Qualitative changes in fetal trabecular meshwork fibers at the human iridocorneal angle

Fumio Hosaka,Jose Francisco Rodríguez-Vázquez,Hiroshi Abe,Gen Murakami,Mineko Fujimiya,Hiroshi Ohguro 대한해부학회 2013 Anatomy & Cell Biology Vol.46 No.1

We examined a series of changes that occur in the trabecular meshwork fibers of human eyes during fetal development at 12-30 weeks of gestation. At 12 and 15 weeks, the uveal meshwork was stained black with silver impregnation (indicating the predominance of collagen types III and IV) in the endomysium of the ciliary muscle. At 20 weeks, in combination with Schlemm’s canal, a dense fibrous tissue mass corresponding to the trabecular meshwork anlage appeared and was colored black. The anlage was continuous with the corneal endothelium rather than with the ciliary muscle. Until 25 weeks, the trabecular meshwork was identifiable as fragmented fiber bundles that stained red-black, suggesting a mixture of collagen types I, III, and IV. At 30 weeks, half of the ciliary muscle fibers were inserted into the scleral spur and not into the meshwork. Therefore, any contribution of ciliary muscle contraction to the differentiation of the trabecular meshwork would appear to be limited. We hypothesize that an uneven distribution of mechanical stresses in the area of the cornea-sclera junction causes a tear thereby creating Schlemm’s canal and is accompanied by a change in the collagen fiber types comprising the meshwork.

Development of the Rectus Abdominis and Its Sheath in the Human Fetus

양재도,조백환,황홍필,김지현,Jose Francisco Rodríguez-Vázquez,Shin-ichi Abe,Gen Murakami 연세대학교의과대학 2012 Yonsei medical journal Vol.53 No.5

Purpose: Although the rectus abdominis and its sheath are well known structures, their development in the human fetus is poorly understood. Materials and Methods:We examined rectus abdominis and sheath development in semiserial horizontal sections of 18 fetuses at 5-9 weeks of gestation. Results: Rectus muscle differentiation was found to commence above the umbilicus at 6 weeks and extend inferiorly. Until closure of the anterior chest wall via fusion of the bilateral sternal anlagen (at 7 weeks), the anterior rectal sheath originated from the external oblique and developed towards the medial margin of the rectus abdominis at all levels, including the supracostal part. After formation of the anterior sheath, fascial laminae from the internal oblique and transversus abdominis contributed to formation of the posterior rectus sheath. However, the posterior sheath was absent along the supracostal part of the rectus abdominis, as the transversus muscle fibers reached the sternum or the midline area. Therefore, it appeared that resolution of the physiological umbilical hernia (8-9 weeks) as well as chest wall closure was not required for development of the rectus abdominis and its sheath. Conversely, in the inferior part of the two largest fetal specimens, after resolution of the hernia, the posterior sheath underwent secondary disappearance, possibly due to changes in mechanical stress. Conclusion: Upward extension of the rectus abdominis suddenly stopped at the margin of the inferiorly developing pectoralis major without facing the external intercostalis. The rectus thoracis, if present, might correspond to the pectoralis.

Female Longitudinal Anal Muscles or Conjoint Longitudinal Coats Extend into the Subcutaneous Tissue along the Vaginal Vestibule: A Histological Study Using Human Fetuses

Yusuke Kinugasa,Takashi Arakawa,Hiroshi Abe,Jose Francisco Rodríguez-Vázquez,Gen Murakami,Kenichi Sugihara 연세대학교의과대학 2013 Yonsei medical journal Vol.54 No.3

Purpose: It is still unclear whether the longitudinal anal muscles or conjoint longitudinal coats (CLCs) are attached to the vagina, although such an attachment, if present, would appear to make an important contribution to the integrated supportive system of the female pelvic floor. Materials and Methods: Using immunohistochemistry for smooth muscle actin, we examined semiserial frontal sections of 1) eleven female late-stage fetuses at 28-37 weeks of gestation, 2) two female middle-stage fetus (2 specimens at 13 weeks), and, 3) six male fetuses at 12 and 37 weeks as a comparison of the morphology. Results: In late-stage female fetuses, the CLCs consistently (11/11) extended into the subcutaneous tissue along the vaginal vestibule on the anterior side of the external anal sphincter. Lateral to the CLCs, the external anal sphincter also extended anteriorly toward the vaginal side walls. The anterior part of the CLCs originated from the perimysium of the levator ani muscle without any contribution of the rectal longitudinal muscle layer. However, in 2 female middle-stage fetuses, smooth muscles along the vestibulum extended superiorly toward the levetor ani sling. In male fetuses, the CLCs were separated from another subcutaneous smooth muscle along the scrotal raphe (posterior parts of the dartos layer) by fatty tissue. Conclusion: In terms of topographical anatomy, the female anterior CLCs are likely to correspond to the lateral extension of the perineal body (a bulky subcutaneous smooth muscle mass present in adult women), supporting the vaginal vestibule by transmission of force from the levator ani.

Nervus terminalis and nerves to the vomeronasal organ: a study using human fetal specimens

Zhe Wu Jin,조광호,Shunichi Shibata,Masahito Yamamoto,Gen Murakami,Jose Francisco Rodríguez-Vázquez 대한해부학회 2019 Anatomy & Cell Biology Vol.52 No.3

The human nervus terminalis (terminal nerve) and the nerves to the vomeronasal organ (VNON) are both associated with the olfactory nerves and are of major interest to embryologists. However, there is still limited knowledge on their topographical anatomy in the nasal septum and on the number and distribution of ganglion cells along and near the cribriform plate of the ethmoid bone. We observed serial or semiserial sections of 30 fetuses at 7–18 weeks (crown rump length [CRL], 25–160 mm). Calretinin and S100 protein staining demonstrated not only the terminal nerve along the anterior edge of the perpendicular lamina of the ethmoid, but also the VNON along the posterior edge of the lamina. The terminal nerve was composed of 1–2 nerve bundles that passed through the anterior end of the cribriform plate, whereas the VNON consisted of 2–3 bundles behind the olfactory nerves. The terminal nerve ran along and crossed the posterior side of the nasal branch of the anterior ethmoidal nerve. Multiple clusters of small ganglion cells were found on the lateral surfaces of the ethmoid’s crista galli, which are likely the origin of both the terminal nerve and VNON. The ganglions along the crista galli were ball-like and 15–20 µm in diameter and, ranged from 40-153 in unilateral number according to our counting at 21-μm-interval except for one specimen (480 neurons; CRL, 137 mm). An effect of nerve degeneration with increasing age seemed to be masked by a remarkable individual difference.

Fetal development of the minor lung segment

Shinichi Abe,Masahito Yamamoto,Taku Noguchi,Toshihito Yoshimoto,Hideaki Kinoshita,Satoru Matsunaga,Gen Murakami,Jose Francisco Rodrí,guez Vá,zquez3 대한해부학회 2014 Anatomy & Cell Biology Vol.47 No.1

The mediobasal segment (S7) of the right lung has been considered to correspond to the cardiac lobe generally seen in mammals. To investigate fetal development of the right mediobasal segmental bronchus (B7), we examined paraffinembedded serial sections of 15 embrynic and fetal lungs at 7-8 weeks (serial sections) as well as semiserial sections of 8 fetuses at 15-18 weeks (semiserial sections). All of the smaller specimens did not contain B7, but 2 of the 8 larger specimens carried B7: one was found in the immediately anterior side of the inferior pulmonary vein, while in the other, the subdivisions (B7a, B7b) were overriding the vein. Although the incidence might be underestimated because of observations using semiserial sections, the B7 was most likely to develop secondarily during a period from 8 to 15 weeks. Fetal topographical changes (mainly, the descent) of the middle lobe and the inferior pulmonary vein might relate with the secondarily budding of B7. The present result does not reduce a clinical relevance of B7 as a segmental bronchus of the lung segment system.

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

Yukio Katori,Jose Francisco Rodrí,guez-Vá,zquez,Samuel Verdugo-Ló,pez,Gen Murakami,Tetsuaki Kawase,Toshimitsu Kobayashi 대한해부학회 2012 Anatomy & Cell Biology Vol.45 No.3

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.

Early Fetal Development of the Human Cochlea

Kim, Ji Hyun,Rodrí,guez-Vá,zquez, Jose Francisco,Verdugo-Ló,pez, Samuel,Cho, Kwang Ho,Murakami, Gen,Cho, Baik Hwan Wiley (John WileySons) 2011 The anatomical record Vol.294 No.6

Reappraisal of intergender differences in the urethral striated sphincter explains why a completely circular arrangement is difficult in females

Hiroshi Masumoto,Atsushi Takenaka,Jose Francisco Rodrí,guez-Vá,zquez,Gen Murakami,Akio Matsubara 대한해부학회 2012 Anatomy & Cell Biology Vol.45 No.2

To investigate why the development of a completely circular striated sphincter is so rare, we examined histological sections of 11 female and 11 male mid-term human fetuses. In male fetuses, the striated muscle initially extended in the frontal, rather than in the horizontal plane. However, a knee-like portion was absent in the female fetal urethra because, on the inferior side of the vaginal end, a wide groove for the future vestibule opened inferiorly. Accordingly, it was difficult for the developing striated muscle to surround the groove, even though there was not a great difference in width or thickness between the female vestibule and the male urethra. The development of a completely circular striated sphincter seems to be impossible in females because of interruption of the frontal plane by the groove-like vestibule. However, we cannot rule out the possibility that before descent of the vagina, the urethral striated muscle extends posteriorly.

Early fetal development of the human cerebellum

Cho, Kwang Ho,Rodrí,guez-Vá,zquez, Jose Francisco,Kim, Ji Hyun,Abe, Hiroshi,Murakami, Gen,Cho, Baik Hwan Springer-Verlag 2011 Surgical and radiologic anatomy Vol.33 No.6

Fetal development of the human trapezius and sternocleidomastoid muscles

Kwang Ho Cho,Ichiro Morimoto,Masahito Yamamoto,Shinya Hanada,Gen Murakami,Jose Francisco Rodrí,guez-Vá,zquez,Shinichi Abe 대한해부학회 2020 Anatomy & Cell Biology Vol.53 No.4

At present, there is no photographic evidence of splitting of the trapezius and sternocleidomastoid muscles (SCMs), which share a common anlage that extends caudally toward the limb bud in the embryo at a length of 9 mm. Therefore, the aim of the present study was to identify which structures divide the caudal end of the common anlage at the first sign of splitting into two muscles. In 11 mm-long specimens, the SCM and trapezius muscles were identified as a single mesenchymal condensation. In 15 and 18 mm-long specimens, the SCM and trapezius muscles were separated and extended posteriorly and lymphatic tissues appeared in a primitive lateral cervical space surrounded by the SCM (anterior). In 21 mm-long specimens, the lymphatic vessels were dilated and the accompanying afferents were forming connections with the subcutaneous tissue through a space between the SCM and trapezius muscles. In 27 mm-long specimens, cutaneous lymphatic vessels were evident and had entered the deep tissue between the SCM and trapezius muscles. Vascular dilation may be viewed as a result of less mechanical stress or pressure after muscle splitting.