Phalanges (of hand)
The phalanges (Latin: phalanx, pl. phalanges) are bones of the fingers that are found in both hands and feet. There are fourteen phalanges within the skeleton of a hand (or foot). The human thumb has two phalanges - proximal and distal, while the rest of the digits have three - proximal, middle, and distal phalanges.
The three phalanges of each finger articulate with one another, forming interphalangeal joints. The proximal phalanges also articulate with the metacarpal bones of the hand to form metacarpophalangeal joints.
Each phalanx has three parts:
- base - at its proximal end;
- body - in the middle of the bone;
- head - at its distal end.
The base or proximal extremity of each phalanx of the first row present oval, concave articular surfaces, while the bases of second-row and third-row phalanges each presents a double concavity separated by a median ridge.
The body or shaft of each phalanx is concave on the palmar surface and convex on the dorsal surface, while the sides of the body have rough areas for attachment of fibrous sheaths of flexor tendons.
The heads or distal extremities of phalanges are smaller than the bases, and each ends in two condyles, forming knuckles.
The proximal phalanges (Latin: phalanx proximalis, pl. phalanges proximales) are the most proximal digital bones in the hand (or foot). Five proximal phalanges correspond to each of the five fingers.
Each proximal phalanx has a proximal end or base with a transverse oval articular facet for communicating with the associated metacarpal bone. The shaft of each proximal phalanx is long and flat on its palmar aspect. They are convex both dorsally and transversally. The lateral and medial borders are sharpened for the attachment of the tendons of the flexor muscles. Distally, the head of the proximal phalanx has an articular surface that communicates with the middle phalanx, or in the case of the thumb, with the distal phalanx.
The middle phalanges (also known as intermediate phalanges, Latin: phalanx media, pl. phalanges mediae) lie between the proximal and distal phalanges of the hand (or foot).
There are four middle phalanges. They are present in each digit of the hand, except for the thumb (or big toe in the foot). They have the same three parts as the proximal phalanges, but their shafts are much shorter. The base of each middle phalanx has a medial and lateral facet that surrounds a smooth midline groove, which contacts the distal end of the proximal phalanx. Distally, the head of each middle phalanx articulates with the corresponding basis of the distal phalanx.
The distal phalanges (Latin: phalanx distalis, pl. phalanges distales) are the digital bones found in the tips of the fingers of the hand (or toes of the foot). There are five distal phalanges in each hand (or foot).
Each distal phalanx is tapered distally and has a broader proximal base for articulation with the middle phalanx, or the proximal phalanx in the case of the thumb. The distal surfaces of the distal phalanges are rough, especially on their palmar aspect, where the tendon of the flexor digitorum profundus inserts. Dorsally, the head of the distal phalanx presents a rough, elevated surface that faces the palmar direction - the tuberosity of the distal phalanx.