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Functions of Blood
Transportation
- 02, CO2, metabolic wastes, nutrients, heat & hormones
Protection and prevents from disease & loss of blood
Regulation
- helps regulate pH through buffers
- helps regulate body temperature
- coolant properties of water
- vasodilatation of surface vessels dump heat
- helps regulate water content of cells by interactions with dissolved ions and proteins
Hemopoietic Growth Factors
Erythropoietin (EPO)
- produced by the kidneys increase RBC precursors
Thrombopoietin (TPO)
- hormone from liver stimulates platelet formation
Cytokines are local hormones of bone marrow not kidneys
Red Blood Cells or Erythrocytes
- Contain oxygen-carrying protein hemoglobin that gives blood its red color
- 1/3 of cell’s weight is hemoglobin
- Biconcave disk 8 microns in diameter
Hemoglobin
- Globin protein consisting of 4 polypeptide chains
- 2 Beta polypeptide chains and Alpha 2
polypeptide chains. - One heme pigment attached to each polypeptide chain
- each heme contains an iron ion (Fe+2)
Erythropoiesis: Production of RBCs
- Erythrocyte formation, called erythropoiesis, occurs in adult red bone marrow of certain bones
- The main stimulus for erythropoiesis is hypoxia
- ## hypoxia is low oxygen
Feedback Control of RBC Production
- Kidney response to hypoxia release/increase erythropoietin increase speeds up development of proerythroblasts into reticulocytes
WHITE BLOOD CELLS
- Leukocytes (white blood cells or WBCs) are nucleated cells and do not contain hemoglobin.
- Two principal types are granular (neutrophils, eosinophils, basophils) and agranular (lymphocytes and monocytes)
- Leukocytes have surface proteins, as do erythrocytes. They are called major histocompatibility antigens (MHC)
Neutrophils (Granulocyte)
- Polymorphonuclear Leukocytes or Polys or PMN or Seg
- Nuclei = 2 to 5 lobes connected by thin strands
- older cells have more lobes
- young cells called band cells because of horseshoe shaped nucleus (band)
- 60 to 70% of circulating WBCs
Eosinophils (Granulocyte)
- Nucleus with 2 or 3 lobes connected by a thin strand
- 2 to 4% of circulating WBCs
Basophils (Granulocyte)
- obscure the nucleus
- Less than 1% of circulating WBCs
Lymphocyte (Agranulocyte)
- amount varies from rim of blue to normal amount
- increase in number during viral infections
- 20 to 25% of circulating WBCs
Monocyte (Agranulocyte)
- Nucleus is kidney or horse-shoe shaped
- Largest WBC in circulating blood
- does not remain in blood long before migrating to the tissues
- 3 to 8% o circulating WBCs
Emigration & Phagocytosis in WBCs
- chemotaxis of both kinins from injury site & toxins
- extracellular destruction
Lymphocyte Functions
Natural killer cells
- attack many different microbes & some tumor cells
- destroy foreign invaders by direct attack
Eosinophil Function
- Leave capillaries to enter tissue fluid
- Release histaminase
- slows down inflammation caused by basophils
- Attack parasitic worms
Basophil Function
- Involved in inflammatory and allergy reactions
- Leave capillaries & enter connective tissue as mast
cells. - Release heparin, histamine & serotonin
- heighten the inflammatory response and account for hypersensitivity (allergic) reaction
Monocyte Function
- Take longer to get to site of infection, but arrive in larger numbers
- Become wandering macrophages, once they leave the capillaries
- Destroy microbes and clean up dead tissue following an infection
Neutrophil Function
- Fastest response of all WBC to bacteria
- Direct actions against bacteria
- release lysozymes which destroy/digest bacteria
- release defensin proteins that act like antibiotics & poke holes in bacterial cell walls destroying them
- release strong oxidants (bleach-like, strong chemicals ) that destroy bacteria
Differential WBC Count
Detection of changes in numbers of circulating WBCs (percentages of each type)
indicates infection, poisoning, leukemia, chemotherapy, parasites or allergy reaction
Normal WBC counts
- neutrophils 60-70% (up if bacterial infection)
- lymphocyte 20-25% (up if viral infection)
- monocytes 3 – 8% (up if fungal/viral infection)
- eosinophil 2 - 4% (up if parasite or allergy reaction)
- basophil <1% (up if allergy reaction or hypothyroid)
- Eosinphil and basophil together is on test
PLATELETS
- Thrombopoietin stimulates myeloid stem cells to produce platelets.
- Myeloid stem cells develop into megakaryocyte-colony-forming cells that develop into megakaryoblasts
- Megakaryoblasts transform into megakaryocytes which fragment.
- Each fragment, enclosed by a piece of cell membrane, is a platelet (thrombocyte).
- a life span of only 5 to 9 days;
Hemostasis
Stoppage of bleeding in a quick & localized fashion when blood vessels are damaged
Prevents hemorrhage (loss of a large amount of blood)
Methods utilized
- vascular spasm
- platelet plug formation
- blood clotting (coagulation = formation of fibrin threads)