Pectoralis major muscle 755375 226143871 2008-07-17T00:43:20Z Ron Ritzman 154046 Reverted edits by [[Special:Contributions/72.75.200.67|72.75.200.67]] to last version by 190.143.16.156 (using [[WP:HG|Huggle]]) {{Muscle infobox | Name = Pectoralis major| Latin = Musculus pectoralis major| GraySubject = 122 | GrayPage = 436 | Image = Pectoralis major.png| Caption = Pectoralis major | Origin = Kank: anterior surface of the medial half of the [[clavicle]].<BR> '''Sternocostal head''': anterior surface of the [[sternum]], the superior six [[costal cartilages]], and the | Insertion = [[intertubercular groove]] of the [[humerus]] | Blood = [[pectoral branch]] of the [[thoracoacromial trunk]] | Nerve = [[lateral pectoral nerve]] and [[medial pectoral nerve]]<BR>'''Clavicular head''': [[C5]] and [[C6]]<BR>'''Sternocostal head''': [[C7]], [[C8]] and [[thoracic nerves|T1]] | Action = '''Clavicular head''': [[flexes]] the [[humerus]]<BR>'''Sternocostal head''': [[extends]] the humerus<BR>As a whole, [[adducts]] and [[medially rotates]] the [[humerus]]. It also draws the [[scapula]] anteriorly and inferiorly. | Antagonist = | MeshName = Pectoralis+Muscles | MeshNumber = A02.633.567.775 | DorlandsPre = m_22 | DorlandsSuf = 12550129 | }} The '''Pectoralis major''' (popularly known as '''pecs''') is a thick, fan-shaped muscle, situated at the upper front ([[anterior]]) of the [[chest]] 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 from the anterior surface of the sternal half of the [[clavicle]]; from breadth of the half of the anterior surface of the [[sternum]], as low down as the attachment of the cartilage of the sixth or seventh [[rib]]; from the cartilages of all the true ribs, with the exception, frequently, of the first or seventh and from the [[aponeurosis]] of the [[ abdominal external oblique muscle]]. From this extensive origin the fibers converge toward their insertion; 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 crest of the greater tubercle of the humerus. ==Laminae== This tendon consists of two [[lamina]]e, 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]] 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]]. 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]] 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]] of the arm. ==Variations== The more frequent variations include greater or less extent of attachment to the [[ribs]] and [[sternum]], varying size of the [[abdomen|abdominal]] part or its absence, greater or less extent of separation of sternocostal and [[clavicle|clavicular]] parts, fusion of clavicular part with [[deltoid]], and [[decussation]] 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]]). ==Training== {{Unreferencedsection|date=July 2007}} The pectoralis muscle can be trained for athletic or [[bodybuilding]] purposes<ref>http://www.exrx.net/Lists/ExList/ChestWt.html</ref>. The following compound exercises are often used to increase the strength and mass of the muscle: *[[Bench press]], with various bench angles (flat, incline, and decline) *[[Press up]] *[[Dip bar|Dips]] Isolation exercises include: *[[Fly (exercise)|Flyes or Flies]] *[[Cable machine|Cable Crossovers]] * "Pec Deck" machines ==Additional images== <gallery> Image:Gray410.png|Superficial muscles of the chest and front of the arm. Image:Illu trunk muscles.jpg|Muscles of the trunk Image:Gray115.png|Anterior surface of sternum and costal cartilages. Image:Gray200.png|Left clavicle. Superior surface. Image:Gray201.png|Left clavicle. Inferior surface. Image:Gray207.png|Left humerus. Anterior view. Image:Gray523.png|The axillary artery and its branches. Image:Gray525.png|The brachial artery. Image:Gray558.png|The veins of the neck, viewed from in front. Image:Gray808.png|The right brachial plexus with its short branches, viewed from in front. Image:Gray809.png|The right brachial plexus (infraclavicular portion) in the axillary fossa; viewed from below and in front. Image:Nerves_of_the_left_upper_extremity.gif|Nerves of the left upper extremity. Image:Gray1215.png|The left side of the thorax. Image:Gray1219.png|Surface anatomy of the front of the thorax and abdomen. </gallery> ==External links== * {{MuscleUWash|pectoralismajor}} * {{MuscleLoyola|pcmj}} * {{GPnotebook|393294}} * [http://faculty.ucc.edu/biology-potter/Musculature/sld013.htm UCC] {{Gray's}} {{Muscles of upper limb}} [[Category:Muscles of the upper limb]] == Notes == *<references/> [[ar:عضلة صدرية كبيرة]] [[de:Musculus pectoralis major]] [[es:Pectoral mayor]] [[fr:Muscle grand pectoral]] [[hr:Veliki prsni mišić]] [[id:Otot pectoralis major]] [[it:Muscolo grande pettorale]] [[he:שריר החזה הגדול]] [[la:Musculus pectoralis maior]] [[hu:Nagy mellizom]] [[nl:Musculus pectoralis major]] [[ja:大胸筋]] [[pl:Mięsień piersiowy większy]] [[pt:Músculo peitoral maior]] [[sk:Veľký prsný sval]] [[sl:Velika prsna mišica]] [[fi:Rintalihas]] [[sv:Stora bröstmuskeln]] [[zh:胸大肌]]