MASTOID

From Big Medical Encyclopedia

MASTOID [processus mastoideus (PNA, BNA), processus mastoides (JNA)] — a posteroexternal part of a temporal bone. The village of the lake serves as the place of an attachment to a temporal bone grudino - the clavicular and mastoidal muscle supporting the head in balance at vertical position of a body.

Anatomy

Fig. 1. Macrodrug of a temporal bone: 1 — a mastoidal opening; 2 — mastoidal cutting; 3 — a mastoid; 4 — a nadprokhodny awn; 5 — an awl-shaped shoot.
Fig. 2. The diagrammatic representation of a mastoid on a section at pneumatic and sclerous types of a structure: 1 — cells of a mastoid; 2 — a mastoidal cave; 3 — an entrance to a mastoidal cave; 4 — a drum cavity.

The village of the lake is a part of a stony part (pars petrosa) of a temporal bone and is located kzad from drum (pars tympanica) and scaly (pars squamosa) of its parts. It is turned by a top down, kpered and slightly inside (fig. 1), has the extended or shortened form. Its length adults on average of 32 mm, width have 27 mm. The outer surface convex, is turned to soft tissues of the head, internal — concave, adjoins to covers of a brain. On an inner surface there is a furrow of a sigmoid sine (sulcus sinus sigmoidei), edges connects to an outer surface of a skull a mastoidal opening (foramen mastoideum). In the tail of S. of the lake mastoidal cutting (incisura mastoidea), behind it — a furrow of an occipital artery is located (sulcus and. occipitalis). The village of the lake it is covered with a layer of compact bone substance, there is a spongy bone substance having cells (cellulae mastoi-deae) representing the air-vessels separated by bone crossbeams more deeply — pneumatic type of a structure (fig. 2, a). Besides, S. the lakes formed by preferential spongy substance with underdevelopment of cells — spongy type of a structure, and also compact substance — sclerous type of a structure meet (fig. 2, b). The sizes of cells at pneumatic type of a structure increase in the direction in front back, the largest cells are located on S.'s periphery of the lake. The total area of cells can reach 30 cm2. At healthy people it averages 12,1 — 12,7 cm2 at the volume of 8,7 — 12,2 cm3. Degree of a pnevmatization of S. of the lake is defined by growth and physical development of the person, hereditary factors, and also depends on inflammatory changes in S. the lake and adjacent areas. So, at hron. an inflammation of a mucous membrane of a drum cavity the area of cells decreases to 3,8 — 4,4 cm2, and volume — to 2,6 — 3,5 cm3.

The largest cell of S. of the lake — a mastoidal cave (antrum mastoide-um) — is located in its anterosuperior part, supporting S.'s limits of the lake of a kpereda and up. It is reported with a drum cavity through the entrance to a cave (aditus ad antrum) located on a mastoidal wall — a back wall of a drum cavity. The depth of a mastoidal cave in the thickness of S. of the lake makes 8 — 20 mm. The mastoidal cave is projected over outside acoustical pass, the projection of its lower part is between projections of a sigmoid sine behind and the lower third of the channel of a facial nerve in front. The projection of a mastoidal cave to a lateral surface of S. of the lake can have oval, round, ankyroid, triangular or irregular shape.

In the first months after S.'s birth of the lake has an appearance of a hillock. Gets a characteristic form C. of the lake on the third year of life (in connection with development grudino - a clavicular and mastoidal muscle), and further there is only an increase in its sizes. Pnevmatization S. of the lake begins pre-natal development still in recent months. The area of cells of S. of the lake intensively increases up to 8 — 10 years, then their sizes are stabilized. The mucous membrane covering S.'s cells of the lake the drum texture (plexus tympanicus) innervates.

S.'s blood supply by the lake is provided by an average meningeal artery (a. meningea media) and a stylomastoid artery (a. stylomastoi-dea). A venous blood flows in a sigmoid sine (sinus sigmoideus) and an upper stony sine (sinus petrosus superior). The lymph drainage occurs in limf, nodes of the head and neck.

Methods of a research

Fig. 3. It is normal of the roentgenogram of a mastoid at pneumatic and sclerous types of a structure (the right side projection according to Schueller): 1 — outside and internal acoustical passes; 2 — a head of a mandible; 3 — a joint hollow of a temporal and mandibular joint; 4 — apical cells; 5 — periantralny cells; 6 — cells of scales of a temporal bone.

At a research C. of the lake the radiological methods including a X-ray analysis in a side projection according to Schueller have major importance (see. Middle ear ) and tomography (see). On roentgenograms outside and internal acoustical passes are defined, temporal and mandibular joint (see); kzad and up from them S. is located with the lake, in Krom distinguish groups of periantralny, angular, apical, perisinuozny cells, cells of scales, etc. (fig. 3). The picture allows to define type of a structure of S. of the lake, to estimate lightness of cells and a condition of partitions between them, the provision of a sigmoid sine, width of a mastoidal opening and helps with diagnosis of diseases and damages.

Pathology

S.'s Pathology of the lake includes malformations, damages, diseases and tumors.

Malformations. Local malformations of S. of the lake are not described. At the expressed hypoplasia or a dysplasia of an outside and middle ear also S.'s underdevelopment of the lake and considerable decrease in degree of its pnevmatization which are not demanding treatment comes to light.

Damages Villages of the lake in peace time meet very seldom, generally at the severe combined injuries of a skull (see. Craniocereberal injury ), treatment to-rykh is performed, as a rule, in neurosurgical hospitals with participation of the otorhinolaryngologist.

Diseases. The village of the lake, being a part of a middle ear (see), as a rule, it is involved in process at its inflammation (see. Otitis ). The inflammation of tissues C. of the island is called a mastoiditis (see). At the same time inflammatory process can preferential be localized in a drum cavity or in a mastoidal cave owing to a delay of evacuation patol. contents (see. Antrit ). Air-vessels of all temporal bone or its separate parts can be involved in inflammatory process — develops petrositis (see), zygomaticitis (see), etc. In a crust, time in connection with broad use of antibiotics, streptocides and other pharmaceuticals and with change of character of pathogenic flora of a middle ear, the general and local reactivity of an organism the mastoiditis proceeds in the erased form more often. At a purulent mastoiditis in case of lack of a natural drainage the urgent operative measure consisting in creation of good outflow patol is necessary. contents from a cavity of a mastoidal cave and other air-vessels of S. of the lake. For this purpose apply an antrotomy (see. Mastoiditis ), and also in connection with considerable injury of this operation antropunktion (see) and antrodrenazh. For implementation of an antrodrenazh by means of endoauralny approach bare a posterosuperior wall of bone department of outside acoustical pass, according to the roentgenogram calculate a necessary corner and a special drill in a temporal bone, to a mastoidal cave, drill an opening with a diameter no more than 4 mm. In this opening insert a drainage tube for washing and administration of medicines into a mastoidal cave and a drum cavity.

Tumors The village of the lake and soft tissues covering it find extremely seldom, occur among them fibromas (see), chondroma (see), neurinoma (see), osteoma (see). Malignant tumors of S. of the lake — cancer (see), sarcoma (see) — are most often localized on average to fish soup or burgeon from an outside ear. At a X-ray analysis blackout of air-vessels decides on destruction of intercellular partitions and switching cortical plates of S. of the lake uneven, various extent.

Treatment operational. The forecast depends on the nature of a tumor.



Bibliography: Zemtsov G. M. Radiodiagnosis of inflammatory diseases of a middle ear, M., 1965; Levin JI. T. Surgical diseases of an ear, book 1, page 197, M. — L., 1936; The Multivolume guide to otorhinolaryngology, under the editorship of A. G. Likhachev, t. 1, page 137, M., 1960; Sinelnikov R. D. Atlas of anthropotomy, t. 1, page 71, M., 1978; Biedermann F. u. a. Standardi-sierungsempfehlimgen zur Rontgendiagnostik des Schlafenbeins, Radiol, diagn. (BerL), Bd 19, S. 419, 1978; Gray’s anatomy, ed. by D. V. Davies, L., 1967; Hals-Nasen-Ohrenheilkunde in Praxis und Klinik, hrsg. v. J. Berendes u. a., Bd 5 — 6, Stuttgart, 1979 — 1980.


C.H. Lapchenko (pathology), B. A. Nicknames bales (An.), T. F. Rostovtseva (mt. issl.).

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