Comparative anatomy of the subclavius muscle and clavicle: a histological study using human, swine and mouse fetuses.

Background: Some mammals including the swine carry a fibrous vestigial clavicle, but a subclavius muscle (SBM) extends between the first rib and the supraspinatus muscle surface fascia. We aimed to examine development of the SBM and clavicle for finding a specific factor to provide the curious morphology.

Materials And Methods: Histological sections of early- and midterm fetuses of the swine, human and mouse were observed and compared at the almost same morphological stage.

Delayed development of the inferior mesenteric vein in human fetuses.

Background: The superior mesenteric vein appears as a fusion between irregularly-shaped slits of the midgut mesentery tissue at 5-6 weeks. In contrast, there might be no report when and how the inferior mesenteric vein (IMV) develops. We aimed to find the human initial IMV.

Development and growth of fasciae in and around the esophageal hiatus: a histological study using human fetuses.

Purpose: An entire fascial configuration at the esophageal hiatus might not be demonstrated histologically. According to observations of human fetus histology, the aim of this study was to consider which factor is likely to make the individual variation in adults.

Methods: We observed frontal histological sections containing the esophageal hiatus from 12 midterm fetuses at 12-16 weeks (crown-rump length: CRL, 85-137 mm) and 10 near-term fetuses at 26-30 weeks (CRL, 214-250 mm).

Ontogenic transformation of the ankle from the initial mediolateral arrangement of the calcaneus and talus: A histological study of human embryos and early fetuses.

The human calcaneus is robust and provides a prominent heel for effective bipedal locomotion, although the adjacent talus has no muscle attachments. However, there is incomplete information about the morphological changes in these prominent bones during embryo development. We examined serial histological sections of 23 human embryos and early-term fetuses (approximately 5-10 weeks' gestational age [GA]).

Growth patterns of facial muscles at the angle of the mouth: A histological study using midterm and near-term human fetuses.

At the angle of the mouth, spoke-like muscle bundles converge at the "modiolus," which is believed to appear in utero. The aim of this study was to investigate the growth of the modiolus histologically. We studied frontal histological sections of the face from 12 midterm and six near-term fetuses.

Transient contribution of the sphenoid ala major to the socket of the temporomandibular joint in near-term fetuses.

The temporomandibular joint (TMJ) is a complex structure that plays a vital role in the movement of the jaw. Some anatomy and dental textbooks show that, at the medial margin, the TMJ capsule attaches to a suture between the sphenoid ala major and the temporal bone squamosa. In near-term fetuses, the ala major extends posterolaterally to approach the TMJ.

Insertions of the striated muscles in the skin and mucosa: a histological study of fetuses and cadavers.

Striated muscle insertions into the skin and mucosa are present in the head, neck, and pelvic floor. We reexamined the histology of these tissues to elucidate their role in transmission of the force. We examined histological sections of 25 human fetuses (gestational ages of ~11-19 weeks and ~26-40 weeks) and 6 cadavers of elderly individuals.

Mentalis nerve branches supplying the lower lip revisited: a study of human fetuses and donated elderly cadavers.

Purpose: Little information is known about the mentalis nerve course from the lower lip approximation margin (free margin) to the upper lip. Likewise, no difference in nerve distribution has been observed between the cutaneous and mucosal parts of the lip. Therefore, this study reexamined mentalis nerve morphology.

Development and growth of the temporal fascia: a histological study using human fetuses.

The temporal fascia is a double lamina sandwiching a thick fat layer above the zygomatic bony arch. To characterize each lamina, their developmental processes were examined in fetuses. We observed histological sections from 22 half-heads of 10 mid-term fetuses at 14-18 weeks (crown-rump length, 95-150 mm) and 12 near-term fetuses at 26-40 weeks (crown-rump length, 215-334 mm).

Growing stylohyoideus muscle insertion to the hyoid bone with special reference to its topographical relation to the intermediate tendon of digastricus muscle: A histological study using human fetuses.

Background: In adults, the intermediate tendon of digastricus muscle usually runs along the medial or lateral side of the stylohyoideus muscle insertion. To provide a better understanding of the variations, we examined the topographical anatomy of the muscle and tendon in fetuses.

Methods: We examined histological sections from six early-term, 26 mid-term and six near-term fetuses (approximately 8-9, 12-18 weeks and 25-33 weeks).

Cochlear aqueduct revisited: A histological study using human fetuses.

Background And Aim: The cochlear aqueduct (CA) connects between the perilymphatic space of the cochlea and the subarachnoid space in the posterior cranial fossa. The study aimed to examine 1) whether cavitation of the CA occurs on the subarachnoid side or the cochlear side and 2) the growth and/or degeneration of the CA and its concomitant vein.

Methods: We examined paraffin-embedded histological sections from human fetuses: 15 midterm fetuses (crown-rump length or CRL, 39-115 mm) and 12 near-term fetuses (CRL, 225-328 mm).

Topohistology of the cranial nerves IX-XII at the cranial base and upper parapharyngeal space: A histological study using human fetuses.

The topographical relationships among the lower cranial nerves, internal carotid artery (ICA), and internal jugular vein (IJV) in the upper parapharyngeal neurovascular bundle remain obscure. Thus, details of the anatomy were examined in human fetus histology. We observed the horizontal histological sections from 20 midterm (9-18 weeks) and 12 near-term (28-40 weeks) fetuses.

Sphenomandibular ligament and degenerating Meckel's cartilage revisited: Sequential variations with temporal bone deformity for ligament attachment in near-term human fetuses.

Background: The sphenomandibular ligament (SML) is considered to originate from Meckel's cartilage (MC). However, no study has examined how the os goniale contributes to SML development.

Methods: Semiserial histological sections of heads from 18 near-term fetuses at 27-40 weeks of gestation were examined.

A marginal branch of the left hepatic artery running along the umbilical vein and supplying the anterior surface of the liver left lobe: a report of 5 cases in 12 Japanese human fetuses.

In human fetuses, the left hepatic artery (LHA) issues the marginal artery that runs along the umbilical vein and, sometimes, reaches the umbilicus. The further observation demonstrated that, in 5 of 12 Japanese midterm fetuses (crown-rump length mm: 46, 50, 54, 59, 102), the marginal artery issued not only a thin umbilical branch but also a liver parenchymal branch that took a posterosuperior recurrent course in a peritoneal fold and supplied the anterior surface of the liver left lobe (segment III). However, in 22 Spanish fetuses of which gestational ages corresponded to the Japanese ones, we did not find the parenchymal branch.

Rectus capitis lateralis muscle revisited: a histological study using human fetuses.

Background: Rectus capitis lateralis muscle (RCLM) is located at the border between the ventral and dorsal muscle groups, but the nerve topographical anatomy around the muscle is obscure.

Materials And Methods: We observed the RCLM in histological sections of 12 midterm and 10 near-term fetal heads (9-18 and 26-40 weeks of gestational age).

Results: At midterm, the RCLM wrapped around the inferiorly protruding inferolateral corner of the cartilaginous occipital bone.

Characteristic findings in the human fetus vestibule: A human temporal bone study.

Objective: The "collapse," a highly flexed, dented, or caved membrane between the endo- and peri-lymph of the saccule and utricle in adults, is considered as a morphological aspect of Ménière's syndrome. Likewise, when mesh-like tissues in the perilymphatic space are damaged or lost, the endothelium loses mechanical support and causes nerve irritation. However, these morphologies were not examined in fetuses.

Transient connection between the vestibular aqueduct and utricle: A study using sagittal sections of human embryonic heads.

Background: The aqeductus vestibuli (aqueduct) is believed to connect to the saccule in embryos and adults. However, in embryos, the saccule and utricle are known to communicate widely to provide a common endolymph space "atrium".

Methods: Using sagittal histological sections from five embryos (crown-rump length or CRL, 14-21 mm), nine early fetuses (CRL 24-35 mm) and 12 midterm and near-term fetuses (CRL 82-272 mm), we revisited the development and growth of the human ear aqueduct.

Nasal capsule ossification: A histological study using human foetuses to find an association between the foetus and adult morphologies of the nasal wall.

Recent molecular biology studies have revealed the process of nasal capsule determination. We aimed to create a fate map showing the association between the adult and embryonic components of the nasal wall and nasal capsule derivatives. We examined paraffin-embedded histological sections between 15 mid-term (9-16 weeks) and 12 near-term (27-40 weeks) foetuses.

Development and growth of median structures in the human tongue: A histological study using human fetuses and adult cadavers.

Glossectomy is a surgical procedure performed to remove all or part of the tongue in patients with cancer. The removal of a significant part of the tongue has a marked effect on speech and swallowing function, as patients may lose not only the tongue muscles but also the median lingual septum (MLS). Therefore, to achieve successful tongue regeneration, it is necessary to investigate the developmental processes of not only the tongue muscles but also the MLS.

Lung fusion with the liver in chick and quail embryos.

Even in mammals with the diaphragm, the lung and liver are likely to attach mutually without separation by any structure in embryos. The aim of this study was to examine whether or not the lung attaches to the liver in embryonic development of birds without diaphragm. First, we ensured the topographical relation between the lung and liver in 12 human embryos at 5 weeks.

Development and growth of the human fetal sacroiliac joint revisited: a comparison with the temporomandibular joint.

The human fetal sacroiliac joint (SIJ) is characterized by unequal development of the paired bones and delayed cavitation. Thus, during the long period, the bony ilium becomes adjacent to the cartilaginous sacrum. This mor-phology may be analogous to that of the temporomandibular joint (TMJ).

The so-called absorption process of the pulmonary vein into the left atrium of the heart: a histological study using human embryos and fetuses.

Background: Embryonic pulmonary veins (PVs) are believed to be absorbed into the left atrium (LA) to provide an adult morphology in which "four" veins drain separately into the atrium.

Materials And Methods: Serial histological sections were obtained from 27 human embryos and fetuses.

Results: Between 5 and 6 weeks, the four PVs joined together to form a trunk-like structure (initial spatium pulmonalis) that was larger than the initial LA (two-ostia pattern).

Development and growth of the calcaneal tendon sheath with special reference to its topographical relationship with the tendon of the plantaris muscle: a histological study of human fetuses.

Background And Purpose: The calcaneal tendon sheath has several vascular routes and is a common site of inflammation. In adults, it is associated with the plantaris muscle tendon, but there are individual variations in the architecture and insertion site. We describe changes of the tendon sheath during fetal development.