The pectoralis minor is a thin, triangular muscle, situated at the upper part of the chest, beneath the pectoralis major in the human body. It arises from the upper margins and outer surfaces of the third and fifth ribs, near their cartilages and from the aponeuroses covering the intercostalis; the fibers pass superior and lateral and converge to form a flat tendon, inserted into the medial border and upper surface of the coracoid process of the scapula. The pectoralis minor muscle is covered anteriorly by the clavipectoral fascia; the Medial pectoral nerve pierces the clavipectoral fascia. In attaching to the coracoid process, the pectoralis minor forms a'bridge' - structures passing into the upper limb from the thorax will pass directly underneath. Axillary nodes are classified according to their positions relative to the pectoralis minor muscle. Level 1 are lateral, Level 2 are deep, Level 3 are medial; the pectoralis minor divides the axillary artery into three parts - first part medial, second part deep/posterior, third part lateral in relation to the pectoralis minor.
The origin is from the second and fourth or fifth ribs. The tendon of insertion may extend over the coracoid process to the greater tubercle, it may be split into several parts. Absence of this muscle is rare but happens with certain uncommon diseases, such as the Poland syndrome; the pectoralis minor depresses the point of the shoulder, drawing the scapula superior, towards the thorax, throwing its inferior angle posteriorly. This article incorporates text in the public domain from page 438 of the 20th edition of Gray's Anatomy Illustration: upper-body/pectoralis-minor from The Department of Radiology at the University of Washington Anatomy figure: 04:04-05 at Human Anatomy Online, SUNY Downstate Medical Center Anatomy figure: 05:02-08 at Human Anatomy Online, SUNY Downstate Medical Center Anatomy photo:05:ov-0200 at the SUNY Downstate Medical Center Anatomy photo:05:01-0102 at the SUNY Downstate Medical Center Slide Muscles/PectoralisMinor at exrx.net
Gray's Anatomy is an English language textbook of human anatomy written by Henry Gray and illustrated by Henry Vandyke Carter. Earlier editions were called Anatomy: Descriptive and Surgical, Anatomy of the Human Body and Gray's Anatomy: Descriptive and Applied, but the book's name is shortened to, editions are titled, Gray's Anatomy; the book is regarded as an influential work on the subject, has continued to be revised and republished from its initial publication in 1858 to the present day. The latest edition of the book, the 41st, was published in September 2015; the English anatomist Henry Gray was born in 1827. He studied the development of the endocrine glands and spleen and in 1853 was appointed Lecturer on Anatomy at St George's Hospital Medical School in London. In 1855, he approached his colleague Henry Vandyke Carter with his idea to produce an inexpensive and accessible anatomy textbook for medical students. Dissecting unclaimed bodies from workhouse and hospital mortuaries through the Anatomy Act of 1832, the two worked for 18 months on what would form the basis of the book.
Their work was first published in 1858 by John William Parker in London. It was dedicated by Gray to 1st Baronet. An imprint of this English first edition was published in the United States in 1859, with slight alterations. Gray prepared a second, revised edition, published in the United Kingdom in 1860 by J. W. Parker. However, Gray died the following year, at the age of 34, having contracted smallpox while treating his nephew, his death had come just three years after the initial publication of his Anatomy Descriptive and Surgical. So, the work on his much-praised book was continued by others. Longman's publication began in 1863, after their acquisition of the J. W. Parker publishing business; this coincided with the publication date of the third British edition of Gray's Anatomy. Successive British editions of Gray's Anatomy continued to be published under the Longman, more Churchill Livingstone/Elsevier imprints, reflecting further changes in ownership of the publishing companies over the years.
The full American rights were purchased by Blanchard and Lea, who published the first of twenty-five distinct American editions of Gray's Anatomy in 1862, whose company became Lea & Febiger in 1908. Lea & Febiger continued publishing the American editions until the company was sold in 1990; the first American publication was edited by Richard James Dunglison, whose father Robley Dunglison was physician to Thomas Jefferson. Dunglison edited the next four editions; these were: the Second American Edition. W. W. Keen edited the next two editions, namely: the New American from the Eleventh English Edition. In September 1896, reference to the English edition was dropped and it was published as the Fourteenth Edition, edited by Bern B. Gallaudet, F. J. Brockway, J. P. McMurrich, who edited the Fifteenth Edition. There is an edition dated 1896 which does still reference the English edition stating it is "A New Edition, Thoroughly Revised by American Authorities, from the thirteenth English Edition" and edited by T. Pickering Pick, F.
R. C. S. and published by Lea Brothers & Co. Philadelphia and New York; the Sixteenth Edition was edited by J. C. DaCosta, the Seventeenth by DaCosta and E. A. Spitzka. Spitzka edited the Eighteenth and Nineteenth editions, in October 1913, R. Howden edited the New American from the Eighteenth English Edition; the "American" editions continued with consecutive numbering from the Twentieth onwards, with W. H. Lewis editing the 20th, 21st, 22nd, 23rd, 24th. C. M. Gross edited the 25th, 26th, 27th, 28th, 29th. Carmine D. Clemente extensively revised the 30th edition. With the sale of Lea & Febiger in 1990, the 30th edition was the last American Edition. Sometimes separate editing efforts with mismatches between British and American edition numbering led to the existence, for many years, of two main "flavours" or "branches" of Gray's Anatomy: the U. S. and the British one. This can cause misunderstandings and confusion when quoting from or trying to purchase a certain edition. For example, a comparison of publishing histories shows that the American numbering kept apace with the British up until the 16th editions in 1905, with the American editions either acknowledging the English edition, or matching the numbering in the 14th, 15th and 16th editions.
The American numbering crept ahead, with the 17th American edition published in 1908, while the 17th British edition was published in 1909. This increased to a three-year gap for the 18th and 19th editions, leading to the 1913 publication of the New American from the Eighteenth English, which brought the numbering back into line. Both 20th editions were published in the same year. Thereafter, it was the British numbering that pushed ahead, with the 21st British edition in 1920, the 21st American edition in 1924; this discrepancy continued to increase, so that the 30th British edition was published in 1949, while the 30th and last American edition was published in 1984. The newest, 41st edition of Gray's Anatomy was published on 25 September 2015 by Elsevier in both print and online versions, and
A nerve is an enclosed, cable-like bundle of nerve fibres called axons, in the peripheral nervous system. A nerve provides a common pathway for the electrochemical nerve impulses called action potentials that are transmitted along each of the axons to peripheral organs or, in the case of sensory nerves, from the periphery back to the central nervous system; each axon within the nerve is an extension of an individual neuron, along with other supportive cells such as Schwann cells that coat the axons in myelin. Within a nerve, each axon is surrounded by a layer of connective tissue called the endoneurium; the axons are bundled together into groups called fascicles, each fascicle is wrapped in a layer of connective tissue called the perineurium. The entire nerve is wrapped in a layer of connective tissue called the epineurium. In the central nervous system, the analogous structures are known as tracts; each nerve is covered on the outside by a dense sheath of the epineurium. Beneath this is a layer of flat cells, the perineurium, which forms a complete sleeve around a bundle of axons.
Perineurial septae subdivide it into several bundles of fibres. Surrounding each such fibre is the endoneurium; this forms an unbroken tube from the surface of the spinal cord to the level where the axon synapses with its muscle fibres, or ends in sensory receptors. The endoneurium consists of an inner sleeve of material called the glycocalyx and an outer, meshwork of collagen fibres. Nerves are bundled and travel along with blood vessels, since the neurons of a nerve have high energy requirements. Within the endoneurium, the individual nerve fibres are surrounded by a low-protein liquid called endoneurial fluid; this acts in a similar way to the cerebrospinal fluid in the central nervous system and constitutes a blood-nerve barrier similar to the blood-brain barrier. Molecules are thereby prevented from crossing the blood into the endoneurial fluid. During the development of nerve edema from nerve irritation, the amount of endoneurial fluid may increase at the site of irritation; this increase in fluid can be visualized using magnetic resonance neurography, thus MR neurography can identify nerve irritation and/or injury.
Nerves are categorized into three groups based on the direction that signals are conducted: Afferent nerves conduct signals from sensory neurons to the central nervous system, for example from the mechanoreceptors in skin. Efferent nerves conduct signals from the central nervous system along motor neurons to their target muscles and glands. Mixed nerves contain both afferent and efferent axons, thus conduct both incoming sensory information and outgoing muscle commands in the same bundle. Nerves can be categorized into two groups based on where they connect to the central nervous system: Spinal nerves innervate much of the body, connect through the vertebral column to the spinal cord and thus to the central nervous system, they are given letter-number designations according to the vertebra through which they connect to the spinal column. Cranial nerves innervate parts of the head, connect directly to the brain, they are assigned Roman numerals from 1 to 12, although cranial nerve zero is sometimes included.
In addition, cranial nerves have descriptive names. Specific terms are used to describe their actions. A nerve that supplies information to the brain from an area of the body, or controls an action of the body is said to "innervate" that section of the body or organ. Other terms relate to whether the nerve affects the same side or opposite side of the body, to the part of the brain that supplies it. Nerve growth ends in adolescence, but can be re-stimulated with a molecular mechanism known as "Notch signaling". If the axons of a neuron are damaged, as long as the cell body of the neuron is not damaged, the axons would regenerate and remake the synaptic connections with neurons with the help of guidepost cells; this is referred to as neuroregeneration. The nerve begins the process by destroying the nerve distal to the site of injury allowing Schwann cells, basal lamina, the neurilemma near the injury to begin producing a regeneration tube. Nerve growth factors are produced causing many nerve sprouts to bud.
When one of the growth processes finds the regeneration tube, it begins to grow towards its original destination guided the entire time by the regeneration tube. Nerve regeneration is slow and can take up to several months to complete. While this process does repair some nerves, there will still be some functional deficit as the repairs are not perfect. A nerve conveys information in the form of electrochemical impulses carried by the individual neurons that make up the nerve; these impulses are fast, with some myelinated neurons conducting at speeds up to 120 m/s. The impulses travel from one neuron to another by crossing a synapse, the message is converted from electrical to chemical and back to electrical. Nerves can be categorized into two groups based on function: An afferent nerve fiber conducts sensory information from a sensory neuron to the central nervous system, where the information is processed. Bundles of fibres or axons, in the peripheral nervous system are called nerves, bundles of afferent fibers are known as sensory nerves.
An efferent nerve fiber conducts signals from a motor neuron in the central nervous system to muscles. Bundles of these fibres are known as efferent nerves; the nervous system is the part of an animal that coordinates its actions by transmitting signals to and from different parts of its body. In vertebrates it consists of two main par
The subscapularis is a large triangular muscle which fills the subscapular fossa and inserts into the lesser tubercle of the humerus and the front of the capsule of the shoulder-joint. It arises from its medial two-thirds and from the lower two-thirds of the groove on the axillary border of the scapula; some fibers arise from tendinous laminae, which intersect the muscle and are attached to ridges on the bone. The fibers pass laterally and coalesce into a tendon, inserted into the lesser tubercle of the humerus and the anterior part of the shoulder-joint capsule. Tendinous fibers extend to the greater tubercle with insertions into the bicipital groove; the tendon of the muscle is separated from the neck of the scapula by a large bursa, which communicates with the cavity of the shoulder-joint through an aperture in the capsule. The subscapularis is separated from the serratus anterior by the subscapularis bursa; the subscapularis is supplied by the upper and lower subscapular nerves, branches of the posterior cord of the brachial plexus.
The subscapularis adducts it. It is a powerful defense to the front of the shoulder-joint, preventing displacement of the head of the humerus; the Gerber Lift-off test is the established clinical test for examination of the subscapularis. The bear hug test for subscapularis muscle tears has high sensitivity. Positive bear-hug and belly press tests indicate significant tearing of subscapularis. There is no singularly imaging device or technique for a satisfying and complete subscapularis examination, but rather the combination of the sagittal oblique MRI / short-axis US and axial MRI / long-axis US planes seems to generate useful results. Additionally, lesser tuberosity bony changes have been associated with subscapularis tendon tears. Findings with cysts seem to be more specific and combined findings with cortical irregularities more sensitive. Another fact for the subscapularis muscle is the fatty infiltration of the superior portions, while sparing the inferior portions. Since the long biceps tendon absents itself from the shoulder joint through the rotator cuff interval, it is possible to distinguish between the supraspinatus and the subscapularis tendon.
Those two tendons build the interval sling. Mack et al. developed an ultrasonographic procedure with which it is possible to explore the complete rotator cuff within six steps. It unveils the whole area from the subedge of the subscapularis tendon until the intersection between the infraspinatus tendon and musculus teres minor. One of six steps does focus on the subscapularis tendon. In the first instance the examinator guides the applicator to the proximal humerus as perpendicularly as possible to the sulcus intertubercularis. Gliding now medially shows the insertion of the subscapularis tendon; the subscapularis tendon lies 3 to 5 cm under the surface. Quite deep for ultrasonography, therefore displaying through a penetrative 5 MHz linear applicator is worth a try, and it turned out to ease a detailed examination of the muscle which just abuts to the scapula. However, the tendon of primary interest does not get mapped as as desired; as anatomical analysis showed, it is only by external rotation possible to see the ventral part of the joint socket and its labrum.
While at the neutral position the tuberculum minus occludes the view. Summing up it is through an external arm rotation and a medially applied 5 MHz sector sonic head possible to display the ventral part of the joint socket and its labrum with notedly lower echogenicity; the following sectional planes are defined for the sonographic examination of the different shoulder joint structures: Primarily in abdominal imaging, tissue harmonic imaging gets more and more valued and used additionally to conventional ultrasonography. THI involves the use of harmonic frequencies that originate within the tissue as a result of nonlinear wave front propagation and are not present in the incident beam; these harmonic signals may arise differently at anatomic sites with similar impedances and thus lead to higher contrast resolution.” Along with higher contrast resolution it has an elevated signal-to-noise ratio and reduced inter- and intraobserver variability compared with conventional US. Additionally it is possible to nearly eliminate ordinary US artifacts, i.e. side-lobe, near-field artifacts, reverberation artifacts.
As aforementioned THI has led to enhanced abdominal, breast and cardiac sonography. For musculo-skeletal aspects THI has not been used that much, although this method features some useful potential. For example, for the still tricky discrimination between the presence of a hypoechoic defect and/or loss of the outer tendon convexity/non-visualization of the tendon, between partial- and full-thickness rotator cuff tears. In comparison to a checking MR Arthrography Strobel K. et al. has arrived at the conclusion that through THI it is possible to achieve a improved visibility of joint and tendon surfaces superior for subscapularis tendon abnormalities. This article incorporates text in the public domain from page 440 of the 20th edition of Gray's Anatomy
The triceps triceps brachii, is a large muscle on the back of the upper limb of many vertebrates. It is the muscle principally responsible for extension of the elbow joint; the long head arises from the infraglenoid tubercle of the scapula. It extends distally anterior to the teres posterior to the teres major; the medial head arises proximally from the groove of the radial nerve. The medial head is covered by the lateral and long heads, is only visible distally on the humerus; the lateral head arises from the dorsal surface of the humerus and proximal to the groove of the radial nerve, from the greater tubercle down to the region of the lateral intermuscular septum. Each of the three fascicles has its own motorneuron subnucleus in the motor column in the spinal cord; the medial head is formed predominantly by small type I fibers and motor units, the lateral head of large type IIb fibers and motor units and the long head of a mixture of fiber types and motor units. It has been suggested that each fascicle "may be considered an independent muscle with specific functional roles."The fibers converge to a single tendon to insert onto the olecranon process of the ulna and to the posterior wall of the capsule of the elbow joint where bursae are found.
Parts of the common tendon radiates into the fascia of the forearm and can cover the anconeus muscle. All three heads of the triceps brachii are classically believed to be innervated by the radial nerve. However, a study conducted in 2004 determined that, in 20 cadaveric specimens and 15 surgical dissections on participants, the long head was innervated by a branch of the axillary nerve in all cases. A tendinous arch is the origin of the long head and the tendon of latissimus dorsi. In rare cases, the long head can originate from the lateral margin of the scapula and from the capsule of the shoulder joint; the triceps is an extensor muscle of the elbow joint and an antagonist of the biceps and brachialis muscles. It can fixate the elbow joint when the forearm and hand are used for fine movements, e.g. when writing. It has been suggested that the long head fascicle is employed when sustained force generation is demanded, or when there is a need for a synergistic control of the shoulder and elbow or both.
The lateral head is used for movements requiring occasional high-intensity force, while the medial fascicle enables more precise, low-force movements. With its origin on the scapula, the long head acts on the shoulder joint and is involved in retroversion and adduction of the arm, it helps stabilise the shoulder joint at the top of the humerus. The triceps can be worked through either isolation or compound elbow extension movements and can contract statically to keep the arm straightened against resistance. Isolation movements include cable push-downs, lying triceps extensions and arm extensions behind the back. Examples of compound elbow extension include pressing movements like the push up, bench press, close grip bench press, military press and dips. A closer grip targets the triceps more than wider grip movements. Static contraction movements include pullovers, straight-arm pulldowns and bent-over lateral raises, which are used to build the deltoids and latissimus dorsi. Ruptures of the triceps muscle are rare, only occur in anabolic steroid users.
The triceps reflex, elicited by hitting the triceps, is used to test the function of the nerves of the arm. This tests spinal nerves C6 and C7, predominately C7, it is sometimes called a three-headed muscle, because there are three bundles of muscles, each of different origins, joining together at the elbow. Though a named muscle, the triceps surae, is found on the lower leg, the triceps brachii is called the triceps; the plural form of triceps was tricipites, a form not in general use today. In the horse, 84%, 15%, 3% of the total triceps muscle weight correspond to the long and medial heads, respectively. Many mammals, such as dogs and pigs, have a fourth head, the accessory head, it lies between the medial heads. In humans, the anconeus is sometimes loosely called "the fourth head of the triceps brachii". Illustration: upper-body/triceps-brachii from The Department of Radiology at the University of Washington Anatomy photo:06:11-0100 at the SUNY Downstate Medical Center Photo at Ithaca College Muscles/TricepsBrachii at exrx.net
The public domain consists of all the creative works to which no exclusive intellectual property rights apply. Those rights may have been forfeited, expressly waived, or may be inapplicable; the works of William Shakespeare and Beethoven, most early silent films, are in the public domain either by virtue of their having been created before copyright existed, or by their copyright term having expired. Some works are not covered by copyright, are therefore in the public domain—among them the formulae of Newtonian physics, cooking recipes, all computer software created prior to 1974. Other works are dedicated by their authors to the public domain; the term public domain is not applied to situations where the creator of a work retains residual rights, in which case use of the work is referred to as "under license" or "with permission". As rights vary by country and jurisdiction, a work may be subject to rights in one country and be in the public domain in another; some rights depend on registrations on a country-by-country basis, the absence of registration in a particular country, if required, gives rise to public-domain status for a work in that country.
The term public domain may be interchangeably used with other imprecise or undefined terms such as the "public sphere" or "commons", including concepts such as the "commons of the mind", the "intellectual commons", the "information commons". Although the term "domain" did not come into use until the mid-18th century, the concept "can be traced back to the ancient Roman Law, as a preset system included in the property right system." The Romans had a large proprietary rights system where they defined "many things that cannot be owned" as res nullius, res communes, res publicae and res universitatis. The term res nullius was defined as things not yet appropriated; the term res communes was defined as "things that could be enjoyed by mankind, such as air and ocean." The term res publicae referred to things that were shared by all citizens, the term res universitatis meant things that were owned by the municipalities of Rome. When looking at it from a historical perspective, one could say the construction of the idea of "public domain" sprouted from the concepts of res communes, res publicae, res universitatis in early Roman law.
When the first early copyright law was first established in Britain with the Statute of Anne in 1710, public domain did not appear. However, similar concepts were developed by French jurists in the 18th century. Instead of "public domain", they used terms such as publici juris or propriété publique to describe works that were not covered by copyright law; the phrase "fall in the public domain" can be traced to mid-19th century France to describe the end of copyright term. The French poet Alfred de Vigny equated the expiration of copyright with a work falling "into the sink hole of public domain" and if the public domain receives any attention from intellectual property lawyers it is still treated as little more than that, left when intellectual property rights, such as copyright and trademarks, expire or are abandoned. In this historical context Paul Torremans describes copyright as a, "little coral reef of private right jutting up from the ocean of the public domain." Copyright law differs by country, the American legal scholar Pamela Samuelson has described the public domain as being "different sizes at different times in different countries".
Definitions of the boundaries of the public domain in relation to copyright, or intellectual property more regard the public domain as a negative space. According to James Boyle this definition underlines common usage of the term public domain and equates the public domain to public property and works in copyright to private property. However, the usage of the term public domain can be more granular, including for example uses of works in copyright permitted by copyright exceptions; such a definition regards work in copyright as private property subject to fair-use rights and limitation on ownership. A conceptual definition comes from Lange, who focused on what the public domain should be: "it should be a place of sanctuary for individual creative expression, a sanctuary conferring affirmative protection against the forces of private appropriation that threatened such expression". Patterson and Lindberg described the public domain not as a "territory", but rather as a concept: "here are certain materials – the air we breathe, rain, life, thoughts, ideas, numbers – not subject to private ownership.
The materials that compose our cultural heritage must be free for all living to use no less than matter necessary for biological survival." The term public domain may be interchangeably used with other imprecise or undefined terms such as the "public sphere" or "commons", including concepts such as the "commons of the mind", the "intellectual commons", the "information commons". A public-domain book is a book with no copyright, a book, created without a license, or a book where its copyrights expired or have been forfeited. In most countries the term of protection of copyright lasts until January first, 70 years after the death of the latest living author; the longest copyright term is in Mexico, which has life plus 100 years for all deaths since July 1928. A notable exception is the United States, where every book and tale published prior to 1924 is in the public domain.
The deltoid muscle is the muscle forming the rounded contour of the human shoulder. It is known as the'common shoulder muscle' in other animals such as the domestic cat. Anatomically, it appears to be made up of three distinct sets of fibers though electromyography suggests that it consists of at least seven groups that can be independently coordinated by the nervous system, it was called the deltoideus and the name is still used by some anatomists. It is called. Deltoid is further shortened in slang as "delt". A study of 30 shoulders revealed an average mass of 191.9 grams in humans, ranging from 84 grams to 366 grams. Previous studies showed that the insertion of the intramuscular tendons of the deltoid muscle formed three discrete sets of muscle fibers referred to as "heads": The anterior or clavicular fibers arise from most of the anterior border and upper surface of the lateral third of the clavicle; the anterior origin lies adjacent to the lateral fibers of the pectoralis major muscle as do the end tendons of both muscles.
These muscle fibers are related and only a small chiasmatic space, through which the cephalic vein passes, prevents the two muscles from forming a continuous muscle mass. The anterior deltoids are called front delts for short. Lateral or acromial fibers arise from the superior surface of the acromion process of the scapula, they are called lateral deltoid. This muscle is called middle delts, outer delts, or side delts for short, they are mistakenly called medial deltoid, wrong, as their origin is the least medial portion of the deltoid. Posterior or spinal fibers arise from the lower lip of the posterior border of the spine of the scapula, they are called posterior deltoid or rear deltoid. Fick divided these three groups of fibers referred to as parts or bands, into seven functional components as did Kapandji and Sakoma Y et al.: the anterior part has two components. In standard anatomical position, the central components lie lateral to the axis of abduction and therefore contribute to abduction from the start of the movement while the other components act as adductors.
During abduction most of these latter components are displaced laterally and progressively start to abduct. From this extensive origin the fibers converge toward their insertion on the deltoid tuberosity on the middle of the lateral aspect of the shaft of the humerus. Though traditionally described as a single insertion, the deltoid insertion is divided into two or three discernible areas corresponding to the muscle's three areas of origin; the insertion is an arch-like structure with strong anterior and posterior fascial connections flanking an intervening tissue bridge. It additionally gives off extensions to the deep brachial fascia. Furthermore, the deltoid fascia contributes to the brachial fascia and is connected to the medial and lateral intermuscular septa; the deltoid is supplied by the posterior circumflex humeral artery and the deltoid branch of the thoracoacromial artery which branches from the axillary artery. The deltoid is innervated by the axillary nerve; the axillary nerve originates from the anterior rami of the cervical nerves C5 and C6, via the superior trunk, posterior division of the superior trunk, the posterior cord of the brachial plexus.
Studies have shown. Three of these lie in the anatomical anterior head of the deltoid, one in the anatomical middle head, three in the anatomical posterior head of the deltoid; these neuromuscular segments are supplied by smaller branches of the axillary nerve, work in coordination with other muscles of the shoulder girdle include pectoralis major and supraspinatus. The axillary nerve is sometimes damaged during surgical procedures of the axilla, such as for breast cancer, it may be injured by anterior dislocation of the head of the humerus. When all its fibers contract the deltoid is the prime mover of arm abduction along the frontal plane; the arm must be medially rotated for the deltoid to have maximum effect. This makes the deltoid an antagonist muscle of the pectoralis major and latissimus dorsi during arm adduction; the anterior fibers assist the pectoralis major to flex the shoulder. The anterior deltoid works in tandem with the subscapularis and lats to internally rotate the humerus; the lateral fibers perform basic shoulder abduction when the shoulder is internally rotated, perform shoulder transverse abduction when the shoulder is externally rotated.
They are not utilized during strict transverse extension such as in rowing movements, which use the posterior fibers. The posterior fibers assist the latissimus dorsi to extend the shoulder. Other transverse extensors, the infraspinatus and teres minor work in tandem with the posterior deltoid as external rotators, antagonists to strong internal rotators like the pecs and lats. An important function of the deltoid in humans is preventing the dislocation of the humeral head when a person carries heavy loads; the function of abduction means that it would help keep carried objects a safer distance away from the thighs to avoid hitting them, as during a farmer's walk. It ensures a precise a