What Is the Ulnar Nerve?

It originates from the medial brachial plexus and contains fibers of the seventh and eighth cervical nerves and the first thoracic nerve. Accompanied by the brachial artery at first, then left the brachial artery downward and downward, to the ulnar nerve groove behind the medial and superior iliac crest. The ulnar nerve is superficial in the groove and can be touched by the skin. Then pass down the ulnar carpi flexor muscle to the inside of the forearm, and descend along the superficial digital flexor and ulnar carpi flexor muscle. At the junction of the forearm middle and lower 1/3, it is divided into thicker palm branches and thinner Dorsal branch of hand. The ulnar nerve does not branch in the arm, and the muscular branch is issued on the upper forearm to the ulnar carpi flexor and the ulnar digit of the deep flexor flexor; the thin cutaneous branch is issued in the middle and passes through the deep fascia and is distributed in small fish Skin.

It originates from the medial brachial plexus and contains fibers of the seventh and eighth cervical nerves and the first thoracic nerve. Accompanied by the brachial artery at first, then left the brachial artery downward and downward, to the ulnar nerve groove behind the medial and superior iliac crest. The ulnar nerve is superficial in the groove and can be touched by the skin. Then pass down the ulnar carpi flexor muscle to the inside of the forearm, and descend along the superficial digital flexor and ulnar carpi flexor muscle. At the junction of the forearm middle and lower 1/3, it is divided into thicker palm branches and thinner Dorsal branch of hand. The ulnar nerve does not branch in the arm, and the muscular branch is issued on the upper forearm to the ulnar carpi flexor and the ulnar digit of the deep flexor flexor; the thin cutaneous branch is issued in the middle and passes through the deep fascia and is distributed in small fish. Skin.

Chinese name

Ulnar nerve

Foreign name

ulnar nerve

At

Wrist

Sensory branch

Palmar branch

Overview of the ulnar nerve

The ulnar nerve (C7 T1) is on the wrist, and the ulnar nerve penetrates outside the wrist

Ulnar nerve anatomy

The shallow side of the flexor support band and the deep side of the palmar aponeurosis enter the palm.

The ulnar nerve in the forearm innervates the ulnar carpi flexor (wrist flexion to the ulnar side), the third and fourth finger deep flexors (flexion of the phalanx at the end of the fourth and fifth fingers), and the short palmar muscle (proximal ulnar side Skin and muscle), little finger abductor (little finger abduction), little finger to palm muscle (little finger to palm), little finger flexor (little finger flexion), third and fourth vermiform muscles (fourth and fifth finger metacarpophalangeal joint flexion and near Interphalangeal joint extension), Interosseous muscle (flexion of the metacarpophalangeal joint and straightening of the proximal interphalangeal joint), Adductor hallucis (Adduction of the thumb and palm) and Deep head of the short flexor hallucis (flexion of thumb 1st knuckle) ).

The ulnar nerve has the following sensory branches: palmar cutaneous branch, which distributes the skin on the surface of the ichthyus muscle; dorsal cutaneous branch, which is distributed on the ulnar side of the back of the hand and the ulnar side of the little finger and ring finger; Distributed on the skin on the distal side of the ulnar side of the palm and the skin on the palm of the ulnar side of the little finger and ring finger

When the ulnar nerve is injured in the arm, the wrist flexion ability is weakened, the distal phalanx of flexion of 4 and 5 fingers cannot flex and the thumb adduction force is weak. The small fish muscles and interosseous muscles are obviously atrophied, and the fingers cannot be close to each other. Each metacarpophalangeal joint is overextended, and the interphalangeal joints of the fourth and fifth fingers are curved, which is called a "claw-shaped hand". The sensory disturbance is mainly the medial edge of the hand. After the ulnar nerve injury, the ulnar side of the little finger and ring finger disappeared, and the paper clip test and Froment sign were positive. It is a method to check the paralysis of the adductor of the thumb.

Ulnar nerve forearm

Walking behavior of the ulnar nerve in the forearm: The superficial surface of the autogenous trunk flexor support belt is accompanied by the ulnar side of the ulnar artery into the palm.

High-frequency ultrasound of ulnar nerve

The cross section of the ulnar nerve at the elbow canal shows a circular or elliptical hypoechoic structure, located between the ulna olecranon and the internal epicondyle of the humerus, immediately adjacent to the internal epicondyle of the humerus, with clear boundaries and strong echoes in the surrounding tissue. In longitudinal section, the ulnar nerve presents several low echoes arranged in parallel, separated by a few parallel linear strong echoes, and the diameter of the tube narrows uniformly from the proximal side to the distal side. Tracing down the ulnar nerve transversely, it can be seen that the ulnar nerve travels in the ulnar carpi flexor muscle, then turns from the dorsal side to the ulnar side, and walks between the ulnar carpi flexor and deep finger flexor muscles. The nerve echo is slightly stronger, and the cross section is a fine mesh echo. At the mid-distal part of the forearm, the ulnar nerve was accompanied by ulnar movements and veins, and color Doppler showed pulsating ulnar artery echoes nearby.

Observation of two-dimensional image of ulnar nerve continuous section

(A) the beginning:

The ulnar nerve originates from the medial bundle of the brachial plexus. Here, the number of internal nerve bundles of the ulnar nerve is 11, mainly mixed nerve bundles.

(B) the arm:

The ulnar nerve descends along the medial side of the brachial artery to the height of the deltoid muscle through the medial muscle space to the back of the arm. Here, the number of internal nerve bundles of the ulnar nerve has increased to 16, including 13 mixed nerve bundles mainly composed of motor nerve fibers. There are 3 mixed nerve bundles mainly composed of sensory nerve fibers. No branch of ulnar nerve in the arm.

(3) Elbow:

The ulnar nerve descends into the ulnar nerve groove between the humerus epicondyle and the ulna olecranon. Here, the number of internal nerve bundles of the ulnar nerve is 12, among which 4 are mixed nerve bundles mainly composed of motor nerve fibers, and sensory nerves. There are 2 fiber-based mixed nerve bundles and 6 mixed nerve bundles.

(4) Forearm:

The ulnar nerve passes from below the medial epicondyle of the humerus and passes between the two heads of the ulnar carpi flexor muscles, from the dorsal side to the medial side of the forearm palmar surface. At the upper part of the forearm, muscles innervate the ulnar carpi flexor and deep finger flexors Ruler side. Here, the number of nerve bundles in the main ulnar nerve is 18, including 3 mixed nerve bundles mainly composed of motor nerve fibers, 5 mixed nerve bundles mainly composed of sensory nerve fibers, and 10 mixed nerve bundles; 2 motor nerves The bundle constitutes the muscular branch. The ulnar nerve continues to descend between the ulnar carpi flexor and the deep digital flexor, medial to the ulnar artery, and the dorsal branch of the hand is issued above the radial wrist joint. Here, the ulnar nerve trunk is composed of 5 mixed nerve bundles and 1 mixed nerve bundle mainly composed of motor nerve fibers; the dorsal branch nerve is 4 mixed nerve bundles mainly composed of sensory nerve fibers, which are distributed in the ulnar side and The skin on the back of the ulnar side of the little finger, ring finger and middle finger. The main stem descends along the radial side of the pea bone.

(5) Wrist:

The ulnar nerve descends on the radial side of the pea bone, and the shallow surface of the flexor support band is divided into two shallow and deep branches, and enters the palm through the deep side of the palmar aponeurosis. Here, the number of deep ulnar nerve bundles is 10, including 4 mixed nerve bundles mainly composed of motor nerve bundles and 6 mixed nerve bundles, which control the small fish muscles, the adductor hallus muscles, the interosseous muscles, and the third, 4 Vermiform muscles; the number of superficial branch nerve bundles is 2, mainly sensory nerve bundles, distributed in the skin of the phalanx of the small fish, the little finger and the ulnar side of the ring finger.