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Late-Gestation and Third Trimester
Published in Mary C. Peavey, Sarah K. Dotters-Katz, Ultrasound of Mouse Fetal Development and Human Correlates, 2021
Mary C. Peavey, Sarah K. Dotters-Katz
The eye forms originates from several cell types, including ectoderm, neural crest cells, and mesenchyme. The neural tube ectoderm will give rise to the retina, the iris, optic nerve, and some of the vitreous humor, while the surface ectoderm will give rise to the lens, and eyelids. The remaining ocular structures originate from mesenchyme. Both mouse and human ocular anatomy are very similar under ultrasound surveillance during fetal development; similar structures are seen in each.
Normal fetal development and growth
Published in Louise C Kenny, Jenny E Myers, Obstetrics, 2017
Fetal skin protects and facilitates homeostasis. The skin and its appendages (nails, hair) develop from the ectodermal and mesodermal germ layers. The epidermis develops from the surface ectoderm; the dermis and the hypodermis, which attaches the dermis of the skin to underlying tissues, both develop from mesenchymal cells in the mesoderm.
Head and neck
Published in Aida Lai, Essential Concepts in Anatomy and Pathology for Undergraduate Revision, 2018
Pharyngeal arch – core mesenchymal tissue enclosed by surface ectoderm– contain their own cranial n., arterial supply and muscular components– externally separated by grooves, and internally separated by pouches– arch I (SS m. of mastication, tensor tympani) (nerve SS: CNV2, V3)– arch II (SS m. of facial expression, stapedius) (nerve SS: CNVII)– arch III (SS stylopharyngeus) (nerve SS: CNIX)– arch IV (SS cricothyroid + intrinsic m. of soft palate except tensor veli palatini) (nerve SS: CNX SLN)– arch VI (SS intrinsic m. of larynx except cricothyroid m.) (nerve SS: CNX RLN)– first pharyngeal groove becomes external ear canal– first pharyngeal pouch (tympanic cavity), second pharyngeal pouch (tonsils), third pharyngeal pouch (thymus), fourth pharyngeal pouch (parathyroid glands)
Lacrimal drainage system anomalies in microphthalmia anophthalmia coloboma complex
Published in Orbit, 2020
Arpita Nayak, Tarjani Vivek Dave, Mohammad Javed Ali, Arundhati Tiwari
Opitz10, in 1985 introduced the ‘developmental field concept’, which states that individual anatomic structures are not developmentally autonomous, but intimately interrelated with that of contiguous or sometimes even more distantly located structures. The orbit and the lacrimal passage could possibly lie in the same developmental field and thus the association between developmental defects in the globe and lacrimal system. It is known that the presence of a normal-sized globe is responsible for the orbital and surrounding soft tissue growth.11 It may be postulated that the total absence of the eyeball or the presence of a rudimentary globe may hamper the formation of lacrimal drainage passages as well. Also, embryologically speaking, surface ectoderm plays a role in both, the eyeball and the adnexal lacrimal system development.12,13 Hence, it can be postulated that if a wider area of the surface ectoderm is involved, there may be a co-incidental eyeball and lacrimal system developmental anomaly. However, the timeline to the development of the eye and lacrimal system do not completely overlap.12–18 The commonest anomaly in our system was a bicanalicular block and hence the timeline of embryonic insult would probably be around 10 weeks when the canalisation process of the lacrimal canaliculi begin.13 Whether there is any genetic cause for the association between developmental anomaly of the globe as well as the LDS is yet to be elucidated.
The Development, Growth, and Regeneration of the Crystalline Lens: A Review
Published in Current Eye Research, 2020
The processes by which de novo and LEC mediated lens regeneration occur can only be understood when placed within the context of the embryologic development and subsequent growth of the lenticular organ. In early eye development the lens is formed by the invagination and closure of the surface ectoderm. The surrounding surface ectodermal tissue goes on to differentiate into the cornea; and the iris and ciliary body differentiate from nearby neural ectoderm.5 With the total removal of the lens organ, de novo regeneration necessitates the new lens tissue to emerge from the transdifferentiation of other surrounding tissues. The conditions necessary to induce the different forms of de novo lens regeneration and the processes by which they occur are informed by the primordial tissues from which the transdifferentiating tissue arises.1,6
Dental stem cells for tooth regeneration: how far have we come and where next?
Published in Expert Opinion on Biological Therapy, 2023
At the beginning of tooth development in the first (mandibular) arch of an embryo the tooth germ consists of two tissues: the dental mesoderm, which originates from neural crest cells, and the dental ectoderm, which is part of the surface ectoderm [3,4]. These two types of cells are the origin of the tooth germ and make up the entire tooth [5]. However, during development these two dental cell types become three tissues, one derived from the ectoderm – enamel organ – and two from the mesoderm – dental papilla and dental follicle (dental sac) [6,7]. While the enamel organ is the source of ameloblasts and is heavily involved in tooth crown morphology, some dental epithelial cells become Hertwig’s epithelial root sheath cells involved in tooth root development [8]. The dental mesodermal tissues deliver stem cells for the development of the tooth root and the dental pulp/dentin complex [9]. Interestingly, both dental mesodermal tissues can be harvested from impacted wisdom teeth and their stem cells isolated and used for different applications [10]. In contrast, the enamel organ and most dental ectodermal cells are lost beforehand. Only epithelial rests of Malassez can be obtained for example from impacted wisdom teeth, but a significant number of dental ectodermal progenitor cells cannot be isolated from this source [11,12]. Moreover, these cells are not the genuine progenitors for ameloblasts and it remains nuclear whether they can be used as ectodermal tooth germ cells in whole tooth regeneration approaches, which is the most advanced goal in regenerative dentistry. This article first summarizes the state of the art in tooth engineering.