English name:

ear

The ear includes three parts: the outer ear, the middle ear and the inner ear. Hearing receptors and position receptors are located in the inner ear, so the ear is also called position hearing device. Some people also list the outer ear and middle ear as appendages of audiometer. The external ear includes auricle and external auditory canal. On the other hand, the external ear also includes the eardrum.

There is a big hole in the front and outside of the auricle, called the external auditory meatus, which communicates with the external auditory meatus. The auricle is funnel-shaped and has the function of collecting external sound waves. Most of them are supported by subcutaneous elastic cartilage, and the lower part only contains subcutaneous connective tissue and fat, which is called earlobe. Auricle is the clinical application site of auricular point therapy and auricular acupuncture anesthesia, and earlobe is the commonly used blood collection site in clinic.

The external auditory canal is a curved tube from the hilum of the external ear to the tympanic membrane, about 2.5~3.5 cm long, and its skin continues from the auricle. The outer third of the external auditory canal wall is composed of cartilage, and the inner two thirds of the external auditory canal wall is composed of bone. There are ear hair, sebaceous glands and cerumen glands on the skin of cartilage.

The tympanic membrane is a translucent membrane, which is shallow funnel-shaped, with the concave surface facing outward and the edge fixed on the bone. The external auditory canal and the middle ear are bounded by it. Sound waves coming through the external auditory canal will cause the eardrum to vibrate.

The tympanum is located between the tympanic membrane and the inner ear, and it is a small cavity containing gas with a volume of about 1 cm3. The tympanum is the main part of the middle ear, in which there are three ossicles: malleus, incus and stapes. The base plate of the stapes is attached to the oval window of the inner ear. These three ossicles are connected by ligaments and joints to form an ossicular chain. The vibration of the eardrum can be transmitted to the oval window through the ossicular chain, causing the vibration of lymph in the inner ear.

There is a thin bone plate at the top of the tympanum, which separates the tympanum from the cranial cavity. Some types of otitis media can corrode and destroy this thin bone plate, invade the brain and lead to brain abscess and meningitis. Therefore, if you have otitis media, you should treat it in time and not be careless. There is a small tube in the tympanum-the eustachian tube leads to the nasopharynx from the front and bottom of the tympanum. It is a slender flat tube with a total length of about 3? 5 ~ 4 cm, the opening near the nasopharynx is usually closed and only opened when swallowing or yawning. The main function of the eustachian tube is to make the air in the drum room communicate with the outside air, so as to keep the air pressure balance inside and outside the eardrum and make the eardrum vibrate well. The air pressure in the drum room is high, and the eardrum will protrude outward; When the air pressure in the tympanum is low, the eardrum will sag inward, which will affect the normal vibration of the eardrum and the transmission of sound waves. When people are flying, the air pressure drops or rises sharply when the plane rises or falls. Because the eustachian tube is not opened, the air pressure in the drum chamber will rise or fall relatively, which will make the eardrum swell or sink, thus making people feel earache or sultry. At this time, if you swallow actively and open the eustachian tube, you can balance the air pressure inside and outside the eardrum and relieve the above symptoms.

The inner ear, including vestibule, semicircular canal and cochlea, is composed of complex curved tubes, so it is also called lost. Labyrinth is full of lymph, vestibule and semicircular canal are the places where sensory receptors are located, which are related to the balance of the body. The vestibule can feel the change of position and speed when the head moves linearly, and the semicircular canal can feel the rotation and variable speed movement of the head. After the central reflex, these stimuli will cause a series of reflexes to maintain the balance of the body. Cochlea is the place where auditory receptors are located, which is related to hearing. So how is listening formed? People's hearing is very sensitive, with vibrations ranging from 16 to 20,000 times per second. When the external sound is collected by the auricle, it travels from the external auditory canal to the eardrum, causing the eardrum to vibrate. The vibration frequency of tympanic membrane is exactly the same as that of sound wave. The louder the sound, the greater the vibration amplitude of the eardrum.

The vibration of the eardrum causes the three ossicles to vibrate at the same frequency. After the vibration is transmitted to the ossicular chain, the vibration force is greatly strengthened and the sound is amplified. The vibration of ossicular chain causes the vibration of lymph in cochlea, which stimulates the auditory receptors in inner ear. The nerve impulse generated by the excitation of auditory receptors is transmitted to the auditory pathway of cerebral cortex along the cochlear nerve in auditory nerve, resulting in hearing. The auditory nerve consists of vestibular nerve and cochlear nerve in the inner ear.

Organs of hearing and sense of position (sense of balance). Animals can perceive the external sound information and their body position through their ears, so as to communicate, find a spouse, avoid enemies, hunt and keep their body balance. The formation and gradual improvement of ears is the expression of animal evolution. The ear structure of different animals is very different. The primitive group of vertebrates only has the inner ear, which mainly plays a role in balancing the body. The inner ear of cartilaginous fish has oval sac, spherical sac and semicircular canal, which has certain auditory function; The inner ear of most teleost fish has a pot-shaped structure. Because there is no eardrum, they can feel the sound waves below 1000 Hz in water through the lateral organs. Frogs and toads in amphibians have produced middle ears with eardrums and ear column bones. The vibration of the eardrum caused by sound waves is introduced into the inner ear through the ear column bone, which causes the excitement of the receptors in the oval sac and the auditory jugular. The eustachian tube balances the pressure inside and outside the eardrum through the pharyngeal cavity. The ears of reptiles have been further developed. There are independent auditory receptors in the pot, the bottle-shaped sac of the inner ear has been obviously elongated, the crocodile has been curled, the lizard has heard, and the tympanic membrane is invaginated, forming the embryonic form of the external auditory canal. The eardrum, middle ear and eustachian tube of the snake degenerate, and sound waves pass through the square bone of the skull along the ground to reach the ear column bone, thus making the inner ear feel. Birds' ears are basically similar to those of reptiles, with only one ossicle (ear column bone) and one embryonic external auditory canal. Owls have well-developed ears and special ear feathers, which help to collect sound waves and determine their direction. Mammalian ears are highly perfect, consisting of outer ear, middle ear and inner ear. The external ear is composed of a rotatable auricle and an external auditory canal, which plays a role in collecting sound waves. The middle ear, also known as the tympanic cavity, is the cavity between the outer ear and the inner ear, and its outer side is the tympanic membrane. The vibration of tympanic membrane caused by sound waves is transmitted to the inner ear through a lever system consisting of three ossicles (malleus, incus and stapes) in the tympanum. There is an eustachian tube (eustachian tube) leading to the pharynx in the front wall of the tympanum, which is closed at ordinary times and opened when swallowing. Some mouth movements can adjust the air pressure of the tympanum. The inner ear consists of cochlea and vestibular organs. Cochlea is formed by curling a bottle-shaped capsule, which looks like a snail, hence the name, and it is an organ that feels sound stimulation. Vestibular organs are balanced and belong to positional receptors. The auricles of cave mammals and aquatic mammals often degenerate, but some mammals have very developed auricles and can capture very fine sound waves. Some aquatic mammals can transmit underwater sound waves to the middle and inner ears through the mandible.

Organ site

The human eye is approximately spherical and located in the orbit. The average diameter of normal adults is 24mm, the average vertical diameter is 23 mm, and the front end protrudes from the orbit 12- 14 mm, which is protected by eyelids. The eyeball includes the wall of the eyeball, the inner cavity of the eye, contents, nerves, blood vessels and other tissues.

[Edit this paragraph] Organ structure

The ocular wall is mainly divided into outer layer, middle layer and inner layer. The outer layer consists of cornea and sclera. The anterior 1/6 is transparent cornea, and the other 5/6 is white sclera, commonly known as "white eyes". The outer layer of eyeball plays a role in maintaining the shape of eyeball and protecting intraocular tissues. Cornea is the highest entrance to receive information. The cornea is the transparent part in front of the eyeball, through which light enters the eyeball. The cornea is slightly oval and slightly forward. The transverse diameter is11.5-12mm, and the longitudinal diameter is about10.5-1mm. The peripheral thickness is about 1mm, and the center thickness is 0.6 mm The tear film in front of the cornea can prevent the cornea from drying and keep the cornea smooth and optical properties. Corneal nerve is rich and sensitive. Therefore, the cornea is not only the main structure of light entering the eye and refracting imaging, but also plays a protective role and is an important part of measuring people's perception. Scleral is a compact collagen fiber structure, opaque, milky and tough. The middle layer, also called uvea and pigmented membrane, is rich in pigments and blood vessels, including iris, ciliary body and choroid. Iris: ring-shaped, located at the forefront of the uvea and in front of the lens, with radial wrinkles on the surface called texture and uneven depressions. People of different races have different iris colors. There is a 2.5-4mm round hole in the center, which is called the pupil. The ciliary body is located in front of the iris root, behind the choroid, on the side of the sclera, and inside the equatorial part of the lens through the suspensory ligament. The choroid lies between the sclera and retina. The blood circulation of choroid nourishes the outer layer of retina, and its rich pigment plays the role of shading darkroom. The inner layer is the retina, a transparent membrane, which is the first stop of nerve information transmission formed by vision. It has a fine network structure and rich metabolic and physiological functions. The end of the retinal visual axis is the fovea maculata. Macular area is the special area with the most acute vision on the retina, with a diameter of about 1-3mm and a small fovea in the center, that is, fovea. There is a reddish area with a diameter of 1.5mm, about 3mm, on the nasal side of the macula. This area is the optic disc, also called the optic papilla, which is the exit part of the retina and the place where the visual fibers converge and transmit to the visual center. There are no photoreceptor cells, so it appears as an inherent dark area in the field of vision, which is called physiological blind spot.

Intraocular cavity and contents

The eye includes anterior chamber, posterior chamber and vitreous cavity. Ocular contents include aqueous humor, crystals and vitreous body. All three are transparent and are called refractive media together with cornea.

Aqueous humor is produced by ciliary process, which nourishes cornea, lens and vitreous body and maintains intraocular pressure. Crystal is an elastic transparent body, shaped like a biconvex lens, located behind the iris and pupil and in front of the vitreous body. Vitreous body is a transparent colloid, which fills the cavity behind 4/5 of eyeball. The main ingredient is water. Vitreous body has refractive effect and also supports retina.

Optic nerve and visual pathway

The optic nerve is a part of the central nervous system. Visual information obtained from retina is transmitted to brain through optic nerve. Visual pathway refers to the whole nerve impulse transmission path from retina to cerebral visual cortex.

Accessory organs of the eye

Eye accessories include eyelid, conjunctiva, lacrimal apparatus, extraocular muscles and orbit. Eyelids are divided into upper eyelids and lower eyelids, which live in front of the orbit and cover the front of the eyeball. The upper eyelid is bounded by eyebrows, and the lower eyelid is connected with facial skin. The gap between the upper and lower eyelids is called blepharoptosis. The joint of the two eyelids is called the inner canthus and the outer canthus respectively. The fleshy bulge in the inner canthus is called lacrimal caruncle. There is a perforated nipple on the inner side of the upper and lower eyelid margins, called lacrimal punctum, which is the opening of lacrimal canaliculus. Physiological function: the main function is to protect the eyeball. Because of frequent blinking, tears can wet the surface of eyeball, keep corneal luster and clean dust and bacteria in conjunctival sac.

Conjunctiva is a thin and transparent mucous membrane covering the back of eyelid and the front of eyeball. According to anatomical position, it can be divided into three parts: eyelid conjunctiva, bulbar conjunctiva and fornix conjunctiva. The saccular space formed by conjunctiva is called conjunctival sac.

Lacrimal gland organs include lacrimal gland and lacrimal duct that secrete tears.

There are six extra-ocular muscles that control the movement of the eyes. The four rectus muscles are: upper rectus, lower rectus, inner rectus and outer rectus. The two oblique muscles are the superior oblique muscle and the inferior oblique muscle.

The orbit consists of seven skulls: frontal bone, sphenoid bone, ethmoid bone, palatal bone, lacrimal bone, maxilla and zygomatic bone. It is a quadrangular cone-shaped nest inclined slightly inward and upward, with its mouth facing forward and its tip facing backward, and has four walls: upper, lower, inner and outer. Adult orbital depth is 4~5cm. Except the eyeball, extraocular muscles, blood vessels, nerves, lacrimal glands and fascia, the tissues in the orbit are full of fat, which plays a buffering role.