The second metacarpal bone (metacarpal bone of the

index finger The index finger (also referred to as forefinger, first finger, second finger, pointer finger, trigger finger, digitus secundus, digitus II, and many other terms) is the second digit of a human hand. It is located between the thumb and the m ...

) is the longest, and its base the largest, of all the

metacarpal bones 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 ( wrist bones), which articulate ...

.''

Gray's Anatomy ''Gray's Anatomy'' is a reference book of human anatomy written by Henry Gray, illustrated by Henry Vandyke Carter and first published in London in 1858. It has had multiple revised editions, and the current edition, the 42nd (October 2020 ...

'' (1918). See infobox.

Human anatomy

Its base is prolonged upward and medialward, forming a prominent ridge. It presents four articular facets, three on the upper surface and one on the

ulna The ulna or ulnar bone (: ulnae or ulnas) is a long bone in the forearm stretching from the elbow to the wrist. It is on the same side of the forearm as the little finger, running parallel to the Radius (bone), radius, the forearm's other long ...

r side: * Of the facets on the upper surface: ** the ''intermediate'' is the largest and is concave from side to side, convex from before backward for articulation with the lesser multangular; ** the ''lateral'' is small, flat and oval for articulation with the greater multangular; ** the ''medial'', on the summit of the ridge, is long and narrow for articulation with the capitate. * The facet on the ulnar side articulates with the

third metacarpal The third metacarpal bone (metacarpal bone of the middle finger) is a little smaller than the second. The dorsal aspect of its base presents on its radial side a pyramidal eminence, the Third metacarpal styloid process, styloid process, which ext ...

. 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. 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 Cricket is a Bat-and-ball games, bat-and-ball game played between two Sports team, teams of eleven players on a cricket field, field, at the centre of which is a cricket pitch, pitch with a wicket at each end, each comprising two Bail (cr ...

, 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.Laven, Kate. "West Indies' Courtney Walsh still in love with cricket." Daily Telegraph ondon5 May 2009 Print.

Evolution

The articulation between the second metacarpal and the capitate is considered uniquely specialized in

hominid The Hominidae (), whose members are known as the great apes or hominids (), are a taxonomic family of primates that includes eight extant species in four genera: '' Pongo'' (the Bornean, Sumatran and Tapanuli orangutan); '' Gorilla'' (the ...

s. 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

ape Apes (collectively Hominoidea ) are a superfamily of Old World simians native to sub-Saharan Africa and Southeast Asia (though they were more widespread in Africa, most of Asia, and Europe in prehistory, and counting humans are found global ...

s, including fossil apes such as ''

Dryopithecus ''Dryopithecus'' is a genus of extinct great apes from the middle–late Miocene boundary of Europe 12.5 to 11.1 million years ago (mya). Since its discovery in 1856, the genus has been subject to taxonomic turmoil, with numerous new species b ...

'' and ''

Proconsul A proconsul was an official of ancient Rome who acted on behalf of a Roman consul, consul. A proconsul was typically a former consul. The term is also used in recent history for officials with delegated authority. In the Roman Republic, military ...

'', these facets are oriented in a

sagittal plane The sagittal plane (; also known as the longitudinal plane) is an anatomical plane that divides the body into right and left sections. It is perpendicular to the transverse and coronal planes. The plane may be in the center of the body and divi ...

. In

quadrupedal Quadrupedalism is a form of Animal locomotion, locomotion in which animals have four legs that are used to weight-bearing, bear weight and move around. An animal or machine that usually maintains a four-legged posture and moves using all four l ...

monkeys these facets are oriented slightly differently due to their locomotor behaviour. In '' Oreopithecus'', a

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

hominid that became extinct , 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 ''Australopithecus'' (, ; or (, ) is a genus of early hominins that existed in Africa during the Pliocene and Early Pleistocene. The genera ''Homo'' (which includes modern humans), ''Paranthropus'', and ''Kenyanthropus'' evolved from some ''Aus ...

''.

Ossification

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.

Additional images

File:Second metacarpal bone (left hand) - animation01.gif, Second metacarpal bone of the left hand (shown in red). Animation. File:Second metacarpal bone (left hand) - animation02.gif, Second metacarpal bone of the left hand. Close up. File:Gray219 - Second metacarpal bone.png, Palmer view of the left hand (second metacarpal shown in yellow). File:Gray220 - Second metacarpal bone.png, Dorsal view of the left hand (second metacarpal shown in yellow). File:Slide6val.JPG, Second metacarpal bone.Deep dissection.

Notes

References