The changes that occur as the bronchial tree gets smaller are what?

The changes that occur as the bronchial tree gets smaller are as follows:

1. Diameter: As the bronchi branch and get smaller, their diameter decreases. This reduction in diameter is necessary to ensure efficient distribution of air to the smaller, more distal parts of the lungs.

2. Wall Structure: The walls of the bronchi undergo changes as they become smaller. The larger bronchi, known as primary, secondary, and tertiary bronchi, have cartilage rings in their walls. These cartilage rings provide structural support and help maintain the patency of the airways. However, as the bronchi get smaller and become known as bronchioles, the cartilage rings become less prominent and eventually disappear.

3. Muscles: The larger bronchi have smooth muscle cells in their walls, which allow for changes in airway caliber. These muscles can contract or relax to regulate the airflow resistance and modify the diameter of the airways. As the bronchi become smaller, the smooth muscle cells become less prominent, and their influence on airway diameter diminishes.

4. Epithelium: The epithelium lining the bronchial tree also changes. In the larger bronchi, the epithelium is pseudostratified ciliated columnar epithelium with goblet cells. This type of epithelium is well-suited for mucus production and removal of foreign particles through the coordinated beating of cilia. As the airways get smaller, the pseudostratified epithelium transitions into cuboidal or simple columnar epithelium, and the number of goblet cells decreases.

5. Mucous Glands: The larger bronchi contain mucous glands in their walls, which secrete mucus. Mucus helps trap dust, debris, and pathogens, preventing them from reaching the smaller, more sensitive airways. As the airways get smaller, the number of mucous glands and the amount of mucus production decrease.

6. Vasculature: The blood vessels supplying the bronchial tree undergo changes. In the larger bronchi, the blood supply is more substantial, and the vessels are thicker. However, as the airways get smaller, the blood supply becomes less abundant, and the vessels become thinner.

These changes in the bronchial tree as it becomes smaller are crucial for the efficient delivery of air to the alveoli, where gas exchange occurs. The modifications ensure proper airflow distribution, mucus production, and airway support.