Maximus Gage
The breasts lie over a large muscle called the pectoralis major muscle, which is located on the chest. The pectoralis major muscle acts as an attachment point for the suspensory ligaments. The breast can be considered to have two regions: the circular body, which is the largest and most prominent part of the breast, and the axillary tail, which is a smaller part that runs along the inferior lateral edge of the pectoralis major towards the axillary fossa.
| Characteristics | Values |
|---|---|
| Location | Anterior thoracic wall |
| Horizontal Extension | Lateral border of the sternum to the mid-axillary line |
| Vertical Extension | Between the 2nd and 6th costal cartilages |
| Muscles | Pectoralis major and serratus anterior |
| Base | Pectoral fascia |
| Ligaments | Suspensory ligaments |
| Blood Supply | Internal thoracic artery (a branch of the subclavian artery) |
| Nerve Supply | Anterior and lateral cutaneous branches of the 4th to 6th intercostal nerves |
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What You'll Learn
The pectoralis major muscle
The pectoralis major is a thick, fan-shaped or triangular convergent muscle of the human chest. It makes up the bulk of the chest muscles and lies under the breast. 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 is the largest and most superficial muscle in the chest area. The pectoralis major is also referred to as "pecs", "pectoral muscle", or "chest muscle".
The primary functions of the pectoralis major are flexion, adduction, and internal rotation of the humerus. It is also responsible for keeping the arm attached to the trunk of the body. The muscle has two distinct parts, each responsible for different actions. The clavicular part is close to the deltoid muscle and contributes to flexion, horizontal adduction, and inward rotation of the humerus. On the other hand, the sternocostal part contributes to the downward and forward movement of the arm and inward rotation when accompanied by adduction.
The pectoralis major receives double motor innervation from the medial pectoral nerve and the lateral pectoral nerve. It maintains its blood supply through the pectoral branch of the thoracoacromial artery. Tears and ruptures of the pectoralis major are uncommon but have become more prevalent due to increased participation in weight lifting. These injuries typically affect healthy individuals, particularly those engaging in high-impact contact sports such as powerlifting.
To target the pectoralis major in strength training, a combination of single-joint and multi-joint exercises is ideal for achieving maximum hypertrophic response. Exercises such as the barbell bench press, dumbbell bench press, and machine bench press induce high activation in the sternocostal region of the muscle.
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Suspensory ligaments
The suspensory ligaments of Cooper are bands of tough, fibrous, flexible connective tissue that shape and support the breasts. They maintain the shape and structure of the breasts and help to prevent sagging by supporting the breasts on the chest wall.
Cooper's ligaments keep the breasts in position and maintain their contour. Over time, or after multiple pregnancies, these ligaments can stretch, causing the breasts to sag. This can also be influenced by age, weight fluctuation, and cigarette smoking. Lower levels of elastin, estrogen, and collagen due to aging also play a part in the stretching of the ligaments.
Breast tissue and suspensory ligaments may also be stretched if a woman is overweight or has fluctuations in weight. During pregnancy, the skin is stretched during engorgement while lactating, causing the ligaments to stretch and loosen. Postpartum hormonal changes also cause depleted milk glands to diminish, which affects the ligaments.
There are exercises that can help strengthen, firm, and tone the chest area attached to Cooper's ligaments, which may help to prevent sagging and even lift the chest muscles, slowing down the process of sagging. For example, one can lie on their back with bent knees and flat feet on the floor, holding a dumbbell in each hand with arms extended straight up and the insides of the wrists facing each other. The individual then slowly lowers their arms to the side, keeping their elbows slightly bent, before returning to the starting position.
It is important to note that once Cooper's ligaments are stretched, it cannot be reversed or repaired, even with surgery. However, investing in supportive and well-fitting bras, especially during pregnancy or breastfeeding, can help support the ligaments and the weight of full, heavy breasts. Maintaining good posture by standing or sitting with a straight back can also help relieve some of the pressure from the ligaments.
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Connective tissue
Breasts are made up of a combination of lobules, ducts, fat, and fibrous connective tissue. Lobules are the small glands that produce milk, while ducts are the tiny tubes that carry the milk from the lobules to the nipple. Together, the lobules and ducts are referred to as glandular tissue. The connective tissue in breasts, along with fat, helps to hold everything in place and gives breasts their size and shape.
Fibrous connective tissue and fat make up the majority of breast tissue, with the amount of each contributing to what is known as breast density. Dense breasts have more glandular and fibrous tissue and less fatty tissue. Breast density can vary significantly between individuals and can change over time, with breasts typically becoming less dense with age.
The specific composition of connective tissue in the breasts is not well understood, but it is known that it plays a crucial role in providing structure and support. The fibrous connective tissue in breasts is composed of collagen and elastin fibres, which give the tissue its strength and elasticity. This connective tissue forms a framework that surrounds and supports the functional components of the breast, including the lobules, ducts, and fat.
While connective tissue plays a significant role in holding the breasts up and maintaining their shape, it is not the only factor involved. The pectoralis muscle, located between the breast and the ribs in the chest wall, also provides some support and can influence the position and appearance of the breasts. Additionally, the overall size and shape of the breasts are influenced by factors such as age, hormones, and weight fluctuations.
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The pectoralis minor muscle
The pectoralis minor is a thin, triangular muscle located in the chest, underneath the pectoralis major. It is one of the most superficial muscles on the anterior aspect of the chest or thoracic wall. The pectoralis minor muscle arises as three separate heads from the anterior surface of the third, fourth, and fifth ribs, near the corresponding costal cartilages. It is covered anteriorly by the clavipectoral fascia, which is a connective tissue layer that forms a fascial layer known as the costocoracoid membrane.
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The serratus anterior muscle
The serratus anterior is a fan-shaped muscle that originates on the superolateral surfaces of the first to eighth or ninth ribs at the lateral wall of the thorax. Its main part lies deep under the scapula and the pectoral muscles. It is a key scapular stabiliser, keeping the shoulder blades against the ribcage when at rest and during movement.
The serratus anterior is divided into three parts according to the points of insertion: the serratus anterior superior is inserted near the superior angle; the serratus anterior intermediate is inserted along the medial border; and the serratus anterior inferior is inserted near the inferior angle. The inferior part of the muscle is the most prominent and powerful. The serratus anterior superior depresses the scapula and acts antagonistically.
The serratus anterior acts in concert with the upper and lower fibres of the trapezius muscle to sustain the upward rotation of the scapula, allowing for overhead lifting. It is occasionally called the "big swing muscle" or the "'boxer's muscle' because it is largely responsible for the protraction of the scapula—the pulling of the scapula forward and around the rib cage that occurs when someone throws a punch.
The serratus anterior is easily palpable between the pectoralis major and latissimus dorsi muscles. In athletic bodies, the muscle may even be visible to the naked eye along the ribs underneath the axilla.
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Frequently asked questions
The pectoralis major muscle and the serratus anterior muscle.
The pectoralis major muscle is a large muscle on the chest that the breast lies on top of.
The serratus anterior muscle is a muscle that the breast also lies on top of.
The pectoralis major muscle is involved in movements of the arm, such as flexion, extension, and adduction.
The serratus anterior muscle is involved in stabilizing the scapula and shoulder girdle.
