The role of the spleen in the lymphatic system is to provide a site for lymphocyte proliferation and immune surveillance.

Figure 21.1Using Figure 21.1, match the following:Constant region.

The adaptive (specific) defense system ________.

Harmful or disease-causing microorganisms from which nonspecific defenses protect the body are called ________.

The atrioventricular valve on the left side of the heart is often called the

Chemotaxis is best described as ________.

Each cardiac muscle cell is bound to its neighboring cells at sites called ________.

Antigen-presenting cells behave as ________.

The average heart beats approximately 75 times each minute at rest.

Blood is returned to the right side of the heart from the lungs.