Hematopoiesis & Physiology of RBC, WBC, and Platelet Formation Flashcards
Define hematopoiesis
Formation and maturation of blood cells from stem cells
Occurs in the extravascular marrow spaces that contain endothelial cells, fibroblasts, macrophages and adipocytes (which provide growth factors, collagen and cell adhesion proteins)
Hematopoietic organs
Fetus: Liver and spleen
Adult: bone marrow
Bone Marrow Function
Tissue comprising of the center of large bones that contains stem cells and is where blood cell are produced
Lined with endothelial cells produces collagen and laminin and stimulating factors/IL6
Define Blood Islands
Cluster of stem cells that appear in the yolk sac in the 3rd week
3 month old fetus:
stem cells migrate to liver and spleen –> chief site of blood cell formation
4 month old fetus:
Hematopoiesis commences in the bone marrow
Birth and up to 18 years:
Bone marrow is the sole source of blood cells & is hematopoietically active
After age 18:
Only the vertebrae, ribs, sternum, skull, pelvis and proximal regions of the humerus and femur are active
Bone marrow stroma
Fibroblasts, Macrophages, Adipocytes
Provides growth factors, collagen and cell adhesion proteins
Stem cells
Become any of the mature hematopoietic cells – pluripotent
Characterized by high-proliferative capacity, potential to differentiate along all lineage pathways, property of self renewal
Define hematopoietic cytokines
Protein molecules actively secreted by cells of the bone marrow and influence proliferation and differentiation of stem cells into mature blood cells
Neutrophils
Most common polymorphnuclear leukocytes Quickly congregate and assist in phagocytosis Fight infection 50-65% Bands: 0-5%
Primary Neutrophils
Proteins –> kill bacteria
Proteolytic enzymes: degrade proteins
Lysozymes: degrade bacterial wall and generate bacterial killing
Secondary Neutrophils
Contain NADH and lactoferrin (takes iron from bacteria)
Eosinophils
Acid loving cells Combat infection by parasites Within intestinal mucosa and lungs Granules contain histamine Contain major basic protein and eosinophil peroxidase 0-3% Fight infection of parasites
MBP does
Induces degranulation of basophils and mast cells
Eosinophil peroxidase does
forms ROS and Nitrogen radicals that promote oxidative stress in the target –> cause cell death
Monocytes and Macrophages
Mono: Present pieces of pathogens to T cells
Macro: Kill pathogens
Monocyte to macrophage occurs when monocytes move out of the tissue and into the blood
Lymphocytes
Very little cytoplasm and large nucleus
T and B cells, Plasma cells, NK cells
T cells do
coordinate immune response
B cells
Make antibodies
Plasma cells
Memory B cells - make only one type of antibody
NK cells
Kill cells of infection (innate)
RBC
Erythrocytes
Most common
Deliver oxygen to body tissues via the blood via Hemoglobin
Flattened ovate shape, depressed center (6-8 microns)
No nucleus or mitochondira
Energy via glycolysis
RBC Production
Erythropoietin Stimulation
Lifespan: 120 days
Aging cells swell up to a sphere like shape and are engulfed by phagocytes within the liver and spleen
Hgb is excreted as bilirubin
Platelets
Thrombocytes
Stick together to form blood clots
Fragmented pieces of megakaryocyte cytoplasm release from the bone marrow into the blood
Via thrombopoietin
CBC
Assess individuals blood counts
W/ differentials: more detail regarding the cells
Hgb
Provides the oxygen carrying capacity of blood
Low in anemia pts
Hematocrit
% volume of blood that is composed of RBCs
3 times the amount of Hgb
RBC Distribution Width
Variation in width of red blood cell volume
Macro: Vit B12 and Folate –> normal
Micro: Iron –> elevated
Mixed iron and B12 –> elevated
Reticulocyte Count
Indirect measurement of recent RBC production
Increased: acute blood loss and hemolysis
Decreased: iron, Vit B12, folate deficiency
Lymphocytes
25-35%
Provide cellular immunity
Monocytes
2-6%
Basophils
Mediators of inflammation via heparin and histamine
1-3%
