Respiratory System Overview

The respiratory system is a complex network of organs and structures that enable breathing and gas exchange. It includes the nose, nasal cavity, mouth, throat, trachea, bronchi, bronchioles, and alveoli within the lungs.

Definition: The respiratory system is responsible for transporting air into the lungs, facilitating the diffusion of oxygen into the blood, and removing carbon dioxide and other gases from the blood.

Key components of the respiratory system include:

1. Nose, nasal cavity, and mouth: These structures warm, filter, and moisten incoming air.
2. Throat (pharynx/larynx): Air passes through these structures on its way to the lungs.
3. Trachea (windpipe): The main airway leading to the lungs.
4. Bronchi and bronchioles: Smaller airways that branch out within the lungs.
5. Alveoli: Tiny air sacs where gas exchange occurs.

Highlight: The trachea, bronchi, and bronchioles are lined with mucous membrane and cilia, which help to trap and remove particles from the air.

Short-term Effects of Exercise on the Respiratory System

During exercise, the respiratory system undergoes several immediate changes:

1. Changes in oxygen and carbon dioxide concentrations trigger increased nervous impulses.
2. Intercostal muscles and diaphragm work harder to expand the thoracic cavity and draw in more air.

Long-term Effects of Training on the Respiratory System

Regular exercise leads to several adaptations in the respiratory system:

1. Increased strength of respiratory muscles (intercostal muscles and diaphragm).
2. Increased vital capacity, allowing for greater air intake.
3. Increased number and diameter of capillaries surrounding the alveoli, improving gas exchange efficiency.

Vocabulary: Vital capacity is the maximum amount of air a person can exhale after taking the deepest breath possible. For men, it's typically 4-5 litres, and for women, 3-4 litres.

Mechanics of Breathing

Inspiration (Breathing In)

During rest:

1. Diaphragm moves down.
2. External intercostal muscles contract.
3. Ribs move out and up.
4. Chest cavity volume increases, lowering air pressure and drawing air into the alveoli.

Example: This process is similar to pulling the handle of a bicycle pump, which creates a low-pressure area that draws air in.

Expiration (Breathing Out)

During rest:

1. External intercostal muscles relax.
2. Diaphragm moves up.
3. Ribs move down and in.
4. Chest cavity volume decreases, pushing carbon dioxide out of the lungs.

Highlight: Expiration is typically a passive process during rest but becomes active during exercise.

Gas Exchange and Diffusion

Gas exchange occurs in the alveoli through diffusion:

Definition: Diffusion is the natural movement of molecules from an area of high concentration to an area of low concentration.

1. Oxygen diffuses from the alveoli into the bloodstream.
2. Carbon dioxide diffuses from the blood into the alveoli to be exhaled.

Vocabulary: Minute ventilation is the amount of air breathed in one minute, measured in litres. It increases during exercise as both breathing rate and depth increase.