Difference between revisions of "Talk:Hearing - Middle Ear Development"

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Closure of the middle ear is believed to be closely related to the evolutionary development of the mammalian jaw. However, few comprehensive descriptions are available on fetal development. We examined paraffin-embedded specimens of 20 mid-term human fetuses at 8-25 weeks of ovulation age (crown-rump length or CRL, 38-220 mm). After 9 weeks, the tympanic bone and the squamous part of the temporal bone, each of which was cranial or caudal to Meckel's cartilage, grew to close the lateral part of the tympanosquamosal fissure. At the same time, the cartilaginous tegmen tympani appeared independently of the petrous part of the temporal bone and resulted in the petrosquamosal fissure. Subsequently, the medial part of the tympanosquamosal fissure was closed by the descent of a cartilaginous inferior process of the tegmen tympani. When Meckel's cartilage changed into the sphenomandibular ligament and the anterior ligament of the malleus, the inferior process of the tegmen tympani interposed between the tympanic bone and the squamous part of the temporal bone, forming the petrotympanic fissure for the chorda tympani nerve and the discomalleolar ligament. Therefore, we hypothesize that, in accordance with the regression of Meckel's cartilage, the rapidly growing temporomandibular joint provided mechanical stress that accelerated the growth and descent of the inferior process of the tegmen tympani via the discomalleolar ligament. The usual diagram showing bony fissures around the tegmen tympani may overestimate the role of the tympanic bone in the fetal middle-ear closure.
 
Closure of the middle ear is believed to be closely related to the evolutionary development of the mammalian jaw. However, few comprehensive descriptions are available on fetal development. We examined paraffin-embedded specimens of 20 mid-term human fetuses at 8-25 weeks of ovulation age (crown-rump length or CRL, 38-220 mm). After 9 weeks, the tympanic bone and the squamous part of the temporal bone, each of which was cranial or caudal to Meckel's cartilage, grew to close the lateral part of the tympanosquamosal fissure. At the same time, the cartilaginous tegmen tympani appeared independently of the petrous part of the temporal bone and resulted in the petrosquamosal fissure. Subsequently, the medial part of the tympanosquamosal fissure was closed by the descent of a cartilaginous inferior process of the tegmen tympani. When Meckel's cartilage changed into the sphenomandibular ligament and the anterior ligament of the malleus, the inferior process of the tegmen tympani interposed between the tympanic bone and the squamous part of the temporal bone, forming the petrotympanic fissure for the chorda tympani nerve and the discomalleolar ligament. Therefore, we hypothesize that, in accordance with the regression of Meckel's cartilage, the rapidly growing temporomandibular joint provided mechanical stress that accelerated the growth and descent of the inferior process of the tegmen tympani via the discomalleolar ligament. The usual diagram showing bony fissures around the tegmen tympani may overestimate the role of the tympanic bone in the fetal middle-ear closure.
 
© 2011 The Authors. Journal of Anatomy © 2011 Anatomical Society of Great Britain and Ireland.
 
© 2011 The Authors. Journal of Anatomy © 2011 Anatomical Society of Great Britain and Ireland.
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PMID: 21477146
 
PMID: 21477146
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 +
===Can you hear me now? Understanding vertebrate middle ear development===
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Front Biosci. 2011 Jan 1;16:1675-92.
 +
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Chapman SC.
 +
Clemson University, Biological Sciences, 132 Long Hall, Clemson, SC 29634, USA. schapm2@clemson.edu
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 +
Abstract
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 +
The middle ear is a composite organ formed from all three germ layers and the neural crest. It provides the link between the outside world and the inner ear, where sound is transduced and routed to the brain for processing. Extensive classical and modern studies have described the complex morphology and origin of the middle ear. Non-mammalian vertebrates have a single ossicle, the columella. Mammals have three functionally equivalent ossicles, designated the malleus, incus and stapes. In this review, I focus on the role of genes known to function in the middle ear. Genetic studies are beginning to unravel the induction and patterning of the multiple middle ear elements including the tympanum, skeletal elements, the air-filled cavity, and the insertion point into the inner ear oval window. Future studies that elucidate the integrated spatio-temporal signaling mechanisms required to pattern the middle ear organ system are needed. The longer-term translational benefits of understanding normal and abnormal ear development will have a direct impact on human health outcomes.
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 +
PMID: 21196256
  
 
==2007==
 
==2007==

Revision as of 23:34, 14 April 2011

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Cite this page: Hill, M.A. (2021, February 27) Embryology Hearing - Middle Ear Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Talk:Hearing_-_Middle_Ear_Development

guinea pig the malleus and incus are normally found as a single complex

2011

Closure of the middle ear with special reference to the development of the tegmen tympani of the temporal bone

J Anat. 2011 Apr 8. doi: 10.1111/j.1469-7580.2011.01378.x. [Epub ahead of print]

Rodríguez-Vázquez JF, Murakami G, Verdugo-López S, Abe SI, Fujimiya M. Department of Anatomy and Human Embryology II, Faculty of Medicine, Embryology Institute, University Complutense of Madrid, Spain Division of Internal Medicine, Iwamizawa Kojin-kai Hospital, Iwamizawa, Japan Oral Health Science Center HRC7, Tokyo Dental College, Chiba-City, Chiba, Japan Department of Anatomy, Sapporo Medical University School of Medicine, Sapporo, Japan.

Abstract Closure of the middle ear is believed to be closely related to the evolutionary development of the mammalian jaw. However, few comprehensive descriptions are available on fetal development. We examined paraffin-embedded specimens of 20 mid-term human fetuses at 8-25 weeks of ovulation age (crown-rump length or CRL, 38-220 mm). After 9 weeks, the tympanic bone and the squamous part of the temporal bone, each of which was cranial or caudal to Meckel's cartilage, grew to close the lateral part of the tympanosquamosal fissure. At the same time, the cartilaginous tegmen tympani appeared independently of the petrous part of the temporal bone and resulted in the petrosquamosal fissure. Subsequently, the medial part of the tympanosquamosal fissure was closed by the descent of a cartilaginous inferior process of the tegmen tympani. When Meckel's cartilage changed into the sphenomandibular ligament and the anterior ligament of the malleus, the inferior process of the tegmen tympani interposed between the tympanic bone and the squamous part of the temporal bone, forming the petrotympanic fissure for the chorda tympani nerve and the discomalleolar ligament. Therefore, we hypothesize that, in accordance with the regression of Meckel's cartilage, the rapidly growing temporomandibular joint provided mechanical stress that accelerated the growth and descent of the inferior process of the tegmen tympani via the discomalleolar ligament. The usual diagram showing bony fissures around the tegmen tympani may overestimate the role of the tympanic bone in the fetal middle-ear closure. © 2011 The Authors. Journal of Anatomy © 2011 Anatomical Society of Great Britain and Ireland.

PMID: 21477146

Can you hear me now? Understanding vertebrate middle ear development

Front Biosci. 2011 Jan 1;16:1675-92.

Chapman SC. Clemson University, Biological Sciences, 132 Long Hall, Clemson, SC 29634, USA. schapm2@clemson.edu

Abstract

The middle ear is a composite organ formed from all three germ layers and the neural crest. It provides the link between the outside world and the inner ear, where sound is transduced and routed to the brain for processing. Extensive classical and modern studies have described the complex morphology and origin of the middle ear. Non-mammalian vertebrates have a single ossicle, the columella. Mammals have three functionally equivalent ossicles, designated the malleus, incus and stapes. In this review, I focus on the role of genes known to function in the middle ear. Genetic studies are beginning to unravel the induction and patterning of the multiple middle ear elements including the tympanum, skeletal elements, the air-filled cavity, and the insertion point into the inner ear oval window. Future studies that elucidate the integrated spatio-temporal signaling mechanisms required to pattern the middle ear organ system are needed. The longer-term translational benefits of understanding normal and abnormal ear development will have a direct impact on human health outcomes.

PMID: 21196256

2007

Incudomalleal joint formation: the roles of apoptosis, migration and downregulation

Amin S, Matalova E, Simpson C, Yoshida H, Tucker AS. BMC Dev Biol. 2007 Dec 5;7:134. PMID: 18053235

"The malleus and incus first appear as a single united condensation expressing early cartilage markers. The incudomalleal joint region forms by cells in the presumptive joint region switching off cartilage markers and turning on joint markers. Failure in this process may result in fusion of this joint, as observed in human syndromes such as Branchio-Oto-Renal Syndrome or Treacher Collins Syndrome."


Anat Anz. 1990;171(3):187-91. [The morphometry of the ear ossicles in humans during development] [Article in German] Olszewski J. Anstalt für Normale Anatomie, Medizinischen Militärakademie Lódź, Polen. Abstract The dimensions and the mass of the auditive ossicles was determined bilaterally in 100 human fetuses, of each sex aged from 21 to 40 weeks and 20 individual adults aged 18 to 40 years. It was found that the development of auditive ossicles in human is not completed during fetal life. The analyzed parameters of malleus (a, b, c, d1, d2, e) in the over fetal life period increased adequately by 14.02%, 11.22%, 16.70%, 12.80%, 12.01%, 21.98%, incus by (a, b, c1, c2, d, e) - 7.61%, 11.48%, 11.40%, 23.59%, 12.14%, 14.94%, stapes by (a, b, c, d, e, f) - 6.28%, 7.66%, 8.40%, 4.54%, 4.54%, 4.16%. In the over fetal life period increase of weight of malleus by 22.05%, incus by 26.49%, stapes by 11.57% was also observed. Described parameters of ossicles system are very important with respect to classification to the operations improving hearing in the system convecting of vibration of the tympanic membrane in children. PMID: 2268059 [PubMed - indexed for MEDLINE]