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Blood

Chapter 19

Introduction •  Functions

– Transport medium – Regulation – Protection

•  Composition – Plasma – fluid – Formed elements – cells & cell fragments

•  Volume varies – Average = 5 liters

Human Anatomy, 3rd edition Prentice Hall, © 2001

Composition of Blood Plasma •  = about 55% of the blood •  Composition

– Mostly water – Plasma proteins – Dissolved foods, wastes, gases, ions

•  Differences between plasma and intersititial fluid – Plasma has more dissolved gases – Plasma has more proteins – Concentrations of small molecules are similar

Plasma Proteins

•  Most are made by the liver – Albumins – transport fatty acids & steroids – Globulins – immune functions – Fibrinogen – blood clotting

Formed Elements •  Blood cells and cell fragments •  Produced by hemopoiesis

– Arise from stem cells called hemocytoblasts •  Types of formed elements

– Erythrocytes – red blood cells (RBCs) – Leukocytes – white blood cells (WBCs) – Thrombocytes – platelets

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Human Anatomy, 3rd edition Prentice Hall, © 2001

Erythrocytes •  Biconcave •  Have no nuclei (or other

organelles) •  Functional for about 120

days •  Production occurs in the

red bone marrow –  Erythropoiesis –  Controlled by

erythropoietin •  Functions

–  Transport O2 & some CO2

Human Anatomy, 3rd edition Prentice Hall, © 2001

SEM of RBCs

Human Anatomy, 3rd edition Prentice Hall, © 2001

Hemoglobin

•  Binds to oxygen & carbon dioxide

•  Anemia •  Polycythemia

(erythrocytosis)

Numbers of RBCs •  Normally 4.3-5.8 million cells/mm3 of blood

–  Males = 5.1-5.8 million/mm3

–  Females = 4.3-5.2 million/mm3

•  Numbers affect viscosity of blood •  The percentage of erythrocytes, by volume, in

whole blood is the hematocrit –  Males = 45% –  Females = 42%

Leukocytes •  About 5000 – 10,000/mm3 of blood •  Produced by leukopoiesis in red bone marrow •  Location – mostly in peripheral tissues •  Functions

–  Defense against pathogens –  Removal of toxins, wastes, abnormal or damaged

cells •  As large or larger than RBCs, contain nuclei

Types of WBCs

•  Granulocytes have granules in their cytoplasm – Neutrophils – Eosinophils – Basophils

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Human Anatomy, 3rd edition Prentice Hall, © 2001

A Neutrophil

•  Neutrophils are phagocytic towards bacteria –  55-65% of circulating WBCs

Human Anatomy, 3rd edition Prentice Hall, © 2001

An Eosinophil

•  Eosinophils are involved in allergic reactions and parasitic infections –  2-4% of circulating WBCs

Human Anatomy, 3rd edition Prentice Hall, © 2001

A Basophil •  Basophils exaggerate inflammation at the site of

an injury – Less than 1% of circulating WBCs

Types of WBCs

•  Agranulocytes do not have granules in their cytoplasm – Monocytes – Lymphocytes

Human Anatomy, 3rd edition Prentice Hall, © 2001

A Monocyte

•  Monocytes are phagocytes and form the macrophages of the tissues –  2-8% of the WBC population

Human Anatomy, 3rd edition Prentice Hall, © 2001

A Lymphocyte

•  Lymphocytes are responsible for specific immunity – B lymphocytes

produce antibodies – T lymphocytes

attack foreign cells directly

–  20-30% of the WBC population

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Human Anatomy, 3rd edition Prentice Hall, © 2001

Thrombocytes

•  Formed from fragments of large cells called megakaryocytes

•  Have no nuclei, lifespan is 10 – 12 days

•  Number about 350,000/mm3 of blood

•  Function –  Involved in the clotting

mechanism

Human Anatomy, 3rd edition Prentice Hall, © 2001

Origins & Differentiation of Blood Cells

Human Anatomy, 3rd edition Prentice Hall, © 2001

Blood Types •  Antigens are specific proteins on RBC membranes

–  A, B, O, Rh •  Antigens are accompanied by antibodies in plasma •  Specific antibodies bind with antigens, cause agglutination