A paraganglion (pl. paraganglia) is a group of non-

neuron A neuron, neurone, or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapses. The neuron is the main component of nervous tissue in all animals except sponges and placozoa. ...

al cells derived of the

neural crest Neural crest cells are a temporary group of cells unique to vertebrates that arise from the embryonic ectoderm germ layer, and in turn give rise to a diverse cell lineage—including melanocytes, craniofacial cartilage and bone, smooth muscle, per ...

. They are named for being generally in close proximity to

sympathetic ganglia The sympathetic ganglia, or paravertebral ganglia are autonomic ganglia, of the sympathetic nervous system. Ganglia are 20,000 to 30,000 Afferent nerve fiber, afferent and Efferent nerve fiber, efferent nerve cell bodies that run along on either s ...

. They are essentially of two types: (1) chromaffin or sympathetic paraganglia made of

chromaffin cell Chromaffin cells, also called pheochromocytes (or phaeochromocytes), are neuroendocrine cells found mostly in the medulla of the adrenal glands in mammals. These cells serve a variety of functions such as serving as a response to stress, monito ...

s and (2) nonchromaffin or parasympathetic ganglia made of

glomus cell Glomus cells are the cell type mainly located in the carotid bodies and aortic bodies. Glomus type I cells are peripheral chemoreceptors which sense the oxygen, carbon dioxide and pH levels of the blood. When there is a decrease in the blood's p ...

s. They are

neuroendocrine cell Neuroendocrine cells are cells that receive neuronal input (through neurotransmitters released by nerve cells or neurosecretory cells) and, as a consequence of this input, release messenger molecules (hormones) into the blood. In this way they bri ...

s, the former with primary endocrine functions and the latter with primary

chemoreceptor A chemoreceptor, also known as chemosensor, is a specialized sensory receptor which transduces a chemical substance (endogenous or induced) to generate a biological signal. This signal may be in the form of an action potential, if the chemorecept ...

functions. Chromaffin paraganglia (also called chromaffin bodies) are connected with the ganglia of the

sympathetic trunk The sympathetic trunks (sympathetic chain, gangliated cord) are a paired bundle of nerve fibers that run from the base of the skull to the coccyx. They are a major component of the sympathetic nervous system. Structure The sympathetic trunk lies j ...

and the ganglia of the celiac,

renal The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; bloo ...

adrenal The adrenal glands (also known as suprarenal glands) are endocrine glands that produce a variety of hormones including adrenaline and the steroids aldosterone and cortisol. They are found above the kidneys. Each gland has an outer cortex whic ...

, aortic and hypogastric plexuses. They are concentrated near the

glands and essentially function the same way as the adrenal medulla. They are sometimes found in connection with the ganglia of other sympathetic plexuses. None have been found with the sympathetic ganglia associated with the branches of the

trigeminal nerve In neuroanatomy, the trigeminal nerve ( lit. ''triplet'' nerve), also known as the fifth cranial nerve, cranial nerve V, or simply CN V, is a cranial nerve responsible for sensation in the face and motor functions such as biting and chew ...

. The largest chromaffin paraganglion is the organ of Zuckerkandl, it is probably the largest source of circulating catecholamines in the fetus and young infants, and gradually atrophies to microscopic loci. Nonchromaffin paraganglia include carotid bodies and aortic bodies, some are distributed in the

ear An ear is the organ that enables hearing and, in mammals, body balance using the vestibular system. In mammals, the ear is usually described as having three parts—the outer ear, the middle ear and the inner ear. The outer ear consists of ...

, along the

vagus nerve The vagus nerve, also known as the tenth cranial nerve, cranial nerve X, or simply CN X, is a cranial nerve that interfaces with the parasympathetic control of the heart, lungs, and digestive tract. It comprises two nerves—the left and righ ...

, in the larynx and at various other places.

Clinical significance

Tumors of the paraganglionic tissues are known as paragangliomas, though this term tends to imply the nonchromaffin type, and can occur at a number of sites throughout the body. Chromaffin paragangliomas are issued from chromaffin cells, and are known as pheochromocytomas. Adrenal pheochromocytomas are usually benign while extraadrenal ones are more malignant. They are most of the time in the adrenals, and only rarely outside of the abdomen. They usually secrete hormones and estimates of a familial history vary. Nonchromaffin paragangliomas are issued from glomus cells, also known as glomus tumors. They are usually benign. They are generally present at the head and neck, most often at carotid body or jugulo-tympanic, they rarely secrete hormones and commonly have a familial history.

References

External links

* * {{Authority control Tissues (biology) Sympathetic nervous system