Lung Anatomy

Basic Anatomy

The right lung has 3 lobes (superior/inferior/middle).

The left lung has 2 lobes (superior/inferior). The heart is on the left size which makes the left lung smaller.

We can also divide the lungs into the airways (where air is moving in and out) and the parenchyma (where oxygen is passed from the air to the blood and carbon dioxide is removed from the blood and exhaled).

The vast majority of lung issues in children occur in the airways.

Airways

When inhaling, air enters the mouth/nose and passes into the throat (medically called the pharynx) where then it passes through the vocal cords and into the windpipe (medically called the trachea).

In the midchest, the trachea splits into the right mainstem bronchi and left mainstem bronchi. These divisions continue with an average adult human having 23 "generations" of airways. While the trachea and bronchi are larger, the bronchioles (smallest airways) have an opening of less than 1mm which is about the thickness of a credit card.

Bronchioles in Asthma

The issue in asthma is that the smallest airways (bronchioles) become constricted limiting the flow of air in and out of the lungs due to:

1) swelling of the airway tissues

2) tightening of the muscles in airway

3) fluid/mucus present in the lumen

Our asthma medications work to counteract these three issues.

1) Steroids (either inhaled or taken by mouth) reduce airway tissue swelling

2) Albuterol/levalbuterol or salmeterol/formoterol/vilanterol work to relax the airway muscles

3) Tiotropium or ipratropium work both to relax the airway muscles and reduce fluid/mucus production

Bronchiolitis

Caused by various viruses (with RSV causing the most severe cases) and affecting children under 2 years of age, bronchiolitis causes similar effects on the bronchioles as asthma. Luckily, symptoms are temporary but, unfortunately, the treatments that we give for asthma are usually not effective.

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