The vestibular apparatus is located in the inner ear of the temporal bone and has a complex and delicate structure that contains the auditory and balance organs. Histologically, the inner ear is divided into the osseous vagus and the membranous vagus, which is located within it. The space between the two is the exolymphatic gap, filled with exolymphatic fluid, and the membranous vagus is filled with endolymphatic fluid. 1. Bone labyrinth The bone wall of the bone labyrinth is about 2~3mm thick and can be histologically divided into 3 layers: the outer layer is the thin outer membrane layer of the bone, which is white and similar in texture to ivory; the middle layer is thicker and called the endogenous cartilage layer, with some chondrocytes remaining in the bone, which is dotted and slightly yellow; and the inner layer is the very thin endosteal layer which is light cyan. There is no vascular distribution in the bony vagus, and the newborn is the same size as the adult, divided into three parts: vestibule, semicircular canal and cochlea. The vestibule is an irregular elliptical cavity located between the semicircular canal and the cochlea, with a narrower anterior and inferior part connected to the vestibular order of the cochlea and a slightly wider posterior and superior part with five openings connected to the semicircular canal, the inner wall of which forms the floor of the internal auditory canal. The superior vestibular wall is bony and crossed by the facial nerve vagus segment. The three semicircular canals are located posteriorly and superiorly in the vestibule and form approximately 2/3 of a circular bony canal, which are called the external (horizontal), anterior (superior), and posterior semicircular canals, respectively, according to their positions. The three semicircular canals are nearly perpendicular to each other, and one end of each semicircular canal has an inflated potbelly shape. The ventral end of the upper and outer hemi-routines is above the vestibule, and the ventral end of the posterior hemi-routine opens below the posterior vestibule; the upper and posterior hemi-routines are connected into a common foot, which opens in the middle of the inner wall of the vestibule, and the outer hemi-routine opens below the common foot; the three hemi-routines are connected to the vestibule by five holes. The cochlea is shaped like a snail shell, with the cochlea axis as the center, coiled around from the bottom to the top for 2.5 weeks, and the total length of the cochlear canal is 31-33 mm. from the tip to the bottom height of 5 mm, the widest diameter at the bottom is about 9 mm, and the top of the cochlea is facing the front and outside, close to the tympanic membrane tensor hallucis and the bulge of the eustachian tube, and the bottom of the cochlea is in the back, forming part of the bottom of the inner ear canal. 2. Membrane vagus The membrane vagus is a system of membranous lumen, similar in morphology to the bone vagus. It is suspended in the exolymphatic fluid by tiny mesh-like fibers and forms a sealed system called endolymphatic system. The membranous vagus is divided into ellipsoid bursa, balloon bursa, semicircular canal, cochlea and endolymphatic duct and endolymphatic sac, and each part communicates with each other.