Metacarpus

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Metacarpals
Metacarpal bones (left hand) 01 palmar view with label.png
Metacarpus shown in red. Left hand, anterior (palmar) view.
Metacarpus ant with label.png
The five metacarpal bones, numbered. Left hand, anterior (palmar) view.
Latinossa metacarpalia
Gray'ssubject #55 227
OriginsCarpus
InsertionsProximal phalanges   
ArticulationsCarpometacarpal, intermetacarpal, metacarpophalangeal  
MeSHMetacarpus
TAA02.4.09.001
FMAFMA:71336
 
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Metacarpals
Metacarpal bones (left hand) 01 palmar view with label.png
Metacarpus shown in red. Left hand, anterior (palmar) view.
Metacarpus ant with label.png
The five metacarpal bones, numbered. Left hand, anterior (palmar) view.
Latinossa metacarpalia
Gray'ssubject #55 227
OriginsCarpus
InsertionsProximal phalanges   
ArticulationsCarpometacarpal, intermetacarpal, metacarpophalangeal  
MeSHMetacarpus
TAA02.4.09.001
FMAFMA:71336

In human anatomy, the metacarpus is the intermediate part of the hand skeleton that is located between the phalanges (bones of the fingers) and the carpus which forms the connection to the forearm. The metacarpus consists of metacarpal bones. Its equivalent in the foot is the metatarsus.

Human anatomy[edit]

Left hand shown with thumb on left.

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 metacarpal bone consists of a body and two extremities (head and base).

Body[edit]

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.

[2]

Base[edit]

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.

[2]

Head[edit]

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 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.

[2]

Articulations[edit]

Besides the metacarpophalangeal joints, the metacarpal bones articulate by carpometacarpal joints as follows:

  1. the first with the trapezium;
  2. the second with the trapezium, trapezoid, capitate and third metacarpal;
  3. the third with the capitate and second and fourth metacarpals;
  4. the fourth with the capitate, hamate, and third and fifth metacarpals;
  5. and the fifth with the hamate and fourth metacarpal;

Insertions[edit]

Extensor Carpi Radialis Longus/Brevis: Both insert on the base of metacarpal II; Assist with wrist extension and radial flexion of the wrist

Extensor Carpi Ulnaris: Inserts on the base of metacarpal V; Extends and fixes wrist when digits are being flexed; assists with ulnar flexion of wrist

Abductor Pollicis Longus: Inserts on the trapezium and base of metacarpal I; Abducts thumb in frontal plane; extends thumb at carpometacarpal joint

Opponens Pollicis: Inserts on metacarpal I; flexes metacarpal I to oppose the thumb to the fingertips

Opponens digiti minimi: Inserts on the medial surface of metacarpal V; Flexes metacarpal V at carpometacarpal joint when little finger is moved into opposition with tip of thumb; deepens palm of hand.[3]

Congenital disorders[edit]

The fourth and fifth metacarpal bones are commonly "blunted" or shortened, in pseudohypoparathyroidism and pseudopseudohypoparathyroidism.

A blunted fourth metacarpal, with normal fifth metacarpal, can signify Turner syndrome.

Blunted metacarpals (particularly the fourth metacarpal) are a symptom of Nevoid basal cell carcinoma syndrome.

Fracture[edit]

The neck of a metacarpal (in the transition between the body and the head) is a common location for a boxer's fracture.

In other animals[edit]

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 and unguligrade 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 and bats, the metacarpals form part of the wing.

See also[edit]

Additional images[edit]

Notes[edit]

  1. ^ Tubiana et al 1998, p 11
  2. ^ a b c Gray's Anatomy. (See infobox)
  3. ^ Saladin, Kenneth S. "Capt. 10." Anatomy & Physiology: the Unity of Form and Function. Dubuque: McGraw-Hill, 2010. 361-64. Print.

This article incorporates text from a public domain edition of Gray's Anatomy.

References[edit]