Processes of inspiration and expiration.

Inspiration and expiration are the processes by which air is taken into and expelled from the lungs, allowing for the exchange of oxygen and carbon dioxide in the body.

Inspiration:

1. During inspiration, the diaphragm contracts and moves downward, while the intercostal muscles between the ribs contract and move outward. This increases the volume of the thoracic cavity, causing a decrease in pressure within the lungs.

2. As a result of the decreased pressure, air is drawn into the lungs through the airways, filling the alveoli with oxygen-rich air.

3. The oxygen in the air is then diffused into the bloodstream through the thin walls of the alveoli, where it is transported to the body's cells for energy production.

Expiration:

1. During expiration, the diaphragm and intercostal muscles relax, causing the thoracic cavity to decrease in volume. This increases the pressure within the lungs.

2. The increased pressure forces air out of the lungs through the airways, expelling carbon dioxide and other waste gases from the body.

3. The process of expiration is passive and does not require any muscular effort, as the relaxation of the diaphragm and intercostal muscles allows the lungs to recoil to their original size and shape.

Overall, the processes of inspiration and expiration work together to ensure that the body receives an adequate supply of oxygen and removes waste gases, maintaining the balance of gases in the bloodstream and supporting cellular function.

Inspiration (Inhalation)

1. Contraction of the diaphragm: The diaphragm, a thin muscle located beneath the lungs, contracts, flattening and descending.
2. Elevation of the rib cage: The intercostal muscles between the ribs contract, lifting the ribs and expanding the chest cavity.
3. Increase in lung volume: As the diaphragm and rib cage expand, the lungs inflate, increasing their volume.
4. Decrease in intrathoracic pressure: The expansion of the chest cavity creates a negative pressure within the pleural space (the space between the lungs and the chest wall).
5. Airflow into the lungs: The negative intrathoracic pressure draws air into the lungs through the nose and mouth.

Expiration (Exhalation)

1. Relaxation of the diaphragm: The diaphragm relaxes, returning to its domed shape.
2. Lowering of the rib cage: The intercostal muscles relax, allowing the ribs to descend.
3. Decrease in lung volume: As the diaphragm and rib cage descend, the lungs deflate, decreasing their volume.
4. Increase in intrathoracic pressure: The deflation of the lungs creates a positive pressure within the pleural space.
5. Airflow out of the lungs: The positive intrathoracic pressure pushes air out of the lungs through the nose and mouth.

Factors Affecting Breathing:

- Respiratory center in the brainstem: Controls the rhythm and depth of breathing.
- Chemical factors: Carbon dioxide and oxygen levels in the blood can stimulate or inhibit breathing.
- Hormones: Adrenaline can increase breathing rate.
- Emotions: Fear or anxiety can lead to hyperventilation (increased breathing rate).
- Lung capacity and elasticity: Healthy lungs allow for optimal breathing.
- Airway resistance: Narrowed airways can make breathing difficult.