Respiratory System: Pharynx to Alveoli

Pharynx

The pharynx, commonly known as the throat, is a crucial part of the respiratory system.
The order of the sections within the pharynx, from superior to inferior, is:
- Naso
- Oral
- Laryngeal

The larynx is the voice box, located in the area with the Adam's apple.
The Adam's apple consists of thyroid cartilage, which protects the voice box.
Vocal cords are located within the larynx, and they vibrate as air passes over them, producing sound.
Air moving up and down through the vocal cords causes the cords to vibrate, thus making sound as they open and close.

The trachea is inferior to the voice box.
The trachea has C-shaped cartilage rings that protect the anterior portion.
Two reasons these cartilages are C-shaped:
- To allow some flexibility in the trachea
- To allow the esophagus to expand and contract because it runs along the posterior side of the trachea
Cervix means neck.

The epiglottis closes to cover the opening to the trachea (glottis) when swallowing, preventing food from entering the airway.
The opening between the vocal cords through which air passes is the glottis.
The epiglottis is located above the glottis.
During speech, air escapes through the vocal cords.

When someone is intubated, a tube is inserted through the mouth, past the vocal cords, and into the trachea.
This can cause the vocal cords to get damaged and develop scar tissue because the tube is where the vocal cords are.

The right lung has three lobes: superior, middle, and inferior.
The left lung has two lobes: superior and inferior.
The left lung has fewer lobes than the right lung to accommodate the heart.
The apex of the heart leans towards the left in the mediastinum, taking up the space where the middle lobe of the left lung would be.
The hilum is where the bronchi enter the lung.
Nurses use the lobes as landmarks for auscultating lung sounds with a stethoscope to determine where there may be issues.
Due to the angle of the bronchi, it is more likely for inhaled items to go down the right side. The right bronchus is straighter, while the left has an angle.

The diaphragm is a muscle that sits at the base of the lungs.
When you inhale, the diaphragm contracts and moves down and back, allowing the lungs to expand.
When you exhale, the diaphragm relaxes and returns to its normal position.

At the end of the bronchioles are the alveoli, which are small, grape-like sacs.
The alveoli expand and contract as the lungs expand and contract.
Gas exchange occurs in the alveoli. Oxygen enters the blood, and carbon dioxide exits the blood to be exhaled.
Alveoli are surrounded by capillaries.

Inhalation is active; the diaphragm contracts and moves down and back to allow the chest to expand.
Exhalation is passive; the diaphragm relaxes, and the chest contracts.
One respiration is one inhalation and one exhalation.
Inhalation is also known as inspiration. Exhalation is also known as expiration.

Inhalation is active, requiring force and energy to expand the lungs.
Exhalation is passive, not requiring force because of external pressure.
Compliance refers to how easily the lungs expand and contract. Good compliance means that the lungs expand and contract easily.
Autonomic, smooth muscle controls main breathing and respiratory rate.
There is skeletal muscle that you can control to change your breathing rate, mainly ribs and intercostal muscles.
As the lungs expand, the pressure on the outside gets greater than the pressure inside, and when you let go, the pressure on the outside forces the air out; this is a negative pressure situation.
Yu Gi Oh cards example: a child threatening to hold their breath until they get what they want will pass out and then automatically start breathing again.