Respiratory Cycle

This lesson will cover the respiratory cycle by looking at:

1. Exhalation
2. Inhalation

1.Exhalation

The respiratory cycle is the process of breathing in and out. When you breathe in, it is called inhalation, and your lungs are expanding. Exhalation, or breathing out, is the part of the cycle when your lungs deflate.

• Respiratory Cycle
• The events that occur during one breath; inhalation + exhalation = 1 respiratory cycle.
• Inhalation
• The events that occur to drive air flow into the lungs; when the diaphragm contracts to expand the thoracic cage and decrease the pressure inside of the chest.
• Exhalation
• The events that occur to drive air flow out of the lungs; when the diaphragm relaxes and the thoracic cage collapses putting a positive pressure on the lungs driving air out.

In the process of exhalation, there are several events going on that aid in exhalation:

• The diaphragm, which is a muscle that separates your chest cavity from your abdominal cavity, is going to relax. When that happens, it moves upwards slightly.
• The intercostal rib muscles, are going to be in a resting position.

These two events cause pressure in your chest cavity to increase relative to pressure in the atmosphere. This pressure gradient is going to cause air to be pushed out of the lungs as you exhale, causing your lungs will deflate.

2. Inhalation

During inhalation the opposite thing is happening:

• The diaphragm is going to contract, moving downward slightly.
• The intercostal rib muscles are going to lift your ribcage up and out.

The pressure in the chest cavity is decreased, and it will be less than the atmospheric pressure around you, causing the lungs to inflate.

Tidal volume is the amount of air that enters your lungs in a normal breath. That's an average of about two cups per person, or about 500 milliliters. Vital capacity is the maximum amount of air you exhale after the deepest breath possible. Tidal volume and vital capacity are going to vary a little bit from person to person, depending on the person's size and dhow in shape they are. People who are more athletic can hold more air in their lungs, on average.

• Tidal Volume
• The volume of air we breathe in per breath; the average tidal volume is 500 mL/breath.

• Vital Capacity
• The maximum amount of air you move during one breathing cycle.

The respiratory cycle includes inhalation and exhalation. Exhalation is when the diaphragm and the intercostal rib muscles relax. This is increases the pressure in the chest cavity compared to atmospheric pressure, and causes air to move out from the lungs. The lungs deflate. Inhalation is when these muscles contract and cause the pressure in the chest cavity to decrease. Air moves into the lungs, and the inflate. Tidal volume is the volume of air we breath in, and vital capacity is the maximum amount of air you move in one breathing cycle.

Keep up the learning and have a great day!