What Is the Patulous Eustachian Tube?

The tympanum is not completely closed, it communicates with the outside world through a "closed path".

The tympanum is not completely closed, it communicates with the outside world through a "closed path".

This secret passage is the Eustachian tube, and its opening in the tympanum is called the tympanic orifice. Entering from the mouth of the tympanum, the passage here is mainly composed of bone. The passage is obliquely downward and gradually tapered. The inner diameter of the isthmus is only one or two millimeters, which is the narrowest place. Moving forward, it gradually widened, and the "building materials" also changed to cartilage. The end of the passage is in the nasopharynx.

The entire channel is about 35 mm long. The height difference between the upper and lower channels is 15-25 mm, so that the nasopharyngeal liquid cannot easily enter the middle ear "counter-current".

The main function of the eustachian tube is to regulate the pressure in the tympanic cavity. In addition, it has the role of drainage to discharge the secretions in the tympanic cavity. The eustachian tube near the tympanic segment is often open; the eustachian tube near the nasopharynx can be reduced or enlarged, usually closed, and only opened when swallowing, yawning, singing, or blowing your nose hard.

Chinese name

Eustachian tube

nickname

Euclidean

Anatomical structure

Bowed

Location

The tympanic mouth is inward, forward, and down to the throat

Eustachian tube and otitis media

The Eustachian tube is a tube that connects the tympanic cavity and the nasopharyngeal cavity, and is an important part of the middle ear transmission mechanism. This tube function is closely related to the human body's adaptation to flight. Armstrong first explained the significance of the Eustachian tube in the development of otitis media in 1938.

Structure and function: The total length of the Eustachian tube of Chinese people is 31 ~ 35mm. The direction of this tube is from the anterior wall of the tympanum forward, inward and downward to the nasopharynx. The tubes are divided into "bone" and "cartilage", both of which are slightly cone-shaped. The joint is the narrowest part of the whole pipe, which is called the "gorge". The two parts of the tube generally form an angle of about 145 ° at the joint. The anatomical variations at this place, such as the connection is not on an axis, forming a "fork connection", the internal diameter of the isthmus is too small or the neoplastic membrane is easy to cause dysfunction of the eustachian tube.

The bone is the outer 1/3 segment of the eustachian tube, starting from the anterior inferior wall of the tympanum, and the inner diameter of the tympanic mouth is about 3 to 4 mm. This segment is located between the scales of the temporal bone and the rock bone, and is a permanently opened pipe. The cartilage part constitutes the inner 2/3 section of the tube. The cartilage wall is above the posterior wall, the top wall and the anterior wall, and the fibrous soft tissue wall is below the anterior wall. It is precisely because of the above-mentioned structural characteristics of the cartilage that this tube has the function of a "one-way valve" (or "flutter valve"). The site that functions as a valve is the cartilage at about 1 cm from the isthmus.

The mucosa of this tube is covered by pseudostratified ciliated columnar epithelium, with the direction of ciliary movement facing the nasopharynx. There are a large number of collagen fibers in the submucosal basal layer, and there are a large number of serous and mucous glands near the pharynx and a certain amount of fatty tissue. The pharyngeal crypt behind the tube and the proliferative mass above are lymphoid tissues; the tube itself, including the pharynx, has no lymphoid tissue.

This tube plays an important role in ensuring the middle ear's sound transmission function. Because the tympanic cavity is an air-containing cavity, it is necessary to maintain a balanced air pressure inside and outside the cavity so that the tympanic membrane and the round window membrane are in the optimal vibration position to obtain normal hearing. The pressure difference between the inside and outside of the drum can be either active or passive. The so-called "active method" is to rely on muscle contraction to pull the membrane wall of the tube apart. At this time, the dominant role is the sternocleidomastoid muscle; related muscle groups, such as the epipharyngeal contractile muscle, also play a supporting role. The physiological actions that cause these muscles to contract are swallowing, sneezing, or yawning. Individuals can move the jaw joint or roll the tongue to contract the soft palate to open the membrane wall. Among them, swallowing is the most effective and often used in flight. The "passive open tube method" includes the method of pinching nose and gas, swallowing and blowing, and catheter blowing. The first method does not require any equipment, so it is also called "home ventilation method", which is commonly used during the flight down. In addition, the Frenzel method is a method of combining active and passive methods while pinching the nose and inflating the air and making the tongue roll and soften the palate. Pilots for single-seater military aircraft are better off by swallowing.