| Second metacarpal bone | |
|---|---|
 Second metacarpal of the left hand (shown in red). Palmar view. | |
 The second metacarpal. (Left.) | |
| Details | |
| Identifiers | |
| Latin | os metacarpale II |
| FMA | 23900 |
| Anatomical terms of bone | |
The second metacarpal bone (metacarpal bone of the index finger ) is the longest, and its base the largest, of all the metacarpal bones. [1]
Its base is prolonged upward and medialward, forming a prominent ridge. [1]
It presents four articular facets, three on the upper surface and one on the ulnar side: [1]
The extensor carpi radialis longus muscle is inserted on the dorsal surface and the flexor carpi radialis muscle on the volar surface of the base. [1] The shaft gives origin to the first palmar interosseus and the first and second dorsal interossei.
This bone is often the most prone to damage from fast bowlers in cricket, as it is furthest down the bat handle on both left- and right-handers, and as such is in danger of being struck by balls that are pitched short. [2]
The articulation between the second metacarpal and the capitate is considered uniquely specialized in hominids. On the second metacarpal, the facet for the capitate is directed proximally, almost perpendicular to the facet for the third metacarpal, while the corresponding facet on the capitate is oriented distally. This is to receive compressive forces generated by the pad-to-pad opposition between the thumb and the index finger. In contrast, in apes, including fossil apes such as Dryopithecus and Proconsul , these facets are oriented in a sagittal plane. In quadrupedal monkeys these facets are oriented slightly differently due to their locomotor behaviour. [3]
In Oreopithecus , a Miocene hominid that became extinct 7 million years ago, the orientation of the facet on the second metacarpal is similar to human conditions — an indication that it had the capability of pad-to-pad precision grip. Oreopithecus also lacks the waisted capitate associated with apes and climbing still present in Australopithecus . [3]
The metacarpal bone of the index finger has two centres of ossification: a primary centre in the shaft and a secondary centre in the head. This contrasts to the first metacarpal bone where the secondary centre is found in the base. The ossification process begins in the shaft during prenatal life, and in the head between 11th and 22nd months. [4]
This article incorporates text in the public domain from page 228 of the 20th edition of Gray's Anatomy (1918)
The carpal bones are the eight small bones that make up the wrist (carpus) that connects the hand to the forearm. The term "carpus" and "carpal" is derived from the Latin carpus and the Greek καρπός (karpós), meaning "wrist". In human anatomy, the main role of the carpal bones is to articulate with the radial and ulnar heads to form a highly mobile condyloid joint, to provide attachments for thenar and hypothenar muscles, and to form part of the rigid carpal tunnel which allows the median nerve and tendons of the anterior forearm muscles to be transmitted to the hand and fingers.
The thumb is the first digit of the hand, next to the index finger. When a person is standing in the medical anatomical position, the thumb is the outermost digit. The Medical Latin English noun for thumb is pollex, and the corresponding adjective for thumb is pollical.
In human anatomy, the wrist is variously defined as (1) the carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand; (2) the wrist joint or radiocarpal joint, the joint between the radius and the carpus and; (3) the anatomical region surrounding the carpus including the distal parts of the bones of the forearm and the proximal parts of the metacarpus or five metacarpal bones and the series of joints between these bones, thus referred to as wrist joints. This region also includes the carpal tunnel, the anatomical snuff box, bracelet lines, the flexor retinaculum, and the extensor retinaculum.
In human anatomy, extensor carpi radialis brevis is a muscle in the forearm that acts to extend and abduct the wrist. It is shorter and thicker than its namesake extensor carpi radialis longus which can be found above the proximal end of the extensor carpi radialis brevis.
The trapezoid bone is a carpal bone in tetrapods, including humans. It is the smallest bone in the distal row of carpal bones that give structure to the palm of the hand. It may be known by its wedge-shaped form, the broad end of the wedge constituting the dorsal, the narrow end the palmar surface; and by its having four articular facets touching each other, and separated by sharp edges. It is homologous with the "second distal carpal" of reptiles and amphibians.
The trapezium bone is a carpal bone in the hand. It forms the radial border of the carpal tunnel.
In human anatomy, the metacarpal bones or metacarpus, also known as the "palm bones", are the appendicular bones that form the intermediate part of the hand between the phalanges (fingers) and the carpal bones, which articulate with the forearm. The metacarpal bones are homologous to the metatarsal bones in the foot.
The capitate bone is a bone in the human wrist found in the center of the carpal bone region, located at the distal end of the radius and ulna bones. It articulates with the third metacarpal bone and forms the third carpometacarpal joint. The capitate bone is the largest of the carpal bones in the human hand. It presents, above, a rounded portion or head, which is received into the concavity formed by the scaphoid and lunate bones; a constricted portion or neck; and below this, the body. The bone is also found in many other mammals, and is homologous with the "third distal carpal" of reptiles and amphibians.
The hamate bone, or unciform bone, Latin os hamatum and occasionally abbreviated as just hamatum, is a bone in the human wrist readily distinguishable by its wedge shape and a hook-like process ("hamulus") projecting from its palmar surface.
Oreopithecus is an extinct genus of hominoid primate from the Miocene epoch whose fossils have been found in today's Tuscany and Sardinia in Italy. It existed nine to seven million years ago in the Tusco-Sardinian area when this region was an isolated island in a chain of islands stretching from central Europe to northern Africa in what was becoming the Mediterranean Sea.
The upper limbs or upper extremities are the forelimbs of an upright-postured tetrapod vertebrate, extending from the scapulae and clavicles down to and including the digits, including all the musculatures and ligaments involved with the shoulder, elbow, wrist and knuckle joints. In humans, each upper limb is divided into the arm, forearm and hand, and is primarily used for climbing, lifting and manipulating objects.
The flexor carpi ulnaris (FCU) is a muscle of the forearm that flexes and adducts at the wrist joint.
The carpometacarpal (CMC) joints are five joints in the wrist that articulate the distal row of carpal bones and the proximal bases of the five metacarpal bones.
The fifth metacarpal bone is the most medial and second-shortest of the metacarpal bones.
The fourth metacarpal bone is shorter and smaller than the third.
The third metacarpal bone is a little smaller than the second.
The first metacarpal bone or the metacarpal bone of the thumb is the first bone proximal to the thumb. It is connected to the trapezium of the carpus at the first carpometacarpal joint and to the proximal thumb phalanx at the first metacarpophalangeal joint.
The Palmar carpometacarpal ligaments are a series of bands on the palmar surface of the carpometacarpal joints that connect the carpal bones to the second through fifth metacarpal bones. The second metacarpal is connected to the trapezium. The third metacarpal is connected to the trapezium, to the capitate, and to the hamate. The fourth and fifth metacarpals are connected to the hamate.
A hand is a prehensile, multi-fingered appendage located at the end of the forearm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs. A few other vertebrates such as the koala are often described as having "hands" instead of paws on their front limbs. The raccoon is usually described as having "hands" though opposable thumbs are lacking.
The extrinsic extensor muscles of the hand are located in the back of the forearm and have long tendons connecting them to bones in the hand, where they exert their action. Extrinsic denotes their location outside the hand. Extensor denotes their action which is to extend, or open flat, joints in the hand. They include the extensor carpi radialis longus (ECRL), extensor carpi radialis brevis (ECRB), extensor digitorum (ED), extensor digiti minimi (EDM), extensor carpi ulnaris (ECU), abductor pollicis longus (APL), extensor pollicis brevis (EPB), extensor pollicis longus (EPL), and extensor indicis (EI).
