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Ascidia (named from the Greek, askos, a wine-skin) is a name given to the Sea-squirts or main section of the Tunicata, a class of animals of low grade, resembling a double-necked bottle, of a leathery or gristly nature, found at low-water mark on the sea-beach, and dredged from deep water attached to stones, shells, and fixed objects. One of the prominent openings admits the food and the water required in respiration, the other is the excretory aperture. A single ganglion represents the nervous system, placed between the two apertures. Male and female reproductive organs exist in each ascidian. They pass through peculiar phases of development, the young ascidian appearing like a tadpole-body. They may be single or simple, social or compound. In social ascidians the peduncles of a number of individuals are united into a common tubular stem, with a partial common circulation of blood. In these animals early evolutionists saw a link between the Mollusca and the Vertebrata.
 Research Ascidia
Molluscoida is a group of animals comprising the Polyzoa, Tunicata and Brachiopoda. The nervous system consists of a single ganglion or a principal pair of ganglia and the heart is imperfect.
Research Molluscoida
The ciliary ganglion is an enlarged cluster of nerve fibres where the oculomotor nerve branches into the many short ciliary nerves which supply the iris and cornea of the eye. These short ciliary nerves run more or less parallel to the long ciliary nerves, which also innervate the iris and cornea, but which originate in the nasociliary nerve before the ciliary ganglion.
Research Ciliary Ganglion
A ganglion is an enlargement occurring somewhere in the course of a nerve, and containing nerve cells in addition to nerve filaments.
Research Ganglion
The stapedius is a small ear muscle. It originates from the walls of the tympanic cavity and inserts in the neck of the stapes. It is innervated by branches of the trigeminal nerve through the otic ganglion.
Research Stapedius
The tensor tympani (Toynbee's muscle) is a small ear muscle. It originates from the cartilage of the eustachian tube and inserts in the handle of the malleus. It is innervated by branches of the trigeminal nerve through the otic ganglion.
Research Tensor Tympani
The tensor veli palatini muscle (tensor palati; palatosalpingeus; sphenosalpingostaphylinus) is a small muscle of the soft palate. It originates from the sphenoid bone and the eustachian tube and inserts in the border of the hard palate. The tensor velati palatini is innervated by branches of the trigeminal nerve through the otic ganglion. This muscle tenses the soft palate, which opens the eustachian tube helping to equalize the air perssure within the middle ear.
Research Tensor Veli Palatini
The trigeminal nerve (or fifth cranial nerve) is the fifth of the cranial nerves which spring from the brain. The roots of the nerve pass into an enlargement, the Gasserian ganglion, from which three main branches of the nerve are given off:
- the ophthalmic nerve
- the superior maxillary nerve
- the inferior maxillary nerve
The first two divisions of the trigeminal nerve are purely sensory; the third is partially sensory and partially motor.
Tic douloureux or neuralgia of the trigeminal nerve is a very severe form of neuralgia, possibly due to an affection of the Gasserian ganglion. The condition generally begins after middle life, with sudden paroxysms of violent pain which may last for a few seconds to a minute. The muscles of the face become quite contracted and the pain is intense. The paroxysms may follow each other for a few hours, and then remission may occur for days or even months. Gradually, however, the periods of remission become shorter, and the patient may never be entirely free from pain.
Research Trigeminal Nerve
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The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
©1993 - 2009 The Probert Encyclopaedia
Southampton, United Kingdom
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