The female reproductive organs or genitalia are divided into external and internal organs.
External Genitalia : These includes :-
1) Labia majora
2) Labia minora
3) Mons pubis
4) Clitoris
5) Vestibule
6) Hymen
7) Greater vestibular glands
8) Breasts, ( 1 to 4 genitalia are collectively called vulva ).
1) Labia majora :
These are two large folds which form the boundary of the vulva. They are homologous to scrotum of males. They are composed of skin, fibrous tissue and fat. These are prominent and longitudinal folds on right and left sides of the vestibule.
2) Labia minora :
These are smaller and thinner lip like folds located just medially to the labia majora. Posteriorly the labia minora are fused together to form the fourchette.
3) Mons pubis :
It is fleshy elevation above the labia majora.
4) Clitoris :
It is small erectile organ lying at the anterior end of the labia minora. It is homologous to the penis of males. It shows presence of erectile tissues.
5) Vestibule :
It is a median vertical depression of vulva enclosing vagina and urethral opening.
6) Hymen :
It is a thin layer of mucous membrane which partially occludes the opening of the vagina.
7) Vestibular glands :
These are a pair of vestibular gland or Bartholin's glands which occur on each sides of the vaginal opening. These glands are homologous to the Cowper's glands of the male. They secrete a lubricating fluid.
8) Breasts :
These are a pair of rounded structures found in pectoral region on ventral thoracic wall. It has an erectile nipple in the middle. These are a pair of modified sweat glands. Each breast contains fatty connective tissue and numerous lactiferous glands. It has 15 - 20 openings of lactiferous ducts which carry milk from mammary glands to nipples. Lactiferous ducts dilate and form lactiferous sinuses just beneath the nipple to store the milk. The base of the nipple shows dark brown rounded area called areola.
Release of milk from breast is under the control of prolactin and oxytocin of pituitary gland.
Internal genitalia : The female reproductive system consists of
1) Ovaries
2) Fallopian tubes
3) Uterus
4) Vagina
1) Ovaries :
A pair of ovaries are the primary sex organs of the female reproductive system. They are almond- shaped bodies each measuring about 3 cm long, 1.5 cm wide and 1 cm thick. The ovaries lie in the lower part of abdomen. Each ovary is suspended from the dorsal body wall ( to broad ligament ) by a fold of peritoneum. -the mesovarium. Ovary is connected to lateral body wall by a suspensory ligament.
Ovaries produce ova and also female sex hormones- oestrogen and progesterone. These two hormones control menstrual cycle and secondary sexual characters.
Structure of Ovary :
Each ovary is a compact structure consisting of inner medulla and outer cortex. The medulla contains connective tissue called stroma. The cortex is lined by germinal epithelium. Oogonia arise from endoderm of the yolk sac and migrate to ovaries during embryonic development.
The process of oogenesis begins even before the birth of female baby. The ovaries contain 2 millions or more oogonia which become primary oocytes about sic months before a human female is born. At the time of birth, about 1 million primordial follicles are present in each ovary and only about 40,000 remain by the time of puberty, rest being degenerated. Out of these, during every menstrual cycle only one Graafian follicle reaches to maturity and then ovulation takes place. The remaining follicles degenerate ( atrefied ). Menarch ( onset of the menstrual cycle ) is at the age of about thirteen years and menopause ( end of menstrual cycle ) is at the age of about forty five years. So the reproductive span is approximately thirty two years. There are about 13 menstrual cycles per years.
So 32 X 13 = 416 eggs may be released.
Histology of Ovary :
Tunica albuginea is a whitish capsule of dense irregular connective tissue located immediately inside the germinal epithelium.
Ovary shows cyclic changes during menstrual cycle. Cortical region shows different stages of development of ovarian follicles or Graafian follicles. Each follicle contains a large ovum surrounded by many layers of follicle cells. The follicle cells of a maturing follicle secrete oestrogen.
Different stages of developing ovarian follicles are seen in the cortex and consists of oocytes in various stages of development. In the beginning, a single layer of follicular cells surround each oocyte and the entire structure is called a primordial follicle.
Although the stimulating mechanism is unclear, a few primordial follicles periodically start to grow even during childhood. They become primary follicles which are surrounded first by one layer of follicular cells and then by 6 - 7 layers of granulosa cells. As the follicle grows, it forms a clean glycoprotein layer, called the zona pellucida between primary oocyte and granulosa cells. The innermost layer of granulosa cells become firmly attached to zona pellucida to form corona radiata ( corona- crown; radiate- radiating )
i) Theca interna -A highly vascularised internal layer of secretory cells
ii) Theca externa - an outer layer of connective tissue cells.
The granulosa cells begin to secrete follicular fluid, which fills up a cavity called antrum in the center of follicle. Now, it is called secondary follicle.
Under the influence of gonadotropins ( follicle stimulating hormone and luteinising hormone ), Meiosis I resumes in secondary follicles. Only one matures and ovulation takes place. The diploid primary oocyte completes Meiosis I and forms secondary oocyte. Secondary oocyte proceeds with Meiosis II and is arrested at Metaphase. The follicle with Secondary oocyte arrested at Metaphase II is called mature ( Graafian ) follicle. It takes 90 days or longer for a primary follicle to develop in to secondary follicle.
One Ovum from mature follicle is released from one ovary in every menstrual cycle ( alternately in right and left ovary ). It may also show presence of mass of yellow cells called corpus luteum, formed in the antrum or follicular cavity of an empty Graafian follicle after the release of its ovum ( ovulation ). If the ovum is fertilized corpus luteum secretes progesterone to maintain pregnancy and relaxin towards the end of pregnancy. The ovarian cortex may also show white body or corpus albicans representing a degenerating corpus luteum in case if the ovum is not fertilized.
Fallopian tubes ( oviducts ) :
These are a pair of tubes lying horizontally over peritoneal cavity close to the ovary. Each fallopain tube is about 10 to 12 cm long, narrow, muscular structure lined by ciliated epithelium. It conducts egg or ovum discharged from the ovary to the uterus. It is supported by a double fold of peritoneum called mesosalpinx.
The free proximal end is dilated into a funnel like processes called fimbriae at its free border. It shows the presence of an opening called ostium. This funnel is quite close to the ovary of its side so that the ova discharged from ovary are received. Ampulla is the of fertilization. Cornua/ isthmus is very short, narrow part opening in the uterus.
Uterus :
It is also known as womb. It is a pear-shaped, highly muscular, thick walled, hollow organ. It is about 8 cm long, 5 cm wide and 2 cm thick. It is present in the pelvic cavity between the rectum from behind and urinary bladder in front. It is attached to the body wall by double fold of peritoneum called mesometrium or broad ligament.
It is differentiated into :
1) A done shaped part above the opening of uterine tubes is called fundus.
2) Broad upper part called body or corpus.
3) Narrow cylindrical part called cervix.
Body of uterus receives the oviduct at its right and left upper angles.
The cervix projects and opens into vagina. The cervix communicates above with the body of the uterus by an aperture, the internal os and with vagina below by ab opening, external os. The highly distensible uterine wall consists of an outer serous layer derived from peritoneum called perimetrium. The middle thick muscular layer of smooth muscles is called myometrium. The inner highly vascular mucosa is called endometrium. It shows many uterine glands. It undergoes cyclic changes in thickness during menstrual cycle.
Uterus receives the ovum from Fallopian tube. It forms placenta for the development of the foetus. It expels the young one at birth.
Vagina :
This is highly collapsible and highly distensible fibro-muscular tube in which cervix opens. It measures about 7.5 cm to 10 cm in length. It opens into the vestibule of vulva. Inner lining cells of vagina store glycogen. Vaginal bacteria mainly Lactobacilli ferment the glycogen and this makes the mucous acidic. Highly acidic medium in vagina prevents infection by fungus. In girls the opening of vagina into the vestibule of vulva is partially covered over by a fold of mucous membrane called hymen.
Vagina is a copulatory passage as it receives erected penis during intercourse. it allows passage of menstrual flow. It serves as the birth canal during parturition.
Puberty in females :
Puberty is the age at which the internal reproductive organs reach maturity. This is called the menarche which marks the beginning of the child bearing period. The ovaries are stimulated by the gonadotropins from the anterior pituitary- the follicle stimulating hormone and luteinising hormone.
The age of puberty varies between 10 to 14 years. Menopause or climactic period is the ceasing of menstrual cycle i.e. end of childbearing period. It usually occurs between the age of 45 to 50 yrs.
During menopause the ovaries gradually become less responsive to the FSH and LH. The menstrual cycle becomes irregular and them stops. It also shows secondary effects of menopause like osteoporosis, increase in blood cholesterol and hot flushing, sweating and palpitation.