IN-DEPTH KNOWLEDGE

Bony Landmarks and Connective Tissue Structures at the Wrist and the Ankle Regions

Bony Landmarks and Connective Tissue Structures at the Wrist and the Ankle Regions

Wrist drop, also known as radial nerve palsy, or Saturday night palsy, is a condition where a person can not extend their wrist and it hangs flaccidly. To demonstrate wrist drop, hold your arm out in front of you with your forearm parallel to the floor. With the back of your hand facing the ceiling (i.e. pronated), let your hand hang limply so that your fingers point downward. A person with wrist drop would be unable to move from this position to one in which the fingers are pointing up towards the ceiling. In anatomical parlance, the forearm is the part of the body which extends from the elbow to the wrist and is not to be confused with the arm which extends from the shoulder to the elbow. The extensor muscles in the forearm are extensor carpi ulnaris, extensor digiti minimi, extensor digitorum, extensor indicis, extensor pollicis longus, extensor pollicis brevis, extensor carpi radialis brevis, extensor carpi radialis longus. These extensor muscles are supplied by the radial nerve. Other muscles in the forearm also innervated by the radial nerve are supinator and abductor pollicis longus. Note that all these muscles are situated in the posterior half of the forearm (posterior when in the anatomical position). Also, brachioradialis, anconeus, triceps brachii, and extensor carpi radialis longus are all innervated by muscular branches of the radial nerve in the arm. The peripheral nervous system is a channel for the relay of sensory and motor impulses between the central nervous system on the one hand and the body surface, skeletal muscles, and internal organs on the other hand. It is composed of (1) spinal nerves, cranial nerves, and certain parts of the autonomic nervous system. As in the central nervous system, peripheral nervous pathways are made up of neurons (that is, nerve cell bodies and their axons and dendrites) as well as the points at which one neuron communicates with the next (that is, the synapse). The structures commonly known as nerves (or by such names as roots, rami, trunks, and branches) are actually composed of orderly arrangements of the axonal and dendritic processes of many nerve cell bodies. Cervical levels C5-C8 and thoracic level T1 contribute to the formation of the brachial plexus; small fascicles also arrive from C4 and T2. Spinal nerves from these levels converge to form superior (C5 and C6), middle (C7), and inferior (C8 and T1) trunks, which in turn split into anterior and posterior divisions. The divisions then form cords (posterior, lateral, and medial), which provide motor, sensory, and autonomic fibers to the shoulder and upper extremity.

The median nerve is a nerve in humans and other animals. It is in the upper limb. It is one of the five main nerves originating from the brachial plexus.

The median nerve is formed from parts of the medial and lateral cords of ...