis:
The process of generating white blood cells (LEUKOCYTES) from the pluripotent HEMATOPOIETIC STEM CELLS of the, BONE MARROW. There are two significant pathways to generate various types of leukocytes -MYELOPOIESIS, in which leukocytes in the blood are derived from MYELOID STEM CELLS, and LYMPHOPOIESIS, in which leukocytes of the lymphatic system (LYMPHOCYTES) are generated from lymphoid stem cells.
Leucopoiesis:
Myeloblast:
15-20 µm has a large round or oval nucleus, evenly stained chromatin in strands or granules with reticular appearance, 1-6 nucleoli. The cell is peroxidase negative.
Promyelocyte:
It is like myeloblast except that it contains azurophilic granules which are peroxidase positive. Nuclear chromatin becomes condenser and nucleoli are less well defined.
Metamyelocyte:
Specific neutrophilic granules appear, nucleus shows no nucleoli, (NUCLEUS: CYTOPLASM) N: C ratio reduces; cytoplasm is pale pink, chromatin thicker and deeply stained.
Meyamyelocyte:
Nucleus is smaller and indented cytoplasm is pink with neutrophilic granules (Purplish).
Band or Stab Form:
Cell becomes still smaller, nucleus has a deep indentation, and chromatin is coarsely clumped. Cytoplasm is pink with purplish granules.
Segmented Neutrophil:
12-14 µm is size, nucleus shows 2-5 lobes, chromatin in dark purple clumps, cytoplasm has numerous, fine evenly distributed purplish granules. In female ai least 6 neutrophils/500 should show drumsticks.
The Mature Eosinophil:
16 µm in size, granules are acidophilic and larger. Nucleus is bilobed and is not masked by granules.
The Mature Basophil:
It usually has a bilobed nucleus, but the nucleus is masked by about 10 large basophilic granules.
Term Paper # 6. Lymphocytic and Mobocytic Series:
Lymphoblast:
15-20 µm in size, resembles myeloblast, cytoplasm is agranular and moderately basophilic. Nuclear chromatin gives fine reticular appearance with up to 2 nucleoli. It is peroxidase negative.
Large Lymphocyte:
12-16 µm in size has abundant pale sky blue cytoplasm with a few purplish red granules seen in about 33% of the cells.
Small Lymphocyte:
9-12 µm in size has scanty cytoplasm. Nucleus is usually round and shows heavily clumped chromatin.
Monocytic Series:
Monoblast:
It resembles myeloblast.
Promonocyte:
Upto 20 µm in size has a large convoluted nucleus, chromatin is seen in abundant. Cytoplasm is dull grey-blue and may contain a few azurophilic granules.
Monocyte:
15-20 µm in size has abundant dull grey-blue cytoplasm with a ground glass appearance and may show vacuolation and fine azurophilic granules. It has a kidney- shaped nucleus.
Term Paper # 7. Thrombopoiesis:
Thrombopoiesis refers to the process of thrombocyte generation. Thromobocytes are ligations of the cytoplasm from megakaryocytes. A single megakaryocyte can give rise to thousands of thrombocytes.
Thrombopoietin stimulates megakaryopoiesis, process of megakaryocyte maturation and differentiation. Thrombopoietin, upon release, binds to its receptor, found on megakaryocyte progenitor cells.
Following binding, intracellular signalling leads to megakaryocyte growth, maturation, membrane stability, platelet granule formation and the demarcation of the cytoplasm into regions destined to fragment into mature platelets.
These “pro-platelet processes” further fragment into platelets. This last step of pro-platelet process and platelet formation, in vitro, has been shown to be independent of thrombopoietin.
Megakaryoblast:
20-30 µm in size has a large oval or kidney-shaped nucleus with several nucleoli. It possesses relatively small amount of agranular cytoplasm.
Promegakaryocyte:
25-30 µm in diameter cytoplasm intensely basophilic with fine azurophilic granules. Nucleus may show mild lobulation and chromatin appears denser.
Megakaryocyte:
30-40 µm in diameter, it contains a single multi-lobulated or indented nucleus. Nuclear lobes may vary from 4-16 in numbers. Cytoplasm is bulky. Light blue with fine azurophilic granulation. The margin is irregular and may show fragmentation or budding. Precursor of circulating-platelets.
Mature Platelet:
1-4 µm. It is formed by fragmentation of megakaryocytic pseudopods. In circulation they acquire a discoid shaped. Cytoplasm stains light blue and contains purple reddish granules which may be clumped centrally.
Control of Platelet Production:
Perhaps by a humoral factor called thrombopoietin acts by a feedback mechanism.
