Internal Vs External Intercostals: A Deep Dive Into Their Functions And Differences

Jedidiah Cremin 16 May 2025

When it comes to understanding the human respiratory system, the intercostal muscles play a crucial role in breathing mechanics. These muscles are often overlooked, but they are essential for expanding and contracting the ribcage during inhalation and exhalation. In this article, we'll break down the differences between internal and external intercostals, their functions, and why they matter in everyday life.

Imagine your ribcage as a box that needs to expand and contract to allow air in and out. The intercostal muscles act as the movers and shakers, ensuring that this process runs smoothly. But here's the twist—there are two main types of these muscles: the external intercostals and the internal intercostals. Each has its own job, and understanding their roles can give you a clearer picture of how your body works.

Whether you're a fitness enthusiast, a medical student, or simply curious about your anatomy, this article will provide you with the knowledge you need to appreciate the complexity of these muscles. So, let's dive in and uncover the secrets of internal vs external intercostals!

Structure of Intercostal Muscles
External Intercostal Muscles
Internal Intercostal Muscles
Function and Role
Key Differences
Exercises to Strengthen Intercostals
Common Injuries
Health Implications
Anatomy in Detail
Conclusion

Structure of Intercostal Muscles

The intercostal muscles are located between the ribs, forming a layered system that supports the ribcage. They are divided into three main groups: external intercostals, internal intercostals, and innermost intercostals. For this article, we'll focus on the external and internal intercostals, as they are the primary players in respiratory mechanics.

These muscles are innervated by the intercostal nerves, which run parallel to the ribs, and they receive their blood supply from the intercostal arteries. The structure of these muscles is designed to provide both strength and flexibility, allowing the ribcage to expand and contract with ease.

External Intercostal Muscles

Let's talk about the external intercostals first. These muscles are the ones that help with inhalation. They run diagonally from the lower border of one rib to the upper border of the rib below it. When you take a deep breath, these muscles contract, lifting the ribs and expanding the thoracic cavity. This creates a negative pressure that draws air into the lungs.

Direction: They run from the back of the ribcage towards the front.
Function: Assist in inspiration by elevating the ribs.
Location: Situated superficially, closer to the skin.

Internal Intercostal Muscles

Now, let's flip the script and talk about the internal intercostals. These muscles are responsible for exhalation. They run in the opposite direction to the external intercostals, from the front of the ribcage towards the back. When you exhale, these muscles contract, pulling the ribs down and reducing the volume of the thoracic cavity. This forces air out of the lungs.

Direction: Opposite to the external intercostals, running from front to back.
Function: Assist in expiration by depressing the ribs.
Location: Situated deeper, closer to the internal organs.

Function and Role

The intercostal muscles play a vital role in both quiet and forced breathing. During normal, relaxed breathing, these muscles work in harmony to ensure a smooth exchange of air. However, during exercise or in situations where you need to take deeper breaths, these muscles kick into high gear.

For example, when you're running or lifting weights, your external intercostals work overtime to help you inhale more air. At the same time, your internal intercostals ensure that you can exhale efficiently, getting rid of carbon dioxide and maintaining a healthy balance of gases in your body.

Key Differences

While both the external and internal intercostals are essential for breathing, they have distinct differences in structure and function. Here's a quick rundown:

Direction: External intercostals run from back to front, while internal intercostals run from front to back.
Function: External intercostals assist with inhalation, whereas internal intercostals help with exhalation.
Location: External intercostals are more superficial, while internal intercostals are deeper.

Exercises to Strengthen Intercostals

Strengthening your intercostal muscles can improve your breathing efficiency and overall respiratory health. Here are a few exercises you can try:

Diaphragmatic Breathing: Lie down on your back and place one hand on your chest and the other on your abdomen. Breathe deeply through your nose, focusing on expanding your abdomen rather than your chest.
Costal Breathing: Sit comfortably and place your hands on your ribcage. Inhale deeply, focusing on expanding your ribcage sideways.
Resistance Breathing: Use a breathing device or create resistance by pursing your lips while inhaling and exhaling.

Common Injuries

Injuries to the intercostal muscles can occur due to overuse, trauma, or improper technique during exercise. Symptoms may include sharp pain, tenderness, and difficulty breathing. Some common injuries include:

Intercostal muscle strain
Rib fractures
Costochondritis

If you suspect an injury, it's important to seek medical attention to rule out more serious conditions.

Health Implications

Healthy intercostal muscles are essential for maintaining good respiratory function. Weak or injured intercostals can lead to shallow breathing, reduced oxygen intake, and even chronic pain. On the flip side, strong intercostal muscles can enhance athletic performance, improve posture, and reduce the risk of respiratory issues.

Regular exercise, proper breathing techniques, and a balanced diet can all contribute to keeping your intercostal muscles in top shape.

Anatomy in Detail

For those who want to dive deeper into the anatomy of the intercostal muscles, here's a more detailed breakdown:

External Intercostals: Located superficially, these muscles are primarily responsible for raising the ribs during inspiration.
Internal Intercostals: Situated deeper, these muscles assist with lowering the ribs during expiration.
Innermost Intercostals: The deepest layer, these muscles provide additional support during forced breathing.

Understanding the layers and functions of these muscles can give you a better appreciation of how they work together to support your respiratory system.

Conclusion

In conclusion, the internal vs external intercostals debate isn't really a debate at all. Both types of muscles are crucial for maintaining healthy respiratory function. Whether you're taking a deep breath during yoga or exhaling forcefully during a sprint, these muscles are working hard to keep you going.

To keep your intercostal muscles in top shape, focus on incorporating breathing exercises into your routine, maintaining proper posture, and staying active. And if you ever experience pain or discomfort, don't hesitate to seek medical advice.

So, what are you waiting for? Take a deep breath, engage those intercostals, and get moving!

Feel free to leave a comment or share this article with your friends. And if you're hungry for more knowledge, check out our other articles on anatomy and fitness. Your body will thank you!

The Intercostal Space Thoracic Surgery Clinics

Intercostals Rehab My Patient

The Intercostal Muscles of the Ribcage

Champions Of Knowledge

Internal Vs External Intercostals: A Deep Dive Into Their Functions And Differences

Table of Contents