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Initial stage of fetal development of the pharyngotympanic tube cartilage with special reference to muscle attachments to the tube.

Katori Y, Rodríguez-Vázquez JF, Verdugo-López S, Murakami G, Kawase T, Kobayashi T - Anat Cell Biol (2012)

Bottom Line: In large fetuses, this loose tissue was occupied by an inferior extension of the temporal bone to cover the artery.This later-developing anterior wall of the carotid canal provided the final bony origin of the levator veli palatini muscle.Consequently, the tubal cartilage development seemed to be accelerated by a surrounding muscle, and conversely, the cartilage was likely to determine the other muscular and bony structures.

View Article: PubMed Central - PubMed

Affiliation: Division of Otorhinolaryngology, Sendai Municipal Hospital, Sendai, Japan.

ABSTRACT
Fetal development of the cartilage of the pharyngotympanic tube (PTT) is characterized by its late start. We examined semiserial histological sections of 20 human fetuses at 14-18 weeks of gestation. As controls, we also observed sections of 5 large fetuses at around 30 weeks. At and around 14 weeks, the tubal cartilage first appeared in the posterior side of the pharyngeal opening of the PTT. The levator veli palatini muscle used a mucosal fold containing the initial cartilage for its downward path to the palate. Moreover, the cartilage is a limited hard attachment for the muscle. Therefore, the PTT and its cartilage seemed to play a critical role in early development of levator veli muscle. In contrast, the cartilage developed so that it extended laterally, along a fascia-like structure that connected with the tensor tympani muscle. This muscle appeared to exert mechanical stress on the initial cartilage. The internal carotid artery was exposed to a loose tissue facing the tubal cartilage. In large fetuses, this loose tissue was occupied by an inferior extension of the temporal bone to cover the artery. This later-developing anterior wall of the carotid canal provided the final bony origin of the levator veli palatini muscle. The tubal cartilage seemed to determine the anterior and inferior margins of the canal. Consequently, the tubal cartilage development seemed to be accelerated by a surrounding muscle, and conversely, the cartilage was likely to determine the other muscular and bony structures.

No MeSH data available.


Related in: MedlinePlus

(A-C) Laterally extending cartilage and the tensor tympani muscle in a crown-rump length 150-mm fetus. Hematoxylin and eosin staining. Horizontal sections. (A [C]) is the most inferior (or superior) side of the figure: the distance is 2 mm. The posterior or lateral orientation is shown by the arrows in (C). The cartilage (C) of the pharyngotympanic tube (PTT) extends along a fascial structure or an adventitia (triangles) that connects with the tensor tympani muscle (TT). Arrows indicate another fascia connecting between the tensor veli palatini muscle (TVP) and Meckel's cartilage (MC). The internal cartotid artery (ICA) is exposed to a loose space (stars) on the posterior side of the PTT. ATN, auriculotemporal nerve; LC, longus capitis muscle; LP, lateral pterygoid muscle; MP, medial pterygoid muscle; PT, pterygoid process. Scale bar=1 mm (A-C).
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Figure 2: (A-C) Laterally extending cartilage and the tensor tympani muscle in a crown-rump length 150-mm fetus. Hematoxylin and eosin staining. Horizontal sections. (A [C]) is the most inferior (or superior) side of the figure: the distance is 2 mm. The posterior or lateral orientation is shown by the arrows in (C). The cartilage (C) of the pharyngotympanic tube (PTT) extends along a fascial structure or an adventitia (triangles) that connects with the tensor tympani muscle (TT). Arrows indicate another fascia connecting between the tensor veli palatini muscle (TVP) and Meckel's cartilage (MC). The internal cartotid artery (ICA) is exposed to a loose space (stars) on the posterior side of the PTT. ATN, auriculotemporal nerve; LC, longus capitis muscle; LP, lateral pterygoid muscle; MP, medial pterygoid muscle; PT, pterygoid process. Scale bar=1 mm (A-C).

Mentions: Figs. 1-3 show horizontal sections, Fig. 4 frontal sections and Fig. 5 sagittal sections. The initial appearance of the tubal cartilage is evident in Fig. 1, and a fascial connection between the cartilage and the tensor tympani muscle is evident in Figs. 1 and 2. Likewise, the topographical relationship between the cartilage and the levator veli palatini muscle is shown in Figs. 1, 3, and 4. Finally, Fig. 5 displays the pharyngeal recess. In addition, all the figures show the underdeveloped carotid canal of the temporal bone, in contrast to the late stage (Fig. 5D inset).


Initial stage of fetal development of the pharyngotympanic tube cartilage with special reference to muscle attachments to the tube.

Katori Y, Rodríguez-Vázquez JF, Verdugo-López S, Murakami G, Kawase T, Kobayashi T - Anat Cell Biol (2012)

(A-C) Laterally extending cartilage and the tensor tympani muscle in a crown-rump length 150-mm fetus. Hematoxylin and eosin staining. Horizontal sections. (A [C]) is the most inferior (or superior) side of the figure: the distance is 2 mm. The posterior or lateral orientation is shown by the arrows in (C). The cartilage (C) of the pharyngotympanic tube (PTT) extends along a fascial structure or an adventitia (triangles) that connects with the tensor tympani muscle (TT). Arrows indicate another fascia connecting between the tensor veli palatini muscle (TVP) and Meckel's cartilage (MC). The internal cartotid artery (ICA) is exposed to a loose space (stars) on the posterior side of the PTT. ATN, auriculotemporal nerve; LC, longus capitis muscle; LP, lateral pterygoid muscle; MP, medial pterygoid muscle; PT, pterygoid process. Scale bar=1 mm (A-C).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3472145&req=5

Figure 2: (A-C) Laterally extending cartilage and the tensor tympani muscle in a crown-rump length 150-mm fetus. Hematoxylin and eosin staining. Horizontal sections. (A [C]) is the most inferior (or superior) side of the figure: the distance is 2 mm. The posterior or lateral orientation is shown by the arrows in (C). The cartilage (C) of the pharyngotympanic tube (PTT) extends along a fascial structure or an adventitia (triangles) that connects with the tensor tympani muscle (TT). Arrows indicate another fascia connecting between the tensor veli palatini muscle (TVP) and Meckel's cartilage (MC). The internal cartotid artery (ICA) is exposed to a loose space (stars) on the posterior side of the PTT. ATN, auriculotemporal nerve; LC, longus capitis muscle; LP, lateral pterygoid muscle; MP, medial pterygoid muscle; PT, pterygoid process. Scale bar=1 mm (A-C).
Mentions: Figs. 1-3 show horizontal sections, Fig. 4 frontal sections and Fig. 5 sagittal sections. The initial appearance of the tubal cartilage is evident in Fig. 1, and a fascial connection between the cartilage and the tensor tympani muscle is evident in Figs. 1 and 2. Likewise, the topographical relationship between the cartilage and the levator veli palatini muscle is shown in Figs. 1, 3, and 4. Finally, Fig. 5 displays the pharyngeal recess. In addition, all the figures show the underdeveloped carotid canal of the temporal bone, in contrast to the late stage (Fig. 5D inset).

Bottom Line: In large fetuses, this loose tissue was occupied by an inferior extension of the temporal bone to cover the artery.This later-developing anterior wall of the carotid canal provided the final bony origin of the levator veli palatini muscle.Consequently, the tubal cartilage development seemed to be accelerated by a surrounding muscle, and conversely, the cartilage was likely to determine the other muscular and bony structures.

View Article: PubMed Central - PubMed

Affiliation: Division of Otorhinolaryngology, Sendai Municipal Hospital, Sendai, Japan.

ABSTRACT
Fetal development of the cartilage of the pharyngotympanic tube (PTT) is characterized by its late start. We examined semiserial histological sections of 20 human fetuses at 14-18 weeks of gestation. As controls, we also observed sections of 5 large fetuses at around 30 weeks. At and around 14 weeks, the tubal cartilage first appeared in the posterior side of the pharyngeal opening of the PTT. The levator veli palatini muscle used a mucosal fold containing the initial cartilage for its downward path to the palate. Moreover, the cartilage is a limited hard attachment for the muscle. Therefore, the PTT and its cartilage seemed to play a critical role in early development of levator veli muscle. In contrast, the cartilage developed so that it extended laterally, along a fascia-like structure that connected with the tensor tympani muscle. This muscle appeared to exert mechanical stress on the initial cartilage. The internal carotid artery was exposed to a loose tissue facing the tubal cartilage. In large fetuses, this loose tissue was occupied by an inferior extension of the temporal bone to cover the artery. This later-developing anterior wall of the carotid canal provided the final bony origin of the levator veli palatini muscle. The tubal cartilage seemed to determine the anterior and inferior margins of the canal. Consequently, the tubal cartilage development seemed to be accelerated by a surrounding muscle, and conversely, the cartilage was likely to determine the other muscular and bony structures.

No MeSH data available.


Related in: MedlinePlus