Intercostal muscles

Definition

Intercostal muscles are a group of muscles located between the ribs that play a vital role in the process of breathing by aiding in the expansion and contraction of the thoracic cavity. These muscles are essential for gas exchange as they help control the volume of air inhaled and exhaled, facilitating the movement of air into and out of the lungs. The intercostal muscles work in tandem with the diaphragm to ensure effective respiration and maintain proper oxygen levels in the body.

5 Must Know Facts For Your Next Test

1. Intercostal muscles are divided into two main types: external intercostal muscles, which assist in inhalation, and internal intercostal muscles, which aid in forced exhalation.
2. During inhalation, external intercostal muscles contract, lifting the rib cage and increasing the volume of the thoracic cavity, allowing air to flow into the lungs.
3. Internal intercostal muscles contract during forceful exhalation, pulling the rib cage downward and inward, which decreases thoracic volume and helps expel air from the lungs.
4. These muscles are innervated by intercostal nerves that originate from the thoracic spinal cord, ensuring coordinated muscle contraction during breathing.
5. Proper function of intercostal muscles is crucial for activities such as exercise, singing, and any situation that requires increased respiratory effort.

Review Questions

• How do intercostal muscles contribute to the mechanics of breathing?
  • Intercostal muscles contribute to breathing mechanics by facilitating the expansion and contraction of the thoracic cavity. When external intercostal muscles contract during inhalation, they elevate the rib cage, increasing thoracic volume and allowing air to fill the lungs. Conversely, during forced exhalation, internal intercostal muscles contract to pull down the rib cage, decreasing thoracic volume and helping to expel air from the lungs.
• What roles do external and internal intercostal muscles play during different phases of respiration?
  • External intercostal muscles are primarily active during inhalation; they contract to lift the rib cage and expand the thoracic cavity for air intake. Internal intercostal muscles are engaged during forced exhalation; their contraction pulls the rib cage downward and inward, reducing thoracic volume to push air out. This coordinated action between both muscle groups is essential for efficient ventilation.
• Evaluate how impaired function of intercostal muscles might affect gas exchange in individuals with respiratory conditions.
  • Impaired function of intercostal muscles can significantly hinder gas exchange in individuals with respiratory conditions. For instance, conditions like muscular dystrophy or spinal cord injuries can weaken these muscles, leading to inadequate expansion of the thoracic cavity. This results in reduced lung volume and insufficient airflow, causing hypoxemia (low blood oxygen) and hypercapnia (high carbon dioxide levels), ultimately compromising overall respiratory function and oxygen delivery to tissues.

Related terms

Diaphragm: A dome-shaped muscle located at the base of the thoracic cavity that plays a primary role in breathing by contracting and relaxing to change lung volume.

Thoracic cavity: The chamber within the body that houses the lungs and heart, enclosed by the ribs and diaphragm, which plays a key role in respiration.

Ventilation: The process of moving air in and out of the lungs, which is crucial for maintaining gas exchange and oxygen supply in the body.