Sense organs (Organa sensuum) can be exteroreceptors for the environment, as well as intero-receptors that receive stimuli from the inner world of our body.
Stimuli from the outer world can be received through contact and touch. The formations that receive such stimuli are contact receptors and evaluate mechanical or chemical stimuli. Visual and auditory senses, on the other hand, form the tele-receptor group because they receive the stimuli of distant, non-direct contact formations.
Each specific receptor makes its own specific evaluation and perceives whatever stimulus effects. For example, a mechanical effect on the eye can be perceived by a living thing as a sense of light, while an electrical stimulus on our tongue can be evaluated as a taste stimulus in various nuances. Sensation received by these receptors in accordance with the conditions, the impulses are transmitted to the relevant areas of the CNS (general sensory, hearing, visual centers of the Cortex cerebri, hypothalamus, respiratory and circulation centers in the brain stem) with sensory nerves.
Receptors are divided into four groups according to their localization. Exteroreceptors to the receptors on the skin that receive direct stimuli from the external environment, blood pressure, oxygen and carbon dioxide concentration etc. in the body. Receptors that can sense are called interreceptors, receptors that can receive sound, vision and smell from afar are called telereceptors, and deep sensory receptors located in the joints, muscles and vestibular part of the ear are called proprioreceptors.
Receptors are called thermoreceptors, chemoreceptors, photoreceptors, mechanoreceptors and baroreceptors according to the types of stimuli they perceive.
The senses are considered in two groups as general senses and special senses. Senses such as Touch, Pressure, Vibration, Hot-Cold, Stereognosis and Proprioception are called General Senses, and senses such as Sight, Hearing, Balance, Smell and Taste are called Special Senses. General Sensory receptors other than proprioception are also found in the skin. Therefore, before going into Special Senses, we will examine the structure of the skin (integumentum communae) functions and attachments.
Skin and Its Attachments
Hairs, Nails, Skin glands and General Sensory receptors in the skin, which have appendages with the skin, are discussed under the heading of integumentum commune or Integumentary System. We will examine the skin and its addons separately.
1. Cutis (Leather)
The skin is the largest organ of the human body, with an approximate area of 1.5-2 m2. average thickness 1-2 mm (skin of the eyelids 0.5 mm. upper part of the back) skin is 5 mm thick). The skin, which protects the body against mechanical, osmotic, chemical, light and thermal harmful factors, also plays a role in the regulation of body temperature (thermoregulation). The formation of vitamin D with the effect of ultraviolet light takes place thanks to the skin. The skin functions as an excretory organ with its sweat and sebaceous glands, and is also the largest general sense organ with the various receptors it carries. The normally existing tension of the skin is called Turgor.
The branch of medicine that deals with the skin and its diseases is called Dermatology.
Leather is made up of two very different layers.
The superficial layer made of stratified keratinized epithelium that develops from the ectoderm is called the Epidermis. The layer that has mesodermal origin and is located under the epidermis is also called the Dermis (Corium).
A.Epidermis: It is the upper layer of the skin and is made up of stratified keratinized epithelium. It is covered with a special layer produced by skin glands and keratinized cells. As this layer contributes to the protection of the skin against chemical and mechanical damage, and creates a barrier for microbes, it does not contain vessels, but is fed by the blood reaching here by Diffusion from the vessels in the Dermis. The thickest parts of the epidermis are the palms and soles of the feet.
The epidermis has a 5-layer structure. The deepest one of these is Stratum basale (Germinativum). The stratum basale is a layer that gives the skin its color because it contains melanocyte cells. The stratum basale is capable of forming other layers of the epidermis when necessary. Stimulation of the stratum basale is achieved by thinning the most superficial layer.
B. Dermis: The dermis is a thick layer composed of interwoven collagen and elastic connective tissue fibers (from Stratum reticulare and Stratum papillare). Dermis, rich in vessels and nerves, contains many sensory nerve endings (they enter or act as receptors), Skin glands and Hair follicles.
C. Hypodermis (Subcutis): It is a layer rich in fat cells, made of loose, fibrous connective tissue, located under the skin. This layer, which is thicker than the dermis, contains subcutaneous sensory nerves, superficial veins and lymphatic vessels. Due to the loose structure of the hypodermis, the overlying skin can be moved freely.
Women have more adipose tissue in the hypodermis than men. Subcutaneous adipose tissue, which accumulates especially in the Breast, Hip and Abdomen region, provides the formation of characteristic contours in the female body. The amount of adipose tissue in this layer varies according to individual and racial differences as well as nutritional status and hormonal effects.
2. Special Attachments of the Skin
Skin glands, hairs, nails and skin receptors are examined under this heading.
Skin Glands: There are two types of glands in the skin: sebaceous and sweat glands (Glandulae sebaceae et sudoriferae).
Glandulae sebaceae (Sebaceous Glands): These are simple branched glands located in the dermis, and they pour their secretions either into the hair follicles or directly on the skin surface. Sebaceous glands are found all over the body skin except the soles of the feet and palms. The special smelling secretion of the sebaceous glands is called Sebum. Sebum lubricates the skin surface and creates a barrier against bacteria and fungi. Chronic inflammation of the sebaceous glands is called acne.
The secretory function of the sebaceous glands is affected by factors such as temperature and sex hormones. Androgens stimulate the sebaceous glands to function.
Glandulae sudoriferae (Sweat glands): Sweat glands located in the deepest part of the dermis or hypodermis have two types as eccrine and apocrine.
Eccrine sweat glands are small glands found in the entire body skin except the lip margins, nail beds, labia minora of the vulva, Clitoris and Glans penis.
When the body temperature rises, the eccrine glands are stimulated and they produce a copious acidic secretion, which causes a decrease in body temperature.
Apocrine sweat glands, Armpit, Areola mammae, Large lips of the vulva, Anal and Genital region skin are abundant. Apocrine sweat glands secrete in response to stress. They have characteristic odors (pheromone).
Pili (Hairs): They are characteristic formations of mammals and are found throughout the human body, except palms, soles, lips, glans penis, nipple and labia minora of the vulva. It has functions such as protection, contribution to the regulation of sense and body temperature.
The part of a hair that enters the skin is called the hair root, and the part outside the skin is called Scapus pili (hair body). The lowest part of the hair root and its surrounding structures are called Bulbus pili. Hair growth occurs via the Bulbus pili. The connective tissue sheath surrounding the hair root attaches to the smooth muscle M. arrector pili at the level of the middle of the folliculus pili. This muscle, which is innervated by sympathetic nerves, is used for emotions, cold, etc. For reasons, it tightens the hair by contracting and puts the skin in a special shape (muscle skin appearance). Melanin pigment in melanocytes gives hair its color.
The distribution of hairs in the human body and their features in various regions vary according to age, gender and race. The last fixed hair growth of the body begins with puberty and continues until the age of 40-50.
Human hair is divided into three groups according to their effects on sexual hormones.
1. Hairs that occur in Puberty, which are under the control of endocrine glands in both sexes (Hirci (armpit hair), Pubes (deep hair – pubis hair), Genital region hair and Head hair-Capilli (Hair)
2. Hairs under the influence of androgens in men (Barba (beard), Tragi (ear canal hair), Vibrissae (nose hair), Hair of the extensor surfaces of the Shoulder, Back, Chest, Abdomen, Arm and Forearm).
3. Hair that is not related to sexual hormones and is seen in the same way in both sexes, Supercilium (eyebrows), Cilia (eyelashes) a part of extremity hair
Nails (Ungues) : Nails, hand and They are horny (keratinous), elastic formations, which are a modification of the epidermis, similar to hair, located on the dorsal parts of the ends of the last phalanges of the toes.
Translucent nails are pink due to the color of the underlying vascular tissue. They appear in color e.
The thickness of the nail in the form of a plate is 0.5 – 0.7 mm. Nails, whose growth is affected by hormones, nutritional conditions and diseases, normally grow 0.5 – 1 mm per week.
The nail has two basic parts, the root and the stem.
Nail root (Radix unguis) is located in Sinus unguis. The nail body (Corpus unguis) and the nail root sit on the Stratum germinativum of the Epidermis in the area called the nail bed.
In the proximal part of the Nail Corpus, there is a crescent-shaped white area (Lanula). The thick cell layer under the nail root and Lanula, which allows the nail to grow, is called Matrix unguis.
General Sensory Receptors Found in the Skin
There are receptors in the skin that receive the senses of Touch, Pain, Heat, Pressure and Vibration, which make the skin a sensory organ. These receptors are of two morphological types, encapsulated and non-encapsulated.
Although some of these receptors are specific for one sense, some senses can also be received by several receptors. For example, the sensation of pain is received only by free nerve endings.
The sense of touch is received by hair follicle receptors, Merkel discs, Meissner corpuscle and Ruffini corpuscle.
We will examine unencapsulated and encapsulated receptors separately.
Unencapsulated Receptors: Free nerve endings, Merkel discs and hair follicle receptors are non-encapsulated receptors.
Free nerve endings: They sense Pain, Touch, Pressure and possibly Heat.
Merkel discs (Meniscus tactus): Pressure receptors found in bald skin and hair follicles.
Hair follicle receptors: They are touch receptors located in the form of a nerve network around all hair follicles.
Encapsulated Receptors: Meissner corpuscle, Vater-Pacini corpuscle, Krause corpuscle, Ruffini corpuscle are encapsulated receptors of the skin.
Meissner corpuscle (Corpusculum tactus): They are receptors that receive the sense of Touch and Two-point Tactile Discrimination, located in the dermal papillae of hairless skin (Palms, Soles, Lips, External denital organs).
Vater-Pacini body (Corpusculum lamellosum): They are receptors that receive vibration and rapid mechanical changes (Pressure – Tension) in Dermis, Hypodermis, Tendos, Joint capsule, Peritoneum and External genital organs.
Krause body (Corpusculum bulboidea): They are receptors that receive spherical shaped cold (sensitive to temperature below 20 °C) and pressure – touch sensations located in the mucous membranes and dermis layer of the skin. More numerous than Ruffini corpuscles.
Ruffini corpuscle : It is a receptor evaluated in the Krause corpuscle category, and it receives the sense of pressure and stretching of hot (walled over 25°C) and touch.
Skin receptors receiving general senses:
Stereognosis: Stereognosis (Stereos=mass, three-dimensional formation, Gnosis=knowing and recognition) The known shape and some qualities of a formation that we hold or touch through the sense of touch. recognition ability. This ability is realized within the framework of the information that has been seen and touched before and stored in the sensory areas of the brain.
Stereognosis is examined by touching and recognizing well-known objects such as coins, keys, combs and pens while the eyes are closed.
2. Organum olfactorium (Organ of Smell)
Regio olfactoria, which contains receptor cells in the nasal cavity mucosa, functions as the Organ of Smell. The olfactory nerve cells here are chemoreceptors that detect odor particles mixed with the atmosphere air.
The olfactory organ is phylogenetically developed in terrestrial animals rather than in aquatic animals. In humans, this sense is less developed than in other vertebrates. For example, dogs can smell 10 million times stronger than humans.
Structure of the Odor Mucosa: The nasal cavity is covered with three different covers. The olfactory mucosa (Tunica mucosa olfactoria) is a special mucosa above the superior turbinate of the nose. The most important feature of the olfactory mucosa is that it contains olfactory receptor cells. Dendritic cilia of these cells face the surface of the mucosa. Support cells in the mucosa and Bowman’s glands moisten the mucosal surface with their secretions. After the odor particles in the inhaled air dissolve in the mucous secretion, they are detected by the olfactory receptor cells. There are 25 million (220 million in dogs) olfactory receptor cells in the human olfactory mucosa.
Olfactory receptor cells convert the odor they perceive into nerve impulses and transmit them to the CNS (Bulbus olfactorius – Tractus olfactorius – Olfactory brain) with their axon-like central extensions (Nn. olfactorii).
3.Organum gustus (Taste Organ)
Tongue, which is an indispensable organ for speech and nutrition in humans, is the taste organ thanks to the taste receptors (neurosensory gustatoric cells) in the special structures (taste buds) contained in the mucosa. functions as well. Taste buds (Calliculus gustatorius) are located on the tongue Papilla vallata and Papilla fungiformis. There are about 10,000 taste buds on the tongue.
Taste buds are barrel-shaped structures and there are taste holes (Porus gustatorius) on the sides facing the tongue surface or the gap around the papillae vallata.
Particles dissolved in water to be tasted enter into the taste bud through this hole. Taste buds contain neuroepithelial taste cells, which are taste receptors similar to olfactory mucosa. Taste sensations perceived by these cells are conveyed to the CNS via N. lingualis (the sense is transferred to N. facialis via the Chorda tympani connection) and N. glossopharyngeus.
Another concept related to the sense of taste is taste. Flavor; It is a common sensation created by the taste, smell, temperature of the food, the sound and appearance of chewing.
Different parts of the tongue have different tastes. Sweet and salty is perceived at the tip of the tongue, sour at the edges of the tongue, and bitterness is perceived near the tongue root.
4.Organum visus (Organ of Vision)
The organ of vision is two eyes located in the right and left eye sockets (Orbita) and allows us to integrate with a visual world. The human eye, which has a camera eye structure, has a special visual layer that contains 70% of the receptors in the whole body.
The images perceived by the vision receptors of the neurons in this layer (retina) are transmitted to the CNS in the form of nerve impulses via N. opticus, which is formed by 1/3 of all afferent fibers in the body. Although many visual stimuli come to our eyes from the outside world, we can only see some of them since we are sensitive to 1/70th of the electromagnetic spectrum. On the other hand, insects can also see the shorter wave UV (Ultraviolet) and longer wave IR (Infrared) light spectrum.
Eye anatomy is examined under two main headings: the eyeball (Bulbus oculi) and the auxiliary organs of the eye (Organa oculi accessoria).
Eyeball (Bulbus oculi)
The eyeball is a round biocamera with a diameter of 2.5 cm and a weight of 10 g, located in the Orbita. The eyeball, the inner cavity of which is divided into three chambers, has a three-layered wall structure.
Wall Structure of the Eyeball: It is made up of three layers: fibrous, vascular and sensorial from the outside to the inside.
1.Tunica fibrosa (Fibrous layer): The outer layer, also called the support layer by some Anatomists, is made of thick, fibrous connective tissue. The fibrous layer, which maintains the shape of the eyeball, also acts as an attachment site for the extra ocular muscles.
5/6 posterior part of the fibrous layer is opaque white and called Sclera, and 1/6 anterior part of it is transparent-transparent and called Cornea. Light enters the eye through the cornea. The cornea has no blood and lymph vessels (it is rich in irritability). The sclera is perforated (Lamina cribrosa) in the part where the fibers of N. opticus leave the eyeball posteriorly.
2. Vascular layer (Tunica vasculosa): It is a layer rich in blood vessels and pigment. Due to its intense pigment content, it is dark brown and absorbs the rays reaching it, not reflecting it. The vascular layer has three sections, from posterior to anterior, Choroidea, Corpus ciliare, and Iris.
Corpus ciliare is the anterior, thick part of the vascular layer, and its structure contains smooth muscle (M. ciliaris) innervated by autonomic nerves with differently oriented fibers. At the same time, the eyepiece (Lens) is attached to the Corpus ciliare with suspension ties.
The iris, on the other hand, is a part like a diaphragm that contracts and relaxes in front of the eye lens, and there are smooth muscles called M. sphincter et M. dilator pupillae in its structure. The opening in the middle of the iris is called the Pupil. The normal pupil is 4 mm in diameter in room light. Its narrowing is called Miosis and its enlargement is called Mydriasis.
3. Tunica sensoria (Tunica nervosa optica-retina): It is the innermost layer of the eyeball and is also called the retina or neural layer. The sensorial layer is very delicate and contains about 130 million photoreceptors and many neurons.
The posterior area of the sensorial layer that sees best is called the Yellow spot (Macula lutea).
The part where N. opticus leaves the retina (Discus nervi optica) is insensitive to light and is called the blind spot. The retina can be examined through the Pupillary opening with the ophthalmoscope method.
Lens: The Lens (eyepiece) located behind the pupil is a highly elastic, biconvex lens with a diameter of about 1 cm. It is devoid of blood vessels and nerves. Its nutrition is provided by the humor aqueosus.
The lens is attached to the Corpus ciliare by suspensory ligaments (Fibrae zonulares, Lig. suspensorium lentis). As a result of the contraction and relaxation of the smooth muscle fibers in the structure of the corpus ciliare, the thickness-refractiveness of the lens changes. Increasing the refraction of the lens so that it can see the nearby objects clearly is called accommodation.
Camera bulbi (Eye cavities)
The inner cavity of the eye is divided into three cameras. Two of them (Camera anterior and Camera posterior) are anterior and filled with humor aqueous secreted by the nonpigmented epithelium of the Corpus ciliare (Proc. ciliaris). Humor aqueous enters the general circulation through the Schlemm channels located between the Cornea and Iris of the anterior camera.
The third space inside the eye is the largest camera and is called Camera vitrea. Camera vitrea, which covers 80% of the inside of the eye, is behind the lens and is filled with the Corpus vitreum, a gelatinous substance. Corpus vitreum is a transparent gel-like formation, 90% of which is water.
Auxiliary organs of the eye (Organa oculi accessoria)
Eyebrows, Eyelids, Eyelashes, Conjunctiva, Tear apparatus and extra ocular eye muscles in the orbit are called auxiliary organs of the eye.
1. Eyebrow (Supercilium): The short, oblique hairs on the skin above each Arcus superciralis in the frontal bone are collectively called Supercilium (eyebrow). The eyebrow, whose opening is in the form of a downward facing curve, protects the eye from intense sun rays, sweat secretion from the forehead and foreign substances.
2. Eyelids (Palpebrae): The two upper and lower eyelids for each eye are skin folds, and when they are open, they reveal an almond-shaped opening around the eyeball in front. When they are closed, a Horizontal slit (Rima palpebrarum) occurs between the lower and upper eyelids. The eyelids meet at an angle on the inner and outer sides of the Orbita. These junctions are called Canthus (junctions of the eyelids) or Commissura palpebrarum. Although the anterior surface of the eyelids is covered with skin, the posterior surfaces in contact with the eyeball are covered with a mucous membrane, Konjunctiva (conjunctiva).
The inner tissue of the eyelids, the fibrous connective tissue called M.orbicularis oculi tarsus, is made up of Meibomian glands (Glandulae tarsales) and Moll and Zeiss glands. Meibomian glands, which are modified sebaceous glands, prevent the eyelids from sticking together with their secretions called sebum, as well as prevent the evaporation of tears from the conjunctival face.
Protects eyelids, eyeball from dust and other harmful external objects. In addition, it causes the conjunctival faces to remain constantly wet due to the dispersion of glandular secretions on the eyeball with periodic opening and closing movements. Eyelids that close during sleep prevent evaporation of secretions from the conjunctival face.
Cilium – Eyelashes are located on the free edges of the eyelids. The eyelashes on the upper eyelid are longer.
Conjunctiva (Conjunctiva): Conjunctiva, which covers the anterior surface of the posterior eyeball of the eyelids, is a thin, transparent mucous membrane. Conjunctiva includes Glandulae conjunctivales. The part of the conjunctiva on the eyelids is called the Palpebral conjunctiva, the part surrounding the eyeball is called the Bulbar conjunctiva. As the eyelids are closed, the lower and upper two conjunctival spaces become the Conjunctival sac (Saccus conjunctivalis). Small accessory lacrimal glands are found in the Lamina propria layer of the conjunctiva. They have sympathetic innervation.
Apparatus lacrimalis (Tear system): The system in which tears are produced, transmitted and distributed is called the tear system. This system consists of the lacrimal gland, lacrimal ducts, lacrimal sac and nasolacrimal duct.
Lacrimal gland (Glandula lacrimalis): The lacrimal gland is an almond-sized gland located in the superolateral part of the Orbita. The secretion called tear is drained into the upper conjunctival sac with 5-12 drainage channels. From here, the tear is distributed over the entire Saccus conjunctivalis by the eyelids in motion. Some of it evaporates and the other part passes to the tear fountain (Lacus lacrimalis) located near the inner cantus, and from there to the excretion ducts (tear ducts, lacrimal sac, nasolacrimal duct). gl. lacrimalis works with parasympathetic stimulation.
Breakthrough wings: There are small holes called Punctum lacrimale on the edge of the eyelids close to the inner canthus. These holes are the beginning of the excretion channels. The ducts that start from here and progress through the eyelids and reach the lacrimal sac are called Canaliculus lacrimalis superior/inferior (upper and lower tear ducts). The lacrimal sac (Saccus lacrimalis) lies with the nasolacrimal duct, which reaches the inferior meatus of the nasal cavity.
Tears constantly moisturize and cleanse the conjunctival surface of the eyeball. With its antibacterial and lysozymal enzymes, tears kill bacteria reaching Saccus conjunctivalis. The tear delivers the nutrients and water it contains to the Cornea.
Extraocular muscles (Mm. externi bulbi): 6 muscles in the striated muscle structure that enable the eyeball to move in all directions are examined under this heading. Of the extraocular muscles, 4 are straight and 2 are oblique.
Straight muscles:
M. rectus superior, It makes elevation, adduction, intorsion.
M. rectus inferior, It causes depression, adduction, and extortion.
M. rectus medialis makes adduction.
M. rectus lateralis makes Abduction.
These muscles start from the ring-shaped Anulus tendineus communis (Zinn ring) posteriorly (at the Orbita apex), and go forward with a straight course and attach to the Sclera.
Muscles with oblique course:
M. obliquus superior, Depression, abduction and intorsion.
M. obliquus inferior, It makes elevation, abduction and extortion.
Apart from these six muscles, there is another muscle that raises the upper eyelid. This muscle, called M. levator palpebrae superioris, has two parts (Pars superficialis, Pars profunda) innervated by somatic and autonomic nerves. Pars profunda (Müllerian muscle) is smooth muscle and has sympathetic innervation.
5. Organon statoacusticus (Hearing and Balance Organ)
Auris (Ear)
The hearing balance organ is called the Ear for short. The ear, which consists of three parts as outer, middle and inner, is an organ with analytical capacity, specialized in perceiving Sound and Gravity changes, thanks to its connections in the central nervous system. Ear-related diseases are treated by Physicians, Specialist of the Ear-Nose-Throat (ENT) Department (Otorhinolaryngology).
We will examine the outer, middle and inner ear separately.
1. Outer ear (Auris externa)
The outer ear is a structure unique to terrestrial mammals and plays a role in collecting, amplifying and transmitting sound to the middle ear. Within the scope of the outer ear, the auricle (Auricula), the external ear canal (Meatus acusticus externus) and the eardrum (Membrana tympani) are examined.
Auricle (Auricula): Embryologically, it is a typical structure consisting of 6 mesenchymal swellings, knitted funnel-shaped. The auricle, which is long and mobile in some mammals, has become small and immobile in humans. The shape of the ear and the prominence of its recesses and protrusions show some differences from person to person.
The part of the lower part of the auricle devoid of the cartilage roof is called the earlobe (Lobulus auriculae).
Meatus acusticus externus (External ear canal): The outer ear canal is an L-shaped tube that transmits the sound waves collected by the auricle to the eardrum. This tube, which is 2-3 cm long in adults, has two parts (Pars cartilaginea, Pars ossea) as cartilage and bone. The direction of the road is not straight because there is an angle of 40° between the cartilage and bone sections. The skin covering the external ear canal is the continuation of the skin surrounding the auricle, and there are glands that secrete earwax in the subcutaneous tissue. These glands are called Glandula ceriminose. In the skin of the cartilage part of the road, there are Ear hairs called Tragi.
Eardrum (Membrana tympani): The eardrum is a thin, translucent membrane located at the end of the external ear canal, at the border of the outer ear and middle ear. In a living person, it has a pearly gray-glossy (pearl-colored) appearance. The eardrum has two parts (Pars tensa, Pars flaccida), tense and loose. The stretched portion occupies most of the membrane.
Kulak zarının ortasındaki çöküntülülere Umbo membrana tympani denir. Umbo membrana tympani, çekiç kemiğinin kulak zarına tutunan sapının (Manubrium) ucuna rastlar. Kulak zarı aydınlatılarak incelendiğinde Umbo membrana tympani’ den başlayıp öne-aşağıya doğru uzanan trianguler şekilde ışıklı bir alan görülür. Bu alana Politzer üçgeni (Işık refleks üçgeni) denir.
Gevşek bölüm kulak zarının üst kısmında dar bir alan işgal eder.
2. Auris media (Orta kulak)
Orta kulak, Temporal kemik içinde yer alan nazofarinks ile bağlantılı havalı boşluklar, işitme kemikçikleri ve bunlara bağlanan kas ve bağlardan ibaret bir bütündür. Bu boşluklar içinde en büyük olan ve işitme kemikçiklerini içinde taşıyan boşluk Timpanik kavite (Cavum tympani) olduğundan birçok Anatomist tarafından Orta kulak ile özdeş olarak kullanılır. Timpanik kavite ve bununla bağlantılı diğer boşlukların havalanması, nazofarinks’ e açılan Tuba auditiva ossea (Östaki borusu) ile sağlanır.
Timpanik kavite ve Mastoid havalı boşlukları :
Timpanik kavite, Os temporale’nin pars petrosa’sı içinde yer alan irregüler şekilli birkaç ml hacimli bir boşluktur. Kulak zarı düzeyine göre epitimpani mezotirmpai ve hipotimpani olarak üç bölüme ayrılır. İşitme kemikçikleri zinciri esas timpanik boşluk olan mezotimpani bulunur.
Timpanik kavitenin 6 duvarı vardır:
1.Üst duvar: Tegmen tympani tarafından oluşturulur. İnce olan bu duvar, orta kulak iltihaplarının kafa boşluğuna yayılmasına imkan verebilir.
2.Alt duvar: Bulbus V. jugularis interna ile Timpanik boşluğu ayıran ince bir duvardır.
3.Ön duvar : A. carotis interna ile komşuluk yapan bu duvarın üst bölümünde iki kanala (Semicanalis M. tensorius tympani ve Tuba auditiva) ait delikler bulunur.
4.Arka duvar : Proc. mastoideus tarafında yer alan bu duvardaki Aditus et Antrum mastoid boşluklarla Timpanik cavite arasındaki bağlantıyı sağlar. Duvarın ortasında, önemli bir buluş noktası niteliğinde Eminentia pyramidalis (içinde M. stapedius’u barındırır) yer alır.
5.İç yan duvar : Orta kulak ile iç kulak arasında yer alan bir duvar olup, yuvarlak ve oval pencere (Fenestra cochleae -yuvarlak pencere, Fenestra vestibuli – oval pencere) içerir. Yuvarlak pencere Membrana tympani secundaria ile kapatılır. Oval pencereye Stapes’ in basis’i oturur. Duvarın ortasında, cohlea’nın ilk kıvrımı tarafından oluşturulan Promontorium bulunur. Üzerinde Plexus tympanicus yer alır.
6.Dış yan duvar : Kulak zarı tarafından oluşturulur.
Mastoid boşlukların en büyüğü Antrum mastoideum olup yeni doğanda dahi mevcuttur. Diğer Mastoid boşluklar (Cellulae mastoideae) 2-4 yaşlarında oluşur.
İşitme kemikçikleri (ossicula auditus) : Timpanik boşluk içinde yer alan ve kulak zarından aldıkları ses titreşimlerini 15-20 kat artışla oval pencereye (Fenestra vestibuli) ileten, birbiri ile eklemleşmiş üç küçük kemikçik (Çekiç-Malleus, Örs-Incus, Üzengi-Stapes)’ tir.
İşitme kemikçikleri ile igili kaslar: İşitme kemikçikleri ile ilgili iki kas vardır. M. tensor tympani (N. mandibularis innerve eder), M. stapedius (N. facialis innerve eder). M. tensor tympani uzun silindir şekilde bir kas olup kulak zarını gerer. M. stapedius kasıldığında, üzengi kemiğinin tabanını oval pencereden uzaklaştırır.
M. tensor tympani ve M.stapedius kemikçik zinciri ile kulak zarının normal tonusunu korurlar, iç kulağa ulaşacak aşırı uyarıları önlerler. Ses ileti aparatında regülatör görevi görürler.
3. Auris interna (İç kulak)
İç kulak; Temporal kemiğin pars petrosa’ sı içine yerleşmiş, insan vücudunun en iyi; korunmuş organıdır. Dış ve orta kulak sadece işitme ile ilgili oldukları halde, iç kulak hem işitme hem de denge duyusunun algılandığı yapıları taşır. Kemik ve membranöz karmaşık kanallar sistemi ile, bu kanal sisteminde bulunan Perilenfa, Endolenfa ve Reseptör hücrelerinden oluşmuş olan iç kulak iki bölüme ayrılarak incelenir.
Kemik labirent (Labyrinthus osseus) : Embriyolojik olarak, zar labirenti oluşturan kulak keseciğini (Vesicula otica) saran mezenşimal dokudan meydana gelen, kapsül niteliğinde bir yapıdır. Kemik labirentin iç yüzü ile zar labirent arasındaki aralık Perilenfa ile doldurulmuştur.
Kemik labirentin Vestibulum, kemik yarım daire kanalları (Canalis semicircularis) ve Cochlea olmak üzere üç bölümü vardır. Vestibulum, kemik labirentin merkezi bölümü olup, önde Cochlea arkada kemik Canalis semicircularis ile devam eder. Vestibulum içinde zar labirentin denge ile ilgili yapılarından Utriculus ve Sacculus bulunur.
Canalis semisircularis (kemik yarım daire kanalları), Ön, arka ve dışyan olmak üzere üç tanedir. Bu kanalların vestibulum’a bağlanan bir uçlarında birer şişkinlik (Ampulla) bulunur. Ön ve arka yarım daire kanallarının nonampuller bacakları, ortak bir bacak (Crus commune) ile Vestibulum’a bağlandığı halde dışyan kanalın nonampuller bacağı tek başına Vestibuluma bağlanır.
Cochlea (salyangoz kabuk) : İç kulağın işitme ile ilgili yapılarını taşıyan kemik bölümüdür. İki buçuk defa bükülmüş bir salyangoz kabuğuna benzer. Cochlea’da merkezi kemik yapı olan Modiolus etrafında dolanan Spiral kanal (Canalis spiralis cochleae) bulunur. Bu kanal ince bir kemik lamı ile (Lamina spiralis) iki Skalaya (Scala tympani, Scala vestibuli) ayrılır.
Zar labirent (Labyrinthus membranaceus) : Zar labirent, kemik labirent içinde yer almış, kabaca onun şekline uyan, içi endolenfa ile dolu, ince, birbirleri ile bağlantılı bir kanal ve keseler sistemidir.
İşitme-denge duyusunun algılandığı esas yapıları taşıyan zar labirentin iki bölümü vardır.
1.Vestibüler labirent : Denge ile ilgili zar labirent bölümleri (Utriculus, Sacculus, Ductus semicirculares) tir.
2.Cochlea labirinti: Zar labirentin işitme ile ilgili bölümü olup, Cohlea içinde uzanan Ductus cochlearis’ten ibarettir. Ductus cochlearis Scala media olarak ta adlandırılır. Burada, mekanik ses uyarılarını, elektrik impulsları haline getiren Corti organı yer alır.
Sağlıklı günler dileği ile…
Uzman Dr.Ali AYYILDIZ -Veteriner Hekim – İnsan Anatomisi Uzmanı Dr. (Ph.D.)
