留学生女性生殖系统(组织学)教案

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Chapter 22. The Female Reproductive System

The Female Reproductive System: Introduction

The female reproductive system consists of two ovaries and oviducts (or uterine tubes), the uterus, the vagina, and the external genitalia (Figure 22–1). The functions of this system are to produce female gametes (oocytes), provide the environment for fertilization, and to hold the embryo during its complete development through the fetal stage until birth. As in the male, the female reproductive system produces

steroidal sex hormones that control organs of the reproductive system and influence other organs of the body. Beginning at menarche, when the first menses occurs, the reproductive system undergoes cyclic changes in structure and functional activity. These modifications are controlled by neurohumoral mechanisms. Menopause is a variable period during which the cyclic changes become irregular and eventually

disappear. In the postmenopausal period there is a slow involution of the reproductive organs. Although the mammary glands do not belong to the genital system, they are included here because they undergo changes directly connected to the functional state of the reproductive system. Figure 22–1.

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The female reproductive system and overview of ovary.

(a): The diagram shows the internal organs of the female reproductive system, which includes as the principal organs the ovaries, uterine tubes, uterus, and vagina. (b): A lateral sectional view of an ovary shows the ovary and the relationship of its main supporting mesenteries, the mesovarium and the

mesosalpinx of the broad ligament. (c): Micrograph of a sectioned ovary, indicating the medullary and cortical regions, with follicles of several different sizes in the cortex. X15. H&E.

Ovaries

Ovaries are almond-shaped bodies approximately 3 cm long, 1.5 cm wide, and 1 cm thick. Each ovary is covered by a simple cuboidal epithelium, the germinal

epithelium, continuous with the mesothelium and overlying a layer of dense

connective tissue capsule, the tunica albuginea, like that of the testis and responsible for the whitish color of the ovary. Most of the ovary consists of the cortex, a region filled with a highly cellular connective tissue stroma and many ovarian follicles,

which in the adult ovary vary greatly in size (Figure 22–1). The most internal part of the ovary is the medulla, which contains loose connective tissue and blood vessels entering the organ through the hilum from mesenteries suspending the ovary (Figures 22–1 and 22–2). There are no sharp limits between the ovarian cortical and medullary regions.

Figure 22–2.

为英文的教案,是给到我国学习的巴基斯坦,阿富汗,印度,叙利亚,沙特等国的留学生上课用的教案

Follicle development and changes within the ovary.

The ovary produces both oocytes and sex hormones. A diagram of a sectioned ovary (a), shows the different stages of follicle maturation, ovulation, and corpus luteum formation and degeneration. All of the stages and structures shown in this diagram actually would appear at different times during the ovarian cycle and do not occur simultaneously. Follicles are arranged here for easy comparisons. The primordial follicles shown are greatly enlarged. The histological sections identify primordial follicles (b), a primary follicle (c), a secondary follicle (d), and a large vesicular follicle (e). After ovulation, the portion of the follicle left behind forms the corpus luteum (f), which then degenerates into the corpus albicans (g). All H&E.

Early Development of the Ovary

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In the first month of embryonic life, a small population of primordial germ cells migrates from the yolk sac to the gonadal primordia. In the gonads these cells pide extensively and differentiate as oogonia. In developing ovaries of a two-month embryo there are about 600,000 oogonia which produce more than 7 million by the fifth month. Beginning in the third month, oogonia begin to enter the prophase of the first meiotic pision but arrest after completing synapsis and recombination, without progressing to later stages of meiosis (see Chapter 3). These cells arrested in meiosis are called primary oocytes (Gr. oon, egg, + kytos, cell). Each primary oocyte becomes surrounded by flattened supportive cells called follicular cells within an ovarian follicle. By the seventh month of development, most oogonia have

transformed into primary oocytes within follicles. Many primary oocytes, however, are lost through a slow, continuous degenerative process called atresia, which

continues through a woman's reproductive life. At puberty the ovaries contain about 300,000 oocytes. Because generally only one oocyte resumes meiosis with ovulation during each menstrual cycle (average duration, 28 days) and the reproductive life of a woman lasts about 30–40 years, only about 450 oocytes are liberated from ovaries by ovulation. All others degenerate through atresia.

Ovarian Follicles

An ovarian follicle consists of an oocyte surrounded by one or more layers of epithelial cells. The follicles that are formed during fetal life—primordial

follicles—consist of a primary oocyte enveloped by a single layer of the flattened follicular cells (Figures 22–2, 22–3, and 22–4). These follicles are found in the

superficial areas of the cortex. The oocyte in the primordial follicle is a spherical cell about 25 m in diameter, with a large nucleus and mostly uncoiled chromosomes in the first meiotic prophase. The organelles tend to be concentrated near the nucleus and include num …… 此处隐藏：18698字，全部文档内容请下载后查看。喜欢就下载吧 ……