Biology of Disease

()*

X]VeiZg&(/

DISORDERS OF THE

BLOOD

13.1 Introduction

Blood is a protein-rich fluid called plasma in which erythrocytes and
leukocytes, sometimes called red and white blood cells respectively, and
platelets are suspended (Figure 13.1). The cells constitute about 40–45% of
the volume of the blood. The blood is pumped around the body by the heart
through the arteries that supply the capillaries and is returned to the heart
in the veins (Chapter 14). The main functions of the blood are to distribute
oxygen, nutrients and hormones and other signaling molecules between
tissues and to remove carbon dioxide and other waste products. Plasma
contains the proteins of the clotting system and of the immune systems
(Chapters 4and 5 ).

Plasma is blood from which the cells have been removed. It contains a range
of plasma proteins in addition to the clotting and immune system proteins
mentioned above, nutrients, such as glucose, waste materials, for example
urea, and a range of electrolytes in solution. If it is allowed to clot, the clear

OBJECTIVES

After studying this chapter you should be able to:

N list the components of the blood;

N describe the structures of blood cells and platelets;

N explain how hemoglobin functions;

N explain how blood clotting occurs;

N give examples of some types of anemias;

N describe the consequences of the genetic defects in sickle cell anemia and

the thalassemias;

N explain the diagnoses and treatments of some types of anemias;

N describe some clinical disorders associated with clotting factors.