Bowman's layer

Layer in the cornea of the eye

Bowman's layer
Vertical section of human cornea from near the margin. Magnified. Epithelium Anterior elastic lamina substantia propria Posterior elastic lamina Endothelium of the anterior chamber Oblique fibers in the anterior layer of the substantia propria Lamellae, the fibers of which are cut across, producing a dotted appearance Corneal corpuscles appearing fusiform in section Lamellae, the fibers of which are cut longitudinally Transition to the sclera, with more distinct fibrillation, and surmounted by a thicker epithelium Small bloodvessels cut across near the margin of the cornea
Details
Identifiers
Latin	lamina limitans anterior corneae
MeSH	D050541
TA98	A15.2.02.019
FMA	58273
Anatomical terminology [edit on Wikidata]

The Bowman's layer (Bowman's membrane, anterior limiting lamina, anterior elastic lamina) is a smooth, acellular, nonregenerating layer, located between the superficial epithelium and the stroma in the cornea of the eye. It is composed of strong, randomly oriented collagen fibrils in which the smooth anterior surface faces the epithelial basement membrane and the posterior surface merges with the collagen lamellae of the corneal stroma proper.^[1]

In adult humans, Bowman's layer is 8-12 μm thick.^[2] With ageing, this layer becomes thinner.

The function of the Bowman's layer remains unclear and it appears to have no critical function in corneal physiology.^[3] Recently, it is postulated that the layer may act as a physical barrier to protect the subepithelial nerve plexus and thereby hastens epithelial innervation and sensory recovery. Moreover, it may also serve as a barrier that prevents direct traumatic contact with the corneal stroma and hence it is highly involved in stromal wound healing and the associated restoration of anterior corneal transparency at the morphological level.^[4]

Part of the Bowman's layer is ablated by the photorefractive keratectomy refractive surgery (commonly known as PRK). As the layer is non-generative, the section of the layer ablated in the procedure is lost forever.

History

The Bowman's layer is named after Sir William Bowman (1816–1892), an English physician, anatomist and ophthalmologist, who discovered this structure. Bowman's layer is not a true basement membrane, despite being originally referred to as such.^[5]^[6]

References

^ Kenyon, KR. Morphology and pathologic responses of the cornea to disease. In: Smolin G, Thoft RA, eds. The Cornea. Scientific Foundations and Clinical Practice. Boston: Little, Brown & Co.; 1983:45.
^ Hogan MJ, Alvarado JA, Weddell E: Histology of the Human Eye. Philadelphia: WB Saunders, 1971
^ Wilson, SE; Hong, JW (Jul 2000). "Bowman's layer structure and function: critical or dispensable to corneal function? A hypothesis". Cornea. 19 (4): 417–20. doi:10.1097/00003226-200007000-00001. PMID 10928749. S2CID 10793246.
^ Lagali, N; Germundsson, J; Fagerholm, P (Sep 2009). "The role of Bowman layer in corneal regeneration after phototherapeutic keratectomy: a prospective study using in vivo confocal microscopy". Invest Ophthalmol Vis Sci. 50 (9): 4192–8. doi:10.1167/iovs.09-3781. PMID 19407024.
^ Mills, Stacey, ed. (2020). Histology for Pathologists (5th ed.). Wolters Kluwer. p. 337. ISBN 978-1496398949.
^ Wilson, S. E. (2020). "Bowman's layer in the cornea– structure and function and regeneration". Experimental Eye Research. 195: 108033. doi:10.1016/j.exer.2020.108033. PMC 7283008. PMID 32339517.

External links

Histology image: 08002loa – Histology Learning System at Boston University
Diagram at sheinman.com
Diagram at cornea_crosssection_en.jpg

Anatomy of the globe of the human eye

Fibrous tunic
(outer)

Sclera	Episcleral layer Schlemm's canal Trabecular meshwork
Cornea	Limbus layers Epithelium Bowman's Stroma Dua's layer Descemet's Endothelium

Uvea / vascular
tunic (middle)

Choroid	Capillary lamina of choroid Bruch's membrane Sattler's layer
Ciliary body	Ciliary processes Ciliary muscle Pars plicata Pars plana
Iris	Stroma Pupil Iris dilator muscle Iris sphincter muscle

Retina (inner)

Layers	Inner limiting membrane Nerve fiber layer Ganglion cell layer Inner plexiform layer Inner nuclear layer Outer plexiform layer Outer nuclear layer External limiting membrane Layer of rods and cones Retinal pigment epithelium
Cells	Photoreceptor cells (Cone cell, Rod cell) → (Horizontal cell) → Bipolar cell → (Amacrine cell) → Retina ganglion cell (Midget cell, Parasol cell, Bistratified cell, Giant retina ganglion cells, Photosensitive ganglion cell) → Diencephalon: P cell, M cell, K cell, Muller glia
Other	Macula Perifoveal area Parafoveal area Fovea Foveal avascular zone Foveola Optic disc Optic cup Ora serrata

Anatomical regions
of the eye

Anterior segment	Adnexa (Eyebrow, Eyelid, Conjunctiva, Lacrimal system, Orbit) Fibrous tunic Anterior chamber Aqueous humour Iris Posterior chamber Ciliary body Lens Capsule of lens Zonule of Zinn
Posterior segment	Vitreous chamber Vitreous body Retina Choroid