How does lung volume change? | Respiratory system physiology | NCLEX-RN | Khan Academy

Summary

This video explains the mechanics of breathing, focusing on the role of muscles and alveoli. It details how inhalation occurs through muscle contractions, such as the diaphragm and intercostal muscles, which expand the chest cavity and stretch the alveoli. This process requires energy, specifically ATP. During exhalation, the muscles relax, and the alveoli recoil due to the elastin proteins, pushing air out of the lungs. The video also highlights the energy difference between inhaling (which uses ATP) and exhaling (which relies on elastic potential energy).

Takeaways

• 😀 The sternum is the large bone in the center of the chest where the ribs attach, and it plays a key role in the structure of the respiratory system.
• 😀 There are 12 pairs of ribs, and 7 pairs attach directly to the sternum, helping form the chest cavity that expands and contracts during breathing.
• 😀 Intercostal muscles, located between the ribs, contract and expand during breathing, controlled by the brain, allowing the ribs to move outward.
• 😀 The diaphragm, a dome-shaped muscle beneath the lungs, contracts and flattens during inhalation, increasing the volume of the chest cavity.
• 😀 During inhalation, the expansion of the chest and diaphragm causes the alveoli (tiny air sacs in the lungs) to stretch and increase in size, facilitating air intake.
• 😀 Alveoli are surrounded by elastin, a protein that acts like a rubber band. When stretched, elastin helps the alveoli expand during inhalation.
• 😀 The process of inhaling requires chemical energy (ATP), which fuels the contraction of muscles like the diaphragm and intercostal muscles.
• 😀 Exhalation is driven by elastic recoil, not energy expenditure. The elastin in the alveoli 'snaps back' to its original state, reducing lung volume.
• 😀 The volume of air in the lungs decreases during exhalation due to the recoil of elastin, causing the alveoli to shrink back to their smaller size.
• 😀 Inhalation and exhalation are different in terms of energy usage: inhalation uses ATP for muscle contraction, while exhalation uses the stored elastic potential energy of the alveoli.
• 😀 The movement of the diaphragm and intercostal muscles during inhalation and exhalation enables the lungs to expand and contract, facilitating the flow of air in and out of the body.

Q & A

What is the sternum, and where is it located?

The sternum, also known as the breastbone, is a large bone located in the middle of your chest. It connects to the ribs and serves as the central point where the ribs attach, forming part of the ribcage.

How many ribs do humans have, and how are they connected to the sternum?

Humans have 12 pairs of ribs, making a total of 24 ribs. Seven pairs of these ribs are directly attached to the sternum, while the remaining ribs either connect to the sternum indirectly or not at all.

What are intercostal muscles, and what role do they play in breathing?

Intercostal muscles are muscles located between the ribs. Their primary function during breathing is to contract and expand the chest cavity. This action helps to increase the volume of the lungs during inhalation and supports the recoil during exhalation.

What is the diaphragm, and how does it contribute to inhalation?

The diaphragm is a dome-shaped muscle located beneath the lungs. During inhalation, it contracts and flattens, increasing the space in the thoracic cavity. This action helps the lungs expand and allows air to flow in.

What happens to the alveoli during inhalation?

During inhalation, the alveoli, which are small air sacs in the lungs, expand as the chest cavity enlarges. The expansion of the alveoli increases lung volume and allows more air to enter the lungs.

What is elastin, and what role does it play in the process of exhalation?

Elastin is a protein found around the alveoli that behaves like a rubber band. During inhalation, the alveoli are stretched open, and when exhalation occurs, the elastin helps the alveoli recoil back to their original size, expelling air from the lungs.

How does the process of exhalation differ from inhalation?

Inhalation requires energy in the form of ATP to contract the intercostal muscles and diaphragm, which expands the lungs. Exhalation, on the other hand, is a passive process driven by the elastic recoil of the alveoli, which does not require additional energy input.

What is the significance of ATP in the process of breathing?

ATP (adenosine triphosphate) is the chemical energy used by the body during inhalation to contract muscles like the intercostals and diaphragm. These muscle contractions are what enable the lungs to expand and take in air.

Why is the recoil of the alveoli important for exhalation?

The recoil of the alveoli, driven by the elastin proteins, is important because it helps to reduce lung volume, forcing air out during exhalation. This elastic recoil provides the driving force for the exhalation process without requiring additional energy expenditure.

How many alveoli are present in the human lungs, and what happens to them during inhalation?

There are approximately 500 million alveoli in the human lungs. During inhalation, these alveoli expand as the chest cavity increases in size, allowing more space for oxygen to enter and be exchanged with carbon dioxide.