The human fingers are long, thin and flexible extensions of the hand, which is commonly referenced as digits. This fingers on the hand correspond to the toes of the feet. Human has five fingers on each hand, and a notable characteristic in humans is the opposable thumb. Separate from the flexibility of the human fingers, which make it such as useful appendage of the hand; there is solo a high concentration of receptors in the finger which it is also important sense organ.
Anatomy of fingers
The human finger is primarily a bony structure with various joints giving it strength and flexibility. A digit carries the hand bones, but these bones are not divided into individual appendages like a dinger. Instead is included within a single structure – the hand. Tendons connected to muscles within the hand and forearm are responsible for the different movements of the fingers.
1st finger – thumb (polex)
2nd finger – index finger (digitus secundus manus)
3rd finger – middle finger (digitus medius)
4th finger – ring finger (digitus annularis)
5th finger – little finger / pinky (digitus minimus manus)
There are two different surfaces of the fingers:
Palmar surface (front of the hand) continuous with the palms of the hand.
Dorsal surface (back of the hand including the fingernail at the tips
The finger bones are known as phalanges * single – phalanx). There are 14 phalanges on each hand. All the fingers have three phalanges excluding the thumb which has two phalanges. All three phalanx in a finger is named according to its location.
Proximal phalanx is the first finger bone resting next to the palm.
Intermediate phalanx is the middle finger bone which is about in the thumb.
Distal Phalanx is the last finger bone lying furthest away from the hand.
The hand bones are called metacarpals and correspond to the phalanges- the first metacarpal articulates with the proximal phalanx of the first finger.
Each phalanx has three portions – the base, shaft, and hand. The base of each phalanx articulates with the head of the preceding plan, notwithstanding the proximal phalanges (first finger bones) which articulate with the head the metacarpals (hand bones). The enlarged end of each phalanx ( finger bone) being either the base or head is known as the knuckle bone.
There are two types of finger joints, all of the which are commonly referred to as knuckle joints;
Between the finger bones- interphalangeal joints (finger-finger joint)
between the hand bones and first finger bones – metacphophlangeral joints (hand finger)
There are two interphalangeal joints (MCP joints) which sit between the proximal phalanx and metacarpal(hand bone). The ends of the bones involved in the joint are aligned with articular cartilage. Synovial membranes line the joint, and a tough capsule surrounds the joint.
Muscles and Movements
The muscles that guide the movement of the fingers are located in the foreman and hand. Tendons running from these muscles attach to various points on the finger bones. When the muscle contracts, the tendon is pulled, and the finger moves at the respective joint. Therefore, this muscle, although not in the finger, should be discussed briefly.
Intrsticnic muscles which are located in the hand. There are three groups thenar and hypothenar, interossei and lumbrical muscles.
Extrinsic muscle which is located in the forearm. There are two groups extensors and flexors.
The other classification of theses muscles is by the fingers movement.
- The region of the fingers where the finger move towards the palm. The muscle groups responsible are the thenar and hypothenar (intrinsic) and the flexors in the forearm (extrinsic).
- Extension of the fingers where the fingers align out by moving away from the palm. The muscle groups accountable are the interossei and lumbrical muscles (intrinsic) and the extensors in the forearm (extrinsic). Volar ligaments covering the palmar side of the IP joints prevents hyperextension.
Other movements such as abduction where the fingers fan out, away from the middle finger, and adduction where the fingers move in towards the middle finger, are also controlled by specific intrinsic and extrinsic muscles. Circumduction is when the finger moves in a circular manner.
Nerves of the Fingers:
Nerves send signals from the brain to the muscles (motor nerves) causing it to close or from receptors in the fingers leading to the brain (sensory nerves) to enable multiple sensations. The motor nerves supplying the muscles guiding the fingers is not addressed here because these muscles are positioned in the hand and forearm. It involves the median, ulnar and radial nerves.
Various nerves provide the skin of the fingers based on the following:
- Ulnar nerve – palmar and dorsal (including the back of the hand) outside of the other half of the ring finger and the little finger.
- Radial nerve – dorsal surface (excluding the tips) of the thumb, index, middle and half of the ring fingers and the web between thumb and index fingers.
- Median nerve – palmar surface, tips and nail beds of the thumb, index, middle and half of the ring fingers.