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Clinical anatomy of the external ear

The outer ear includes the auricle (auricula) and the external auditory meatus (meatus acusticus extemus).

The auricle is located between the temporomandibular joint in front and the mastoid process in the back. It distinguishes between the external concave and internal convex surface facing the mastoid process. The basis of the auricle is a plate of elastic cartilage of complex shape (thickness 0.5-1 mm), covered on both sides by over-cartilage and skin.

The auricle consists of a curl (helix) and an antihelix (anthelix), located in the form of a roller inside the curl. Between them is a depression - a boat (scapha). In front of the entrance to the external auditory canal is the protruding part of it - the tragus (tragus). and posterior to the entrance is the proton carts (antitragus). Between them below there is a notch (incisura intertragica). Down the auricle ends with a lobe. It is devoid of cartilage and is formed only of fatty tissue covered with skin.

The auricle, narrowing in a funnel-like manner, passes into the external auditory meatus, which is a curved tube about 2.5 cm long in an adult. Its lumen resembles an ellipse with a diameter of up to 0.7-0.9 cm. It ends at the eardrum, which is the border between the outer and middle ear.

The external auditory meatus consists of two sections: the external membrano-cartilaginous and the internal bone. The outer section is 2/3 of the length of the ear canal. In this case, only the front and lower walls of it are cartilaginous, and the posterior and upper ones are formed by dense fibrous-connective tissue. Here are two Santorinia cracks, covered with fibrous tissue. The membrano-cartilaginous section is connected to the bone using a circular ligament. The narrowest part of the external auditory meatus - the isthmus - is located in the middle of the bony section.

Walls of the external auditory meatus:

The front delimits the temporal-mandibular joint from the outer ear, so when an inflammatory process occurs in it, chewing movements are sharply painful. There may be an injury to the anterior wall when falling on the chin.

The upper delimits the outer ear from the middle cranial fossa, therefore, with fractures of the base of the skull, blood or cerebrospinal fluid can leak out of the ear.

The back wall, being the front wall of the mastoid process, is often involved in the process with mastoiditis. At the base of this wall is the facial nerve.

The lower wall delimits the parotid salivary gland from the outer ear.

The external auditory meatus is covered with skin, which is a continuation of the skin of the auricle. In the membranous-cartilaginous department, it reaches a thickness of 1-2 mm, is richly supplied with hair, sebaceous and sulfur glands, which are a modification of the sebaceous glands. They secrete a brown secret, which together with separable sebaceous glands and with torn away skin epithelium forms earwax. In the bone section, the skin is thin (up to 0.1 mm), lies directly on the periosteum, contains neither glands nor hair. Medially, it passes to the outer surface of the eardrum

Blood supply to the external ear comes from the external carotid artery system: in front of a. lemporalis superficialis, behind - a.auricularis posterior, a.occipitalis. Deeper sections of the external auditory meatus; blood from a. auricularis profunda (branch a. maxillaris interna).
Venous outflow occurs in two directions: anteriorly - in v. facialis posterior and posteriorly - in v. auricularis posterior.

Lymphatic drainage occurs in the nodes located in front of the tragus, on the mastoid process and under the lower wall of the external auditory meatus. From here, lymph flows into the deep lymph nodes of the neck.

The outer ear is innervated by the sensitive branches of n.auriculotcmporalis (3 branch of the trigeminal nerve), P. auricularis magnus (branch of the cervical plexus), as well as from the city auricularis n.vagi. The motor nerve for the rudimentary muscles of the auricle is P. auricularis posterior (a branch of P. facialis).

Eardrum

The eardrum is the outer wall of the tympanum. It limits the outer ear from the middle, is an irregular oval (height 10 mm, width 9 mm), very elastic, inelastic and very thin (up to 0.1 mm). The membrane is funnel-shaped retracted into the tympanum. It consists of three layers: the outer - cutaneous (epidermal), which is a continuation of the skin of the external auditory canal, the inner - mucous, which is a continuation of the mucous membrane of the tympanic cavity and the middle - connective tissue, represented by two layers of fibers: the outer radial and inner circular, of which radial fibers are more developed.

The handle of the malleus is tightly spliced ​​with the inner and middle layers of the eardrum, the lower end of which is slightly lower than the middle of the eardrum forms a funnel-shaped depression - umbilicus. The handle of the malleus, continuing from the navel upward and anteriorly, gives in the upper third of the membrane a short process visible from the outside (processus brevis), which protrudes outward and protrudes the membrane, forming two folds on it - front and back. A small portion of the membrane located in the region of the rivine notch (above the short process and folds) does not have a middle (fibrous) layer and is called the unstretched part, in contrast to the rest - the stretched part.

The eardrum under artificial lighting has a pearl-gray-gray color, and the light source forms a light cone. For practical purposes, the eardrum is divided into four squares in two lines, one of which is held along the handle of the malleus to the lower edge of the membrane, and the other perpendicular to it through the navel. Thus, quadrants are distinguished: anteroposterior, anteroposterior. front-lower and back-lower.

Blood supply to the tympanic membrane: from the side of the outer ear - from a.auricularis profunda (branches a. Maxillaris), from the side of the middle ear - from a.tympanica. The vessels of the outer and inner layers of the tympanic membrane anastomose with each other. Venous outflow: veins from the outer surface of the tympanic membrane flow into the external jugular vein, and from the inner surface into the plexus around the auditory tube, into the transverse sinus and dura mater.

Lymphatic drainage occurs to the anterior, posterior, posterior cervical lymph nodes.

The tympanic membrane is innervated by the auricle of the vagus nerve (g.auricularis n. Vagi), the tympanic branch of n.auriculotemporalis and the tympanic branch of the glossopharyngeal nerve.

When examining a normal eardrum, one can see: the handle of the malleus, the short process of the malleus, the light cone, the anterior and posterior malleus folds.
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