In human anatomy, the metacarpus is the intermediate part of the hand A hand is a prehensile, multi-fingered body part located at the end of an arm or forelimb of primates and some[which?] other vertebrates skeleton In biology, a skeleton is a rigid framework that provides structure as well as protection in humans and many types of animals, particularly those of the phylum Chordata and of the superphylum Ecdysozoa. Exoskeletons are external, as is typical of many invertebrates; they enclose the soft tissues and organs of the body. Exoskeletons may undergo that is located between the phalanges In anatomy, phalanx bones are those that form the fingers and toes. In primates such as humans and monkeys, the thumb and big toe have two phalanges, while the other fingers and toes consist of three. Phalanges are classified as long bones (bones of the fingers) distally Standard anatomical terms of location are employed in science which deal with the anatomy of animals to avoid ambiguities which might otherwise arise. They are not language-specific, and thus require no translation. They are universal terms that may be readily understood by zoologists who speak any language and the carpus In tetrapods, the carpus is the sole cluster of bones in the wrist between the radius and ulna and the metacarpus. The bones of the carpus do not belong to individual fingers , whereas those of the metacarpus do. The corresponding part of the foot is the tarsus. The carpal bones allow the wrist to move and rotate vertically which forms the connection to the forearm The forearm is the structure and distal region of the upper limb, between the elbow and the wrist.. The term forearm is used in anatomy to distinguish it from the arm, a word which is most often used to describe the entire appendage of the upper limb but in anatomy, technically means only the region of the upper arm whereas the lower "arm&. The metacarpus consists of metacarpal bones. Its equivalent in the foot is the metatarsus The metatarsus or metatarsal bones are a group of five long bones in the foot located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the medial side : the first, second, third, fourth, and fifth metatarsal. The metatarsals are analogous to the.
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Human anatomy
The metacarpals form a transverse arch to which the rigid row of distal carpal bones are fixed. The peripheral metacarpals (those of the thumb and little finger) form the sides of the cup of the palmar gutter and as they are brought together they deepen this concavity. The index metacarpal is the most firmly fixed, while the thumb metacarpal articulates with the trapezium and acts independently from the others. The middle metacarpals are tightly united to the carpus by intrinsic interlocking bone elements at their bases. The ring metacarpal forms a transitional element of the semi-independent last metacarpal. [1]
Each consists of a body and two extremities.
Body
The body (corpus; shaft) is prismoid in form, and curved, so as to be convex in the longitudinal direction behind, concave in front.
It presents three surfaces: medial, lateral, and dorsal.
- The medial and lateral surfaces are concave, for the attachment of the interosseus muscles, and separated from one another by a prominent anterior ridge.
- The dorsal surface presents in its distal two-thirds a smooth, triangular, flattened area which is covered in by the tendons of the Extensor muscles. This surface is bounded by two lines, which commence in small tubercles situated on either side of the digital extremity, and, passing upward, converge and meet some distance above the center of the bone and form a ridge which runs along the rest of the dorsal surface to the carpal extremity. This ridge separates two sloping surfaces for the attachment of the Interossei dorsales.
To the tubercles on the digital extremities are attached the collateral ligaments of the metacarpophalangeal joints.
Base
The base or carpal extremity (basis) is of a cuboidal form, and broader behind than in front: it articulates with the carpus, and with the adjoining metacarpal bones; its dorsal and volar surfaces are rough, for the attachment of ligaments.
Head
The head or digital extremity (capitulum) presents an oblong surface markedly convex from before backward, less so transversely, and flattened from side to side; it articulates with the proximal phalanx.
It is broader, and extends farther upward, on the volar than on the dorsal aspect, and is longer in the antero-posterior than in the transverse diameter.
On either side of the head is a tubercle for the attachment of the collateral ligament of the metacarpophalangeal The metacarpophalangeal joints are of the condyloid kind, formed by the reception of the rounded heads of the metacarpal bones into shallow cavities on the proximal ends of the first phalanges, with the exception of that of the thumb, which presents more of the characters of a ginglymoid joint[citation needed]. Arthritis of the MCP is a joint.
The dorsal surface, broad and flat, supports the tendons of the extensor muscles; the volar surface is grooved in the middle line for the passage of the Flexor tendons, and marked on either side by an articular eminence continuous with the terminal articular surface.
Articulations
Besides the metacarpophalangeal joints, the metacarpal bones articulate A joint is the location at which two or more bones make contact. They are constructed to allow movement and provide mechanical support, and are classified structurally and functionally by carpometacarpal joints The carpometacarpal joints are five joints in the wrist that articulates the distal row of carpal bones and the proximal bases of the five metacarpal bones as follows:
- the first with the trapezium;
- the second with the trapezium, trapezoid, capitate and third metacarpal;
- the third with the capitate and second and fourth metacarpals;
- the fourth with the capitate, hamate, and third and fifth metacarpals;
- and the fifth with the hamate and fourth metacarpal.
Congenital disorders
The fourth and fifth metacarpal bones are commonly "blunted," or shortened, in pseudohypoparathyroidism Pseudohypoparathyroidism is a condition associated primarily with resistance to the parathyroid hormone. Patients have a low serum calcium and high phosphate, but the parathyroid hormone level is actually appropriately high (due to the hypocalcemia). Its pathogenesis has been linked to dysfunctional G Proteins (in particular, Gs alpha subunit) and pseudopseudohypoparathyroidism Pseudopseudohypoparathyroidism is an inherited disorder, named for its similarity to pseudohypoparathyroidism in presentation. The term pseudopseudohypoparathyroidism is used to describe a condition where the individual has the phenotypic appearance of pseudohypoparathyroidism type 1a, but is biochemically normal.
A blunted fourth metacarpal, with normal fifth metacarpal, can signify Turner syndrome Turner syndrome or Ullrich-Turner syndrome encompasses several conditions, of which monosomy X (absence of an entire sex chromosome) is most common. It is a chromosomal abnormality in which all or part of one of the sex chromosomes is absent (unaffected humans have 46 chromosomes, of which two are sex chromosomes). Typical females have two X.
Blunted metacarpals (particularly the fourth metacarpal) are a symptom of Nevoid basal cell carcinoma syndrome.
In other animals
In four-legged animals, the metacarpals form part of the forefeet, and are frequently reduced in number, appropriate to the number of toes. In digitigrade A digitigrade is an animal that stands or walks on its digits, or toes. Digitigrades include walking birds , cats, dogs, and most other mammals, but not humans, bears, and a few others (cf. plantigrade, unguligrade). Digitigrades are generally quicker and move more quietly than other mammals and unguligrade Ungulates are several groups of mammals, most of which use the tips of their toes, usually hoofed, to sustain their whole body weight while moving. They make up several orders of mammals, of which six to eight survive. There is some dispute as to whether Ungulata are a cladistic (evolution-based) group, or merely a phenetic group or folk taxon ( animals, the metacarpals are greatly extended and strengthened, forming an additional segment to the limb, a feature that typically enhances the animal's speed. In both birds Birds are winged, bipedal, endothermic (warm-blooded), egg-laying, vertebrate animals. There are around 10,000 living species, making them the most varied of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from the 5 cm (2 in) Bee Hummingbird to the 2.75 m (9 ft) Ostrich and bats Bats are flying mammals in the order Chiroptera . The forelimbs of bats are webbed and developed as wings, making them the only mammals naturally capable of true and sustained flight. By contrast, other mammals said to fly, such as flying squirrels, gliding possums and colugos, glide rather than fly, and only for short distances. Bats do not flap, the metacarpals form part of the wing.
See also
- Bone terminology Bones are rigid organs that form part of the endoskeleton of vertebrates. They function to move, support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue. Because bones come in a variety of shapes and have a complex internal and external structure
- Boxer's fracture A boxer's fracture is the common name for a fracture at the neck of the bones which form the knuckles of the hand. The fracture usually occurs at the neck of the fifth metacarpal, which forms the knuckle of the little finger, but the same name may also be used for a fracture at the neck of any of the metacarpals. This injury is also known as the
- Terms for anatomical location Standard anatomical terms of location are employed in science which deal with the anatomy of animals to avoid ambiguities which might otherwise arise. They are not language-specific, and thus require no translation. They are universal terms that may be readily understood by zoologists who speak any language
- Carpometacarpal bossing Carpometacarpal bossing is a condition in one of the joints between the carpus and metacarpus of the hand, called the carpometacarpal joints, where a small immovable protuberance occurs when this joint becomes swollen or bossed
Additional images
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First metacarpal bone |
Second metacarpal bone |
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Third metacarpal bone |
Fourth metacarpal bone |
Fifth metacarpal bone |
Notes
| This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be and removed. (July 2009) |
- ^ Tubiana et al 1998, p 11
References
- Tubiana, Raoul; Thomine, Jean-Michel; Mackin, Evelyn (1998). Examination of the Hand and Wrist. Taylor & Francis. ISBN The International Standard Book Number is a unique numeric commercial book identifier based upon the 9-digit Standard Book Numbering (SBN) code created by Gordon Foster, now Emeritus Professor of Statistics at Trinity College, Dublin, for the booksellers and stationers W.H. Smith and others in 1966 1853175447. http://books.google.com/books?id=G1gWHR1_J9UC&pg=PA10.
This article was originally based on an entry from a public domain Works are in the public domain if they are not covered by intellectual property rights at all, if the intellectual property rights have expired, and/or if the intellectual property rights are forfeited. Examples include the English language, the formulae of Newtonian physics, as well as the works of Shakespeare and the patents over powered flight edition of Gray's Anatomy Henry Gray's Anatomy of the Human Body, commonly shortened to Gray's Anatomy, by Henry Gray, is an English-language human anatomy textbook widely regarded as a classic work on the subject. As such, some of the information contained within it may be outdated.
Categories: Bones of the upper limb | Skeletal system | Hand
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