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A cuticle (/ ˈ k juː t ɪ k əl /), or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non- homologous , differing in their origin, structure, function, and chemical composition.
Together, the eponychium and the cuticle form a protective seal. The cuticle is the semi-circular layer of almost invisible dead skin cells that "ride out on" and cover the back of the visible nail plate. The eponychium is the fold of skin cells that produces the cuticle. They are continuous, and some references view them as one entity.
Once the parasite has entered the host's gut, the spores open and emerging sporozoites penetrate the gut wall and migrate to the hypoderm (the layer of cells that secrete the larva's cuticle), where they undergo two phases of vegetative reproduction. [7] After the caterpillar pupates, O. elektroscirrha starts reproducing sexually.
The zona pellucida is a translucent matrix of cross-linked glycoprotein filaments that surrounds the mammalian oocyte and is 6.5–20 μm thick depending on the species. Its formation, which depends on a conserved zona pellucida-like (ZP) module that mediates the polymerization of egg coat components, [2] is critical to successful fertilization. [3]
In chicken eggs, the blastoderm represents a flat disc after embryonic fertilization. [3] At the edge of the blastoderm is the site of active migration by most cells. [4] DNA repair genes are highly expressed in chicken blastoderms. [5]
The human skin is the outer covering of the body and is the largest organ of the integumentary system. The skin has up to seven layers of ectodermal tissue guarding muscles, bones, ligaments and internal organs. Human skin is similar to most of the other mammals' skin, and it is very similar to pig skin.
The female reproductive system has two functions: The first is to produce egg cells, and the second is to protect and nourish the offspring until birth. The male reproductive system has one function, and it is to produce and deposit sperm. Humans have a high level of sexual differentiation.
Human egg cell. The egg cell or ovum (pl.: ova) is the female reproductive cell, or gamete, [1] in most anisogamous organisms (organisms that reproduce sexually with a larger, female gamete and a smaller, male one). The term is used when the female gamete is not capable of movement (non-motile).