Ascent of the Conus Medullaris in Human Foetuses: A Systematic Review and Meta-Analysis

The aim of the present systematic review and meta-analysis was to identify when the ascent of the conus medullaris occurs in human foetuses considering differences in evaluation methods and sample characteristics. Five databases were searched for relevant articles using different combinations of keywords. Article selection and data extraction were performed independently by two reviewers. Disagreements were resolved by a third reviewer. The variables were distributed into four groups according to the gestational age of the specimens: I (13 to 18 weeks); II (19 to 25 weeks); III (26 to 32 weeks); IV (33 weeks to the probable date of birth). Eighteen articles were included. The majority used imaging exams as the evaluation method. Cadaveric dissections were reported in the remaining articles. Only morphological studies were included in the meta-analysis. Significant ascent occurs between groups I and III as well as groups II and IV. Despite the considerable heterogeneity among the studies included in the present review, the findings enabled the determination that the conus medullaris reaches its normal birth level by the 26th week. Further analyses should be performed based on nationality and ethnicity to diminish the heterogeneity of the data.

FETAL ANATOMICAL VARIABILITY OF STRUCTURES IN INFRAHYOID AREA

When performing myoplastic operations and surgical interventions on the thyroid gland, trachea and esophagus, information on the variant anatomy of the infrahyoid muscles, the features of their innervation and blood supply are of great clinical importance. Moreover, when additional muscles are attached to the thyroid gland, intraoperative bleeding can occur resulting in hematoma and tissue scarring in the postoperative period. There are fragmentary data in the literature on the variants of the structure and topography of the human infrahyoid area muscles. The specificity of branching nerves and blood vessels, their vascular-nervous relationships in a separate part of the sternohyoid, sternothyroid, thyrohyoid, and omohyoid muscles should be taken into account when performing rational incisions in the neck, moving both the flaps and the above muscles in plastic surgery. The purpose of study was to establish the anatomical variability and features of innervation and blood supply of the infrahyoid muscles of the neck in human foetuses of 4 – 10 gestational months age. Material and methods. The study was performed on 36 human foetuses, whose parieto-coccygeal length was 81.0 – 375.0 mm, without visible signs of anatomical abnormalities or anomalies in the cervical region. Thin sections of the structures from the anterior and lateral parts of the neck were prepared under the control of binocular magnifier, vascular injection technique, and morphometry. Foetal preparations weighing over 500.0 g were studied directly at Chernivtsi Regional Paediatric Pathological Bureau. Foetal preparations were taken from the Museum of M.G. Turkevich Human Anatomy Department, Bukovinian State Medical University. Results and discussion. The study demonstrated anatomical variability of the infrahyoid area muscles during the foetal period of human ontogenesis. Human foetuses were mainly found to have loose extending intramuscular branching of the nerves of the cervical loop in the infrahyoid muscles. The only exception is the inferior belly of the omohyoid muscle, where main nerve branching is found out. The distribution of nerves in the thickness of the infrahyoid muscles is uneven. Macroscopic examination revealed the smallest number of nerve branches was found within the middle third of the sternohyoid and upper third of the sternothyroid muscles. Arteries and nerves enter the sternothyroid and thyrohyoid muscles through the anterior surface, and the omohyoid and sternohyoid muscles enter mainly through the posterior surface of these muscles. The infrahyoid muscles are characterized by the main form of intramuscular branching of the arteries. The data on the peculiarities of intramuscular branching of arteries and nerves in the infrahyoid muscles we obtained, as well as the variant anatomy of the infrahyoid area muscles must be taken into account when performing a surgical access to the neck, or when operating on in the anterior cervical region, in particular myoplastic and reconstructive operations, in order to avoid muscle injuries.

Lineage tracing of human embryonic development and foetal haematopoiesis through somatic mutations

To date, ontogeny of the human haematopoietic system during foetal development has been characterized mainly through careful microscopic observations. Here we used whole-genome sequencing (WGS) of 511 single-cell derived haematopoietic colonies from healthy human foetuses of 8 and 18 post-conception weeks (pcw) coupled with deep targeted sequencing of tissues of known embryonic origin to reconstruct a phylogenetic tree of blood development. We found that in healthy foetuses, individual haematopoietic progenitors acquire tens of somatic mutations by 18 pcw. Using these mutations as barcodes, we timed the divergence of embryonic and extra-embryonic tissues during development and estimated the number of blood antecedents at different stages of embryonic development. Our analysis has shown that ectoderm originates from a smaller set of blood antecedents compared to endoderm and mesoderm. Finally, our data support a hypoblast origin of the extra-embryonic mesoderm and primitive blood in humans.

ANATOMY OF TULP’S VALVE

Introduction: Tulp’s valve is also known as ileocaecal valve which is situated at ileocaecal junction. Tulp’s valve is a diverse anatomical valve where the ileum makes an access into the caecum. Earlier researchers have observed that there is occurrence of high densities of neurons in the Tulp’s valve, though meticulous anatomical depiction about constitution of the myenteric plexus in and around the Tulp’s valve has thus far to be obtained in humans. In array to add contribution to this vicinity of explore, the present work was performed to appreciate the anatomical composition of myenteric plexus in and around the Tulp’s valve in human foetuses. Materials and Methods: The research was performed on ileocaecal sections obtained from human foetuses (n=17) of various gestational ages after obtaining ethical authorization from the ethical clearance committee of Hind Institute of Medical Sciences, Sitapur. Cresyl Violet staining and NADPH- diaphorase enzyme histochemistry was performed over the obtained ileocaecal sections. Study Group-1(G-1) included foetuses of 9 to 14 week of gestational age group while Group-2(G-2) comprised of foetuses of 15 to 33 week of gestational age group. The Neuronal cell profiles (area, perimeter, ferret diameter) and Neuronal cell density were assessed in and around the Tulp’s valve in human foetuses. Results: In Cresyl violet stained sections, the difference in the neuronal cell profile area between G-1 (50.10±2.26 µm2 )and G-2 (61.25±4.07 µm2 ) was found to be statistically significant (p=0.0028).The perimeter of myenteric neuronal cells in G-1 (26.32±0.51 µm ) was significantly (p=0.0028) lower than G-2 (29.17±0.85 µm). The differences in Feret diameter of neuronal cells between G-1 (9.49±0.27 µm) and G-2 (10.53±0.21 µm) was statistically significant (p=0.0028). The neuronal cell density in Myenteric Ganglia (MG) in G-1 and G-2 was 60.01±9.77 and 52.27±6.54 respectively, which was statistically insignificant (p=0.1367) difference. The difference in the nitrergic neuronal cell area between G-1 (66.35±8.43 µm2) and G-2 (74.93±0.53 µm2) was statistically significant (p=0.0038). The mean perimeter of nitrergic neuronal cells in G-1 (32.01±2.57µm) was insignificantly (p=0.2001) lower than G-2 (33.83±0.73 µm). The mean Feret diameter of G-1 (11.97±1.26) was also insignificantly (p=0.2624) lower than G-2 (12.91±0.75). The nitrergic neuronal cell density in Myenteric Ganglia in G-1 was 22.41±4.13 and in G-2 it was 18.61±2.09, which was statistically insignificant (p=0.0983). acquaintance of the innervations of the Tulp’s valve in human foetuses may help in restoration of it for improved movement of ileum inside into the caecum, as well as to check retrospective run of caecal inside into the ileum. Keywords: Tulp’s Valve, Cresyl Violet, NADPH- diaphorase, Nitrergic Neurons

The relationship between the thyroid gland and body at different gestational age of developing human foetuses

Background: Thyroid gland is one of the organs of interest for researchers since a long time. Though, detailed study about adult thyroid gland is there in the literature but thyroid gland at different stages in the foetal period is far less available.Aims and Objective: To find out the morphological and morphometric features on the development of foetal thyroid gland in relation with different gestational weeks.Materials and Methods: The study was carried in the Department of Anatomy, Manipal College of Medical Sciences, Pokhara, Nepal, on 40 human foetuses of known gestational age. The midline dissection of the neck was done to expose the thyroid gland. The shape and measurements like length, breadth and thickness of both lobe of the gland were noted.Results: The mean values of all parameters by gestational age were calculated. In the present study, the weight of foetuses showed gradual increase from 10th week to 38th weeks of gestation. In the normally developing foetuses the thyroid gland dimension and its weight also increases with increase gestational age.Conclusion: There was no more difference between the dimension of right and left lobe of thyroid gland. The study provides morphological and morphometric knowledge on the development of foetal thyroid gland from 10th week to 38th weeks of gestation. The knowledge of thyroid gland weight and dimension and body weight in relation to the gestational age might be helpful to judge the thyroid structure in preterm babies.Asian Journal of Medical Sciences Vol.9(6) 2018 40-44