Anatomical terms of motion
Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints and specific sections of the body; the terminology used describes this motion according to its direction relative to the anatomical position of the joints. Anatomists use a unified set of terms to describe most of the movements, although other, more specialized terms are necessary for describing the uniqueness of the movements such as those of the hands and eyes. In general, motion is classified according to the anatomical plane. Flexion and extension are examples of angular motions, in which two axes of a joint are brought closer together or moved further apart. Rotational motion may occur at other joints, for example the shoulder, are described as internal or external. Other terms, such as elevation and depression, describe movement above or below the horizontal plane. Many anatomical terms derive from Latin terms with the same meaning. Motions are classified after the anatomical planes they occur in, although movement is more than not a combination of different motions occurring in several planes.
Motions can be split into categories relating to the nature of the joints involved: Gliding motions occur between flat surfaces, such as in the intervertebral discs or between the carpal and metacarpal bones of the hand. Angular motions occur over synovial joints and causes them to either increase or decrease angles between bones. Rotational motions move a structure in a rotational motion along a longitudinal axis, such as turning the head to look to either side. Apart from this motions can be divided into: Linear motions, which move in a line between two points. Rectilinear motion is motion in a straight line between two points, whereas curvilinear motion is motion following a curved path. Angular motions occur when an object is around another object decreasing the angle; the different parts of the object do not move the same distance. Examples include a movement of the knee, where the lower leg changes angle compared to the femur, or movements of the ankle; the study of movement is known as kinesiology.
A categoric list of movements of the human body and the muscles involved can be found at list of movements of the human body. The prefix hyper- is sometimes added to describe movement beyond the normal limits, such as in hypermobility, hyperflexion or hyperextension; the range of motion describes the total range of motion. For example, if a part of the body such as a joint is overstretched or "bent backwards" because of exaggerated extension motion it can be described as hyperextended. Hyperextension increases the stress on the ligaments of a joint, is not always because of a voluntary movement, it may be other causes of trauma. It may be used in surgery, such as in temporarily dislocating joints for surgical procedures; these are general terms. Most terms have a clear opposite, so are treated in pairs. Flexion and extension describe movements; these terms come from the Latin words with the same meaning. Flexion describes a bending movement that decreases the angle between a segment and its proximal segment.
For example, bending the elbow, or clenching a hand into a fist, are examples of flexion. When sitting down, the knees are flexed; when a joint can move forward and backward, such as the neck and trunk, flexion refers to movement in the anterior direction. When the chin is against the chest, the head is flexed, the trunk is flexed when a person leans forward. Flexion of the shoulder or hip refers to movement of the leg forward. Extension is the opposite of flexion, describing a straightening movement that increases the angle between body parts. For example, when standing up, the knees are extended; when a joint can move forward and backward, such as the neck and trunk, extension refers to movement in the posterior direction. Extension of the hip or shoulder moves the leg backward. Abduction is the motion of a structure away from the midline while adduction refer to motion towards the center of the body; the centre of the body is defined as the midsagittal plane. These terms come from Latin words with similar meanings, ab- being the Latin prefix indicating "away," ad- indicating "toward," and ducere meaning "to draw or pull".
Abduction refers to a motion that pulls a part away from the midline of the body. In the case of fingers and toes, it refers to spreading the digits apart, away from the centerline of the hand or foot. Abduction of the wrist is called radial deviation. For example, raising the arms up, such as when tightrope-walking, is an example of abduction at the shoulder; when the legs are splayed at the hip, such as when doing a star jump or doing a split, the legs are abducted at the hip. Adduction refers to a motion that pulls a structure or part toward the midline of the body, or towards the midline of a limb. In the case of fingers and toes, it refers to bringing the digits together, towards the centerline of the hand or foot. Adduction of the wrist is called ulnar deviation. Dropping the arms to the sides, bringing the knees together, are examples of adduction. Ulnar deviation is the hand moving towards the ulnar styloid. Radial deviation is the hand moving towards the radial styloid; the terms elevation and depression refer to movement below the horizontal.
They derive from the Latin terms with similar meaningsElevation refers to movement in a superior direction. For example
Mucus is a polymer. It is a slippery aqueous secretion produced by, covering, mucous membranes, it is produced from cells found in mucous glands, although it may originate from mixed glands, which contain both serous and mucous cells. It is a viscous colloid containing inorganic salts, antiseptic enzymes and glycoproteins such as lactoferrin and mucins, which are produced by goblet cells in the mucous membranes and submucosal glands. Mucus serves to protect epithelial cells in the respiratory, urogenital and auditory systems. Most of the mucus produced is in the gastrointestinal tract. Bony fish, snails and some other invertebrates produce external mucus. In addition to serving a protective function against infectious agents, such mucus provides protection against toxins produced by predators, can facilitate movement and may play a role in communication. In the human respiratory system, mucus known as airway surface liquid, aids in the protection of the lungs by trapping foreign particles that enter them, in particular, through the nose, during normal breathing.
Further distinction exists between the superficial and cell-lining layers of ASL, which are known as mucus layer and pericilliary liquid layer, respectively. "Phlegm" is a specialized term for mucus, restricted to the respiratory tract, whereas the term "nasal mucus" describes secretions of the nasal passages. Nasal mucus is produced by the nasal mucosa. Small particles such as dust, particulate pollutants, allergens, as well as infectious agents and bacteria are caught in the viscous nasal or airway mucus and prevented from entering the system; this event along with the continual movement of the respiratory mucus layer toward the oropharynx, helps prevent foreign objects from entering the lungs during breathing. This explains why coughing occurs in those who smoke cigarettes; the body's natural reaction is to increase mucus production. In addition, mucus aids in moisturizing the inhaled air and prevents tissues such as the nasal and airway epithelia from drying out. Nasal and airway mucus is produced continuously, with most of it swallowed subconsciously when it is dried.
Increased mucus production in the respiratory tract is a symptom of many common illnesses, such as the common cold and influenza. Hypersecretion of mucus can occur in inflammatory respiratory diseases such as respiratory allergies and chronic bronchitis; the presence of mucus in the nose and throat is normal, but increased quantities can impede comfortable breathing and must be cleared by blowing the nose or expectorating phlegm from the throat. In general, nasal mucus is thin, serving to filter air during inhalation. During times of infection, mucus can change color to yellow or green either as a result of trapped bacteria or due to the body's reaction to viral infection; the green color of mucus comes from the heme group in the iron-containing enzyme myeloperoxidase secreted by white blood cells as a cytotoxic defense during a respiratory burst. In the case of bacterial infection, the bacterium becomes trapped in already-clogged sinuses, breeding in the moist, nutrient-rich environment. Sinusitis is an uncomfortable condition.
A bacterial infection in sinusitis will cause discolored mucus and would respond to antibiotic treatment. All sinusitis infections are viral and antibiotics are ineffective and not recommended for treating typical cases. In the case of a viral infection such as cold or flu, the first stage and the last stage of the infection cause the production of a clear, thin mucus in the nose or back of the throat; as the body begins to react to the virus, mucus may turn yellow or green. Viral infections cannot be treated with antibiotics, are a major avenue for their misuse. Treatment is symptom-based. Increased mucus production in the upper respiratory tract is a symptom of many common ailments, such as the common cold. Nasal mucus may be removed by using nasal irrigation. Excess nasal mucus, as with a cold or allergies, due to vascular engorgement associated with vasodilation and increased capillary permeability caused by histamines, may be treated cautiously with decongestant medications. Thickening of mucus as a "rebound" effect following overuse of decongestants may produce nasal or sinus drainage problems and circumstances that promote infection.
During cold, dry seasons, the mucus lining nasal passages tends to dry out, meaning that mucous membranes must work harder, producing more mucus to keep the cavity lined. As a result, the nasal cavity can fill up with mucus. At the same time, when air is exhaled, water vapor in breath condenses as the warm air meets the colder outside temperature near the nostrils; this causes an excess amount of water to build up inside nasal cavities. In these cases, the excess fluid spills out externally through the nostrils. Excess mucus production in the bronchi and bronchioles, as may occur in asthma, bronchitis or influenza, results from chronic airway inflammation, hence may be treated with anti-inflammatory medications. Impaired mucociliary clearance due to conditions such as primary ciliary dyskinesia may result in its accumulation in the bronchi; the dysregulation of
The phalanges are digital bones in the hands and feet of most vertebrates. In primates, the thumbs and big toes have two phalanges; the phalanges are classed as long bones. The phalanges are the bones that make up the toes of the foot. There are 56 phalanges in the human body, with fourteen on each foot. Three phalanges are present on each finger and toe, with the exception of the thumb and large toe, which possess only two; the middle and far phalanges of the fourth and fifth toes are fused together. The phalanges of the hand are known as the finger bones; the phalanges of the foot differ from the hand in that they are shorter and more compressed in the proximal phalanges, those closest to the body. A phalanx is named according to whether it is proximal, middle, or distal and its associated finger or toe; the proximal phalanges are those that are closest to foot. In the hand, the prominent, knobby ends of the phalanges are known as knuckles; the proximal phalanges join with the metacarpals of the hand or metatarsals of the foot at the metacarpophalangeal joint or metatarsophalangeal joint.
The intermediate phalanx is not only intermediate in location, but also in size. The thumb and large toe do not possess a middle phalanx; the distal phalanges are the bones at the tips of the toes. The proximal and distal phalanges articulate with one another through interphalangeal articulations; each phalanx consists of a central part, called the body, two extremities. The body is flat on either side, concave on the palmar surface, convex on the dorsal surface, its sides are marked with rough areas giving attachment to fibrous sheaths of flexor tendons. It tapers from above downwards; the proximal extremities of the bones of the first row present oval, concave articular surfaces, broader from side to side than from front to back. The proximal extremity of each of the bones of the second and third rows presents a double concavity separated by a median ridge; the distal extremities are smaller than the proximal, each ends in two condyles separated by a shallow groove. In the foot, the proximal phalanges have a body, compressed from side to side, convex above, concave below.
The base is concave, the head presents a trochlear surface for articulation with the second phalanx. The middle are rather broader than the proximal; the distal phalanges, as compared with the distal phalanges of the finger, are smaller and are flattened from above downward. In the hand, the distal phalanges are flat on their palmar surface and with a roughened, elevated surface of horseshoe form on the palmar surface, supporting the finger pulp; the flat, wide expansions found at the tips of the distal phalanges are called apical tufts. They support the fingertip nails; the phalanx of the thumb has a pronounced insertion for the flexor pollicis longus, an ungual fossa, a pair of unequal ungual spines. This asymmetry is necessary to ensure that the thumb pulp is always facing the pulps of the other digits, an osteological configuration which provides the maximum contact surface with held objects. In the foot, the distal phalanges are flat on their dorsal surface, it is tapers to the distal end.
The proximal part of the phalnx presents a broad base for articulation with the middle phalanx, an expanded distal extremity for the support of the nail and end of the toe. The phalanx ends in a crescent-shaped rough cap of bone epiphysis — the apical tuft which covers a larger portion of the phalanx on the volar side than on the dorsal side. Two lateral ungual spines project proximally from the apical tuft. Near the base of the shaft are two lateral tubercles. Between these a V-shaped ridge extending proximally serves for the insertion of the flexor pollicis longus. Another ridge at the base serves for the insertion of the extensor aponeurosis; the flexor insertion is sided by two fossae — the ungual fossa distally and the proximopalmar fossa proximally. The number of phalanges in animals is expressed as a "phalangeal formula" that indicates the numbers of phalanges in digits, beginning from the innermost medial or proximal. For example, humans have a 2-3-3-3-3 formula for the hand, meaning that the thumb has two phalanges, whilst the other fingers each have three.
In the distal phalanges of the hand the centres for the bodies appear at the distal extremities of the phalanges, instead of at the middle of the bodies, as in the other phalanges. Moreover, of all the bones of the hand, the distal phalanges are the first to ossify; the distal phalanges of ungulates carry and shape nails and claws and these in primates are referred to as the ungual phalanges. The term phalanx or phalanges refers to an ancient Greek army formation in which soldiers stand side by side, several rows deep, like an arrangement of fingers or toes. Most land mammals including humans have a 2-3-3-3-3 formula in feet. Primitive reptiles had the formula 2-3-4-4-5, this pattern, with some modification, remained in many reptiles and in the mammal-like reptiles; the phalangeal formula in the flippers of cetaceans is 2-12-8-1. In vertebrates, proximal phalanges have a similar placement in the corr
Extensor hallucis longus muscle
The extensor hallucis longus is a thin muscle, situated between the tibialis anterior and the extensor digitorum longus, that functions to extend the big toe and dorsiflects the foot, assists with foot eversion and inversion. It arises from the anterior surface of the fibula for about the middle two-fourths of its extent, medial to the origin of the Extensor digitorum longus; the anterior tibial vessels and deep peroneal nerve lie between the Tibialis anterior. The fibers pass downward, end in a tendon, which occupies the anterior border of the muscle, passes through a distinct compartment in the cruciate crural ligament, crosses from the lateral to the medial side of the anterior tibial vessels near the bend of the ankle, is inserted into the base of the distal phalanx of the great toe. Opposite the metatarsophalangeal articulation, the tendon gives off a thin prolongation on either side, to cover the surface of the joint. An expansion from the medial side of the tendon is inserted into the base of the proximal phalanx.
United at its origin with the extensor digitorum longus. The extensor ossis metatarsi hallucis, a small muscle, sometimes found as a slip from the extensor hallucis longus, or from the tibialis anterior, or from the extensor digitorum longus, or as a distinct muscle. Deep peroneal nerve, branch of common peroneal nerve; this article incorporates text in the public domain from page 481 of the 20th edition of Gray's Anatomy Anatomy photo:15:st-0402 at the SUNY Downstate Medical Center - "The Leg: Muscles" University of Washington
Toes are the digits of the foot of a tetrapod. Animal species such as cats that walk on their toes are described as being digitigrade. Humans, other animals that walk on the soles of their feet, are described as being plantigrade. There are five toes present on each human foot; each toe consists of three phalanx bones, the proximal and distal, with the exception of the big toe. For a minority of people, the little toe is missing a middle bone; the hallux only contains the proximal and distal. The joints between each phalanx are the interphalangeal joints; the proximal phalanx bone of each toe articulates with the metatarsal bone of the foot at the metatarsophalangeal joint. Each toe is surrounded by skin, present on all five toes is a toenail; the toes are, from medial to lateral: the first toe known as the hallux, the innermost toe. Toe movement is flexion and extension via muscular tendons that attach to the toes on the anterior and superior surfaces of the phalanx bones. With the exception of the hallux, toe movement is governed by action of the flexor digitorum brevis and extensor digitorum brevis muscles.
These attach to the sides of the bones. Muscles between the toes on their top and bottom help to abduct and adduct the toes; the hallux and little toe have unique muscles: The hallux is flexed by the flexor hallucis longus muscle, located in the deep posterior of the lower leg, via the flexor hallucis longus tendon. Additional flexion control is provided by the flexor hallucis brevis, it is extended by the adductor hallucis muscle. The little toe has a separate set of control muscles and tendon attachments, the flexor and abductor digiti minimi. Numerous other foot muscles contribute to fine motor control of the foot; the connective tendons between the minor toes account for the inability to actuate individual toes. The toes receive blood from the digital branches of the plantar metatarsal arteries and drain blood into the dorsal venous arch of the foot. Sensation to the skin of the toes is provided by five nerves; the superficial fibular nerve supplies sensation to the top of the toes, except between the hallux and second toe, supplied by the deep fibular nerve, the outer surface of the fifth toe, supplied by the sural nerve.
Sensation to the bottom of the toes is supplied by the medial plantar nerve, which supplies sensation to the great toe and inner three-and-a-half toes, the lateral plantar nerve, which supplies sensation to the little toe and half of the sensation of the fourth toe. In humans, the hallux is longer than the second toe, but in some individuals, it may not be the longest toe. There is an inherited trait in humans, where the dominant gene causes a longer second toe while the homozygous recessive genotype presents with the more common trait: a longer hallux. People with the rare genetic disease fibrodysplasia ossificans progressiva characteristically have a short hallux which appears to turn inward, or medially, in relation to the foot. Humans have five toes on each foot; when more than five toes are present, this is known as polydactyly. Other variants may include arachnodactyly. Forefoot shape, including toe shape, exhibits significant variation among people; such deviations may fit for various shoe types.
Research conducted for the U. S. Army indicated that larger feet may still have smaller arches, toe length, toe-breadth; the human foot consists of multiple bones and soft tissues which support the weight of the upright human. The toes assist the human while walking, providing balance, weight-bearing, thrust during gait. A sprain or strain to the small interphalangeal joints of the toe is called a stubbed toe. A sprain or strain where the toe joins to the foot is called turf toe. Long-term use of improperly sized shoes can cause misalignment of toes, as well as other orthopedic problems. Morton's neuroma results in pain and numbness between the third and fourth toes of the sufferer, due to it affecting the nerve between the third and fourth metatarsal bones; the big toe is the most common locus of ingrown nails and the proximal phalanx joint of the hallux is the most common locus for gout attacks. Deformities of the foot include hammer toe, trigger toe, claw toe. Hammer toe can be described as an abnormal contraction or “buckling” of a toe.
This is done by a complete dislocation of one of the joints, which form the toes. Since the toes are deformed further, these may press against a cause pain. Deformities of the foot can be caused by rheumatoid arthritis and diabetes mellitus. Deformities may predispose to ulcers and pain when shoe-wearing. A common problem involving the big toe is the formation of bunions; these are structural deformities of the bones and the joint between the foot and big toe, may be painful. Similar deformity involving the fifth toe is described as tailor's bunionette. A favourable option for the reconstruction of missing adjacent fingers/multiple digit amputations, i.e. such as a metacarpal hand rec
Anatomical terms of muscle
Muscles are described using unique anatomical terminology according to their actions and structure. There are three types of muscle tissue in the human body: skeletal and cardiac. Skeletal striated muscle, or "voluntary muscle" joins to bone with tendons. Skeletal muscle maintains posture. Smooth muscle tissue is found in parts of the body; the majority of this type of muscle tissue is found in the digestive and urinary systems where it acts by propelling forward food and feces in the former and urine in the latter. Other places smooth muscle can be found are within the uterus, where it helps facilitate birth, the eye, where the pupillary sphincter controls pupil size. Cardiac muscle is specific to the heart, it is involuntary in its movement, is additionally self-excitatory, contracting without outside stimuli. As well as anatomical terms of motion, which describe the motion made by a muscle, unique terminology is used to describe the action of a set of muscles. Agonist muscles and antagonist muscles refer to muscles that inhibit a movement.
Agonist muscles cause a movement to occur through their own activation. For example, the triceps brachii contracts, producing a shortening contraction, during the up phase of a push-up. During the down phase of a push-up, the same triceps brachii controls elbow flexion while producing a lengthening contraction, it is still the agonist, because while resisting gravity during relaxing, the triceps brachii continues to be the prime mover, or controller, of the joint action. Agonists are interchangeably referred to as "prime movers," since they are the muscles considered responsible for generating or controlling a specific movement. Another example is the dumbbell curl at the elbow; the "elbow flexor" group is the agonist. During the lowering phase the "elbow flexor" muscles lengthen, remaining the agonists because they are controlling the load and the movement. For both the lifting and lowering phase, the "elbow extensor" muscles are the antagonists, they shorten during the dumbbell lowering phase.
Here it is important to understand that it is common practice to give a name to a muscle group based on the joint action they produce during a shortening contraction. However, this naming convention does not mean; this term describes the function of skeletal muscles. Antagonist muscles are the muscles that produce an opposing joint torque to the agonist muscles; this torque can aid in controlling a motion. The opposing torque can slow movement down - in the case of a ballistic movement. For example, during a rapid discrete movement of the elbow, such as throwing a dart, the triceps muscles will be activated briefly and to accelerate the extension movement at the elbow, followed immediately by a "burst" of activation to the elbow flexor muscles that decelerates the elbow movement to arrive at a quick stop. To use an automotive analogy, this would be similar to pressing your gas pedal and immediately pressing the brake. Antagonism is not an intrinsic property of a particular muscle group. During slower joint actions that involve gravity, just as with the agonist muscle, the antagonist muscle can shorten and lengthen.
Using the example above of the triceps brachii during a push-up, the elbow flexor muscles are the antagonists at the elbow during both the up phase and down phase of the movement. During the dumbbell curl, the elbow extensors are the antagonists for both the lifting and lowering phases. Antagonist and agonist muscles occur in pairs, called antagonistic pairs; as one muscle contracts, the other relaxes. An example of an antagonistic pair is the triceps. "Reverse motions" need antagonistic pairs located in opposite sides of a joint or bone, including abductor-adductor pairs and flexor-extensor pairs. These consist of an extensor muscle, which "opens" the joint and a flexor muscle, which does the opposite by decreasing the angle between two bones. However, muscles don't always work this way. Sometimes during a joint action controlled by an agonist muscle, the antagonist will be activated, naturally; this occurs and is not considered to be a problem unless it is excessive or uncontrolled and disturbs the control of the joint action.
This serves to mechanically stiffen the joint. Not all muscles are paired in this way. An example of an exception is the deltoid. Synergist muscles help perform, the same set of joint motion as the agonists. Synergists muscles act on movable joints. Synergists are sometimes referred to as "neutralizers" because they help cancel out, or neutralize, extra motion from the agonists to make sure that the force generated works within the desired plane of motion. Muscle fibers can only contract up to 40% of their stretched length, thus the short fibers of pennate muscles are more suitable where power rather than range of contraction is required. This limitation in the range of contraction affects all muscles, those that act over several joints may be unable to shorten sufficiently to produce
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