CARDIOVASCULAR SYSTEM: BLOOD (Chapter 13)
1. The cardiovascular system consists of:
B. Functions of Blood
Blood is a liquid connective tissue that performs three major functions:
transportation of oxygen and nutrients to the body cells and removal of carbon dioxide and wastes
transports hormones from endocrine glands to target cells and organs
regulation of body temperature by diverting blood to the skin for heat loss
protection against infection by foreign microbes and toxins by conducting cells of the body defences to the
site of infection.
C. Physical Characteristics of Blood
Blood has the following major characteristics:
more viscous than water
temperature of 38 degrees Celsius
pH that ranges between 7.35 and 7.45
constitutes 8% of total body weight
volume of 5 to 6 liters in males and 4 to 5 liters in females
D. Components of Blood Blood consists of:
i. blood plasma or plasma, contains 90%water, sodium and chloride ions, proteins, sugars, lipids, oxygen,
vitamins and hormones and waste products of cell metabolismurea, ammonia, carbon dioxide.
Clotting factors in blood are activated by certain messenger molecules.
Serum is the clear fluid that forms when blood is coagulated , thus serum is plasma from which the clotting
factors have been removed.
ii. formed elements or blood cells, including the following:
a. erythrocytes (red blood cells)
b. leukocytes or leucocytes (white blood cells):
- granular leukocytes (granulocytes): neutrophils, eosinophils, basophils
- agranular leukocytes (agranulocytes): lymphocytes (T cells, B cells), monocytes
E. Erythrocytes (Red Blood Cells)
1. Greater than 99% of the formed elements in blood are erythrocytes (red blood cells or RBCs).
2. Each is a flexible, biconcave disc that lacks a nucleus and other organelles.
3. The cytosol contains numerous dissolved hemoglobin molecules (oxygen carrying protein).
4. Each hemoglobin molecule consists of four chains of amino acids bonded to 4 iron atoms (binding site
5. Hemoglobin can bind reversibly to oxygen (gives red color to blood); this permits erythrocytes to
transport oxygen from the lungs to other tissues of the body.
6. Hemoglobin can also bind reversibly to carbon dioxide (waste molecule); this permits erythrocytes to
transport carbon dioxide from the tissues to the lungs to be expelled.
7. Erythrocytes live approximately 120 days due to absence of organelles; the latter results in an inability to
replace plasma membrane components that are damaged as RBCs squeeze through narrow capillaries.
8. A healthy male has about 5.4 million erythrocytes per cubic millimeter of blood; a healthy female has
about 4.8 million erythrocytes per cubic millimeter.
9. RBC’s are produced in the red bone marrow
F. Leukocytes (White Blood Cells)