Polymer Gels by Unknown

Author:Unknown
Language: eng
Format: epub
ISBN: 9789811060830
Publisher: Springer Singapore

The vagina is a thin-walled fibromuscular tube located between the rectum, urethra and bladder in women, and extending from outside the body to the cervix, which is the central organ of reproduction in women (Alexander et al. 2004; Forsberg 1996; Huszar 1986; Sjoberg 1992). Although the anterior and posterior walls of the vagina are in contact with each other in a relaxed state, it is an easily distensible organ and may be considered as a potential area, albeit not a real open area (Baloglu et al. 2009; Huszar 1986; Woolfson et al. 2000). It performs multiple functions, such as providing an outlet for menstrual fluids, facilitating the entry of seminal fluid, and during childbirth is the organ that provides structure at the base of the birth canal (Baloglu et al. 2009).

The interindividual variability of the dimensions of the vagina is extremely high and is especially modified depending on age and sexual arousal. The average length of the vagina in women of reproductive age varies between 6 and 8 cm for the front wall and up to 14 cm for the back wall, including the length of the cervix (Pendergrass et al. 1996). The average vaginal surface area, important for drug administration through this route, is 87.46 cm2 (which may vary within a range of 65–107 cm2) (Pendergrass et al. 2003). However, the prevalence of vaginal folds greatly hinders its calculation, and the above data are therefore only an estimate of the true area (Ferguson and Rohan 2011).

Not only is the size of the vagina highly variable, but the shape also changes significantly from one woman to another, although a common pattern has been found in the form acquired by the vagina in women of the same race (Pendergrass et al. 1996, 2000, 2003). The different potential forms of the vagina are also important from the point of view of pharmaceutical development, as this factor may affect the acceptability of certain forms of vaginal dosage and require the development of multiple dosage forms for vaginal administration, with formulations always designed to cover the largest possible vaginal area. In some applications such as vaginal microbicides for the prevention of sexually transmitted diseases, there is speculation as to the possible influence of the amount of vaginal surface covered by the formulation, and it remains to be seen whether the microbicide must completely cover the vagina to achieve complete protection (Ferguson and Rohan 2011).

Both the vagina and the ectocervix (the portion of the cervix exposed to the vaginal environment) are lined by keratinized and non-keratinized stratified squamous epithelium composed of several layers, which is continually renewed during the reproductive years. There are three clearly differentiated areas in this epithelium: a basal layer composed of germinal cells, a middle zone also called stratum spinosum—the most abundant—and finally the surface area where the most mature cells are found and whose function is to protect the cells below and the subepithelial vasculature from trauma and infection (Huszar 1986). During ripening, the cells migrate from the basal layer

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