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Ultrastructure of the human posterior tunica vasculosa lentis during early gestation
1Universitäts-Augenklinik, Bonn, Federal Republic of Germany.
Insights
The posterior tunica vasculosa lentis (TVL) in human embryos is fully developed by 7.6 weeks gestational age. This vascular layer features capillaries with fenestrated endothelial cells and a basement membrane that thickens over time.
Area of Science:
- Embryology
- Ophthalmology
- Histology
Background:
- The tunica vasculosa lentis (TVL) is a vascular layer supplying the lens in developing embryos.
- Previous studies have not fully detailed the microvasculature of the posterior TVL in early human development.
Purpose of the Study:
- To investigate the ultrastructural development of the posterior tunica vasculosa lentis (TVL) in early human embryos.
- To characterize the morphology of capillaries and associated cells within the TVL.
Main Methods:
- Scanning and transmission electron microscopy were used to examine human embryos.
- Gestational ages ranged from 7.6 to 14.0/15.0 weeks.
Main Results:
- The posterior TVL was found to be fully developed by 7.6 weeks gestational age.
- It comprises a network of tortuous capillaries with endothelial cells, basement membrane, and pericytes.
- Endothelial cells showed transitory fenestrations, and basement membrane thickness increased with gestational age.
- Macrophages were observed near the posterior TVL.
Conclusions:
- The posterior TVL exhibits a complex and developed vascular structure early in human embryonic development.
- The presence of fenestrations and thickening basement membrane suggests active vascular processes.
- Further research into the functional role of these vascular components is warranted.
Abstract:
In human embryos with a gestational age of from 7.6 to 14.0/15.0 weeks, the posterior tunica vasculosa lentis (TVL) was examined by both scanning and transmission electron microscopy. Even at the very early age of 7.6 weeks the tunica was found to be fully developed. It consisted of a radiating network of tortuous capillaries. Their walls were composed of a continuous layer of endothelial cells, surrounded by a basement membrane and a discontinuous sheath of pericytes. The thickness of the basement membrane increased with increasing gestational age. As opposed to previous studies, the endothelial cells exhibited transitory fenestrations. In the neighborhood of the posterior TVL macrophages were found.