Table of Contents
Anatomy of the Hand
The hand is a complex structure made up of bones, ligaments, muscles, and nerves. The hand has four metacarpal bones, five digits, and several small bones in the palm. The metacarpals are the long bones in the palm of the hand, and the digits are the fingers and thumb. The bones in the palm are the carpal bones. The carpal bones are arranged in two rows. The proximal row has the scaphoid, lunate, and triquetral bones. The distal row has the trapezium, trapezoid, capitate, and hamate bones.
The muscles of the hand are divided into three groups: the extrinsic muscles, the intrinsic muscles, and the adductor muscles. The extrinsic muscles are the muscles that attach to the hand bones and originate in the forearm. The intrinsic muscles are the muscles that originate in the hand and attach to the hand bones. The adductor muscles are the muscles that attach to the fingers and thumb and close the hand.
The nerves of the hand are divided into three groups: the radial nerve, the median nerve, and the ulnar nerve. The radial nerve supplies the muscles on the back of the hand and the thumb. The median nerve supplies the muscles on the palm of the hand. The ulnar nerve supplies the muscles on the little finger and the inside of the hand.
Bones of the Hand
The bones of the hand are the carpals, metacarpals, and phalanges. The carpals are the eight small bones in the wrist, the metacarpals are the five long bones in the hand, and the phalanges are the 14 small bones in the fingers. The carpals, metacarpals, and phalanges are all connected by ligaments.
Proximal Row (Lateral to Medial)
There are four bones in the proximal row of the wrist: the scaphoid, the lunate, the triquetrum, and the pisiform. The bones are arranged laterally to medial. The scaphoid is the most lateral, and the pisiform is the most medial.
Distal Row (Lateral to Medial)
The distal row (lateral to medial) is the row of bones that make up the back of the hand. These bones are located in the fingers and thumb. The distal row is made up of the:
Thumb bone (proximal phalanx)
First finger bone (distal phalanx)
Second finger bone (distal phalanx)
Third finger bone (distal phalanx)
Fourth finger bone (distal phalanx)
Muscles of the Hand
The hand muscles can be divided into three groups: the extrinsic muscles, the intrinsic muscles, and the adductor muscles.
The extrinsic muscles are the muscles that originate from the bones of the arm and insert into the hand. The four muscles in this group are the flexor carpi radialis, the flexor carpi ulnaris, the palmaris longus, and the pronator teres. These muscles control the movement of the hand and the fingers.
The intrinsic muscles are the muscles that originate and insert in the hand itself. There are twelve muscles in this group. These muscles control the movement of the fingers, and the thumb.
The adductor muscles are the muscles that attach to the fingers and thumb and pull them towards the palm. There are three muscles in this group.
Thenar Muscles
The thenar muscles are a group of muscles located on the palm of the hand. They are responsible for movement of the thumb and are innervated by the radial nerve. The thenar muscles are made up of the abductor pollicis brevis, flexor pollicis brevis, and opponens pollicis muscles.
Hypothenar Muscles
The hypothenar muscles are a group of five muscles located on the palm of the hand. They are named for their location on the palm, below the thumb. The hypothenar muscles are responsible for the movement of the little finger and the thumb. They are also responsible for the movement of the skin on the palm of the hand.
Lumbrical Muscles
The lumbrical muscles are four small muscles that originate from the tendons of the flexor digitorum profundus muscles. They insert into the medial sides of the proximal phalanges of the second to fifth toes.
The lumbrical muscles are responsible for flexing the toes at the metatarsophalangeal joints.
Palmar Interossei Muscles
Origin:
The palmar interossei muscles originate from the medial sides of the metacarpal bones.
Insertion:
The palmar interossei muscles insert into the proximal phalanges of the fingers.
Action:
The palmar interossei muscles adduct the fingers.
Dorsal Interossei Muscles
The dorsal interossei muscles are four small muscles located on the back of the hand. They originate from the metacarpal bones and insert into the proximal phalanges. The dorsal interossei muscles are responsible for abducting (moving away from the body) and adducting (moving towards the body) the fingers.
