The Blood I Functions Components Formation of blood cells D.Rezazadeh Department of Medical Laboratory Science Kermanshah,Faculty of Paramedical

Hematology, also spelled haematology is the study of blood, the blood-forming organs, and blood diseases. Hematology includes the study of etiology, diagnosis, treatment, prognosis, and prevention of blood diseases that affect the production of blood and its components, such as blood cells, hemoglobin, blood proteins, and the mechanism of coagulationalso spelledbloodetiology diagnosisprognosispreventionblood cellshemoglobin blood proteinscoagulation

Functions of Blood  Transportation O 2, nutrients, waste, hormones, heat  Regulation—maintain homeostasis of body fluids Regulate pH, body temperature, maintain fluid volume  Protection Clotting prevents loss of fluids White blood cells protect against disease Blood proteins protect against disease

Physical characteristics and volume  Salty and metallic tasting  More dense than water  Slightly alkaline, pH between 7.35 and 7.45  Temperature ~ 37 o C or 99 o F  Makes up 8% of body weight  Volume in adult males is 5-6 L and in females 4-5 L

Blood components  Blood plasma 55%  Formed elements 45% RBCs—measurement is hematocrit Leukocytes and platelets

Blood plasma  Includes over 100 different dissolved solutes

Formed elements

Erythrocyte structure  Flexible structure, large surface area  Lack a nucleus and other organelles.  33% of weight is hemoglobin molecules.  Other proteins include antioxidants and those to maintain RBC shape (spectrin)

Erythrocyte function  Dedicated to carry respiratory gas

Hematopoiesis  Occurs in the red bone marrow in reticular connective tissue next to blood sinusoids  Arises from pleuripotent stem cells.  Appearance of receptors that respond to hormones leads to specialization.  Erythropoeitin initiates erythropoiesis 15 days

Regulation of RBCs

Dietary needs to produce RBCs  Iron, AAs, lipids, and carbohydrates.  Iron is absorbed from the diet 65% found in hemoglobin The rest stored in liver, spleen and bone marrow  Iron is toxic and requires transferrin as a transporter  Some iron is lost in feces and menstrual blood  Vitamin B 12 and folic acid are necessary for DNA synthesis

Fate and death of RBCs  RBCs have a lifespan of 100 to 120 days  Age makes them less flexible and the hemoglobin begins to degenerate.  Old RBCs get trapped in the small capillaries of the spleen  Macrophages destroy and digest RBCs Heme and globin are separated Globin broken down into AAs Haptoglobin captures hemoglobin in plasma that escapes from RBCs

Erythrocyte disorders  Anemias Low hematocrit Low hemoglobin content Abnormal hemoglobin  Thalassemias  Sickle-cell anemia  Polycythemia Polycythemia vera Secondary polycythemia

Leukocytes or White Blood Cells  WBCs have a nucleus and other organelles.  WBCs can emigrate--slip out of blood vessels.  When out of the blood stream the WBC moves using amoeboid motion.  Use chemical chemotaxis to follow trail to infection or damaged tissue. chemotaxis

Leukocytes

Types of WBCs: Granular leukocytes  Neutrophils—multilobed nucleus, inconspicuous granules  Eosinophils—bilobed nucleus, red granules  Basophils—lobed nucleus, purple-black cytoplasmic granules

Types of WBCs: Agranular leukocytes  Lymphocyte—nucleus spherical or indented, pale blue cytoplasm  Monocytes—nucleus U or kidney shaped, gray- blue cytoplasm

Production of leukocytes  Leukopoiesis is stimulated by interleukins and colony-stimulating factors (CSFs)  Pluripotent stem cells have the capacity to differentiate into several types of cells. Myeloid stem cells Lymphoid stem cell

Leukocyte disorders  Leukopenia—low WBC count  Leukemia—unchecked growth of a single unspecialized clone Acute leukemia occurs if it derives from blast-type cells Chronic leukemia occurs if it derives from later stages Bone marrow is compromised and defense system becomes nonfunctional  Infectious mononucleosis derives from excessive numbers of agranulocytes (Epstein-Barr virus)

Platelets  Under the influence of thrombopoietin, myeloid stem cells develop into megakaryocytes (huge cells).  These cells fragment into platelets.  platelets have a very short life about 9-11 days.

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