Female Reproductive System: Structure and Function
Describe the reproductive organs in Human Females?
In this articles we will discuss about the female reproductive system and organs structure and function.
Accessory glands in females
Histology of ovary
Structure of Graafian follicle
Female Reproductive System
The female reproductive system in humans consists of paired ovaries, paired fallopian tubes, uterus, vagina and the accessory glands.
The ovaries are a pair of small almond-shaped organs located in the lower abdominal cavity. Each ovary is about 1.5 to 3 cm long and 8 mm thick. It weighs about 4 gm. The ovaries lie suspended from the dorsal body wall by peritoneal folds and mesenteries called mesovarium. The ovaries produce ova and female hormones such as estrogen and progesterone. At birth the ovaries contain about 2 million primary oocytes and 300,000 to 400,000 at puberty, But during active reproductive phase spanning 13 to 46 years, only about 400 of them develop to expel ova, one each month and the rest degenerate by a process called atresia.
A pair of muscular follopian tubes, each about 12 cm long carries female sex cells from the ovary to the uterus. The proximal end of the fallopian tube opens into the pelvic cavity by a funnel shaped structure called ampulla or infundibulum which lies in close proximity to the ovary. The infundibulum is provided with a number of finger-like processes called fimbriae. Internally, the fallopian tube is lined with ciliated epithelium which facilitates the easy passage of female gametes. The distal end of of the fallopian tube opens into the uterus. After ovulation, the ovum enters into the fallopian tube through the infundibulum.
The womb or the uterus is a pear-shaped, thick walled, muscular organ of about 7.5 cm long and 5 cm wide. It lies in the lower part of the abdominal cavity, just behind the urinary bladder. Its anterior part is wide and is called body or the corpus while the posterior narrow part is called cervix. The cervix projects into the vagina which opens to the outside through an orifice. The lumen of uterus is narrow and raughly triangular. It accommodates the fetus until the time of birth.
The cervix of the uterus opens into the vagina which is a highly distensible tube, averaging 7.5 to 10 cm long. It opens to outside through the vaginal orifice which receives the penis during copulation.
The vulva comprises of a group of external genitalia. They are mons veneris covered with pubic hairs, labia majora, labia minora, vestibule, clitoris,urethral orifice, vaginal orifice and openings of the ducts of Bertholin’s gland.
The mons veneris is the elongated pad-like part formed of a mass of fatty tissue. It is provided with course hairs which grows at puberty. Labia majora are two thick outer folds of skin covered with hairs. They enclose two hairless folds of skin called labia minora. The labia majora encloses the vestibule. Below the junction of labia minora is a small, sensitive rectile organ called clitoris. It is homologous to the male penis. The opening of urethra (urethral orifice) is located below the clitoris. It is meant for the passage of urine. The vaginal orifice lies just below the urethral orifice. The vaginal orifice is usually covered by a hymen in vergin women and it ruptures during first intercourse.
Accessory glands in females :
The Bertholin’s glands are two bean-shaped structures situated on either side of the vaginal orifice. The small duct of each gland opens into the vestibule. Its secretion helps in lubricating the vagina during intercourse.
Histology of ovary:
The ovary is a solid organ. It is covered externally by peritoneum. The germinal epithelium lies inner to the peritoneal covering. The whole mass of connective tissue containing blood vessels, lymph vessels, nerve fibres and the ova in different stages of development is called stroma.
The stroma is divided into an outer compact cortex and inner relatively loose medulla. A large number of ovarian follicles (8-10) develop from the germinal epithelium and subsequently invade into the stroma. A young follicle is initially formed of an oogonium surrounded by a layer of follicular cells. Such a follicle is called the primary follicle. A primary follicle gradually grows in size and finally matures to become the matured follicle or the Graafian follicle.
Structure of Graafian follicle:
The Graafian follicle is surrounded by a thick, transparent, non-cellular layer called zona pellucida. It is chiefly composed of polysaccharides. Inter-digitations of microvilli of oocyte and follicular cells are found in the zona pellucida. The zona pellucida is covered by another membrane called corona radiata comprising of columnar follicular cells. The matured follicle comprises of an eccentrically placed oocyte. The oocyte is surrounded by a mass of follicular cells called discuss proligerus which is attached to the membrana granulosa by a germ hill. A large follicular cavity or antrum is present inside the graafian follicle which is filled up with a fluid. The follicular cavity is externally bounded by the membrana granulosa comprising of many layers of granulosa cells. Two more coverings theca externa and theca interna surround the membrana granulosa. The theca externa is made up of fibrous connective tissue while the theca interna is the inner cellular covering.
The cortical portion of the stroma contains young follicles while the growing follicles are present in the medulla. The graafian follicles when fully matured come again to the cortex. During ovulation, the egg is expelled at the secondary oocyte stage. After ovulation, the ruptured graafian follicle becomes an endocrine gland called corpus luteum. It secretes progesterone which prepares the uterine bed for implantation of the embryo. It also plays a key role in maintaining pregnancy. If the egg is not fertilized, the corpus luteum shrinks and degenerates into a white scar of tissue comprising of small mass of cells called corpus albicans.