Histological investigation of the eyelids of Egyptian agama
Histological investigation of the upper and lower eyelids of T .mutabilis revealed that the histological structure of both eyelids’ external and internal surfaces is similar (Figs. 3 and 4)\RL.
The histological structure of the upper and lower eyelids and the superior extension of T . mutabilis revealed that the superior extension and the external surface of the upper eyelid are composed of keratinized stratified squamous epithelium with 2-4 nucleated cell layers, covered with a hard keratin layer forming the horny epidermal scales. The horny scales are connected by hinge regions (Figs. 3 and 4). The internal surface of the upper eyelid is composed of stratified cuboidal epithelium with 2-5 nucleated cell layers with oval and rounded nuclei. The superficial cells have small protrusions (Figs. 4C1 and C2)\RL.
The dermal layer (stroma) located between the external and internal surfaces is formed of fibrous connective tissue filled with densely packed collagen fibers of varying orientations, blood vessels, muscle fibers, and two types of pigment cells: iridophores and melanophores. Iridophores contain brownish-yellow granules and are located beneath the basement membrane of the keratinized stratified squamous epithelium. Melanophores appear as black cells with dendrite-like extensions scattered within the dermis (Figs. 3 and 4)\RL.
Histological investigation of the nictitating membrane of T .mutabilis revealed that it has two surfaces: an external surface (upper surface) and an internal surface (basal surface) (Fig. 5). The external surface of the nictitating membrane is composed of stratified squamous epithelium. In contrast, the internal surface comprises one or two nucleated cell layers with rounded nuclei connected to the conjunctival epithelium. The connective tissue stroma of the nictitating membrane is mainly made up of collagen fibers running in transverse directions and containing blood vessels (Fig. 5d). The conjunctival epithelium consists of one to three nucleated layers, and the connective tissue comprises collagen fibers, blood vessels, and hyaline cartilage (Fig. 5e).