Human Biology Ch.3.2

The integumentary, respiratory, and digestive systems are the first line of defense against pathogens. (disease causing agents which can enter through skin, air, food, and liquids you drink.)

Integumentary system-forms physical barrier to pathogens. (ex. Skin, substances contained in tears…etc)

- A common way pathogens can enter the body is through a cut. The circulatory system is then able to help defend the body with blood cell which respond to foreign materials.

Respiratory system
-Cilia and mucus traps and expels the particles in the air.

-Sneezing and coughing are two ways to defend the body.

Digestive system-destroys pathogens that enters through food and drink with saliva, mucus, enzymes, and stomach acids.

The body relies on the immune system to respond when foreign materials manage to get past the first line of defense.

Tissues in the bone marrow, the thymus gland, the spleen, and the lymph nodes produce white blood cells
to destroy pathogens.


Some white blood cells produce a nonspecific response to injury or infection.

Some white blood cells produce proteins called antibodies, which are part of a specific immune response to foreign materials.


Symptoms of illnesses are result of the immune system’s response to foreign materials in the body.

Nonspecific response occurs first as histamine is released from irritated or damages tissues, increases blood flow and causes inflammation.

When a foreign material affects more than one area of your body, many tissues produce histamine and results your whole body temperature to rise.


Specific responses are triggered by antigens and provides protection from future exposure to the same material.

Antigen: a chemical marker on a cell’s surface that indicates whether the cell is from your body or is a foreign material.

Three major types of white blood cells that functions together in a specific response: phagocytes, T cells, and B cells
Phagocytes ingest and break down foreign materials -> Small pieces of the foreign materials (antigen)are incorporated into the surface of the phagocyte’s cell membrane -> they are detected as foreign by T cells-> T cells divide rapidly and some T cells attack the foreign antigens-> B cells recognize the same foreign antigen, divide rapidly and begin to produce antibodies that help destroy pathogens->Antibodies attach to the foreign antigens, marking the pathogens for killer T cells.