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

neuron A neuron (American English), neurone (British English), or nerve cell, is an membrane potential#Cell excitability, excitable cell (biology), cell that fires electric signals called action potentials across a neural network (biology), neural net ...

al cells derived of the

neural crest The neural crest is a ridge-like structure that is formed transiently between the epidermal ectoderm and neural plate during vertebrate development. Neural crest cells originate from this structure through the epithelial-mesenchymal transition, ...

. 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 and efferent nerve cell bodies that run along on either side of the spinal cord. Afferent nerve cel ...

. 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 adrenal medulla, medulla of the adrenal glands in mammals. These cells serve a variety of functions such as serving as a response to ...

s and (2) nonchromaffin or parasympathetic paraganglia 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 ...

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 The endocrine system is a messenger system in an organism comprising feedback loops of hormones that are released by internal glands directly into the circulatory system and that target and regulate distant organs. In vertebrates, the hypotha ...

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 chemorece ...

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

ganglia A ganglion (: ganglia) is a group of neuron cell bodies in the peripheral nervous system. In the somatic nervous system, this includes dorsal root ganglia and trigeminal ganglia among a few others. In the autonomic nervous system, there a ...

of the

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

and the ganglia of the

celiac Celiac (or coeliac in British English) may refer to: * Coeliac disease * Celiac artery * Celiac lymph nodes * Celiac plexus The celiac plexus, also known as the solar plexus because of its radiating nerve fibers, is a nerve plexus, complex net ...

renal In humans, the kidneys are two reddish-brown bean-shaped blood-filtering organs that are a multilobar, multipapillary form of mammalian kidneys, usually without signs of external lobulation. They are located on the left and right in the retrop ...

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 which ...

aortic The aorta ( ; : aortas or aortae) is the main and largest artery in the human body, originating from the left ventricle of the heart, branching upwards immediately after, and extending down to the abdomen, where it splits at the aortic bifurc ...

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 (literal translation, lit. ''triplet'' nerve), also known as the fifth cranial nerve, cranial nerve V, or simply CN V, is a cranial nerve responsible for Sense, sensation in the face and motor functions ...

. The largest chromaffin paraganglion is the

organ of Zuckerkandl The organ of Zuckerkandl is a chromaffin body derived from the neural crest located at the bifurcation of the aorta or at the origin of the inferior mesenteric artery. It can be the source of a paraganglioma. The term para-aortic body is also som ...

, 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 The aortic bodies are one of several small clusters of peripheral chemoreceptors located along the aortic arch. They are important in measuring partial pressures of oxygen and carbon dioxide in the blood, and blood pH. Structure The aortic b ...

, some are distributed in the

ear In vertebrates, an ear is the organ that enables hearing and (in mammals) body balance using the vestibular system. In humans, the ear is described as having three parts: the outer ear, the middle ear and the inner ear. The outer ear co ...

, along the

vagus nerve The vagus nerve, also known as the tenth cranial nerve (CN X), plays a crucial role in the autonomic nervous system, which is responsible for regulating involuntary functions within the human body. This nerve carries both sensory and motor fibe ...

, in the

larynx The larynx (), commonly called the voice box, is an organ (anatomy), organ in the top of the neck involved in breathing, producing sound and protecting the trachea against food aspiration. The opening of larynx into pharynx known as the laryngeal ...

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 Pheochromocytoma is a rare tumor of the adrenal medulla composed of chromaffin cells and is part of the paraganglioma (PGL) family of tumors, being defined as an intra-adrenal PGL. These neuroendocrine tumors can be sympathetic, where they relea ...

. Adrenal pheochromocytomas are usually benign while extra-adrenal 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 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