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Pectoralis major muscle

 

 
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Pectoralis major muscle
 
 
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The Pectoralis major (popularly known as pecs) is a thick, fan-shaped muscle, situated at the upper front (anterior) of the chest
Chest

The chest is a part of the anatomy of humans and various other animals sometimes referred to as the thorax....
 wall. It makes up the bulk of the chest muscles in the male and lies under the breast in the female.

a class="link1" onMouseover='showByLink("m2527166",this)' onMouseout='hide("m2527166")'href="http://www.absoluteastronomy.com/topics/Origin_%28anatomy%29">arises
Origin (anatomy)

The anatomical origin is a concept used when describing muscles, tendons, ligaments, nerves, and blood vessel and lymph vessels. While it often has a slightly different meaning depending on which kind of origin is referred to, it is generally used to explain the relative location of the anatomical structure in question....
 from the anterior surface of the sternal half of the clavicle
Clavicle

In human anatomy, the clavicle or collar bone is classified as a flat bone that makes up part of the shoulder girdle . It receives its name from the Latin clavicula because the bone rotates along its axis like a key when the shoulder is Abduction ....
; from breadth of the half of the anterior surface of the sternum
Sternum

The sternum is a long flat bone located in the center of the chest . It connects to the rib via cartilage, forming the rib cage with them, and thus helps to protect the lungs, heart and major blood vessels from physical trauma....
, as low down as the attachment of the cartilage of the sixth or seventh rib
Rib

In vertebrate anatomy, ribs are the long curved bones which form the ribcage. In most vertebrates, ribs surround the chest and protect the lungs, heart, and other internal Organ s of the thorax....
; from the cartilages of all the true ribs
True ribs

The first seven ribs are connected behind with the vertebral column, and in front, through the intervention of the costal cartilages, with the sternum; they are called true ribs or vertebro-sternal ribs....
, with the exception, frequently, of the first or seventh and from the aponeurosis
Aponeurosis

Aponeuroses are layers of flat broad tendons. They have a shiny, whitish-silvery color, and are histologically similar to tendons, but are very sparingly supplied with blood vessels and nerves....
 of the abdominal external oblique muscle
Abdominal external oblique muscle

The external oblique muscle is the largest and the most superficial of the three flat muscles of the lateral anterior abdomen....
.

From this extensive origin the fibers converge toward their insertion
Insertion (anatomy)

An insertion is the point at which a muscle attaches to the skin, a bone, or another muscle. The insertion attaches to the structure that will be moved by the Muscle contraction of the muscle....
; those arising from the clavicle pass obliquely downward and outwards (laterally), and are usually separated from the rest by a slight interval; those from the lower part of the sternum, and the cartilages of the lower true ribs, run upward and laterally, while the middle fibers pass horizontally.

They all end in a flat tendon, about 5 cm in breadth, which is inserted into the bicipital groove of the humerus
Humerus

The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow.Anatomically, it connects the scapula and the ulna, and consists of the following three sections:...
.

tendon consists of two laminae, placed one in front of the other, and usually blended together below.





These deep fibers, and particularly those from the lower costal cartilages, ascend the higher, turning backward successively behind the superficial and upper ones, so that the tendon appears to be twisted.

The posterior lamina reaches higher on the humerus than the anterior one, and from it an expansion is given off which covers the intertubercular groove of the humerus
Humerus

The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow.Anatomically, it connects the scapula and the ulna, and consists of the following three sections:...
 and blends with the capsule of the shoulder-joint.

From the deepest fibers of this lamina at its insertion an expansion is given off which lines the intertubercular groove, while from the lower border of the tendon a third expansion passes downward to the fascia
Fascia

Fascia , pl. fas?ci?ae , adj. fascial is the soft tissue component of the connective tissue system that permeates the human body....
 of the arm.

more frequent variations include greater or less extent of attachment to the ribs and sternum
Sternum

The sternum is a long flat bone located in the center of the chest . It connects to the rib via cartilage, forming the rib cage with them, and thus helps to protect the lungs, heart and major blood vessels from physical trauma....
, varying size of the abdominal
Abdomen

In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity....
 part or its absence, greater or less extent of separation of sternocostal and clavicular
Clavicle

In human anatomy, the clavicle or collar bone is classified as a flat bone that makes up part of the shoulder girdle . It receives its name from the Latin clavicula because the bone rotates along its axis like a key when the shoulder is Abduction ....
 parts, fusion of clavicular part with deltoid
Deltoid

Deltoid can refer to:* The deltoid muscle, a muscle in the shoulder* Kite , also known as a deltoid, a type of quadrilateral* A deltoid curve, a three-sided hypocycloid...
, and decussation
Decussation

Decussation is used in biological contexts to describe a crossing.Examples include:* In the brain, where nerve fibers cross from one lateral part to the other....
 in front of the sternum.

Deficiency or absence of the sternocostal part is not uncommon.

Absence of the clavicular part is less frequent.

Rarely, the whole muscle is missing.






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Encyclopedia


The Pectoralis major (popularly known as pecs) is a thick, fan-shaped muscle, situated at the upper front (anterior) of the chest
Chest

The chest is a part of the anatomy of humans and various other animals sometimes referred to as the thorax....
 wall. It makes up the bulk of the chest muscles in the male and lies under the breast in the female.

Origin and insertion

It arises
Origin (anatomy)

The anatomical origin is a concept used when describing muscles, tendons, ligaments, nerves, and blood vessel and lymph vessels. While it often has a slightly different meaning depending on which kind of origin is referred to, it is generally used to explain the relative location of the anatomical structure in question....
 from the anterior surface of the sternal half of the clavicle
Clavicle

In human anatomy, the clavicle or collar bone is classified as a flat bone that makes up part of the shoulder girdle . It receives its name from the Latin clavicula because the bone rotates along its axis like a key when the shoulder is Abduction ....
; from breadth of the half of the anterior surface of the sternum
Sternum

The sternum is a long flat bone located in the center of the chest . It connects to the rib via cartilage, forming the rib cage with them, and thus helps to protect the lungs, heart and major blood vessels from physical trauma....
, as low down as the attachment of the cartilage of the sixth or seventh rib
Rib

In vertebrate anatomy, ribs are the long curved bones which form the ribcage. In most vertebrates, ribs surround the chest and protect the lungs, heart, and other internal Organ s of the thorax....
; from the cartilages of all the true ribs
True ribs

The first seven ribs are connected behind with the vertebral column, and in front, through the intervention of the costal cartilages, with the sternum; they are called true ribs or vertebro-sternal ribs....
, with the exception, frequently, of the first or seventh and from the aponeurosis
Aponeurosis

Aponeuroses are layers of flat broad tendons. They have a shiny, whitish-silvery color, and are histologically similar to tendons, but are very sparingly supplied with blood vessels and nerves....
 of the abdominal external oblique muscle
Abdominal external oblique muscle

The external oblique muscle is the largest and the most superficial of the three flat muscles of the lateral anterior abdomen....
.

From this extensive origin the fibers converge toward their insertion
Insertion (anatomy)

An insertion is the point at which a muscle attaches to the skin, a bone, or another muscle. The insertion attaches to the structure that will be moved by the Muscle contraction of the muscle....
; those arising from the clavicle pass obliquely downward and outwards (laterally), and are usually separated from the rest by a slight interval; those from the lower part of the sternum, and the cartilages of the lower true ribs, run upward and laterally, while the middle fibers pass horizontally.

They all end in a flat tendon, about 5 cm in breadth, which is inserted into the bicipital groove of the humerus
Humerus

The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow.Anatomically, it connects the scapula and the ulna, and consists of the following three sections:...
.

Laminae

This tendon consists of two laminae, placed one in front of the other, and usually blended together below.

  • The anterior lamina, which is thicker, receives the clavicular and the uppermost sternal fibers. They are inserted in the same order as that in which they arise: the most lateral of the clavicular fibers are inserted at the upper part of the anterior lamina; the uppermost sternal fibers pass down to the lower part of the lamina which extends as low as the tendon of the Deltoid
    Deltoid muscle

    In human anatomy, the deltoid muscle is the muscle forming the rounded contour of the shoulder.It was previously called the Deltoideus and the name is still used by some anatomists....
     and joins with it.


  • The posterior lamina of the tendon receives the attachment of the greater part of the sternal portion and the deep fibers, i. e., those from the costal cartilages
    Costal cartilages

    The costal cartilages are bars of hyaline cartilage which serve to prolong the ribs forward and contribute very materially to the elasticity of the walls of the thorax....
    .


These deep fibers, and particularly those from the lower costal cartilages, ascend the higher, turning backward successively behind the superficial and upper ones, so that the tendon appears to be twisted.

The posterior lamina reaches higher on the humerus than the anterior one, and from it an expansion is given off which covers the intertubercular groove of the humerus
Humerus

The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow.Anatomically, it connects the scapula and the ulna, and consists of the following three sections:...
 and blends with the capsule of the shoulder-joint.

From the deepest fibers of this lamina at its insertion an expansion is given off which lines the intertubercular groove, while from the lower border of the tendon a third expansion passes downward to the fascia
Fascia

Fascia , pl. fas?ci?ae , adj. fascial is the soft tissue component of the connective tissue system that permeates the human body....
 of the arm.

Variations

The more frequent variations include greater or less extent of attachment to the ribs and sternum
Sternum

The sternum is a long flat bone located in the center of the chest . It connects to the rib via cartilage, forming the rib cage with them, and thus helps to protect the lungs, heart and major blood vessels from physical trauma....
, varying size of the abdominal
Abdomen

In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity....
 part or its absence, greater or less extent of separation of sternocostal and clavicular
Clavicle

In human anatomy, the clavicle or collar bone is classified as a flat bone that makes up part of the shoulder girdle . It receives its name from the Latin clavicula because the bone rotates along its axis like a key when the shoulder is Abduction ....
 parts, fusion of clavicular part with deltoid
Deltoid

Deltoid can refer to:* The deltoid muscle, a muscle in the shoulder* Kite , also known as a deltoid, a type of quadrilateral* A deltoid curve, a three-sided hypocycloid...
, and decussation
Decussation

Decussation is used in biological contexts to describe a crossing.Examples include:* In the brain, where nerve fibers cross from one lateral part to the other....
 in front of the sternum.

Deficiency or absence of the sternocostal part is not uncommon.

Absence of the clavicular part is less frequent.

Rarely, the whole muscle is missing. This may accompany absence of the breast in females. (See Poland syndrome
Poland syndrome

Poland syndrome is a rare birth defect characterized by underdevelopment or absence of the chest muscle on one side of the body and webbing of the fingers of the hand on the same side mostly common on the right side of body and found more in males than females....
).

Actions


The Pectoralis Major has three actions. It flexes the humerus, as in throwing a ball side-arm, and in lifting a child. It also adducts the humerus, as when flapping arms. It also rotates the humerus medially, as occurs when arm-wrestling.

Training

The pectoralis muscle can be trained for athletic or bodybuilding
Bodybuilding

Bodybuilding is the process of maximizing muscle hypertrophy; an individual who engages in this activity is referred to as a bodybuilder. In competitive bodybuilding, bodybuilders display their physiques to a panel of judges, who assign points based on their aesthetic appearance....
 purposes. The following compound exercises are often used to increase the strength and mass of the muscle:
  • Bench press
    Bench press

    The bench press is a strength training exercise in which, while lying on his back, the person performing the bench press lowers a weight to the level of the chest, then pushes it back up until the arm is straight and the elbows locked ....
    , with various bench angles (flat, incline, and decline)
  • Push up
  • Dips
    Dip (exercise)

    The dip is an exercise used in strength training. Normal, shoulder-width dips primarily train the triceps, with major synergists being the anterior deltoid, the pectoralis muscles , and the rhomboid muscles of the back ....


Isolation exercises include:
  • Flyes or Flies
    Fly (exercise)

    A fly is a strength training exercise in which the hand and arm move through an range of motion while the elbow is kept at a constant angle. Flies are used to work the muscles of the Torso....
  • Cable Crossovers
    Cable machine

    A cable machine is an item of equipment used in weight training or functional training. It consists of a rectangular, vertically-oriented steel frame about 3 meters wide and 2 meters high, with a weight stack at each end....
  • "Pec Deck" machines


Additional images


External links