Bony labyrinth (labyrinthus osseus), in turn, consists of three parts.
Vestibule (vestibulum) is an oval cavity, located in the central part of the maze between the tympanic cavity and the internal acoustic meatus, and has a common wall with the middle ear, which is the window arches. On the inner wall of the vestibule there are two so-called pockets, which are spherical depression (recessus sphericus) and an elliptical depression (recessus ellipticus). They are connected to each other by a narrow vertical pocket comb called the vestibule (pyramis vestibuli). Inside pockets are lined with squamous epithelium, except for areas which are lattice spots (maculae cribrosae) - small holes lined with columnar epithelium. Here are the supporting and hair cells, which depart from the nerve fibers of the vestibular auditory nerve. The surface epithelium is covered by the otolithic membrane containing otoliths and statokonii - crystals of calcium carbonate.
The rear elliptical depression has five holes, connecting it with the semicircular canals. In the front there is a small spherical recess cochlear depression (recessus cochlearis), where is the dead end membranous cochlea.
Semicircular canals (canales semicirculares) are located in the posterior part of the bone of the labyrinth and represent three mutually perpendicular arc tubes filled with endolymph. On both sides of each channel are bony legs, one of which is slightly expanded ampullar bone leg (crus osseum ampullae), and another - a simple bone leg (crus osseum simplex). Simple legs front and rear channels are combined into a common bone leg (crus osseum commune). In extensions of the legs, the ampoules are hearing combs containing cells of the sensory epithelium, which are branches of the vestibular nerve.
Snail (cochlea) is located in front of the bone of the labyrinth, is cone-shaped and membranous spiral represents the channel, forming a two and a half curl around the core (modiolus) and blind-ended in the dome of the cochlea (cupula cochleae). The dome rises above the base of the cochlea (basis cochleae) to 4-5 mm. Each curl is separated from the other wall formed bone substance cochlea.
The rod consists of snails, spongy bone and an inner wall of the channel. The base of the rod (basis modioli) goes to the internal auditory canal. In the cavity of the spiral channel along the entire length of the rod is the spiral osseous lamina (lamina spiralis ossea). Through her cochlear cavity is divided into two parts: the upper course, which is combined with the threshold of the labyrinth and is called the vestibule staircase (scala vestibuli), and the lower course, which combines with the window cochlea tympanic cavity and tympanic are called ladder (scala tympani ). In the cupola of the cochlea, both are combined to form a hole snails (helicotrema).
|In Fig. 290.
Bony labyrinth, front view
1 - front semicircular canal;
2 - ampullar bony legs;
3 - total bone pin;
4 - snail curls;
5 - the dome of the cochlea;
6 - posterior semicircular canal;
7 - lateral semicircular canal;
8 - a simple leg bone;
9 - threshold
Spiral lamina, starting from the rod does not reach the wall of the spiral canal, and ends in the middle of the width of the channel. Between the free edge of the osseous spiral lamina and the wall of the cochlea is a spiral membrane (membrana spiralis), which is a continuation of the membranous cochlea.
|In Fig. 291.
1 - upper curl snails;
2 - opening the cochlea;
3 - core;
4 - tympani;
5 - vestibular canal;
6 - the spiral osseous lamina
a., aa. — arteria, arteriae (artery, the artery)
lig., ligg. — ligamentum, ligamenta (ligament, the ligaments)
m., mm. — musculus, musculi (muscle, the muscle)
n., nn. — nervus, nervi (nerve, the nerve)
r., rr. — ramus, rami (branch)
s. — seu (or)
v., vv. — vena, venae (vienna)