Читать книгу Understanding Anatomy and Physiology in Nursing - John Knight - Страница 42

This consists of several layers of thin, flat cells (Figure 1.8E). The epidermis which forms the outer layer of the skin is composed of a stratified squamous epithelium. The initial layer of cells that resides on the basement membrane is continually dividing by mitosis and is the origin of the cells above. As cells move up through the layers, they accumulate the tough, dense protein called keratin. This makes the epidermal layer very strong but also renders the cells near the surface impermeable to oxygen so that they gradually die.

This means that the outer layer of the epidermis is composed of entirely dead skin cells which gradually slough off and flake away from the surface. There are examples of stratified cuboidal epithelium found surrounding developing ovarian follicles and stratified columnar epithelium found lining the male urethra, and these are discussed further in subsequent chapters.