The stapes has diverging crura and consequently a wide canal.
Further forward in front of the stapesis the small opening for the exit of the facial nerve, and seen in a lateral view close to the orbitosphenoid, that for the trigeminal (fig.
The stapes is always normal in character, never becoming at all columelliform.
Priodon has a lower type of stapes than Dasypus and Tatusia.
The stapes frequently has no canal, or only a very small one.
The stapes is very much like a reptilian columella, having a single crus with no perforation.
The Didelphyidae on the other hand have the most highly developed ossicles, the malleus much resembling that of many Insectivores, and the stapes having two definite crura separated by a canal.
The incus has the stapedial end greatly developed, and the stapes has very thick crura with hardly any canal.
The malleus is homologous to the extra-columella of Crocodiles and the stapes to the columella.
Lying laterally to these nerve openings is seen a patch of cartilage, the =stapes=, which is homologous with the stapes or proximal element of the columellar chain in the frog.
In the Carnivora vera the incus and stapes are small as compared with the malleus, but in the Pinnipedia they are large.
The columella and stapes are together homologous with the mammalian auditory ossicles and with the hyomandibular of Elasmobranchs.
Other observations have shown the movements at the stapesto have a still smaller amplitude, varying from 0.
Each push in and out of the base of the stapes must cause a movement of the fluid, or a pressure, in the scalae as a whole.
Hurst's view is that with each movement of the stapes a wave is generated which travels up the scala vestibuli, through the helicotrema into the scala tympani and down the latter to the fenestra rotunda.
He supposes that with each movement of thestapes corresponding to a vibration, a wave travels up the scala vestibuli, pressing the basilar membrane downwards.
If only the crura be broken off, it does not matter; but if the stapes itself be dislodged from the fenestra ovalis, the subsequent symptoms may be attacks of vertigo, nausea, and vomiting.
If the membrane be completely adherent to the inner wall at its upper posterior quadrant, especially if this is of long standing, as the stapes will almost certainly also be fixed by adhesions.
The chief difficulty is to obtain a good view; even if this be obtained it is difficult to extract the stapes without fracture of its crura.
The same result should be obtained after the complete mastoid operation, provided there be no internal-ear deafness and provided the stapes be not already ankylosed within the fenestra ovalis.
If the head of the stapes cannot be seen, it is advisable, as suggested by Dench of America, to punch out part of the upper posterior margin of the attic-wall with the attic forceps (see p.
Adhesions surrounding the articulation between the incus and stapes, and the stapes itself.
If the stapesbe not firmly ankylosed it can usually be removed by slight traction.
To determine whether the stapes is ankylosed or not, direct pressure of the probe on the head of the stapes may be necessary.
The chief advocate of the removal of the stapes is Jack of Boston (Boston Med.
There is no actual danger in the operation, but if the stapes is fixed or if much force is used, it is by no means difficult to fracture the crura of the stapes.
If the meatus be very narrow the intrameatal method may fail to bring the stapes into view.
The operation is also performed as a preliminary measure to removal of the stapes (see p.
In cases in which mobilization of the malleus has caused no improvement, and it is hoped, from the history of the case, that this is due to fibrous adhesions fixing the stapes within the fenestra ovalis.
If there be marked middle-ear deafness with extensive adhesions on both sides and evidence points to the stapes being freely movable.
It must also be remembered that adhesions in the region of the stapes cannot be seen, unless a large perforation of the membrane already exists.
Pertaining to that part of the columella of the ear which, in some animals, connects the stapes with the other parts of the columella.
Pertaining to a part of the columella of the ear, between the stapes and the mediostapedial.
It is, therefore, the homologue of the stapes in mammals.
In some Anura it formed the ossicle of the ear (homologue of the columella of birds and the stapes of mammals), in others it disappeared.
The stapes forms a close connection with the hammer and the incus.
There is a contrast between Anura and most Urodela in the relative positions of the stapes and facial nerve, as shown in DeBeer's (1937) diagrams.
Although the stapes and otic region are readily visible in a number of labyrinthodonts and lepospondyls, no indication of an operculum seems to be reported among them.
The stapes has a large footplate, and its stylus articulates with the quadrate, but no true operculum or opercularis has been described in the Apoda.
It does not seem necessary to regard the conditions in this order as related directly to those of either salamanders or frogs, but a reduction of the stapes comparable to that in salamanders has occurred.
The limbs of the stapes are relatively narrow, weak, and gently curved.
The limbs of the stapes are narrow, weak, and abruptly curved.
The limbs of the stapes are wide-spread and heavy.
The vestibule lies just internal to the posterior part of the tympanum, and there would be a communication between the two, through the fenestra ovalis, were it not that the footplate of the stapes blocks the way.
It will thus be seen that the stapes lies nearly at right angles to the long process of the incus.
The two branches of thestapes are anterior and posterior, while the footplate fits into the fenestra ovalis and is bound to it by a membrane.
The long process of the incus runs downward and ends in a little knob called the os orbiculare, which is jointed on to the stapes or stirrup bone (fig.
Defn: Pertaining to a part of the columella of the ear, between the stapes and the mediostapedial.
Defn: Pertaining to that part of the columella of the ear which, in some animals, connects the stapes with the other parts of the columella.
Pressure of the base of the stapes is exerted on the utricle.
The base of thestapes communicates pressures to the utricle.
Laterally the stapes carries a short, broad process that probably made contact with a dorsally placed tympanic membrane.
The bone that we take to be the stapesis blunt, flattened (perhaps by crushing), 5.
The stapes apparently reaches the quadrate, and could therefore serve in hyostylic suspension of the upper jaw.
Thus the bone was a hyomandibular in the sense that it articulated with the quadrate, but it may also have served as a stapes in sound-transmission.
The incus is articulated with the quadrate end of the mandibular arch, and its rounded head comes in contact with the stapes (fig.
Salensky however holds that it is formed from a mass of mesoblast surrounding the artery of the mandibular arch, and that the form of the stapes is due to its perforation by the mandibular artery.
A product of this artery permanently perforates thestapes in a few Mammalia, though in the majority it atrophies.
Salensky has recently arrived at a view, which is in accord with that of Parker, in so far as the independence of the stapes of both the hyoid and mandibular arches is concerned.
While the account of the formation of the malleus, incus, and stapes just given is that usually accepted in this country, a somewhat different view of the development of these parts has as a rule been adopted in Germany.
Sound waves enter the liquids of the internal ear at this point, the foot of the stapes being attached to the membrane.
The bridge of bones, being pivoted at one point to the walls of the middle ear, forms a lever in which the malleus is the long arm, and the incus and stapes the short arm, their ratio being about that of three to two.
A rod-like columella auris replaces the chain of ear ossicles, and may, or may not, answer to the stapes alone, or even possibly to the entire series.
The posterior and anterior crus of the stapes are more nearly straight than in taylori.
The short process of the incus is knoblike in Calomys and Thaptomys, and the general conformation of malleus and stapes in those two genera is nearly identical to that in B.
In Holochilus the anterior crus and posterior crus of the stapes are similar to those in B.
The posterior and anterior crus of the stapes are bowed, and the muscular process is either absent or much reduced.
In Akodon, the anterior and posterior crus of the stapes is more rounded than in B.
The stapes is only very slightly perforated in both specimens; while a small circular disc firmly fixed to the incus represents the orbicular bone in the second skull.
The auditory ossicles of Grypotherium, therefore, are very different from those of Myrmecophaga, in which the malleus is less sharply bent, the incus has divergent arms of unequal length, and the stapes exhibits a large perforation.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "stapes" in a variety of sentences. We hope that you will now be able to make sentences using this word.
