What muscle goes over the sternum? An anatomical guide to your pectoral muscles

The human chest contains several important muscles, but a large, fan-shaped muscle covers the sternum, forming the bulk of the upper chest. Understanding the anatomy of this muscle is key to grasping its critical role in arm movement, shoulder stability, and overall upper body strength, which has significant implications for general health.

Quick Summary

The pectoralis major is the largest and most superficial muscle that goes over the sternum and covers the chest, with its sternocostal head originating directly from the breastbone itself. It works alongside the smaller pectoralis minor to facilitate various arm and shoulder movements, and its health is vital for proper posture and function.

Key Points

• Pectoralis Major: The large, superficial, fan-shaped pectoralis major is the primary muscle covering the sternum and forming the bulk of the chest.

• Sternocostal Head: The pectoralis major has a sternocostal head that specifically originates from the sternum and upper ribs, giving it direct attachment to the breastbone.

• Functional Movement: The pectoralis major is essential for arm movements such as adduction (bringing the arm across the body), medial rotation, and flexion.

• Pectoralis Minor: A smaller, triangular muscle, the pectoralis minor lies underneath the pectoralis major and is vital for stabilizing and depressing the scapula.

• Posture and Health: Strengthening and stretching the pectoral muscles can improve posture, enhance upper body strength, and contribute to overall shoulder stability.

• Accessory Breathing Muscle: In cases of forced or deep inhalation, the pectoral muscles can act as accessory muscles of respiration by helping to elevate the chest wall.

The Pectoralis Major: The Primary Muscle Covering the Sternum

The pectoralis major is the most prominent muscle that covers the sternum. It's a large, fan-shaped muscle also known as the "pec" and makes up the bulk of the upper chest. Its broad connections allow for various arm and shoulder actions.

Anatomy of the Pectoralis Major

The pectoralis major has two heads:

• Clavicular head: Originates from the collarbone.
• Sternocostal head: This larger head attaches to the sternum (manubrium and body) and the costal cartilages of the first six or seven ribs.

Both heads attach to the upper arm bone (humerus).

Functions of the Pectoralis Major

The pectoralis major's functions depend on which head is active:

• Adduction: Moving the arm towards the body's center.
• Medial rotation: Rotating the arm inward.
• Flexion: The clavicular head helps lift the arm forward.
• Extension: The sternocostal head helps bring the arm down from a raised position.

The Pectoralis Minor: A Deeper Muscle

Beneath the pectoralis major is the smaller pectoralis minor. It doesn't directly cover the sternum but is an important chest muscle. It originates from ribs 3-5 and attaches to the shoulder blade (scapula). It helps stabilize and move the scapula downward and forward.

Comparison of Pectoralis Major and Minor

Feature	Pectoralis Major	Pectoralis Minor
Location	Superficial	Deep
Origin	Clavicle, sternum, and ribs	Ribs 3, 4, and 5
Insertion	Humerus	Scapula
Primary Function	Arm adduction, rotation, flexion	Scapular stabilization and depression
Size	Large	Small

Strengthening and Maintaining Chest Health

Regular strength training is important for pectoral muscle health and upper body strength. Proper form is crucial to prevent injury. Effective exercises include:

• Push-ups: A bodyweight exercise for the chest.
• Bench press: Builds strength and size (dumbbells or barbell).
• Chest flyes: Isolates pectoral muscles.
• Dips: Targets the lower pectoralis major.

Potential Health Issues and Importance

Poor posture or training can cause pectoral issues. A tight pectoralis minor can lead to rounded shoulders. Weak pecs can create muscle imbalance and stress on the shoulder joint.

Strong and flexible pecs offer several general health benefits:

1. Improved Posture: Helps counteract rounded shoulders.
2. Enhanced Upper Body Strength: Useful for daily activities.
3. Better Breathing: Can assist in deep breathing by helping lift the rib cage.
4. Shoulder Stability: Works with other muscles to stabilize the shoulder.

Conclusion

The pectoralis major is the main muscle covering the sternum. It's the most visible and powerful chest muscle, vital for arm movement. The pectoralis minor, located deeper, is also crucial for shoulder mechanics and posture. Keeping both muscles healthy through exercise and stretching is essential for upper body strength, stability, and well-being. Understanding their anatomy helps in making informed fitness choices.

For more in-depth anatomical information, consider visiting the official NCBI Bookshelf at https://www.ncbi.nlm.nih.gov/.

Frequently Asked Questions

What is the largest muscle that goes over the sternum?

The pectoralis major is the largest and most prominent muscle that covers the sternum. Its broad sternocostal head originates directly from the breastbone, covering most of the chest region.

Does the sternum have muscles attached to it?

Yes, several muscles attach to the sternum. The largest and most notable is the pectoralis major, but other muscles, like the sternocleidomastoid in the neck and transversus thoracis on the inside of the chest wall, also have attachments.

What are the two parts of the pectoralis major muscle?

The pectoralis major muscle is composed of two heads: the clavicular head, which originates from the clavicle (collarbone), and the sternocostal head, which originates from the sternum and upper ribs.

What is the difference between the pectoralis major and minor?

The pectoralis major is the larger, more superficial muscle that provides the bulk of the chest mass and controls major arm movements. The pectoralis minor is a smaller, deeper muscle that primarily functions to stabilize the shoulder blade.

What happens if my pectoral muscles are weak?

Weak pectoral muscles can contribute to poor posture, such as rounded shoulders, and can lead to imbalances that may cause shoulder instability and increase the risk of injury during physical activity.

How can I strengthen the muscle over my sternum?

You can strengthen the pectoralis major muscle through exercises like push-ups, the bench press, and chest flyes. Proper form is crucial for targeting the muscle effectively and preventing injuries.

Can pectoral muscles affect breathing?

Yes, under certain conditions. While not a primary breathing muscle, the pectoral muscles, particularly the pectoralis minor, can act as accessory muscles of respiration during forced or deep inhalation by helping to elevate the rib cage.