Chapter 13
THE BLOOD
Introduction
• Specialized connective tissue
– Plasma: fluid part (55%)
– Formed blood cells (45%)
• Erythrocytes
• Leukocytes
• Thrombocytes
2
FUNCTIONS OF THE BLOOD
Functions of the Blood (cont’d.)
• Transports: O2, CO2, nutrients, waste,
hormones
• Regulates: body pH, body temperature
• Clotting mechanism
• Protection against foreign microbes and
toxins
• Osmosis
THE CLASSIFICATION OF BLOOD CELLS AND THE
COMPOSITION OF PLASMA
The Classification of Blood Cells
• Erythrocytes (RBCs)
– 95% of the volume of blood cells
• Leukocytes (WBCs)
– Granular: neutrophils, eosinophils, basophils
– Agranular: monocytes, lymphocytes
• Thrombocytes: platelets
The Composition of Plasma
• Fluid portion of blood is 91% water
• Plasma proteins: 7%
– Albumin, globulin, fibrinogen
• Plasma solutes: 2%
– Ions, nutrients, waste products, gases,
enzymes, hormones
FORMATION OF BLOOD CELLS: HEMATOPOIESIS
Formation of Blood Cells:
Hematopoiesis (cont’d.)
• Produced in red bone marrow
• Lymphocytes and monocytes produced by
– Lymph nodes, spleen, tonsils
• Stem cells: undifferentiated mesenchymal
cells
BLOOD CELL ANATOMY AND FUNCTIONS
Blood Cell Anatomy and
Functions (cont’d.)
• Erythrocytes
– Biconcave disks
– No nucleus
– Contain hemoglobin
• Heme: binds O2
• Globin: binds CO2
Blood Cell Anatomy and
Functions (cont’d.)
• Granular leukocytes
– Neutrophils
• Phagocytize foreign substances
– Eosinophils
• Produce antihistamines
– Basophils
• Produce heparin, histamine, serotonin
Blood Cell Anatomy and
Functions (cont’d.)
• Agranular leukocytes
– Monocytes
• Phagocytize bacteria and cellular debris
• Macrophages: in tissues
– Lymphocytes
• T lymphocytes
• B lymphocytes
Blood Cell Anatomy and
Functions (cont’d.)
• Thrombocytes or platelets
– Disk-shaped cellular fragments with a nucleus
– Prevent fluid loss when blood vessels
damaged
– Produced from large megakaryocytes
THE CLOTTING MECHANISM
The Clotting Mechanism (cont’d.)
Ruptured blood vessel attracts Thrombocytes

Damaged tissue releases Thromboplastin

Thromboplastin + Ca+, ions, and proteins
Prothrombin activator + Ca+  Prothrombin 
Thrombin  Fibrinogen  Fibrin
The Clotting Mechanism (cont’d.)
• Clot
– Fibrin forms long threads acting like a net
– Platelets get enmeshed
• Syneresis: clot retraction
• Fibrinolysis: dissolution of blood clot
The Clotting Mechanism (cont’d.)
• Thrombosis: unwanted clotting
• Embolus: circulating blood clot
• Infarction
– Tissues killed as a result of loss of blood
supply
The Clotting Mechanism (cont’d.)
Animation – Blood
Click Here to Play Blood Animation
THE BLOOD GROUPS
Introduction
• Human blood is of different types
– Only certain combinations are compatible
• Agglutination: clumping of RBCs
– Occurs when blood groups mismatched
– Transfusion reaction
The ABO Blood Group
• Type A
– Anti-B antibodies
• Type B
– Anti-A antibodies
• Type AB
– No antibodies
The ABO Blood Group (cont’d.)
• Type O
– Anti-A and anti-B antibodies
The Rh Blood Group
• Eight Rh antigens
• Antigen D: most important
• Anti-Rh antibodies develop after exposure
– Rh-negative mother carrying Rh-positive baby
• Erythroblastosis fetalis
• RhoGAM - protects Rh-positive fetus
Summary
• Described the functions of blood
• Classified blood cells into different groups
based on anatomy and function
• Discussed how and where blood cells are
formed
• Explained the clotting mechanism
• Named the different blood groups