Hello, welcome to my channel! Today we are going to give the Ear Embryology In the adult, the Ear is part of an anatomical unit which is good for hearing as for balance And in the embryo it develops from of 3 well differentiated parts 1- It is the External Ear 2- The Middle Ear 3- The Inner Ear The External Ear is an organ that captures sounds The Inner Ear converts sound waves into nerve impulses and records the balance changes And the Middle Ear is a conductor of sound from the outer to the inner ear Let's start
by talking about the INTERNAL EAR The first indication of the developing ear it is identified in embryos of approximately 22 days as a thickening of the superficial ectoderm on both sides of the hindbrain These thickenings called Placodas Óticas invaginate soon to form the Otic or Auditory Vesicles, also known as Otocistos Octocyst cells differentiate by creating ganglion cells to form the Statoacoustic Ganglia During further development, Each gallbladder is divided into: A ventral component, which gives rise to the Sacules and the Cochlear Duct And a dorsal component, which forms the Utricle, Semicircular Canals and Endolymphatic Duct Put
these epithelial structures together produce the Membranous Labyrinth Well, now we are going to talk about Saculum, the Cochlea and the Organ of Corti In the 6th week of development The Saculum forms a tubular evagination at its bottom is evagination, known as Cochlear Duct, penetrates the surrounding mesentery spirally until the end of the 8th week, when he completes 2.5 laps In the 7th week, the duct cells cochlear differ in the Spiral Organ of Corti that convert sound vibrations in electrical signals for hearing A connection between the duct and the remaining part of the Saccule remains, but
confined to a narrow channel receiving the name of Hensen's Conduit In the mesenchyme surrounding the Cochlear Duct soon differs into cartilage In the 10th week this cartilaginous shell experiences Vacuolization, then two perilymphatic spaces appear: the Tympanic Ramp and the Vestibular Ramp So the Vestibular Membrane separates the Cochlear Duct of the Vestibular Ramp and the Bacillary Membrane separates it of the Tympanic Ramp The side wall of the Cochlear Duct is attached to the surrounding cartilage by means of the Spiral Ligament While its middle angle, is connected to a long cartilaginous process which is called Modiolo and
is supported by it, which in the future will form the axis of the Bone Cochlea At the beginning they appear cochlear duct epithelial cells but as development continues they give rise to 2 edges: the Inner Edge and the Outer Edge The inner edge will be the future Spiral Limbo The outer edge produces an inner row and 3 or 4 outer rows of hair cells known as Sensitive cells of the auditory system, these are covered by the tectory membrane being a fibrillary gelatinous substance attached to the Spiral Limbus whose end rests on the hair cells Sensory
cells along with the tectory membrane constitute the Organ of Corti The impulses received by him, transmitted to spiral ganglion and then to the Nervous System through the auditory fibers of the 8th cranial nerve UTRICLE AND SEMICIRCULAR CHANNELS During the 6th week of development the semicircular canals appear as flattened evaginations in the utricular part of the Otic Vesicle Over time the central parts of the walls of the evaginations unite and disappear giving rise a 3 Semicircular Ducts One end of each channel, expands to produce the Ampullary Branch, not so the other to form the Non-Ampullary Branch
However as the 2 of the second type merge only 5 branches enter the Utricle 3 with a blister and 2 without it Cells in blisters form a ridge known as Ampullary Ridge containing sensory cells to keep balance other similar sensitive areas which are called Acoustic Macules develop in the Utricle and Saccule walls When the body changes position vestibular fibers of the 8th cranial nerve transmit impulses generated to the brain in the sensory cells of the ridges and macules During the formation of the Otic Vesicle a small group of cells will comes off your wall to
constitute the Statoacoustic Ganglion other ganglion cells originate from the neural crest Subsequently, the node is divided into a cochlear and a vestibular part that innervate the sensory cells of the Organ of Corti as well as those of the Saculum, the Utricle and the Semicircular Canals, speci Now we are going to talk about MIDDLE EAR Starting with The Tympanic Cavity and the Ear Tube The Tympanic Cavity originates from the endoderm and comes from the 1st Pharyngeal Bag The Stock Market expands laterally contacting with the ground in the 1st Pharyngeal Cleft The distal part of the Bag
called recess Tympanic Tube widens to produce the Early Tympanic Cavity The proximal part remains narrow and forms the Auditory Tuba or Eustachian Tube through which the tympanic cavity communicates with the nasopharynx Regarding the HOLES The Hammer and the Anvil originates from the cartilage of the 1st Pharyngeal Arch The Stirrup in the cartilage of the 2nd Arch While the little pots emerge in the first half of fetal life are embedded in the mesenchyme until the 8th month when the surrounding tissue dissolves The endodermal epithelial lining of the Early Tympanic Cavity spreads across the wall of the
newly formed space Now the Tympanic Cavity is at least twice the size above When the huecesillos are released completely from the surrounding mesenchyme The endodermal epithelium connects them to the wall of the cavity through structures similar to the mesentery. and the supporting ligaments of the ossicles develop later within those mesentery The hammer develops from the 1st pharyngeal arch So your muscle, the Tensor Tympani is innervated by the Maxillary Branch of the Trigeminal Nerve The Facial Nerve, the nerve of the 2nd Pharyngeal Arch innervates the stapedius muscle which is attached to the stirrup During the last
stages of fetal life the Tympanic Cavity expands dorsally as the surrounding tissue is vaccinated to form the Tympanic Club After birth the epithelium of the Tympanic Cavity invades the Bone of the Mastoid Process then the air sacs appear lined with epithelium Later most of the bags enter in contact with the antrum and the tympanic cavity And now we are going to talk EXTERNAL EAR regarding the External Auditory Canal It develops from the dorsal portion of the 1st Pharyngeal Cleft At the beginning of the 3rd month the epithelial areas of the canal bottom proliferates producing a
solid epithelial plate being the Meatal Plug In the 7th month of development the plug dissolves and then the epithelial lining duct floor participates in the creation of the definitive eardrum Sometimes the plug persists until the Birth and cause Congenital Deafness The Tympanum consists of 3 parts 1- It is the ectodermal epithelial lining deep in the ear canal 2- It is the epithelial lining endodermal cavity of the tympanic cavity 3- It is the intermediate layer of the connective tissue which forms the fibrous layer Most of the eardrum is firmly attached to the hammer handle and the
remaining part form the separation between the auditory canal External and Tympanic Cavity AND THE EARPHONE PAVILION develops from 6 proliferations mesenchymal at the dorsal ends of the 1st and 2nd Pharyngeal Arch that surround the 1st Pharyngeal Cleft Later, these prominences known as Ear Mounds, 3 on both sides of the External Duct will merge giving rise to the final auricular pavilion Frequently, anomalies occur in the development of the Auricle due to the complexity of the formation and fusion of the Mounds Furthermore, like the mounds derived from the Neural Crest cells, often abnormalities of the outer ear
are accompanied by malformations in other organs coming from those cells such as defects of the face, skull and heart Initially the External Ears are located in the Lower Neck Region but the posterior and cranial growth of the jaw shifts them to the side of the head at eye level And well, this is the end of the video I hope it has been useful to you And if you liked it please SUBSCRIBE
