Oxygen as you likely know, is vital for life. That’s why the process of respiration happens in our bodies day in day out. Did you know that the average adult uses 250ml of oxygen every minute while resting?
Air enters nasal cavities/mouth where the air is warmed, moistened and cleaned. Tiny hairs and mucous line our nasal cavities and they function to prevent the entrance of foreign particles.
Next we come to the Pharynx (throat). This is an air filled channel in your mouth. Two openings branch from the Pharynx: the esophagus -which leads to the stomach, and the trachea or windpipe. Cilia also line the trachea and sweep debris away.
Then comes the Epiglottis. The Epiglottis is a flap of cartilage that covers the glottis (opening to the trachea). The Epiglottis blocks the trachea and does not allow food to enter the windpipe. If food enters the trachea it is swept away by cilia.
The air then moves down the trachea to the larynx (voice box). The larynx is protected by a thick band of cartilage- 'Adam's apple.
Did you know? Following puberty the cartilage and larynx increase in size and thickness, hence the voice deepens. This rapid change can be difficult on young men because of voice cracks. When you have a cold, there is an inflammation of your vocals cords, and this lowers your voice.So the organs we have looked at: the nasal cavities, mouth, pharynx, epiglottis, glottis, trachea and larynx are all organs of the upper respiratory tract.
Next the air moves into the lower respiratory tract, from the trachea to two bronchi. The bronchi contain large cartilage rings, and each bronchi branches into smaller bronchioles. Bronchioles however, have no cartilage. The smooth muscles of the bronchioles allow the diameter of the bronchioles to be adjusted. The closing of the bronchioles leads to wheezing. Asthma attacks happen due to the narrowing of the bronchioles.
So now the air moves from the bronchioles to alveoli (tiny blind-ended sacs). The alveoli are about 0.1-0.2mm in diameter. Each alveolus is surrounded by capillaries. The cells of the alveoli allow for rapid gas exchange. The lung has 15 million alveoli, enough surface area to cover 1/2 a tennis court.
Lipoprotein is a chemical that lines the alveoli and prevents them front sticking together in exhalation. Some babies do not produce enough Lipoprotein and so this makes breathing difficult. (Respiratory Distress Syndrome- can result in death).
The Pleural membrane surrounds the lungs, reducing friction between lungs and chest cavities
The Mechanic of Breathing
Breathing is controlled by the diaphragm.
When muscle contracts, diaphragm flattens and pulls downwards. Chest volume increases while the pressure in the chest decreases. Air moves into the lungs!
When muscle relaxes, diaphragm relaxes and pushes upwards. The chest volume decreases and chest pressure increases. Air moves out of the lungs.
The movement of the ribs will also assist in the inhalation/exhalation process. The diaphragm is assisted by the movement on ribs.
What happens with a collapsed lung? (pneumothorax) A wound in the lung makes it impossible to establish pressure differences. So the air flows through the wound and the lung remains collapsed. The chest cavity must be sealed and excess fluid must be removed before lungs can function properly.
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