How the Respiratory System Works

• The primary function of the respiratory system is to supply the blood with oxygen and remove carbon dioxide.

How the Respiratory System Works

• Air enters through the mouth or nasal cavity, travels through the pharynx and larynx, and moves down the trachea.
• The air then moves to the bronchi tubes, which enter the lungs.
• Once in the lungs, air enters separate branches called the bronchioles.
• Oxygen travels from the lungs through the bloodstream to the cells.
• Cells use oxygen and fuel, giving off carbon dioxide.
• Carbon dioxide passes from the blood into the alveoli and is exhaled.

Parts of the Respiratory System

Nasal Cavity

• Warms incoming air to close to body temperature via an extensive capillary network.
• Filters incoming air via thousands of hairs lining the cavity.

Pharynx

• The throat carries air, food, and fluid down from the nose and mouth.

Larynx

• Generates sound, pitch, and volume.
• Also known as the voice box
• Houses the vocal folds, or chords

Trachea

• The windpipe directs air further down towards the lungs.
• Has a mucous lining that helps trap any foreign material.
• Cilia, or microscopic hairs, line the walls and act as a filter.
• Supported by cartilage rings.

Bronchi

• Two tubes (left and right bronchus) that branch out towards the lung tissue.
• Similar in structure and function to the trachea.

Bronchioles

• Further branches of the bronchi.
• Divide like branches on a tree, leading to alveoli.

Alveoli

• Air sacs that look like millions of closely joined bubbles.
• Increase surface area for air to expose itself to capillaries.
• Gas transfer (oxygen and carbon dioxide) occurs here.

Process of Respiration

• Inhale: Air enters the nasal cavity.
• Passes through the pharynx, then the larynx into the trachea.
• Further filtered by cilia.
• Arrives and enters the left or right bronchus into the bronchioles.
• Then into alveoli, where gas transfer occurs.
• Exhale.

Diaphragm

• A flat, dome-shaped muscle at the bottom of the chest cavity.
• Functions in breathing.

Inspiration

• Draws air into lungs.
• The diaphragm pulls down, increasing space in the chest cavity.
• Intercostals pull together and draw the rib cage up and outwards.

Expiration

• At rest, muscles relax, and gravity and pressure force air out of the lungs.
• During heavy exercise, air is propelled out via muscular force.
• Abdominals pull the rib cage down towards the pelvis, decreasing the size of the chest cavity and forcibly expelling air.

Respiratory Measurements

• Total Lung Capacity (TLC): Volume of air in the lungs at maximal inflation.
• Average TLC: Men: 6.0L, Women: 4.2L.
• Ventilation (V): Amount of air breathed per minute (litres).
• Tidal Volume (TV): Amount of air inspired or expired per breath (normally around 500ml).
• Respiration Rate (RR): Breaths in or out per minute (12 on average).
• V = TV x RR
• Residual Volume (RV): Amount of air left in the lungs after maximal exhalation.

Interesting Facts

• About half a litre of water per day is lost through breathing.
• Yawning brings more oxygen to the lungs.
• The right lung is larger than the left.
• We breathe 7.3 Litres of air every minute.
• People under 30 take in double the amount of oxygen compared to someone who's 80 years old.