ganglion

Definition

A ganglion is a small, usually hard bump above a tendon or in the capsule that encloses a joint. A ganglion is also called a synovial hernia or synovial cyst.

Description

A ganglion is a non-cancerous cyst filled with a thick, jelly-like fluid. Ganglions can develop on or beneath the surface of the skin and usually occur between the ages of 20 and 40.

Most ganglions develop on the hand or wrist. This condition is common in people who bowl or who play handball, raquetball, squash, or tennis. Runners and athletes who jump, ski, or play contact sports often develop foot ganglions.

— Maureen Haggerty

1. Anatomy. A group of nerve cells forming a nerve center, especially one located outside the brain or spinal cord.
2. A center of power, activity, or energy.
3. Pathology. A benign cystic lesion resembling a tumor, occurring in a tendon sheath or joint capsule.

[From Greek, cystlike tumor, nerve bundle.]

For more information on ganglion, visit Britannica.com.

A group of nerve cell bodies, usually located outside the brain and spinal cord. A ganglion located inside the central nervous system is called a nucleus.

The dorsal root ganglia are rounded clusters of cell bodies and fibers, surrounded by a connective tissue covering, located on the dorsal, or sensory, root of each spinal nerve. Other ganglia are given specific names which indicate their function or location, such as acoustic, cardiac, carotid, jugular, celiac, and sympathetic ganglia. Sympathetic ganglia, lying on either side of the vertebral column, unite by fiber strands to form a sympathetic chain. See also Sympathetic nervous system.

The term ganglion may be applied to a tumorlike, often cystic growth found on tendons, joints, and other connective tissues, but this usage is rare. See also Brain; Spinal cord.

Any collection or mass of nerve cells that serves as a center of nervous influence.

1. A cyst-like mass of fibrous tissue on a tendon or in an aponeurosis. The ganglion is a fibrous sac that fills with fluid. It develops into a relatively painless swelling on the top of the wrist, where its formation is triggered by irritation of the tendons that run across the top of the wrist joint. Ganglia also commonly occur on the top of the feet. If painless, they are usually left; if painful during an activity, for example, during golf or racket sports, medical advice should be sought. A ganglion may be aspirated with a needle to release the viscous fluid, or surgically removed.

2. A collection of neurone cell bodies located outside the central nervous system.

Pertaining to a ganglion.

• g. blockade — inhibition by drugs of nerve impulse transmission at autonomic ganglionic synapses.
• g. blocking agent — see ganglion blocking.

"Ganglia" redirects here. For other uses, see Ganglia (disambiguation).

A dorsal root ganglion (DRG) from a chicken embryo (around stage of day 7) after incubation overnight in NGF growth medium stained with anti-neurofilament antibody. Note the axons growing out of the ganglion

In anatomy, a ganglion (pronounced /ˈɡæŋɡliən/, GANG-glee-ən, plural ganglia) is a biological tissue mass, most commonly a mass of nerve cell bodies.^[1] Cells found in a ganglion are called ganglion cells, though this term is also sometimes used to refer specifically to retinal ganglion cells.

In some dinosaurs, the ganglion in the pelvis was so large relative to its brain in its head that it could almost be said to have two brains.^[2]

Contents 1 Neurology 1.1 Basal ganglia 2 See also 3 References

Neurology

In neurological contexts, ganglia are composed mainly of somata and dendritic structures which are bundled or connected together. Ganglia often interconnect with other ganglia to form a complex system of ganglia known as a plexus. Ganglia provide relay points and intermediary connections between different neurological structures in the body, such as the peripheral and central nervous systems.

There are two major groups of ganglia:

• Dorsal root ganglia (also known as the spinal ganglia) contain the cell bodies of sensory (afferent) nerves.
• Autonomic ganglia contain the cell bodies of autonomic nerves.

In the autonomic nervous system, fibers from the central nervous system to the ganglia are known as preganglionic fibers, while those from the ganglia to the effector organ are called postganglionic fibers.

Basal ganglia

The term "ganglion" usually refers to the peripheral nervous system.^[3]

However, in the brain (part of the central nervous system), the "basal ganglia" is a group of nuclei interconnected with the cerebral cortex, thalamus and brainstem, associated with a variety of functions: motor control, cognition, emotions and learning.

Partly due to this ambiguity, the Terminologia Anatomica recommends using the term basal nuclei instead of basal ganglia.

See also

• Ganglion cell
• Ganglion cyst
• Nervous system
• Neuron

References

1. ^ ganglion at Dorland's Medical Dictionary
2. ^ Dawkins R (2009). The Greatest Show on Earth: The Evidence for Evolution. London: Bantam Press
3. ^ "UNSW Embryology- Glossary G". http://embryology.med.unsw.edu.au/Notes/Index/G.htm. Retrieved 2008-01-13. 

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)