Special visceral afferent
Encyclopedia
' refers to afferent nerves that develop in association with the gastrointestinal tract
. They carry the special senses
of smell (olfaction
) and taste
(gustation). The cranial nerves containing SVA fibers are the olfactory nerve
(I), the facial nerve
(VII), the glossopharyngeal nerve
(IX) and the vagus nerve
(X). The facial nerve receives taste from the anterior two-thirds of the tongue
; the glossopharyngeal from the posterior third. SVA fibres in the vagus originate in the epiglottis
and pharynx
. The special visceral afferent plays a role in keeping homeostasis and the malfunction of these can lead to conditions such as irritable bowel syndrome and over-active bladder.
Gastrointestinal tract
The human gastrointestinal tract refers to the stomach and intestine, and sometimes to all the structures from the mouth to the anus. ....
. They carry the special senses
Special senses
In medicine and anatomy, the special senses are the senses that have specialized organs devoted to them:*vision *hearing and balance *smell *taste...
of smell (olfaction
Olfaction
Olfaction is the sense of smell. This sense is mediated by specialized sensory cells of the nasal cavity of vertebrates, and, by analogy, sensory cells of the antennae of invertebrates...
) and taste
Taste
Taste is one of the traditional five senses. It refers to the ability to detect the flavor of substances such as food, certain minerals, and poisons, etc....
(gustation). The cranial nerves containing SVA fibers are the olfactory nerve
Olfactory nerve
The olfactory nerve, or cranial nerve I, is the first of twelve cranial nerves. It is instrumental in the sense of smell. Derived from the embryonic nasal placode, the olfactory nerve is capable of regeneration.-Anatomy:...
(I), the facial nerve
Facial nerve
The facial nerve is the seventh of twelve paired cranial nerves. It emerges from the brainstem between the pons and the medulla, and controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity...
(VII), the glossopharyngeal nerve
Glossopharyngeal nerve
The glossopharyngeal nerve is the ninth of twelve pairs of cranial nerves . It exits the brainstem out from the sides of the upper medulla, just rostral to the vagus nerve...
(IX) and the vagus nerve
Vagus nerve
The vagus nerve , also called pneumogastric nerve or cranial nerve X, is the tenth of twelve paired cranial nerves...
(X). The facial nerve receives taste from the anterior two-thirds of the tongue
Tongue
The tongue is a muscular hydrostat on the floors of the mouths of most vertebrates which manipulates food for mastication. It is the primary organ of taste , as much of the upper surface of the tongue is covered in papillae and taste buds. It is sensitive and kept moist by saliva, and is richly...
; the glossopharyngeal from the posterior third. SVA fibres in the vagus originate in the epiglottis
Epiglottis
The epiglottis is a flap that is made of elastic cartilage tissue covered with a mucous membrane, attached to the entrance of the larynx. It projects obliquely upwards behind the tongue and the hyoid bone, pointing dorsally. The term, like tonsils, is often incorrectly used to refer to the uvula...
and pharynx
Pharynx
The human pharynx is the part of the throat situated immediately posterior to the mouth and nasal cavity, and anterior to the esophagus and larynx. The human pharynx is conventionally divided into three sections: the nasopharynx , the oropharynx , and the laryngopharynx...
. The special visceral afferent plays a role in keeping homeostasis and the malfunction of these can lead to conditions such as irritable bowel syndrome and over-active bladder.