Maternal Anatomy: Introduction

Maternal Anatomy: Introduction

The organs of reproduction of women are classified as either external or internal. There may be marked variation in anatomical structures in a given woman, and this is especially true for major blood vessels and nerves.

External Generative Organs

The pudenda—commonly designated the vulva—includes all structures visible externally from the pubis to the perineum, that is, the mons pubis, labia majora and minora, clitoris, hymen, vestibule, urethral opening, and various glandular and vascular structures (Fig. 2–1). The embryology of the external genitalia is discussed in Chapter 4 (see Fig. 4–17).

Figure 2–1.

External female reproductive organs. The lower anterior vaginal wall is visible through the labia minora. In nulliparous women, the vaginal orifice is not so readily visible (inset) because of the close apposition of the labia minora.

Mons Pubis

The mons pubis, or mons veneris, is the fat-filled cushion that lies over the symphysis pubis. After puberty, the skin of the mons pubis is covered by curly hair that forms the escutcheon. In women, it is distributed in a triangular area, the base of which is formed by the upper margin of the symphysis. In men, the escutcheon is not so well circumscribed.

Labia Majora

These structures vary somewhat in appearance, principally according to the amount of fat that is contained within the tissues. Embryologically, the labia majora are homologous with the male scrotum. The round ligaments terminate at the upper borders. After repeated childbearing, the labia majora are less prominent. They are 7 to 8 cm in length, 2 to 3 cm in width, and 1 to 1.5 cm in thickness, and are somewhat tapered at the lower extremities. In children and nulliparous women (see Fig. 2–1), the labia majora usually lie in close apposition, whereas in multiparous women, they may gape widely. They are continuous directly with the mons pubis above and merge into the perineum posteriorly at a site where they are joined medially to form the posterior commissure.

Before puberty, the outer surface of the labia is similar to that of the adjacent skin, but after puberty the labia are covered with hair. In nulliparous women, the inner surface is moist and resembles a mucous membrane, whereas in multiparous women, the inner surface becomes more skinlike. The labia majora are richly supplied with sebaceous glands. Beneath the skin, there is a layer of dense connective tissue that is rich in elastic fibers and adipose tissue but is nearly void of muscular elements. Unlike the squamous epithelium of the vagina and cervix, there are epithelial appendages in parts of the vulvar skin. A mass of fat beneath the skin provides the bulk of the volume of the labium, and this tissue is supplied with a rich plexus of veins.

Labia Minora

The labia minora vary greatly in size and shape. In nulliparous women, they usually are not visible behind the nonseparated labia majora. In multiparas, it is common for the labia minora to project beyond the labia majora.

Each labium minus is a thin fold of tissue that is moist and reddish, similar in appearance to a mucous membrane. The labia minora are covered by stratified squamous epithelium. Although there are no hair follicles in the labia minora, there are many sebaceous follicles and, occasionally, a few sweat glands. The interior of the labial folds is composed of connective tissue with many vessels and some smooth muscular fibers. They are supplied with a variety of nerve endings and are extremely sensitive. The tissues of the labia minora converge superiorly, where each is divided into two lamellae; the lower pair fuse to form the frenulum of the clitoris, and the upper pair merge to form the prepuce. Inferiorly, the labia minora extend to approach the midline as low ridges of tissue that fuse to form the fourchette.

Clitoris

The clitoris is the principal female erogenous organ. It is the homologue of the penis and is located near the superior extremity of the vulva. This erectile organ projects downward between the branched extremitie

sumber : buku Williams Obstetrics 22e 2005

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