Question

bio - 202 topic 2: blood and lymphatic system physiology
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what is the immune system?
a network of blood vessels that transport oxygen throughout the body.
a complex network of cells, tissues, and organs that work together to protect the body from pathogens.
a collection of cells that produce and secrete hormones.
a group of organs responsible for breaking down food and absorbing nutrients.
a system of muscles that helps the body move.

Explanation:

The immune system is a complex network. It has cells (like white blood cells), tissues (such as lymphoid tissues), and organs (e.g., thymus, spleen). Its main function is to protect the body from pathogens (disease - causing agents like bacteria, viruses).

• The first option describes the circulatory system (blood vessels transporting oxygen).
• The third option describes the endocrine system (cells producing hormones).
• The fourth option describes the digestive system (organs for food breakdown and nutrient absorption).
• The fifth option describes the muscular system (muscles for body movement).

Answer:

A complex network of cells, tissues, and organs that work together to protect the body from pathogens.