Dominic Stone
The pectoralis muscle is any of the muscles that connect the front walls of the chest with the bones of the upper arm and shoulder. There are two pectoralis muscles on each side of the sternum (breastbone) in the human body: the pectoralis major and the pectoralis minor. 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 and forms the anterior wall of the axilla. The pectoralis minor lies, for the most part, beneath the pectoralis major, arising from the middle ribs and inserting into (attaching to) the scapula (shoulder blade).
Explore related products
What You'll Learn
Pectoralis major
The pectoralis major is the thickest and largest muscle of the anterior chest wall. It is a fan-shaped or triangular convergent muscle that lies underneath the breast tissue and forms the anterior wall of the axilla. The pectoralis major is the most superficial muscle in the pectoral region.
The pectoralis major has two heads: the clavicular and the sternocostal, which reference their area of origin. The clavicular head 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 upper part of the aponeurosis of the external oblique muscle. The upper and lower fibres of the pectoralis major insert into the crest of the greater tubercle of the humerus.
The pectoralis major has several functions, including flexion, adduction, and internal rotation of the humerus, as well as keeping the arm attached to the trunk of the body. The clavicular part contributes to flexion, horizontal adduction, and inward rotation of the humerus, while the sternocostal part contributes to downward and forward movement of the arm. The pectoralis major also assists in breathing when the diaphragm and intercostal muscles are insufficient.
The pectoralis major receives dual motor innervation from the medial pectoral nerve and the lateral pectoral nerve, also known as the lateral anterior thoracic nerve. The medial pectoral nerve arises posterior to the axillary artery and inserts into the posterior surface of the pectoralis major. The lateral pectoral nerve is distributed over the deep surface of the muscle. The sensory feedback from the pectoralis major follows a reverse path, returning via first-order neurons to the spinal nerves.
The Muscular Advantage: Men's Muscles Explored
You may want to see also
Explore related products
Pectoralis minor
Pectoralis muscles are those that connect the front walls of the chest with the bones of the upper arm and shoulder. There are two such muscles on each side of the sternum (breastbone) in the human body: the pectoralis major and the pectoralis minor.
The pectoralis minor is triangular in shape and is located under the pectoralis major. It arises from the margins of the third to fifth ribs adjacent to the costochondral junction. The fibres pass upward and laterally to insert into the medial border and superior surface of the coracoid process of the scapula (shoulder blade). The pectoralis minor is one of the most superficial muscles on the anterior aspect of the chest or thoracic wall. It is located deep only to the pectoralis major muscle. Together, the pectoralis major and minor form the anterior wall of the axilla.
The pectoralis minor aids in drawing the shoulder forward and downward. It depresses the point of the shoulder, drawing the scapula superior, towards the thorax, and throwing its inferior angle posteriorly. It is crucial in the stabilization of the scapula by pulling it downward and anteriorly against the thoracic wall. It also acts as an accessory muscle of inspiration. When the scapula is stabilized, the pectoralis minor brings the scapula forward.
The pectoralis minor is important clinically and as a surgical landmark. Running deep to the pectoralis minor muscle are the nerves and blood supply to the upper limb: the posterior, lateral, and medial cords of the brachial plexus. The primary nerve supply to the pectoralis minor muscle comes via the medial pectoral nerve (C8, T1), one of the minor branches of the brachial plexus that arises from the cervical portion of the spinal cord.
The Anus and Muscles: What's the Connection?
You may want to see also
Explore related products
Adduction and internal rotation
The pectoral muscles are a group of skeletal muscles that connect the front walls of the chest with the bones of the upper arm and shoulder. There are two pectoral muscles on each side of the sternum (breastbone) in the human body: the pectoralis major and the pectoralis minor.
The pectoralis major is the most prominent and superficial muscle in the chest area, constituting the bulk of the chest muscles. It is a fan-shaped muscle that arises from parts of the clavicle and sternum, costal cartilages of the true ribs, and the aponeurosis of the abdominal external oblique muscle. The pectoralis major has four primary functions: flexion, adduction, internal rotation, and depression of the humerus.
Adduction refers to the movement of the arm towards the body, bringing it across the chest. This is in contrast to abduction, which is the movement of the arm away from the body. Adduction of the arm is an important function of the pectoralis major muscle, working in opposition to the deltoideus muscle. This movement is crucial for various activities, such as flapping the arms or throwing a ball underhand.
Internal rotation, or medial rotation, of the humerus is another key function of the pectoralis major muscle. This movement involves rotating the arm inward, towards the centre of the body, as occurs during arm wrestling. The pectoralis major acts as a strong internal rotator of the humerus at the shoulder joint, facilitating this rotational movement.
The absence or dysfunction of the pectoralis major can significantly impact the range of motion in the shoulder joint, particularly in adduction and internal rotation movements. Poland's syndrome is an example of an embryonic malformation of the thoracic wall that can result in the partial or complete absence of the pectoralis major. Individuals with this condition may experience difficulties in performing certain activities that require a full range of motion in the shoulder, such as crossing the arms or throwing a grenade.
Muscle Mass: The Strength Myth Explained
You may want to see also
Explore related products
Poland syndrome
The pectoralis muscle is any of the muscles that connect the front walls of the chest with the bones of the upper arm and shoulder. There are two pectoralis muscles on each side of the sternum (breastbone) in the human body: the pectoralis major and the pectoralis minor.
People with Poland syndrome are typically missing a part of one of the major chest muscles, called the pectoralis major. The abnormal pectoralis major muscle may cause the chest to appear concave. In some cases, additional muscles on the affected side of the torso, including muscles in the chest wall, side, and shoulder, may be missing or underdeveloped. There may also be rib cage abnormalities, such as shortened ribs, and the ribs may be noticeable due to less fat under the skin (subcutaneous fat).
Many people with Poland syndrome have hand abnormalities on the affected side, including an underdeveloped hand with abnormally short fingers; small, underdeveloped fingers; and some fingers that are fused together. This combination of hand abnormalities is called symbrachydactyly. The bones of the forearm (radius and ulna) may also be shortened in some people with Poland syndrome.
Treatment for Poland syndrome depends on its severity and may include surgical correction. Correction by custom implant is the first-line treatment, allowing for a wide variety of patients to be treated with good outcomes.
The Muscular Might of Ants: An Exploration
You may want to see also
Explore related products
Exercises to strengthen
Pectoral muscles are those that connect the front or ventral walls of the chest with the bones of the upper arm and shoulder. There are two pectoral muscles on each side of the sternum (breastbone) in the human body: the pectoralis major and the pectoralis minor.
Bodyweight exercises
You can perform chest exercises with just your body weight for resistance. For example, you can do push-ups, varying the challenge by placing your toes on an elevated surface such as a bench or table.
Dumbbell exercises
You can also use dumbbells to target your pectoral muscles. It is recommended to use light weights (no heavier than five pounds) and higher repetitions to build lean and long muscles.
Resistance bands
You can work your chest muscles with resistance bands. For example, you can stand with a resistance band anchored overhead, grasping the ends as you step forward with one foot. Keep tension and control on the handles to keep them in front of your chest, then bring the handles down and forward across your body at roughly belly button level.
Stretches
Stretching the chest can improve pectoral muscle flexibility over time, reducing tightness and allowing you to take deeper breaths. You can perform a stretch by standing facing a wall with your arm straight out to the side at shoulder height. Press your palm against the wall and slowly push your arm into the wall as you turn your body away from the wall, so that your arm is behind you. Hold for 30 seconds before switching sides and stretching the other arm.
Diet
In addition to exercise, you can increase muscle definition by decreasing body fat. This will likely involve increasing calorie burn through aerobic exercise and managing your diet.
Kali Muscle's Incarceration: What's the Truth?
You may want to see also
Frequently asked questions
Pectoral muscles are the muscles that connect the front walls of the chest with the bones of the upper arm and shoulder. There are two such muscles on each side of the sternum (breastbone) in the human body: the pectoralis major and the pectoralis minor.
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. It makes up the bulk of the chest muscles.
The pectoralis major has four primary functions: flexion, adduction, internal rotation of the humerus, and keeping the arm attached to the trunk of the body.
