Fetal Development of Fasciae around the Arm and Thigh Muscles: A Study Using Late Stage Fetuses

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). The superficial lamina of the temporal fascia was not evident at mid-term. Instead, a loose subcutaneous tissue was attached to the thin, deep lamina of the temporal fascia covering the temporalis muscle. At near-term, the deep lamina became thick, while the superficial lamina appeared and exhibited several variations: i) a mono-layered thick membrane (5 specimens); ii) a multi-layered membranous structure (6) and; iii) a cluster of independent thick fasciae each of which were separated by fatty tissues (1). In the second and third patterns, fatty tissue between the two laminae was likely to contain longitudinal fibrous bands in parallel with the deep lamina. Varying proportions of the multi-layered superficial lamina were not attached to the zygomatic arch, but extended below the bony arch. Whether or not lobulation or septation of fatty tissues was evident was not dependent on age. The deep lamina seemed to develop from the temporalis muscle depending on the muscle contraction. In contrast, the superficial lamina developed from subcutaneous collagenous bundles continuous to the cheek. Therein, a difference in development was clearly seen between two categories of the fasciae.

Growth of muscles and nerves in the upper eyelid: a morphometrical and immunohistochemical study using term human fetuses

BACKGROUND

There is no information about muscle growth in eyelids with infrequent blinking in fetuses.

METHODS

To examine the muscle and nerve morphology, we morphometrically and immunohistochemically examined sagittal sections of unilateral upper eyelids obtained from 21 term fetuses (approximately 30-42 weeks of gestation) and, for the comparison, those from 10 midterm fetuses (12-15 weeks).

RESULTS

The approximation margin of the upper eyelid always corresponded to the entire free margin in midterm fetuses, whereas it was often (18/21) restricted in the posterior part in term fetuses. Thus, in the latter, the thickness at the approximation site to the lower lid often ranged from 0.8 to 1.6 mm and corresponded to 18-56% of the nearly maximum thickness of the lid. In the lower part of the upper eyelid, a layer of the orbicularis oculi muscles often (14/21) provided posterior flexion at 90-120° to extend posteriorly. Nerve fibers running along the mediolateral axis were rich along the approximation surface at term, but they might not be reported in the upper eyelid of adults.

CONCLUSION

Being different from adult morphologies, the term eyelid was much thicker than the approximation surface and it carried a flexed muscle layer and transversely-running nerve. The infrequent blinking in fetuses seemed to provide a specific condition for the muscle-nerve growth. Plastic and pediatric surgeons should pay attention to a fact that infants' upper eyelid was unlikely to be a mini-version of the adult morphology.

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.

MATERIALS AND METHODS

Histological sections of the unilateral ankles of 20 fetuses were examined, ten at 8-12 weeks gestational age (GA) and twelve at 26-39 weeks GA.

RESULTS

At 8-12 weeks GA, the tendon sheath simply consisted of a multilaminar layer that involved the plantaris tendon. At 26-39 weeks, each calcaneal tendon had a multilaminar sheath that could be roughly divided into three layers. The innermost layer was attached to the tendon and sometimes contained the plantaris tendon; the multilaminar intermediate layer contained vessels and often contained the plantaris tendon; and the outermost layer was thick and joined other fascial structures, such as a tibial nerve sheath and subcutaneous plantar fascia. The intermediate layer merged with the outermost layer near the insertion to the calcaneus.

CONCLUSION

In spite of significant variations among adults, the fetal plantar tendon was always contained in an innermost or intermediate layer of the calcaneal tendon sheath in near-term fetuses. After birth, mechanical stresses such as walking might lead to fusion or separation of the multilaminar sheath in various manners. When reconstruction occurs postnatally, there may be individual variations in blood supply routes and morphology of the distal end of the plantaris tendon.

Fetal Fascial Reinforcement Development: From "a White Tablet" to a Sculpted Precise Organization by Movement

Simple Summary

Nowadays, the number of studies concerning fasciae is increasing, but few studies focus on fetal fasciae development and there is no study on the retinacula. The latter are fascial reinforcements with a crucial role in proprioception and coordination. We aimed to identify their structural organization by qualitative and quantitative assessments, to establish their role in myofascial development, highlighting their appearance and organization. Our data strongly suggest that the movement models the fascial reinforcements, structuring the fascial system, particularly at the end of the pregnancy.

Abstract

Fasciae have received much attention in recent years due to their important role in proprioception and muscular force transmission, but few studies have focused on fetal fasciae development and there is no study on the retinacula. The latter are fascial reinforcements that play a key role in proprioception and motor coordination. Furthermore, it is still unclear if they are genetically determined or if they are defined by movements, and if they are present during gestation or if they appear only later in the childhood. We aim to identify their structural organization by qualitative and quantitative assessments to establish their role the myofascial development, highlighting their appearance and organization. Samples from the wrist retinacula, posterior forearm, ankle retinacula, anterior leg, iliotibial tract and anterior thigh of six fetus body donors (from 24th to 40th week of gestation) and histological sections were obtained and a gross anatomy dissection was performed. Sections were stained with hematoxylin-eosin to observe their overall structure and measure their thicknesses. Using Weigert Van Gieson, Alcian blue and immunostaining to detect Hyaluronic Acid Binding Protein (HABP), Collagens I and III (Col I and III) were realized to assess the presence of elastic fibers and hyaluronan. This study confirms that the deep fasciae initially do not have organized layers and it is not possible to highlight any reinforcement. The fascial development is different according to the various area: while the deep fascia and the iliotibial tract is already evident by the 27th week, the retinacula begin to be defined only at the end of pregnancy, and their complete maturation will probably be reached only after birth. These findings suggest that the movement models the retinacula, structuring the fascial system, in particular at the end of pregnancy and in the first months of life. The fasciae can be imagined, initially, as “white tablets” composed of few elastic fibers, abundant collagens and HA, on which various forces, u movements, loads and gravity, “write their history”.

Fetal development of the thoracolumbar fascia with special reference to the fascial connection with the transversus abdominis, latissimus dorsi, and serratus posterior inferior muscles

PURPOSE

The three-layered thoracolumbar fascia (TLF) encapsulates the erector spinae and the quadratus lumborum and has been a major concern for physical therapists. However, knowledge of its prenatal development and growth is limited.

METHODS

Histological examination of 25 embryos and fetuses at 6-37 weeks (CRLs, 15-310 mm).

RESULTS

At the posterior end, the abdominal muscles continued toward an initial posterior layer of the TLF (pTLF) at 6 weeks, but the connection became narrow and limited to the obliquus externus aponeurosis until near term. The middle layer of the TLF (mTLF) appeared as a posterior continuation of the transversalis fascia at 9 weeks and, depending on a mechanical demand for the vertebral column extension near term, it grew as a thick intermuscular septum between the iliocostalis and quadratus lumborum. Thus, the mTLF lateral end changed from the abdominal wall to the back or pTLF. The serratus posterior inferior originated from the pTLF after 9 weeks, but a connection of the latissimus dorsi with the fascia was established much later. Near term, the gluteus maximus was attached to an aponeurosis covering the multifidus behind the sacrum. Therefore, the pTLF extended to cover the gluteal muscles.

CONCLUSION

We rejected the hypothesis that the mTLF develops as a marginal tissue between the primitive epaxial and hypaxial muscles. This study seemed to be the first report showing a fact that, within prenatal life, a drastic change is likely to occur in interfascial connections and their topographical relation to muscles; the TLF might be the best sample.

Subsynovial connective tissue development in the rabbit carpal tunnel

The carpal tunnel contains the digital flexor tendons and the median nerve, which are embedded in a unique network of fibrovascular interconnected subsynovial connective tissue (SSCT). Fibrous hypertrophy of the SSCT and subsequent adaptations in mechanical response are found in patients with carpal tunnel syndrome (CTS), but not much is known about the development of the SSCT. This observational study describes the morphological development of SSCT using histology and ultramicroscopy in an animal model at four time points between late‐term fetuses through adulthood. A transition is seen between 3 days and 6 weeks post‐partum from a dense solid SSCT matrix to a complex multilayered structure connected with collagenous fibrils. These preliminary data show a developmental pattern that matches an adaptive response of the SSCT to loading and motion. Understanding the anatomical development aids in recognizing the pathophysiology of CTS and supports research on new therapeutic approaches.

Umbilicus and the rectus sheath: a study using human fetuses

PURPOSE

The newborn umbilicus is provided by a fibrous ring after closure with a scar at the bottom. Since it is believed to be embedded in the linea alba, a specific connection with the rectus sheath was not yet hypothesized for the umbilicus. However, there are no or few descriptions about the development and growth.

METHODS

We histologically examined 28 fetuses at 8-40 weeks: 6 fetuses at 8 weeks, 12 at 10-14 weeks and 10 at 31-40 weeks.

RESULTS

An initial rectus sheath issued a linear mesenchymal condensation toward the umbilical cord at 10-14 weeks and, an established sheath provided a fibrous band around the umbilical cord at 31-40 weeks. The rectus sheath margins made an acute turn toward the skin at the superior and lateral rims of umbilicus and dispersed into a loose tissue of the cord. In contrast, the sheath margin changed its direction gradually to the superficial side at the inferior rim and inserted at a border between the skin epidermis and a mesothelium-like covering of the cord. The developing umbilical ring contained no or few elastic fibers.

CONCLUSION

Instead of the underdeveloped linae alba, the rectus sheath seemed to be tightly connected with the umbilicus at birth. Rather than an expected elasticity, the rectus muscle contraction was likely to play a critical role in the closure after birth. Via the umbilical ring, the fetal rectus sheath also seemed to tightly connect with the skin at the inferior rim of umbilicus.

Suboccipital myodural bridges revisited: Application to cervicogenic headaches

There seems to be no complete demonstration of the suboccipital fascial configuration. In 30 human fetuses near term, we found two types of candidate myodural bridge: (1) a thick connective tissue band running between the rectus capitis posterior major and minor muscles (rectus capitis posterior major [Rma], rectus capitis posterior minori [Rmi]; Type 1 bridge; 27 fetuses); and (2) a thin fascia extending from the upper margin of the Rmi (Type 2 bridge; 20 fetuses). Neither of these bridge candidates contained elastic fibers. The Type 1 bridge originated from: (1) fatty tissue located beneath the semispinalis capitis (four fetuses); (2) a fascia covering the multifidus (nine); (3) a fascia bordering between the Rma and Rmi or lining the Rma (13); (4) a fascia covering the inferior aspect of the Rmi (three); and (5) a common fascia covering the Rma and obliquus capitis inferior muscle (nine). Multiple origins usually coexisted in the 27 fetuses. In the minor Type 2 bridge, composite fibers were aligned in the same direction as striated muscle fibers. Thus, force transmission via the thin fascia seemed to be effective along a straight line. However, in the major Type 1 bridges, striated muscle fibers almost always did not insert into or originate from the covering fascia. Moreover, at and near the dural attachment, most composite fibers of Type 1 bridges were interrupted by subdural veins and dispersed around the veins. In newborns, force transmission via myodural bridges was likely to be limited or ineffective. The postnatal growth might determine a likely connection between the bridge and headache. Clin. Anat. 32:914-928, 2019. © 2019 Wiley Periodicals, Inc.