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As a prelude to this, one needs to first understand the anatomy. The foreskin is composed of an outer layer that is keratinized (as is skin generally), and an inner lining that is a mucosal surface. The inner lining thus resembles other mucosal epithelia such as constitute the cervix, nasal passages and rectum. It had been suggested that the foreskin protected the glans from drying out and becoming keratinized. However, histological examination has shown the same amount of keratin in the skin of the head of the penis irrespective of circumcision status . The inner layer lines a `preputial sac', which becomes a repository for shed cells, secretions, and urinary residue that accumulates [71, 265]. It is also a hospitable environment for the growth of bacteria and other microorganisms. During an erection the head and shaft of the penis extend so that the inner layer becomes exteriorized along the distal half of the shaft.