The Elasmobranchs (Elasmobranchii) is an order of fishes, including the sharks, dog-fishes, rays, and chimsera, in which the skull is not composed of distinct bones, but simply forms a kind of cartilaginous box, the vertebral column sometimes cartilaginous, sometimes consisting of distinct vertebrae, the integumentary skeleton in the form of placoid scales, the intestine being very short, and provided with a spiral valve. They have two pairs of fins (pectorals and ventrals), corresponding to the fore and hind limbs, and the ventral fins are close to the anus. The heart consists of an auricle, a ventricle, and a muscular arterial bulb. The gills are fixed, and form a number of pouches, which open internally into the pharynx, communicating outwardly by a series of apertures placed on the side of the neck. Research Elasmobranchs
The cervical lymph nodes are located in the neck. They are divided into two sets: superficial and deep. There are three sets of superficial lymph glands: the submaxillary, near the jaw, the suprahyoid, near the hyoid bone in the throat, and the cervical which are located along the course of the external jugular vein. The deep cervical glands are large glands that are situated near the pharynx, esophagus, and trachea. When you have a sore throat, white blood cells mass together in these nodes to fight the infection, which is why your throat will often feel swollen and tender. Research Cervical Lymph Nodes
Cilia are tiny hairs which cover the inside of many mucous linings. They are found throughout the body and, by their wave-like motion, they serve to filter and transport particulate material along the surface of the mucosal lining. Respiratory cilia are responsible for helping to filter dust and debris out of inhaled air and transmitting it with mucous to the pharynx to be swallowed. The nasal cavity, pharynx, trachea, and bronchimucous linings each have these structures. Research Cilia
The twelve cranial nerves innervate the muscles and skin of the head, neck, and, in the case of the vagus, sacral, and spinal accessory nerves, many other important structures throughout the body. These nerves originate in the pons, the forebrain, medulla oblongata, and the uppermost part of the spinal cord, between the first few cervical vertebrae.
The first four include the olfactory (1st), which innervates the nasalmucous layer and allows the sense of smell, the optic (2nd) which innervates the retina and allows the sense of sight, the oculomotor (3rd) which innervates the pupil and cilia of the eye, and the trochlear (4th) which innervates the superior oblique eyemuscles. The next cranial nerve is the trigeminal (5th) which has three divisions: the ophthalmic (eye), maxillary (upper palate and face), and mandibular (jawbone, tongue, and auriculotemporal region). The sixth, seventh, and eighth nerves are the abducens (lateral rectus of eye), the facial (face and earmuscles), and the acoustic (outer and inner ear structures), respectively. The ninth cranial nerve is the glossopharyngeal, which innervates the pharynx, tongue, and tympanus of the ear. The tenth cranial nerve, the vagus, has many branches which innervate a number of important structures, including the heart, lungs, and stomach. The eleventh cranial nerve is the accessory spinal nerve, which innervates structures of the neck and throat, including the pharynx and the cervical lymph glands. The twelfth cranial nerve is the hypoglossal nerve, which innervates the tongue. Research Cranial nerve
The ear is the organ used for hearing. It converts sound into electrical impulses that are fed to the brain. The external ear is composed of the auricle (the pinna), and the auditory canal (the meatus auditorius externus). The Pinna or auricle surrounds the entrance to the auditory canal. It consists of cartilage covered by skin, with small muscles connecting it to the scalp. At the base of the ear is a fleshy lobe. The meatus auditorius is a canal about three centimeters long in the adult, partly bony and partly cartilaginous, leading from the pinna of the ear to the drum. The lining cells secrete the waxy substance found in the canal. In young children the canal is much shorter. The ear drum (tympanic membrane) is a thin oval-shaped membrane, inserted into a groove around the auditory canal. Normally it is white, glistening and somewhat transparent, so that some of the structures of the middle ear are partly visible when viewed through an auroscope. It separates the auditory canal from the middle ear.
The Tympanum or middle ear is a cavity within the temporal bone. It contains several important structures, including three small bones which connect the drum with the internal ear; they are the malleus or hammer, the incus or anvil, and the stapes or stirrupbone. They transmit the vibrations of sound waves to the inner ear. The Eustachian Tube is a channel of communication between the tympanum and the upper part of the pharynx. It admits air from the throat to the tympanum and so maintains an equal pressure on both sides of the drum. The Labyrinth or internal ear is a series of chambers through the petrous bone, comprising the vestibule, a three-cornered cavity within the tympanum; the semicircular canals communicating with the vestibule; and the cochlea, which makes two and a half turns around an axis called the modiolus. The human ear is capable of detecting sounds in the frequency range 20 hz to 20 khz, approximately. Research Ear
In anatomy, the fauces is the narrow passage from the mouth to the pharynx, situated between the soft palate and the base of the tongue. On either side of the passage two membranous folds, called the pillars of the fauces, enclose the tonsils. Research Fauces
The palate forms the roof of the mouth. The hard palate is located in the front of the mouth. Portions of the maxillary bones make up the front of the roof of the mouth creating the hard palate. The soft palate is a continuation of the hard palate. It is a moveable fold of mucousmembrane suspended in the back of the mouth, forming an arch and an incomplete septum between the mouth and pharynx. Research Hard Palate
The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
Abbreviations
Research Elasmobranchs
