HEMA 1 MIDTERMS P2

• HEMATOPOIESIS


  The process of blood cell production, differentiation, and development

  
• Blood cells


  • Very important component of the human body
  • Play a key role in the normal functioning of the human body
• Red blood cells


  Carry oxygen, transport oxygen, and distribute it to the tissues while at the same time removing/getting carbon dioxide
• White blood cells


  Very important part of our immune system
• Platelets


  Play a key role in the clotting process to prevent hemorrhage or bleeding
• Totipotential Stem Cell


  Most versatile type of stem cell<|>Can develop into any human cell type, including development from embryo into fetus

  
• Pluripotential Stem Cells


  Present several days after fertilization<|>Can develop into any cell type, except they cannot develop into a fetus<|>Limited lineage; source of stem cells
• Multipotential Stem Cells


  Derived from pluripotent stem cells<|>They can be found in adults, but they are limited to specific types of cells to form tissues<|>For example, bone marrow stem cells can produce all types of blood cells, bone cartilage, and adipose (fat) cells

  
• Embryonic blood cells


  Excluding the lymphocyte type of white blood cell, originate from the mesenchymal tissue that arises from the embryonic germ layer, the mesoderm

  
• Aorta-gonad-mesenephros region


  Mesodermally derived intraembryonic region<|>Also known as the paraaortic splanchnopleure at a slightly earlier developmental stage<|>Produces, respectively, potent HSCs and multipotent progenitor cells before their appearance in the yolk sac
• Yolk Sac (Fetal Stage)


  Site of primitive hematopoiesis<|>Divided into blood islands which contains predominantly primitive erythroblasts<|>Formed during the first 2 - 8 weeks of life<|>Synthesis of embryonic hemoglobins starts here<|>Produce hemoglobin (Gower-1, Gower2, and Portland)

  
• Liver


  Sixth week (2nd to 5th month)<|>Major hematopoietic organ of early and midfetal life<|>Gives rise to fetal Hgb [Hgb F]<|>In the middle part of fetal life, the spleen and, to a lesser extent, lymph nodes have a minor role in hematopoiesis
• Bone Marrow


  Begins in the 4th month of gestation<|>After the fifth fetal month it becomes the primary site of hematopoiesis<|>Until post-natal life
• Medullary hematopoiesis


  1. Occurs in the medulla or inner part of the bone

  2. Begins in the bone marrow cavity prior to the fifth month of fetal development
• By the end of 24 weeks' gestation, the bone marrow becomes the primary site of hematopoiesis. The yolk sac and liver stop and continues in the bone marrow
• Types of Human Stem Cells

  • Totipotential
  • Pluripotential
  • Multipotential

  
• THREE PHASES OF HEMATOPOIESIS

  1. MESOBLASTIC PHASE

  2. HEPATIC PHASE

  3. MEDULLARY (MYELOID) PHASE

  
• Bone marrows starts being the main hematopoietic organ during the fourth fetal month which means that all bone marrow in the human body is utilized. During postnatal life, some of the long bones are still utilized but through time, they start to be covered with adipose tissue so, the red marrow of the long bones are gradually replace w/ the yellow marrow. Thus, on post natal, flat bones become a major site of hematopoiesis.
• Retrogression


  The process of replacing the active marrow (red marrow) by adipocytes (yellow marrow) during development
• Yellow marrow


  Normally inactive and composed mostly of fat (adipose) tissue
• Red marrow


  Normally active in the production of most types of leukocytes, erythrocytes, and thrombocytes
• Bone marrow


  • One of the body's largest organs (next to skin)
  • Represents approximately 3.5% to 6% of total body weight
  • Averages around 1,500 g in adults
• Hematopoietic marrow


  Organized around the bone vasculature (haversian canal system)
• During the first few years of life, the marrow of all bones is red and cellular.
• Extramedullary Hematopoiesis


  Abnormal circumstances, the spleen, liver, and lymph nodes revert back to producing immature blood cells<|>Occurs when the bone marrow becomes dysfunctional or unable to meet the demands placed on it
• Hematopoietic microenvironment


  Described as a mesh work of stromal cells that is composed of reticulum cells

  
• Stromal cells


  • Endothelial Cells
  • Adipocytes
  • Macrophages
  • Osteoblasts
  • Osteoclasts
  • Fibroblasts
• Endothelial Cells


  Broad, flat cells that form a single continuous layer along the inner surface of the arteries, veins, and vascular sinuses<|>Regulates the flow of particles entering and leaving hematopoietic spaces in the vascular sinuses<|>Maintain the integrity of the hematopoietic environment

  
• Adipocytes


  Large cells with a single flat vacuole<|>They play a role in regulating the volume of the marrow in which active hematopoiesis occurs

  
• Macrophages


  Function in phagocytosis, and both macrophages and lymphocytes secrete various cytokines that regulate hematopoiesis<|>Located throughout the marrow space
• Osteoblasts


  Bone-forming cells
• Osteoclasts


  Bone-resorbing cells
• Reticular Adventitial Cells


  Form an incompetent layer of cells on the abluminal surface of the vascular sinuses<|>Cells that forms the spaces where megakaryoblast would go near and extends its cytoplasm to undergo the proplatelet process

  
• Multipotent Stem Cells (CD34)

  Have the capacity for self-renewal as well as proliferation and differentiation into progenitor cells<|>Become the primitive progenitor cells, committed precursor cells, and lineage committed cells

  
• Hematopoietic stem cells


  1. Can become either the common myeloid or common lymphoid progenitor cells

  2. The determination of stem cells depends on the cytokines that act on them

  
• Lineage committed cells


  From the lineage committed cells arise the various developmental stages of each cells
• Committed precursor cells


  • Myeloid erythroid
  • Granulocyte monocyte
  • T cell and NK cell (TNK)
  • B-cell Common progenitor cell (BCP)

  
• Erythropoiesis


  Occurs in distinct anatomical sites called erythropoietic islands, specialized niches in which erythroid precursors proliferate, differentiate, and enucleate<|>Strictly for your Red Blood Cells (RBCs) and has a longer lifespan of 120 days

  
• Granulopoiesis


  Can be recognized as a maturational unit<|>Maturing cells spend an average of 3 to 6 days in the proliferating pool<|>Average life span of 6 to 10 hours in circulation<|>Strictly for your White Blood Cells (WBCs)

  
• Lymphocytes and plasma cells

  Are produced in lymphoid follicles<|>Lymphocytes can have memory cells