- Unlike the continuous sperm production of the male, the maturation of the female gamete (the ovum) followed by its release from the ovary—ovulation—is cyclical.
- The female germ cells, like those of the male, have different names at different stages of development.
- However, the term egg is often used to refer to the female germ cells; we will use the two terms—egg and ovum— interchangeably hereafter. The structure and function of certain components of the female reproductive system (e.g., the uterus) are synchronized with these ovarian cycles.
- In human beings, these cycles are called menstrual cycles.
- The length of a menstrual cycle varies from woman to woman, and even in any particular woman, but averages about 28 days. The first day of menstrual flow (menstruation) is designated as day 1.
- Menstruation is the result of events occurring in the uterus.
- However, the uterine events of the menstrual cycle are due to cyclical changes in hormone secretion by the ovaries.
- The ovaries are also the sites for the maturation of gametes.
- One oocyte usually becomes fully mature and is ovulated around the middle of each menstrual cycle.
The interactions among the ovaries, hypothalamus, and anterior pituitary gland produce the cyclical changes in the ovaries that result in
- (1) maturation of a gamete each cycle and
- (2) hormone secretions that cause cyclical changes in all of the female reproductive organs (particularly the uterus).
- The interaction of these different structures in the adult female reproductive cycle is an excellent example of the general principle of physiology that the functions of organ systems are coordinated with each other.
- These changes prepare the uterus to receive and nourish the developing embryo; only when there is no pregnancy does menstruation occur.
- Haploid cells that contain 23 chromosomes
- Formed by meiosis
- (when another gamete fuses eg sperm, a diploid cell is created with all necessary chromosomes)
- Produce and release female gametes and sex hormones like oestrogen and progesterone.
- The ovaries are almond-sized organs in the upper pelvic cavity, one on each side of the uterus.
Tunica albuginea & germinal epithelium
- Tunica albuginea: connective tissue
- Germinal epithelium: cuboidal epithelial cells. Part of the peritoneum [lines the abdominal cavity]
- Cortex: houses developing eggs
- Medulla: contains most of the ovary's blood vessels and nerves
Female reproductive tract
- The female reproductive system includes the two ovaries and the female reproductive tract—two fallopian tubes (or oviducts), the uterus, the cervix, and the vagina.
- These structures are termed the female internal genitalia
- The ends of the fallopian tubes are not directly attached to the ovaries but open into the abdominal cavity close to them.
- The opening of each fallopian tube is funnel-shaped and surrounded by long, fingerlike projections (the fimbriae) lined with ciliated epithelium.
- The other ends of the fallopian tubes are attached to the uterus and empty directly into its cavity.
- The uterus is a hollow, thick-walled, muscular organ lying between the urinary bladder and rectum.
- The uterus is the source of menstrual flow and is where the fetus develops during pregnancy.
- The lower portion of the uterus is the cervix
- The lower portion of the uterus is the cervix.
- A small opening in the cervix leads to the vagina.
- A small opening in the cervix leads to the vagina, the canal leading from the uterus to the outside.
Female external genitalia
- The female external genitalia (Figure 17.18) include the mons pubis, labia majora, labia minora, clitoris, vestibule of the vagina, and vestibular glands.
- The term vulva is another name for all these structures.
- The mons pubis is the rounded fatty prominence over the junction of the pubic bones.
- The labia majora, the female homologue of the scrotum, are two prominent skin folds that form the outer lips of the vulva.
- (The terms homologous and analogous mean that the two structures are derived embryologically from the same source
- The labia minora are small skin folds lying between the labia majora.
- They surround the urethral and vaginal openings, and the area thus enclosed is the vestibule, into which secretory glands empty.
Partially overlying the vaginal opening is a thin fold of mucous membrane, the hymen.
The clitoris, the female homologue
of the penis
, is an erectile structure located at the top of the vulva.