Blood rich in _____________ flows to the body cells. Blood rich in __________ flows to the lungs.

__________________ is a mechanical process that involves inhaling air.

The lungs are made up of many tiny air spaces called__________

The respiratory system in humans and other mammals consists of breathing muscles, air passages and __________

During inhalation, air enters the nose and/or mouth, and moves into the _______________

The bronchi pair branch into smaller and smaller tubes called the ___________________

Breathing is ___________ and controlled by the brain.

________________diffuses across the walls of the alveolus.

Carbon dioxide diffuses from the __________ into the alveolus, and is exhaled out of the body.

The walls of the alveolus and capillaries are _______ cell thick, allowing for ease of diffusion of gases.

Globlet cells in the membrane of the respiratory tract produce ___________

The trachea is lined with microscopic, hair-like extensions called ____________

The thorax is a cage formed by your ribs and ____________.

When you inhale, the ___________ muscles between the ribs contract.

When you exhale, the diaphragm ____________

Which of these is NOT a suitable characteristic for a gaseous exchange surface.