External intercostals

Definition

External intercostals are muscles located between the ribs that play a critical role in the mechanics of breathing, specifically during inhalation. They are responsible for elevating the ribs and expanding the thoracic cavity, which decreases pressure in the lungs and allows air to flow in. Their function is vital for effective ventilation and contributes significantly to respiratory mechanics.

5 Must Know Facts For Your Next Test

1. External intercostals account for about 25% of the work of breathing at rest, increasing during physical exertion.
2. These muscles are innervated by the intercostal nerves, which arise from the thoracic spinal cord.
3. During inhalation, external intercostals contract, leading to rib elevation and an increase in thoracic volume.
4. Their action works synergistically with the diaphragm to create a pressure gradient necessary for effective ventilation.
5. External intercostals are essential in maintaining normal respiratory function and can be affected by conditions such as spinal injuries or neuromuscular diseases.

Review Questions

• How do external intercostals contribute to inhalation and what happens during their contraction?
  • External intercostals play a key role in inhalation by contracting to elevate the ribs. This action increases the volume of the thoracic cavity, leading to a decrease in pressure within the lungs. As a result, air is drawn into the lungs due to this pressure difference. The coordinated movement of these muscles with the diaphragm enhances overall efficiency in breathing.
• Discuss the differences in function between external intercostals and internal intercostals during respiration.
  • While external intercostals are primarily involved in inhalation by elevating the ribs and expanding the thoracic cavity, internal intercostals mainly function during forced exhalation by depressing the ribs. This makes external intercostals crucial for drawing air into the lungs during restful breathing and physical activity, whereas internal intercostals are more active during strenuous exhalation or forced breathing situations. Together, they coordinate to regulate airflow effectively.
• Evaluate how dysfunction of external intercostals can affect overall respiratory mechanics and what implications this might have on health.
  • Dysfunction of external intercostals can severely impact respiratory mechanics by limiting airflow into the lungs. Conditions such as spinal cord injuries or neuromuscular disorders can lead to weakened or paralyzed external intercostal muscles, reducing lung capacity and efficiency in gas exchange. This impairment can result in respiratory distress and increased effort required for breathing, significantly affecting an individual's quality of life and necessitating medical intervention for adequate ventilation.

Related terms

internal intercostals: Muscles located beneath the external intercostals that primarily assist in forced exhalation by depressing the ribs.

diaphragm: A dome-shaped muscle that separates the thoracic cavity from the abdominal cavity and is the primary driver of breathing during quiet respiration.

thoracic cavity: The chamber of the body protected by the ribs, containing the lungs and heart, which plays a key role in respiratory function.