Question

How do bronchioles affect airflow to alveoli?

Answer 1

Bronchioles are air passages inside the lungs that branch off like tree limbs from the bronchi- the two main air passages into which air flows from the trachea after being inhaled through the nose or mouth.
The bronchioles deliver air to tiny sacs called alveoli where oxygen and carbon dioxide are exchanged.

Complete answer:
The bronchioles are the part of the lower respiratory system. They become smaller and smaller, traversing the interior of each lung before ending at clusters of alveoli when they branch off from the bronchi. Bronchioles are the air passages inside the lungs that branch off like tree limbs from bronchi. The bronchioles deliver air to alveoli (tiny sacs) that exchange oxygen and carbon dioxide.

There are three types of bronchioles on the basis of size:
1.Lobular Bronchioles; larger passage that first enters the lobes of lungs.
2.Respiratory Bronchioles; two or more branches from each terminal bronchiole that, in turn, lead to 2 to 10 alveolar ducts.
3.Terminal Bronchioles; 50 to 80 smaller passages in lungs.

The bronchioles deliver air to a diffuse network of around 300 million alveoli in lungs. When air is inhaled oxygenated air is pulled into bronchioles and the carbon dioxide collected by the alveoli is expelled from the lungs when air is exhaled. The bronchioles are not inert. The smooth muscles that surround the airways will automatically close and open to control the flow of air in and out of the lungs. These smooth muscles regulate how much air comes into the lungs. The sympathetic nervous system stimulates cardiac muscles to increase the heart rate this causes the dilation of bronchioles of lungs by relaxing smooth muscles.

Note: Bronchioles rely on the bundles of protein fibers called elastin to hold their shape by anchoring themselves into lung tissue. The lining of bronchioles is called lamina propria is thin. It is surrounded by a layer of smooth muscles that contracts when the flow of blood is decreased and dilates when flow of blood is increased.