Question

During inhalation, the ____________. a. thoracic cavity expands b. glottis closes c. diaphragm relaxes d. alveoli deflate

Short answer

During inhalation, the thoracic cavity expands.

Step-by-step solution

Understand Inhalation

Inhalation is the process of taking air into the lungs. During this phase, the body must create more space in the thoracic cavity to allow the lungs to expand and fill with air.

Analyze Each Option

- Option a: **Thoracic cavity expands** - This option aligns well with the inhalation process since the expanding thoracic cavity creates space for the lungs to inflate. - Option b: **Glottis closes** - Closing the glottis would prevent air from entering the trachea and lungs, which is contrary to inhalation. - Option c: **Diaphragm relaxes** - During inhalation, the diaphragm contracts (not relaxes) to push downward, decreasing pressure in the thoracic cavity. - Option d: **Alveoli deflate** - During inhalation, alveoli expand as they fill with air; they deflate during exhalation.

Determine the Correct Answer

Considering how each option relates to the process of inhalation, the correct answer is "thoracic cavity expands" because it correctly describes what happens during the inhalation phase, allowing the lungs to inflate. The other options (b, c, and d) contradict the process of inhalation.

Key concepts

Thoracic Cavity

The thoracic cavity is a crucial component in the process of inhalation. It is the part of your body that houses the lungs and heart, protected by the rib cage. When you breathe in, the thoracic cavity needs to expand. This expansion is essential because it creates more space for the lungs to expand and fill with air.
During inhalation, several actions take place to ensure this expansion:

• The diaphragm contracts and moves downward.
• The rib cage lifts upward and outward by the action of intercostal muscles.

Together, these movements lead to a reduction in air pressure inside the thoracic cavity compared to the outside environment, enabling air to rush into the lungs. Understanding how the thoracic cavity expands is key to understanding the physical changes that allow us to breathe effectively.
Breathing might seem simple, but it's a precisely coordinated movement involving different parts of your body.

Diaphragm Contraction

The diaphragm is a large, dome-shaped muscle located at the base of the lungs. During inhalation, this muscle plays a vital role by contracting and moving downward. This contraction of the diaphragm creates a vacuum effect in the chest, similar to how a syringe draws liquid when the plunger is pulled back.
With the diaphragm contracting:

• The space in the thoracic cavity increases.
• The pressure inside decreases, pulling air into the lungs.
  

It's fascinating how this simple movement can have such a profound impact on our ability to breathe. The diaphragm is often considered the main muscle of respiration, highlighting its importance in the breathing process.
Anyone can appreciate the fact that something as complex as breathing relies heavily on the action of this one muscle. Each contraction is an integral part of the chain reaction that enables us to inhale effectively.

Alveoli Function

Alveoli are tiny air sacs located at the end of the bronchial tubes in the lungs. They might be small, but they play a pivotal role in the respiratory system. During inhalation, here's what happens in the alveoli:

• They expand as air fills them.
• They facilitate the exchange of gases, allowing oxygen to enter the bloodstream and carbon dioxide to be expelled.
  

The process is quite efficient, thanks to the large number of alveoli and their surface area, which provides ample room for gas exchange. Each alveolus is surrounded by capillaries, which help in the transfer of oxygen and carbon dioxide.
This transfer means the oxygen can be delivered to cells all over the body, providing them with the energy they need to function.
The working of alveoli is a fine example of how intricate and well-designed the human body is, performing complex tasks so naturally and effortlessly.