Athena Vale
The pectoralis major is a thick, fan-shaped chest muscle that acts on the shoulder joint. It is the most superficial muscle in the pectoral region, lying underneath the breast tissue. The pectoralis major is involved in flexion, adduction, and internal rotation of the humerus. It is also active in deep or forced inspiration. The pectoralis minor lies beneath the pectoralis major, attaching to the scapula (shoulder blade) and aiding in drawing the shoulder forward and downward. Poland syndrome is a rare congenital condition in which the pectoralis major muscle is absent or malformed.
| Characteristics | Values |
|---|---|
| Number of muscles | 2 |
| Names | Pectoralis major, Pectoralis minor |
| Location | Front walls of the chest, connecting to the bones of the upper arm and shoulder |
| Pectoralis Major Location | Anterior chest wall, underneath the breast tissue |
| Pectoralis Minor Location | Beneath the Pectoralis Major, arising from the middle ribs and attaching to the scapula (shoulder blade) |
| Pectoralis Major Functions | Adduction, internal rotation of the humerus, flexion, inspiration |
| Pectoralis Minor Functions | Drawing the shoulder forward and downward |
| Common Exercises | Barbell bench press, dumbbell bench press, machine bench press |
| Related Conditions | Poland syndrome, Moebius syndrome, congenital anomalies (e.g., chest malformations, absence of breast) |
Explore related products
What You'll Learn
Pectoralis major and minor
The pectoralis major is the superior most and largest muscle of the anterior chest wall. It is thick and fan-shaped, lying underneath the breast tissue. The pectoralis major arises from parts of the clavicle and sternum, costal cartilages of the true ribs, and the aponeurosis of the abdominal external oblique muscle. It has two heads: the clavicular and the sternocostal, which reference their area of origin. The clavicular head contributes to flexion, horizontal adduction, and inward rotation of the humerus, while the sternocostal part contributes to downward and forward movement of the arm, along with inward rotation during adduction. The pectoralis major is active during deep or forced inspiration and assists in breathing, along with other muscles like the serratus anterior, when the diaphragm and intercostal muscles are insufficient.
The pectoralis minor is a thin, triangular muscle located under the pectoralis major. It originates from the anterior surface of the third, fourth, and fifth ribs near the corresponding costal cartilages and inserts into the medial border and coracoid process of the scapula. The pectoralis minor is crucial for stabilizing the scapula by pulling it downward and anteriorly against the thoracic wall. It also acts as an accessory muscle of respiration and inspiration.
Both the pectoralis major and minor muscles work together with the serratus anterior muscle to create a full range of movement for the scapula. The lateral and medial pectoral nerves penetrate the pectoralis minor muscle to innervate it, and it receives its vascular supply from several sources, including branches of the axillary and thoracic arteries.
The pectoralis major and minor muscles form the anterior wall of the axilla, along with their associated fascia. The pectoralis major is completely invested within a deep fascial layer known as the pectoral fascia, which is distinct from the underlying clavipectoral fascia that invests the pectoralis minor muscle.
Injuries to the pectoralis major, such as tendon rupture, are more commonly seen in weightlifters performing exercises like the bench press. Poland Syndrome is a rare congenital condition where the pectoralis major muscle is missing, usually on one side of the body.
Ankle Movement: Muscles and Their Functions
You may want to see also
Explore related products
Clavicular and sternocostal parts
The pectoralis major is a prominent chest muscle that has two heads: the clavicular and the sternocostal. The clavicular head of the pectoralis major originates from the anterior surface of the medial half of the clavicle, while the sternocostal head originates from the anterior surface of the manubrium and body of the sternum, the anterior surface of the superior six costal cartilages, and the superior part of the aponeurosis of the external oblique muscle. The sternocostal head is the larger of the two heads.
The clavicular part of the pectoralis major is close to the deltoid muscle and contributes to flexion, horizontal adduction, and inward rotation of the humerus. It assists in flexion of the arm at the glenohumeral joint. When the arm is at approximately a 110-degree angle, it contributes to adduction of the humerus. The clavicular head derives its nerve supply from the lateral pectoral nerve, which arises from the lateral cord of the brachial plexus.
The sternocostal part of the pectoralis major is antagonistic to the clavicular part, contributing to the downward and forward movement of the arm and inward rotation when accompanied by adduction. It assists in the extension of the arm at the glenohumeral joint. The sternal fibres can also contribute to extension, but not beyond the anatomical position. The sternocostal head can be tested by adducting the arm at the glenohumeral joint against resistance, and it can be seen and palpated. Deficiency or absence of the sternocostal part is not uncommon and is more frequent than the absence of the clavicular part.
The pectoralis major as a whole acts as a strong adductor and internal rotator of the humerus at the shoulder joint. It is responsible for keeping the arm attached to the trunk of the body. When acting together with the latissimus dorsi muscle, the pectoralis major pulls the trunk forwards or upwards when its humeral attachment is fixed, which is important in activities such as climbing.
Muscle Testing: New Age or Legitimate Practice?
You may want to see also
Explore related products
Poland syndrome
The most common muscle affected in Poland syndrome is the pectoralis major, which is one of the two pectoralis muscles. This muscle normally runs from the upper arm to the breastbone (sternum) and its absence can cause the chest to appear concave. In addition to the pectoralis major, other muscles on the affected side of the torso, including those in the chest wall, side, and shoulder, may also be missing or underdeveloped. Furthermore, individuals with Poland syndrome may have rib cage abnormalities, such as shortened ribs, and reduced fat under the skin (subcutaneous fat).
The diagnosis of Poland syndrome is typically made at birth based on physical characteristics, but mild cases may go unnoticed until puberty when asymmetry between the two sides of the chest becomes more apparent. Imaging techniques such as CT scans can help reveal the extent of muscle involvement. Treatment options depend on the severity of the condition and may include implants or surgical correction to improve physical appearance and emotional well-being. In recent years, lipomodelling has emerged as a promising treatment option for severe cases, offering improved reconstruction with minimal scarring.
Gaining Muscle: How Many Pounds Can You Add?
You may want to see also
Explore related products
Pectoralis exercises
The pectoralis muscle is composed of two muscles: the pectoralis major and the pectoralis minor. The pectoralis major is the larger and more superficial of the two, and it sits above the pectoralis minor. The pectoralis major is responsible for a variety of movements, including abduction (moving the arm away from the body), adduction (moving the arm towards the body), flexion (bringing the arm up and across the body), and internal and external rotation (rotating the arm inwards and outwards).
Bench Press
The bench press is one of the most common exercises for targeting the pectoralis major. It can be performed with a barbell or a pair of dumbbells. To perform this exercise, lie on a bench with your feet flat on the ground. Using either a barbell or a pair of dumbbells, extend your arms and slowly lower the weight towards your nipple line, then bring the weight back up to the starting position above your face at arm's length. This exercise can also be performed on an incline bench, which provides a greater challenge than a flat or decline bench.
Push-ups
Push-ups are another effective exercise for targeting the pectoralis major. To perform a push-up, position yourself with your arms straight and resting on the ground, keeping your body in a straight line. Drop your chest towards the ground by bending your elbows, then push back up to the starting position.
Chest Flies
Chest flies are a great exercise for targeting the pectoralis muscles. This exercise can be performed with dumbbells or a cable machine. When using dumbbells, lie on a bench with your feet flat on the ground. Bring the dumbbells above your chest with your arms slightly bent and internally rotated so that your elbows are facing outwards. Lower the dumbbells to your sides, maintaining the slight bend in your arms, then bring them back up to the starting position. When using a cable machine, stand with one foot in front of the other and hold a cable machine handle in each hand. Drive one handle towards your chest, maintaining tension on the pectoral muscle, then bring it back up and repeat with the opposite arm.
Alternating Cable Crossovers
Alternating cable crossovers are an effective exercise for targeting the lower and inner chest muscles. Stand with one foot in front of the other and hold a cable machine handle in each hand. Bend your elbows slightly and retract your shoulder blades. Drive one handle towards your chest, keeping tension on the pectoral muscle, then bring it back up and repeat with the opposite arm.
It is important to remember that chest exercises should be part of a well-rounded strength training program that includes exercises for muscles throughout the body. Additionally, strength training should be balanced with other forms of exercise such as aerobic activity and flexibility exercises. Always consult with your doctor before starting any new exercise program.
Understanding Muscle Knots: Causes, Symptoms, and Treatment Options
You may want to see also
Explore related products
Pectoralis injuries
The pectoralis muscle has a major and a minor component. The pectoralis minor lies beneath the pectoralis major and connects the front walls of the chest with the bones of the upper arm and shoulder. The pectoralis major is the superior most and largest muscle of the anterior chest wall. It is a thick, fan-shaped muscle that lies underneath the breast tissue.
Injuries to the pectoralis muscle are rare but are becoming an increasingly frequent cause of disability. The pectoralis major is typically injured when the muscle contracts while stretching out, also known as an eccentric contraction. This injury most commonly occurs due to excessive tension on a maximally contracted muscle during the downward portion of a bench press, with the arm in the final 30 degrees of humeral extension and external rotation. Other activities commonly associated with pectoralis major injury include skiing, football, wrestling, rugby, martial arts, gymnastics, and direct trauma.
A ruptured pectoralis major tendon, sometimes referred to as a "pec tear", occurs most frequently in men aged 20 to 40. Symptoms of a pectoral muscle rupture or tendon rupture include sudden pain in the chest and upper arm, bruising, weakness, and a "popping" sensation. There may also be a visible change to the contour of the upper arm and armpit.
The treatment of pectoralis major injuries depends on the extent of the injury and the patient's health. Minor injuries to the muscle and injuries in elderly patients are generally treated with pain medications and physical therapy. In contrast, complete or near-complete ruptures of the tendon or myotendinous junction in younger and athletic patients require surgery to restore function. Surgery involves repairing the ruptured tendon back to its original location on the upper arm. This is completed by making an incision on the upper arm near the armpit and sewing the tendon to small plastic screws or metal buttons placed in the arm bone (humerus). Surgery should be performed within the first 2 to 3 weeks after injury, after which the tendon and biceps muscle begin to scar and shorten, and restoring arm function with surgery may not be possible.
Muscle Aches, Water Retention: What's the Link?
You may want to see also
Frequently asked questions
The pectoralis muscles are the group of skeletal muscles that connect the upper extremities to the anterior and lateral thoracic walls. There are two pectoralis muscles on each side of the sternum: pectoralis major and pectoralis minor.
The primary muscles involved in the actions of the pectoralis major include the pectoralis minor, serratus anterior, and subclavius.
Common exercises that target the pectoralis major include the flat barbell bench press, flat dumbbell bench press, and dumbbell fly.
The pectoralis major acts as an adductor and internal rotator of the humerus at the shoulder joint. It also facilitates inspiration, particularly during physical distress.
