Nerve

German: Nerv
Latin: Nervus

1 Definition

A nerve is an anatomical structure which transmits stimuli. A nerve consists of numerous nerve fibers and the connective tissue surrounding each of them.

2 Histology

Nerves can be described in more details by its histology. The nerve consists of tissue that can be distingushed by three zones:

2.1 Endoneurium

The endoneurium is the loose connective tissue that surrounds the Schwann cells of each single nerve fiber. The Schwann cells as well as the numerous nerve fibers are supplied by many small blood- and lymph vessels. There are only a few free cells (eg. macrophages) present.

2.2 Perineurium

The perineurium is dense connective tissue that fuses many single nerve fibers to one bundle, called fascicle. It supports and seperates the nerve – comparable to a cable. The connective tissue cells are connected tightly to each other by so-called tight junctions (like in epithelium).

2.3 Epineurium

The epineurium surrounds the nerve and is supplying greater vessels. It consists of connective tissue with many collagen fibers. This tissue can have additional loose connective tissue or fatty tissue.

3 Classification

3.1 …by function

One divides the fibers by their function:

• motoric nerves
• sensoric nerves
• mixed nerves

3.2 …by topography

Another way to describe and distinguish the fibers is by their origin:

• cranial nerves: Nerves that arise directly from the brain
• spinal nerves: Nerves that arise from spinal cord
• peripheral nerves: Nerves that supply organs; are the final pathway of the sensorimotor and autonomous nervous system

4 Clinic

The inflammation of a nerve is called neuritis. The neuritis can be a mononeuritis or a polyneuritis. It depends on the number of inflammed nerves what kind of neuritis it is.