Vision - Lens Development: Difference between revisions

Revision as of 11:29, 7 September 2011

Introduction

Human lens development (Carnegie stage 22, Week 8)

The lens or crystalline lens or aquula (Latin, aquula = a little stream) has a key role in focussing light (with the cornea) upon the neural retina. The lens embryonic origin is from surface ectoderm of the sensory placodes that form in the head region (More? Week 4 - Placodes). The lens focusses by refracting light as it passes through the biconvex lens, which can be altered in shape (accommodation) by surrounding ciliary muscles. These ciliary muscles are activated (contracted) by parasympathetic innervation from the ciliary ganglion itself innervated by the oculomotor nerve (Cranial Nerve III) (More? Cranial Nerves).

Historic Embryology - Vision
Historic Embryology: 1906 Eye Embryology \| 1907 Development Atlas \| 1912 Eye Development \| 1912 Nasolacrimal Duct \| 1917 Extraocular Muscle \| 1918 Grays Anatomy \| 1921 Eye Development \| 1922 Optic Primordia \| 1925 Eyeball and optic nerve \| 1925 Iris \| 1927 Oculomotor \| 1928 Human Retina \| 1928 Retina \| 1928 Hyaloid Canal \| Historic Disclaimer

| Placodes

Some Recent Findings

On the growth and internal structure of the human lens^[1] "Growth of the human lens and the development of its internal features are examined using in vivo and in vitro observations on dimensions, weights, cell sizes, protein gradients and other properties. In vitro studies have shown that human lens growth is biphasic, asymptotic until just after birth and linear for most of postnatal life."
Activated Ras alters lens and corneal development^[2] "The murine lens and cornea have a common embryonic origin and arise from adjacent regions of the surface ectoderm. ...Collectively, these results suggest that Ras activation a) induces distinct sets of downstream targets in the lens and cornea resulting in distinct cellular responses and b) is sufficient for initiation but not completion of lens fiber differentiation."

Development Overview

surface ectoderm -> lens placode -> lens pit -> lens vesicle -> lens fibres -> lens capsule and embryonic/fetal nucleus.

Week 4

Human Embryo Carnegie stage 11

Human Embryo Carnegie stage 12

Human Embryo Carnegie stage 11 optic pit

Week 5

Week 8

Human embryo Carnegie stage 22

Molecular Signaling

Wnt mediates lens repression by neural crest cells and Transforming growth factor-β^[3] (open image for full description)

References

↑ <pubmed>20171212</pubmed>
↑ <pubmed>20105280</pubmed>
↑ Grocott T, Johnson S, Bailey AP, Streit A. Neural crest cells organize the eye via TGF-β and canonical Wnt signalling. Nat Commun. 2011 Apr;2:265. PMID21468017 | Nat Commun.

Glossary Links

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Cite this page: Hill, M.A. (2024, June 26) Embryology Vision - Lens Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Vision_-_Lens_Development

What Links Here?

[1] <pubmed>20171212</pubmed>

[2] <pubmed>20105280</pubmed>

[3] Grocott T, Johnson S, Bailey AP, Streit A. Neural crest cells organize the eye via TGF-β and canonical Wnt signalling. Nat Commun. 2011 Apr;2:265. PMID21468017 | Nat Commun.

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 ==Week 4==
 [[File:Stage11_sem8.jpg|thumb|Human Embryo [[Carnegie stage 11]]]]
+[[File:Stage12 sem6.jpg|thumb|Human Embryo [[Carnegie stage 12]]]]
 [[File:Stage11_histology-optic_pit.jpg|600px]]