Human Respiratory System

Figure 10.1

Components of the Upper Respiratory Tract

Figure 10.2

Passageway for respiration Receptors for smell Filters incoming air to filter larger foreign

material Moistens and warms incoming air Resonating chambers for voice

Upper Respiratory Tract Functions

The nasal passages and lungsAir is drawn into the body via the nose or mouth. There are advantages to breathing through your nose:

the air is warmed so that it is closer to body temperature

tiny hairs and mucus in the nose filter the air, preventing larger dust and pollen particles reaching the alveoli

mucus moistens the air, making it easier for the alveoli to absorb.

Components of the Lower Respiratory Tract

Figure 10.3

Functions: Larynx: maintains an open airway, routes food and air

appropriately, assists in sound production Trachea: transports air to and from lungs Bronchi: branch into lungs Lungs: transport air to alveoli for gas exchange

Lower Respiratory Tract

When you breathe in:

intercostal muscles between the ribs contract, pulling the chest walls up and out

the diaphragm muscle below the lungs contracts and flattens, increasing the size of the chest

the lungs increase in size, so the pressure inside them falls. This causes air to rush in through the nose or mouth.

Mechanisms of breathing – inspiration

Diaphragm contracts and moves down

Intercostal muscles pull ribs up and out

Mechanisms of breathing – inspiration

Mechanisms of breathing – expirationWhen you breathe out:

Intercostal muscles between the ribs relax so that the chest walls move in and down.

The diaphragm muscle below the lungs relaxes and bulges up, reducing the size of the chest.

The lungs decrease in size, so the pressure inside increases and air is pushed up the trachea and out through the nose or mouth.Diaphragm

relaxes and bulges up

Ribs move in and down

Mechanisms of breathing – expiration

Respiratory Cycle

Figure 10.9

Gas exchange at the alveoliThe alveoli are bunches of tiny air sacks inside the lungs.

Each individual sack is called an alveolus.

When you breathe in, they fill with air.

The alveoli are covered in tiny capillaries (blood vessels).

Gases can pass through the thin walls of each alveolus and capillary, and into the blood stream.

Gases can also pass from the blood stream, into the alveolus.

Gas exchange at the alveoli