Blood and Hemopoesis
- Blood is a connective tissue
- It is formed from formed elements
- Cells
- Platelets
- It is suspended in extracellular matrix (plasma)
- Blood volume in an average adult is 5-6L
- It functions in a number of ways
- Acid-base balance
- Osmotic balance
- Helps regulate body temperature
- Plasma is composed of the following:
- 90% water
- 7% protein
- fibrinogen (converts to fibrin during clotting)
- albumin (osmotic pressure)
- globulins (antibodies)
- 2% amino acids
- vitamins
- hormones
- 1% inorganic salts
- serum – the yellowish fluid remaining after blood has clotted, similar to plasma but lacks fibrinogen and other clotting factors
- mature RBC’s (erythrocytes) lack:
- mitochondria
- ribosomes
- certain enzymes
- Erythrocytes metabolize glucose for their energy needs
- Hematocrit is (estimated percent volume of RBC’s / unit blood)
- RBC’s are 80-90% of all blood cells
- 33% is hemoglobin
- anemia – low concentration of RBC’s
- hypochromic anemia – abnormally low concentration of hemoglobin in each cell due to iron deficiency
- pernicious anemia is due to a lack of/ or uptake problems with vitamin B12
- polycythemia – increased concentration of circulating RBC’s
- malaria – form of anemia
- parasitic destruction of RBC’s
- alterations in RBC membranes that cause aggregation and obstruction of small cerebral blood vessels
- life span of an RBC is approximately 120 days
- as they age, RBC’s swell and are destroyed after they are trapped in the spleen
- peripheral proteins are associated with the internal aspect of the cell membrane
- spectrin – maintains RBC shape
- actin – maintains RBC shape
- ankyrin – binds actin and spectrin to integral proteins on the cytoplasmic surface of the plasma membrane
- leukocytes or WBC’s there are 2 types
- agranulocytes – either lymphocytes or monocytes ; both lack granules
- monocytes
- 12 to 25 microns in diameter
- filopodia
- microvilli
- phagosomes
- pinocytotic vesicles
- large nuclei, acentric and kidney shaped
- live less than 3 days in the blood, or from months to years in connective tissue as macrophages
- lymphocytes
- round cells prominent nuclei
- 20-35% of all WBC’s
- classified as small, medium, or large
- 2 classes
T lymphocytes – cell mediated immunity
- Most numerous
- Can produce lymphokines (attract macrophages)
- Can secrete cytotoxic substances
B lymphocytes – humoral immunity
- Can differentiate into plasma cells and secrete antibodies
- granulocytes – characterized by the specific granules present
- neutrophils
- 10 to 15 microns in diameter
- has Barr body (evagination from the nucleus)
- granules contain:
lysozyme
collagenase
and other enzymes
functions in phagocytosing bacteria
1st line of defense
- eosinophils
- 12 to 16 microns in diameter
- granules stain reddish orange
- contains major basic protein
acts against parasitic worms
- live for less than 2 weeks in connective tissue
- allergic reactions and helminthic (worm) infections cause an increase in there numbers (eosinophilia)
- corticosteroids cause a decrease
- have an anti-inflammatory role – inactivation of histamine during allergic reactions
- basophils
- 10 to 15 microns in diameter
- contain dark, large granules when stained
- live very long time 1-1.5 years in mice
- contain heparin and histamine
- has an inflammatory role
- determination is based on the presence or lack of granules
- all leukocytes contain:
- azurophilic granules – lysosomal in activity
- hydrolytic enzymes
- impart phagocytic ability
- diapedesis is the means by which all leukocytes can cross through connective tissues and provide immunological defense
- Platelets – cell fragments from megakaryocytes in the bone marrow
- Hyalomere – peripheral region
- Granulomere – central region
- Rich in fibrinogen and PDGF (platelet-derived-growth-factor)
- Survive about 10 days
- Function in blood clotting
- Hemopoesis
- 6-8 weeks the liver and spleen as well as lymph vessels function in hemopoesis
- 4th-6th month developing bone marrow becomes site of hemopoesis – by birth it is the only site where it occurs
- involves mitotic division and differentiation of cells derived from pluripotent stem cells (CFU-S) ( colony forming units spleen)
- CFU-S are present in bone marrow cords
- Erythropoesis
- Proerythroblast
- Normoblast
- Starts to produce hemoglobin
- Reticulocyte
- No nucleus
- No more mitosis
- Mature form of hemoglobin produced
- Number of reticulocytes is dependant on physiological oxygen demand
- It is a measure of RBC formation
- Erythrocyte
- Formed after ubiquitin destroys the remaining organelles
- Granulopoesis
- Myeloblast
- Myelocyte
- Band or stab cell
- Granulocyte
- Monopoesis
- Monoblast
- Differentiated mature cells
- Monocyte
- Macrophage
- Lymphopoesis
- Lymphoblast
- Prolymphocyte
- Lymphocyte
- Platelet formation
- Megakaryoblast
- Megakaryocyte
- Fragmentation along internal membranes called platelet demarcation channels
- platelet
J. Maguire
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