These arteries form three arches over the dorsal and palmar aspects of the hand, the dorsal carpal arch (across the back of the hand), the deep palmar arch, and the superficial palmar arch. Together these three arches and their anastomoses provide oxygenated blood to the palm, the fingers, and the thumb. The hand is drained by the dorsal venous network of the hand with deoxygenated blood leaving the hand via the cephalic vein and the basilic vein. Skin
The glabrous (hairless) skin on the front of the hand, the palm, is relatively thick and can be bent along the hands flexure lines where the skin is tightly bound to the underlying tissue and bones. Compared to the rest of the bodys skin, the hands palms (as well as the soles of the feet) are usually lighter—and even much lighter in dark-skinned individuals, compared to the other side of the hand. Indeed, genes specifically expressed in the dermis of palmoplantar skin inhibit melanin production and thus the ability to tan, and promote the thickening of the stratum lucidum and stratum corneum layers of the epidermis. All parts of the skin involved in grasping are covered by papillary ridges (fingerprints) acting as friction pads. In contrast, the hairy skin on the dorsal side is thin, soft, and pliable, so that the skin can recoil when the fingers are stretched.
The nerve is particularly vulnerable to injury when there has been a disruption in the normal anatomy. The most common site of ulnar nerve entrapment is at the elbow, followed by the wrist.Causes or structures which have been reported to cause ulnar nerve entrapment include:
Problems originating at the neck: thoracic outlet syndrome, cervical spine pathology, compression by anterior scalene muscles
Problems originating in the chest: compression by pectoralis minor muscles
Brachial plexus abnormalities
Elbow: fractures, growth plate injuries, cubital tunnel syndrome, flexorpronator aponeurosis, arcade of Struthers
Forearm: tight flexor carpi ulnaris muscles
Wrist: fractures, ulnar tunnel syndrome, hypothenar hammer syndrome
Artery aneurysms or thrombosis
Other: Infections, tumors, diabetes, hypothyroidism, rheumatism, and alcoholism

Cubital tunnel syndrome
The most common location of ulnar nerve impingement at the elbow is within the cubital tunnel, and is known as cubital tunnel syndrome. The tunnel is formed by the medial epicondyle of the humerus, the olecranon process of the ulna and the tendinous arch joining the humeral and ulnar heads of the flexor carpi ulnaris muscle. While most cases of injury are minor and resolve spontaneously with time, chronic compression or repetitive trauma may cause more persistent problems. Commonly cited scenarios include:

Sleeping with the arm folded behind neck, elbows bent. Pressing the elbows upon the arms of a chair while typing. Resting or bracing the elbow on the arm rest of a vehicle. Bench pressing. Intense exercising and strain involving the elbow.Compression of the ulnar nerve at the medial elbow may occasionally be caused by an epitrocheloanconeus muscle, an anatomical variant.