The second metacarpal bone (metacarpal bone of the index finger

Index finger

The index finger, , is the first finger and the second digit of a human hand. It is located between the first and third digits, between the thumb and the middle finger...

) is the longest, and its base the largest, of all the metacarpal bones.

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 ulnar 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 extensor carpi radialis longus muscle

Extensor carpi radialis longus muscle

Extensor carpi radialis longus is one of the five main muscles that control movements at the wrist. This muscle is quite long, starting on the lateral side of the humerus, and attaching to the base of the second metacarpal bone .-Function:As the name suggests, this muscle is an extensor at the...

 is inserted on the dorsal surface and the flexor carpi radialis muscle

Flexor carpi radialis muscle

In anatomy, flexor carpi radialis is a muscle of the human forearm that acts to flex and abduct the hand.-Origin and insertion:This muscle originates on the medial epicondyle of the humerus...

 on the volar

Volar

Volar may refer to:*Volar, Afghanistan*Flight*Volar Airlines*Anatomical terms of location#Relative_directions_in_the_limbs**Volar arches**Volar branch of ulnar nerve**Volar radioulnar ligament**Volar carpal branch...

 surface of the base.

This bone is often the most prone to damage from fast bowlers in cricket

Cricket

Cricket is a bat-and-ball game played between two teams of 11 players on an oval-shaped field, at the centre of which is a rectangular 22-yard long pitch. One team bats, trying to score as many runs as possible while the other team bowls and fields, trying to dismiss the batsmen and thus limit the...

, 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.

Evolution

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 ape

Ape

Apes are Old World anthropoid mammals, more specifically a clade of tailless catarrhine primates, belonging to the biological superfamily Hominoidea. The apes are native to Africa and South-east Asia, although in relatively recent times humans have spread all over the world...

s, including fossil apes such as Dryopithecus

Dryopithecus

Dryopithecus was a genus of apes that is known from Eastern Africa into Eurasia during the late Miocene period. The first species of Dryopithecus was discovered at the site of Saint-Gaudens, Haute-Garonne, France, in 1856...

and Proconsul, these facets are oriented in a sagittal plane

Sagittal plane

Sagittal plane is a vertical plane which passes from front to rear dividing the body into right and left sections.-Variations:Examples include:...

. In quadrupedal monkeys these facets are oriented slightly differently due to their locomotor behaviour.
Interestingly, in Oreopithecus, a Miocene

Miocene

The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...

 hominid that went 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

Australopithecus is a genus of hominids that is now extinct. From the evidence gathered by palaeontologists and archaeologists, it appears that the Australopithecus genus evolved in eastern Africa around 4 million years ago before spreading throughout the continent and eventually becoming extinct...

.

See also

• Metacarpus
• First metacarpal bone
  First metacarpal bone
  The first metacarpal bone or the metacarpal bone of the thumb is the first bone of 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....
  
  
• Third metacarpal bone
  Third metacarpal bone
  The third metacarpal bone is a little smaller than the second.The dorsal aspect of its base presents on its radial side a pyramidal eminence, the styloid process, which extends upward behind the capitate; immediately distal to this is a rough surface for the attachment of the extensor carpi...
  
  
• Fourth metacarpal bone
  Fourth metacarpal bone
  The fourth metacarpal bone is shorter and smaller than the third.The base is small and quadrilateral; its superior surface presents two facets, a large one medially for articulation with the hamate, and a small one laterally for the capitate.On the radial side are two oval facets, for articulation...
  
  
• Fifth metacarpal bone
  Fifth metacarpal bone
  The fifth metacarpal bone is the most lateral metacarpal.-Surfaces:It presents on its base one facet on its superior surface, which is concavo-convex and articulates with the hamate, and one on its radial side, which articulates with the fourth metacarpal.On its ulnar side is a prominent tubercle...