Gas exchange takes place between the respiratory and the ________ systems.

• nervous

• muscular

• circulatory

Sacs where gas exchange occurs.

• pharynx

• larynx

• trachea

• alveoli

Leads into the lungs and is held open by C-shaped rings.

• pharynx

• larynx

• trachea

• alveoli

This organ fills with air and expands when we breathe in.

• pharynx

• diaphragm

• lung

Two tubes that branch off of the trachea.

• bronchi

• diaphragm

• lungs

The large muscle that we use to breathe.

• bronchi

• diaphragm

• lungs

Which activity is a function of the circulatory system?

• move materials through the body

• react to stimuli in the environment

• regulate heartbeat and blood pressure

These are the smallest blood vessels in the body.

• arteries

• capillaries

• veins

Blood vessels that take blood away from the heart are called _____.

• arteries

• capillaries

• veins

Which are blood vessels that move blood toward the heart?

• arteries

• capillaries

• veins