Annular ligaments of fingers
Encyclopedia
In human anatomy
, the annular ligaments of the fingers, often referred to as A pulleys and less frequently vaginal ligaments, are the annular part of the fibrous sheathes of the finger
s.
Four or five such annular pulleys, together with three cruciate pulleys, form a fibro-osseous tunnel through which passes the deep and superficial flexor tendons
. In the thumb there are two annular pulleys and a single oblique pulley.
The first annular pulley (A1 pulley), near the head of the metacarpal bone, lies in the flexor groove in the deep transverse metacarpal ligament
. All other annular pulleys are attached directly to the phalanx bones
. The second (A2) is located volarly on the shaft of the proximal phalanx; the third (A3) distally on the proximal phalanx; the fourth (A4) centrally on the middle phalanx; and, occasionally, a fifth (A5) is found on the base of the distal phalanx.
Together, the A pulleys form a continuous tunnel and, because each A pulley's attachments on the bone is wider than its roof, its shape prevents the pulley from pinching its neighbours at extremes of flexion. The short roof also minimises pressure on the tendon under tension, instead distributing pressure throughout the tunnel.
Human anatomy
Human anatomy is primarily the scientific study of the morphology of the human body. Anatomy is subdivided into gross anatomy and microscopic anatomy. Gross anatomy is the study of anatomical structures that can be seen by the naked eye...
, the annular ligaments of the fingers, often referred to as A pulleys and less frequently vaginal ligaments, are the annular part of the fibrous sheathes of the finger
Finger
A finger is a limb of the human body and a type of digit, an organ of manipulation and sensation found in the hands of humans and other primates....
s.
Four or five such annular pulleys, together with three cruciate pulleys, form a fibro-osseous tunnel through which passes the deep and superficial flexor tendons
Flexor digitorum superficialis muscle
Flexor digitorum superficialis is an extrinsic flexor muscle of the fingers at the proximal interphalangeal joints....
. In the thumb there are two annular pulleys and a single oblique pulley.
The first annular pulley (A1 pulley), near the head of the metacarpal bone, lies in the flexor groove in the deep transverse metacarpal ligament
Deep transverse metacarpal ligament
The deep transverse metacarpal ligament is a narrow fibrous band which runs across the palmar surfaces of the heads of the second, third, fourth and fifth metacarpal bones, connecting them together.It is blended with the palmar metacarpophalangeal ligaments....
. All other annular pulleys are attached directly to the phalanx bones
Phalanx bones
In anatomy, phalanx bones are those that form the fingers and toes. In primates such as humans and monkeys, the thumb and big toe have two phalanges, while the other fingers and toes consist of three. Phalanges are classified as long bones.The phalanges do not have individual names...
. The second (A2) is located volarly on the shaft of the proximal phalanx; the third (A3) distally on the proximal phalanx; the fourth (A4) centrally on the middle phalanx; and, occasionally, a fifth (A5) is found on the base of the distal phalanx.
Together, the A pulleys form a continuous tunnel and, because each A pulley's attachments on the bone is wider than its roof, its shape prevents the pulley from pinching its neighbours at extremes of flexion. The short roof also minimises pressure on the tendon under tension, instead distributing pressure throughout the tunnel.