ANATOMY OF EXTERNAL EAR - Dr.G.Bhanu Prakash

in today's lecture we are going to discuss about the anatomy of the ear in the anatomy of the ear in the first part we are going to discuss about the anatomy of external ear next is the middle ear and third is the internal ear so by this we can say that the ear has been divided into three parts the external ear the external ear consists of the oracle or also known as pinna second is the external auditory meters and we will also consider the tympanic membrane is also a part of the external ear even though it forms a boundary line between the external air as well as the material but we will study the tympanic membrane also in the external ear next coming towards the middle ear in the middle layer we will discuss about the middle ear cavity its boundaries as well as the ear ossicles at last we will discuss about the mechanism of hearing along with the structures which are present at the internal ear okay now coming towards the structures which are presented external here the external ear is made up of pinna it is also called as oracle and second is called as the auditory tube it is also called as the external auditory meatus or the external acoustic meatus now let us discuss one by one at first we will begin with the anatomy of the pinna or it is also called as the oracle if you see the entire pinna except its lobule because the lower part of the pinna is called as the lobule the entire pinna except its lobule is made up of a single framework of yellow elastic cartilage how it is made up of the entire pinna except the part in the lobule it is made up of the single frame of yellow elastic cartilage because the lobule contains some amount of fat here okay so by this we know that the skeleton of the pinna or the framework of the pinna is a low elastic cartilage so we already studied in our histology class that all connective tissues are covered by a layer in the same way the cartilage is also covered by a layer called as perichondrium peri means upon the con ah chondria means the cartilage so the perichondrium is the covering of this yellow elastic cartilage it covers in the same the framework of the pinna now if you see the pinna or the oracle it is covered with the skin means it is mainly covering the framework as well as the perichondrium by the skin on its lateral surface as well as on its medial surface right so by this we can say that the skin which is the covering of this cartilaginous framework that is pinna is firmly adherent to the underlying perichondrium on its lateral aspects so by this i want to tell you that on the lateral aspect the skin of the pinna is tightly other entered to the perichondrium and but on the medial aspect the skin is loosely attached to the perichondrium and if you see the pinna from the lateral aspect if you see the pinna from the lateral view the pinna contains various depressions as well as elevations right so what are the depressions and elevations what are the parts of the pinna we are going to see here let's start from the lobule the lower part of the pinna is called as a lobule and immediately if you go above the lobule the structure which is present elevated part is called as the triggers so this is the triggers which contain the elevated cartilage genius part immediately opposite to the triggers we have anti tragus and if you go above the if you continue with the triggers you will see a structure called as incisor terminals but remember one important point that industrial terminalis is a part of the pinna it does not contain the cartilage or we can say it is devoid of cartilage this insular terminalis extends from the tragus to the crust of the helix so we can say that between the triggers this is called as the cross cross of the lx between the triggers as well as the cross of the lx the part of the pinna is devoid of cartilage so that is the reason if you want to do any surgeries or in the neural uh approaches of surgeries of the mastoid or if you want to perform the surgeries of the auditory canal the incision has been made at the insular terminalis so there is no need to cut the cartilage right so that is the reason we can say that this insular terminalis where the incision is made in this area will not cut through the cartilage and it is used for the endural approach in surgery for the external auditory canal or the mastoid and next part is called as i already told you it is called as the crust of the helix and the crust of the helix continues with the helix and lx which continues upwards as well as downwards to end with the lobule and if you see the parts inside the lateral aspect the depressions as well as elevations are one is the antihelics next one is called the simba concave symbol immediately above the crust there is a depression called as a symbol and between the symbol as antihelix we have the triangular fossa triangular depression that is called the triangular fossa and the root where it is the pinna is directed towards the external auditory canal it is called as the concha so concha is the area where the pinna is directed towards the external auditory canal so what are the parts of the pinna here we have a lobule try this next is the crust of the helix between the triggers and crust of the helix the part of the pinna where it is devoid of cartilage called as institute terminalis next is called as the helix afterwards we have the anti triggers next is called as anti helix concha where it is root towards the external auditory meters next is simba concave after the symbol concave we have the triangular fossa right so here uh what is the importance of the pinna here remember that the pinna for he here it is very useful for the graft materials for example if you want to do if you want to perform any reconstructive surgeries of the middle ear the pinna can serve as a important graft material for the surgeon that is the cartilage from the tragus perichondrium from the tragus as well as concave as well as the cartridge from the concave as well as the fat from the lobule all these parts used as a graft materials for the reconstructive surgeries of the middle ear sometimes the cartilage of the pinna is also used to correct the depressed nasal bridge and also for the corrections of the alloy of the nose these are the importance of the oracle or pinna after the oracle arpina now next structure which is present in the external ear which is called as external auditory meniators so this is the external auditory meters in this diagram you can see the external auditory meters as a straight tube but remember one important point that this external auditory meters is not a straight tube uh it has been divided into the outer part of the tube as well as inner part of the tube the outer part of the tube is directed upwards backwards and medially remember the outer part of the tube is directed medially upwards and backwards but if you see the inner part of the tube it is directed same medially but it directed downwards as well as forwards so i will repeat again the outer part of the tube the outer part of the auditory canal is directed upwards backwards medially but inner part of the tube is directed downwards forwards medially that is the reason because it is not a straight tube if you want to examine the tympanic membrane you cannot see immediately from this container area that is the reason if you want to examine the tympanic membrane or if you want to see the tympanic membrane the pinna has to be pulled upwards backwards and laterally for the better visualization of the tympanic membrane okay after knowing the auditory tube structure how it exactly present now let us see its anatomical description of the auditory tube the auditory tube is a total 24 mm in length so i will write here it is totally 24 mm in length it has been divided into the outer cartilaginous part or we can say the outer mustard is called as a cartilaginous part and next is the inner two third is called as the bony part so the outer one that is the cartilaginous part one third means it is eight centimeters and inner bony part is uh two third so it is sorry it is mm 8 mm total it is 24 mm the outer part is 8 mm and the inner part is 16 mm so totally it is 24 mm in length now let us discuss about uh some more details about the cartilage genius part so i already told you that the cartilaginous part of the auditory tube is totally 8 mm in length and this cartilage is the continuation of the framework of the pinna we already studied that the framework of the pinna is a single piece of elastic cartilage so the cartilage which is present in the cartilaginous part of the external auditory tube is the continuation of the cartilage which forms the framework of the pinna but if you see the cartilage it has two deficiencies right the cartilage is not continuous you can see some gaps here is one gap here is one gap so you can see two deficiencies which are present at this cartilaginous part this deficiencies are called as fissures of santorini what are these deficiencies these deficiencies are called fissures fissures of santorini okay fissures of santorini so the this fissures of santorini are the gaps which are present at the cartilaginous part this acts as the spread of infections from the auditory tube that is outer part of the auditory tube towards the mastoid or to the parotid this is the parotid gland this is the parotid gland so this is the parotid gland so if you have a perioditis where for example inflammation of the parotid gland the inflammation may spread to the outer part of the external canal through the gaps which are present at the cartilaginous part these gaps are called as the fissures of santorini and not only that the infection may spread to and flow it is not compulsory that the infection is only going from the parotid gland to the outer part of the canal the from the outer part of the canal the infection may reach the period or from the outer part of the canal the infection may reach the mastoid or from the mastoid also if you have any master auditors information or infection of the mastoid the infection may spread toward the outer part of the can also we can say vice versa so remember in the cartilaginous part we have the we have two deficiencies that is gaps called as fishers of santorini that acts as a root for the spread of the infections from the outer part of the canal to the parotid as well as to the mastoid or vice versa right now if you see the outer part of the canal i will draw the outer part of the canal right this is the cartilaginous part let's see here this is the cartilaginous part right so this is the cartilaginous part so i will draw the skin of the cartilage in your spot so remember here the skin of the cartilaginous part is thick the skin of the or the skin which is covering the cartilaginous part of the auditory tube is thick and it contains the ceruminous cerumenous and sebaceous glands you know the ceremonies and sebaceous glands will secrete the wax as well as the oil right so the outer part of the canal that is the cartilaginous part of the canal is totally eight mm in length and the skin which is covering the cartilaginous part is very thick which means the the skin which is covering the boney part is thin automatically right so that is the reason i want to say that the skin which is covering the cartilage in a spot is thick and it contains the importance of luminous as well as sebaceous glands not only that it also contains hair hair follicles so that that is the reason the outer part is more vulnerable to the infections like infections of the hair follicles like staphylococcal infections like foreign commonly seen in the outer part that is cartilaginous part of the external acoustic meatus mainly because of it contains the hair follicles and the infections the most common infections which are seen towards the hair follicles or the staphylococcus infection so that is the reason the freckles are more commonly seen at the cartilaginous part of the auditory tube so what are the what is the importance here the skin covering the cartilaginous part is thick right next is it contains the numerous hair follicles and next stress it contains the important glands that is the cerumenous glands as well as phylocerbicious glands that is hair is only confined to the outer part of the canal that is the reason i told you that the frontal that is staphylococcal infections of hair follicles are only seen in the outer third of the canal now if you see next is the bony part this is the bony part the bony part is called as the inner two third outer one third is the cartilaginous part and angle 230 is the bony part and it is a 16 mm in length right it is 16 mm in length but 6 mm lateral to the tympanic membrane or you can say i will write this point 6 mm 6 mm and here it is 10 mm right so 6 mm lateral to the tympanic membrane the bony part is narrowed here you can see 6 mm lateral to the tympanic membrane the bony part is narrowed this narrowed bony part of the external auditory meatus is called as the isthmus so if you have any foreign material which is logic medial to the stomas that is lateral to the tympanic membrane and medial to the ester muscles for example if you see this is the tube right and it is narrow and again it is wider if any material which is large at the lateral aspect of the establish that medial aspect of the stomach as well as the lateral aspect of the tympanic membrane what happens these foreign bodies are very difficult to remove and where they lodge near to the tympanic membrane and that can cause perforations infections as well as discharge at the internal part of the um external acoustic measures so i want to tell you that so 6 mm lateral to the tympanic membrane the bony meatus is narrowed this narrow bony meatus is called as ischamus and at the islamist area itself that is uh immediately median to the estimas you can see a rss you can see a present terraces the research is called as anterior vessels so i told you that a foreign material may lodge media to the estimates that is lateral to the tympanic membrane so after a foreign material is lodged it is difficult to remove because it is difficult to remove and it can cause infections as well as perforations and not only that immediately medial to the stomach the structure which is present is called an anterior resist so at the anterior resist all these discharges as well as perforations may launch so that is the reason i want to tell you that this anterior resist acts like a spool for the discharge of the debris from the external as well as the middle ear infections right not only that what exactly the middle uh the external auditory mutants you are seeing the anterior view anterior uh boundary got cut here but if you see the antro inferior aspect of the meatus and antro inferior part of the bony canal may presence a deficiency called as the foramen of hashgraph so what it is the antro inferior part of the bony canal has a deficiency called as foramina fasca and this foramina of oscar is generally present between uh in the children up to four years of age but sometimes this foramina foster is also seen in the adults so what is the importance of these foreign immediately below that it is a deficiency means what it is a direct route towards the period if you have any infections of the inner part of the canal or if you have any infection from the parotid through the phenomena of ashka the infections may spread to and fro that is the reason the antro inferior part of the bony canal has a deficiency called as the phenomenon of fascia and it is seen mainly in the children up to the age of four and sometimes it is in the adults and it can permeate the infections mainly from the periodic gland so if you talk about the skin which is lining the bony part i told you that the skin which is learning the bony part is very thin it does not contain the pilosebaceous glands it does not contain the waxy luminous glands and it is also devoid of hair so what is the importance between the outer part of the canal as well as inner part of the canal the total length is 24 mm the outer part is cartilaginous part how much what is the length 8 mm and it has two deficiencies called as fissures of santorini so what is the importance of the features of center knee two and fro infections may spread from the outer part of the canal towards the parotid as well as towards the mastoid and also the skin which is covering the cartilaginous part is thick and it is covered by the pyro services glands as well as numerous hair follicles are present that is the reason the staphylococcal infections of the hair follicles are very common in this area and that is the reason frontals are more commonly seen in the outer part of the canal and the inner part of the canal is bony and the skin which is covering the inner part of the canal is very thin it is devoid of hair as well as it is devoid of glands and it is totally 16 mm in length and 6 mm natural to the tympanic membrane the bony canal is narrowed called as estamos so any foreign material which is lodged medial to the estrous and lateral to the tympanic membrane are difficult to remove so because of the lord in that area they can cause infections as well as perforations and immediately in that body can all you have the rest is called as anterior resist so these perforations as well discharges can accumulate in these anterior resistance that is the reason we can say that the anterior process may act as a cesspool for the discharge for the debris as well as perforations from the middle ear as well as the infections which are seen at the um inner part of the bony canal right not only that the anti-inferior part of the bony canal also presents the deficiency called as paramila fasca this foramen is mainly seen in the children up to the age of four and sometimes also seen in the adults and this phenomena of sky is very important route for the transmission of the infection from the peritoneal gland to and fro to the inner part of the body can all so by this we finish the external yeah that is we finish with the oracle that is pinna as well as the external acoustic meatus