McKenna's Pharmacology for Nursing, 2e

597

C H A P T E R 3 9 Introduction to the reproductive system

T he reproductive systems in males and females are composed of the structures that support conception and development of a fetus and the endocrine glands that produce the hormones necessary for the regu- lation and maintenance of these structures and that facilitate reproduction. Though anatomically the two systems appear to be very different, they have many underlying similarities. The same fetal cells in males and females give rise to the glands that produce sexual hormones (gonads). In the female, those cells remain in the abdomen and develop into the ovaries , the female sexual glands. In the male, the cells migrate out of the abdomen to form the testes (the male sexual glands), which are suspended from the body in the scrotum. Both male and female glands respond to follicle-stimulating hormone (FSH) and luteinising hormone (LH), which are released from the anterior pituitary in response to stimulation from gonadotropin-releasing hormone (GnRH) released from the hypothalamus. FEMALE REPRODUCTIVE SYSTEM The female reproductive system consists of two ovaries, two fallopian tubes, the uterus and accessory structures, including the vagina, clitoris, labia and breast tissue. The hormones that stimulate and maintain these struc- tures are oestrogen and progesterone. See Figure 39.1.

Structures The ovaries are almond-shaped organs located on each side of the pelvic cavity. The ovaries store the ova , or eggs. Eggs contain half of the genetic material needed to produce a whole cell. At birth, a female’s ovaries contain all of the ova that a woman will have. No new ova will ever be produced by the ovaries. The ova are released into the abdomen throughout a woman’s life or slowly degenerate over time. Each ovum is contained in a storage site called a follicle ; the follicles act as endo- crine glands producing the hormones oestrogen and progesterone . The primary goal of these hormones is to prepare the body for pregnancy and to maintain the pregnancy until delivery. Very near to each ovary is a fallopian tube. The fallopian tube is a muscular tube with a ciliated lining that is constantly moving. This movement propels the ovum released into the abdomen down the fallopian tube and into the uterus , or womb, for the developing embryo and fetus. The uterus is a muscular organ that can develop a blood-filled inner lining, or endometrium, which allows for implantation of the fertilised egg and supports the development of the placenta. The placenta provides nourishment for the developing fetus and acts as an endocrine gland producing the hormones needed to maintain the active metabolic state of the pregnancy. The muscular walls of the uterus are important for expel- ling the developed fetus through the vagina at delivery.

Fallopian

tube Ovary

Uterus

Bladder

Rectum

Vagina

Labia

FIGURE 39.1  The female reproductive system.