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

The Blood I

FunctionsComponents

Formation of blood cellsD.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 coagulation

Functions of Blood Transportation

O2, 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 ~ 37o C or 99o 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 B12 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.

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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