The ulnar nerve innervates the two ulnar lumbricals. The third and fourth lumbricals originate from the ulnar aspect of the medial three flexor digitorum profundus tendons and insert at the radial lateral bands. The median nerve provides innervation to the two radial lumbricals. The first two lumbricals originate from the radial aspect of the first and second tendons of flexor digitorum profundus and insert at the radial lateral bands. If you make the shape of an L by straightening your second through fifth fingers, via the extension at the proximal interphalangeal joints, and flexion at the metacarpophalangeal joints, you are using muscles of the hand called lumbricals. This muscle allows for the adduction and flexion of the metacarpophalangeal joint. The transverse head arises at the third metacarpal and also inserts at the medial aspect of the proximal phalanx of the thumb. The oblique head originates at the capitate, second and third metacarpals, and inserts at the ulnar base of the proximal phalanx of the thumb. The adductor pollicis muscle originates from two places, the oblique and transverse heads. The adductor pollicis muscle occupies the adductor compartment. The ulnar nerve innervates all muscles of the hypothenar compartment.
#NUMBER OF HAND COMPARTMENTS SKIN#
It permits the wrinkling of the skin on the palmar surface of the hand and protects the ulnar nerve. Palmaris brevis originates at the transverse carpal ligament and inserts on the skin of the medial palm. Flexor digiti minimi brevis originates at the hook of hamate and the transverse carpal ligament and inserts at the base of the proximal phalanx of the small finger. Contraction of this muscle allows for abduction, just as the abductor pollicis brevis muscle directs the thumb away from the midline. Abductor digiti minimi originates from the pisiform bone and the tendon of flexor carpi ulnaris and inserts at the ulnar base of the proximal phalanx of the small finger. The action of the opponens pollicis and opponens digiti minimi allow for the thumb and the little finger to touch. Contraction of the opponens digiti minimi draws the small finger radially, reaching across the palm by flexion and supination, thus performing opposition. The opponens digiti minimi originates at the hook of hamate and associated transverse carpal ligament and inserts at the ulnar side of the fifth metacarpal. The hypothenar muscles act on the little finger and form a bulge on the medial palmar surface, called the hypothenar eminence, which is less prominent then the thenar eminence.
The superficial head is innervated by the median nerve while the deep head is innervated by the ulnar nerve. The flexor pollicis brevis receives dual innervation with fibers from both the median and ulnar nerves. These three muscles are all innervated by the recurrent branch of the median nerve. The f lexor pollicis brevis originates at the tubercle of the trapezium via the deep head, and the associated flexor retinaculum via the superficial head, and inserts at the base of the proximal phalanx of the thumb. Abductor pollicis brevis also acts by drawing the thumb away from the midline, which is the action of abduction for all muscles. It originates at the tubercles of the scaphoid and trapezium and inserts at the lateral aspect of the proximal phalanx of the thumb. The abductor pollicis brevis muscle is positioned anterior to the opponens pollicis and is the primary muscle providing the act of opposition. It permits the thumb to perform opposition which is the motion of reaching across the palm towards the little finger, by flexing and medially rotating the metacarpal on the axis of the trapezium. The largest of the three muscles, opponens pollicis, originates at the tubercle of the trapezium and inserts at the lateral margin of the metacarpal of the thumb. These muscles form the bulge on the palmar surface of the thumb and palm, called the thenar eminence. The thenar muscles are a group of three muscles that act on the thumb.
These muscles primarily produce fine motor movements. These muscles are divided into thenar, hypothenar, and adductor compartments. Intrinsic hand muscles originate and insert from the bones, ligaments, and fascia of the hand.
For example, muscles of the forearm that cross the carpometacarpal joint will produce flexion or extension at the wrist joint. A rule of thumb is that any muscle tendon that crosses a joint will act on that joint. The extrinsic muscles of the hand originate outside the hand, commonly the forearm, and insert into hand structures. The intrinsic muscles of the hand contain the origin and insertions within the carpal and metacarpal bones. The hand serves as the origin and/or insertion for a vast number of muscles.
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