Immune System

functions of the immune system

• Protects against infectious organisms: Bacteria, Viruses, Fungi, Parasites

• Identifies and destroys abnormal cells

• Supports tissue healing and recovery

• Maintains physiological homeostasis

host

A person (or animal) that harbors an infectious organism

vector

an insect or organism that transmits the disease-causing

organism between two individual hosts

Communicable diseases

can be passed from any animal to any other

contagious diseases

Infectious diseases that can pass from person to person

bone marrow

• Produces all blood cells from hematopoietic stem cells

• Site of B-lymphocyte maturation

• Source of leukocytes involved in immune defense

thymus

• Most active during infancy through adolescence

• Site of T-lymphocyte maturation

• Develops immunocompetent T cells capable of recognizing antigens

spleen

• Filters blood and removes aged or abnormal blood cells

• Contains macrophages that remove pathogens and cellular debris

• Serves as an important site for immune surveillance

lymphatic

• Lymphatic vessels transport lymph fluid and immune cells

• Lymph nodes filter pathogens and foreign substances

• Sites where immune responses are initiated

Leukocytes (White Blood Cells)

Produced in the bone marrow and specialized for immune defense

Granulocytes