The organ of hearing and balance

The pre-cochlear organ (organum vestibulocochleare) in the process of evolution in animals arose as a complex organ of equilibrium (pre-door), perceiving the position of the body (head) as it moved through space, and the organ of hearing. The organ of equilibrium in the form of a primitively arranged formation (static bubble) appears also in invertebrates. In fish in connection with the complication of their motor functions, first one and then the second semicircular canal is formed. In terrestrial vertebrates with their complex movements, an apparatus was formed which in man is represented by a vestibule and three semicircular canals located in three mutually perpendicular planes and perceiving not only the position of the body in space and its movements along a straight line, but also the movements (turns) of the body, head in any plane.

The organ of hearing in aquatic vertebrates is poorly developed. With the emergence of vertebrates on land, the hearing organ underwent a progressive development and was formed largely due to the restructuring of the gill apparatus. Along with the sound-receiving device, which belongs to the inner ear, a sound-conducting apparatus has appeared, which includes the middle ear (a drum cavity with its auditory ossicles, an auditory tube). The outer ear was formed with its sound-absorbing device - the auricle, the mobile and turning towards the sound of many mammals. Subcortical and cortical centers of hearing appeared which reached their highest development in the human cerebral cortex, where not only the analysis of nerve impulses entering the brain from the hearing organ is made, but also abstract "sound" thinking connected with the peculiarities of the second signal system.

The pre-cochlear organ is divided into three parts, closely related anatomically and functionally: the outer, middle and inner ear. The outer ear includes the auricle and the external auditory canal, to the middle there is a drum cavity with auditory ossicles, with mastoid cells and an auditory (eustachian) tube. The most difficult is the inner ear, in which the bone and membranous labyrinths are distinguished, forming the actual organ of hearing and the organ of balance (the vestibule), located only in the inner ear. The outer, middle ear and part of the inner (snail) belong to the hearing organ. The organ of equilibrium (vestibule) is located only in the inner ear.

Vessels and nerves of the pre-cochlear organ. The pre-cochlear organ (the organ of hearing and balance) is supplied from several sources. The branches from the external carotid artery system approach the outer ear: the anterior ear branches from the superficial temporal artery, the ear branch from the occipital artery and the posterior ear artery. In the walls of the external auditory canal a deep ear artery from the maxillary artery branches . This same artery is involved in the blood supply of the tympanic membrane, which also receives blood from the arteries that supply blood to the mucous membrane of the tympanic cavity. As a result, two vascular networks are formed in the membrane: one in the skin layer, the other in the mucous membrane.

Venous blood from the external ear along the veins of the same name flows into the submandibular vein, into the external jugular vein.

In the mucosa of the tympanic cavity there is a vascular network formed by the branches of several arteries.

The walls of the auditory tube supply the anterior drum artery and pharyngeal branches of the ascending pharyngeal artery, as well as the stony branch from the middle meningeal artery. To the auditory tube gives branches of the artery of the pterygoid canal (branch of the maxillary artery).

The veins of the middle ear accompany the same-named arteries and flow into the pharyngeal venous plexus, into the meningeal veins (tributaries of the internal jugular vein) and into the submandibular vein.

The artery of the labyrinth (a labyrinthi - branch of the basilar artery) that accompanies the pre-cochlear nerve and feeds the branch to the vestibule, semicircular canals and the cochlea corresponds to the inner ear . Venous blood from the inner ear flows from the inner ear to the upper stony sine, as well as through the vein of the cochlea of the cochlea and the vein of the aqueduct of the vestibule located in the same channels and opening into the lower stony sine or directly into the internal jugular vein.

Lymph from the external and middle ear flows into the mastoid, parotid, deep cervical - internal jugular, and also into the throat (from the auditory tube) lymph nodes.

The nerves of the organ of hearing and balance come from several sources. The external ear receives a sensible innervation from the large ear, wandering and ear-temporal nerves. To the tympanic membrane branches from the ear-temporal and vagus nerves, as well as from the drum plexus of the cavity of the same name, are suitable. In the mucosa of the tympanic cavity there is a drum plexus (plexus tympanicus) formed by the branches of the drum nerve (n. Tympanicus - branch of the glossopharyngeal nerve), connective branch of the facial nerve with the plexus and sympathetic fibers of the drowsy nerves (from the inner somnolence). The drum plexus continues in the mucosa of the auditory tube, where the branches from the pharyngeal plexus also penetrate. The drum string passes through the tympanum in transit, it does not participate in its innervation. Muscles attached to the auditory ossicles receive innervation from different sources: the stremnaya muscle - from the facial nerve, the muscle that strains the eardrum, - the branch of the same name from the mandibular nerve.