Histological structure of ovary
- Each ovary has a compact structure called the medulla and the outer part is called the cortex
- The cortex is covered by a layer of germinal epithelium on the outside, while the medulla contains loose connective tissue containing stroma or blood vessels, lymph vessels, and nerve fibers.
- The cortex shows different stages of development of ovarian follicles. In the center of each primitive follicle is a large primary oocyte (2n) surrounded by a layer of flat follicular cells, which then gradually matures.
- During each menstrual period, the ovary matures primordial follicles in the primary, secondary, and graphene follicles.
- Each Graafian follicle has three layers, e.g. Theka extrna, Theka interna and membrane granulosa which are on the outside to the inside. A space called antrum filled with liqueur follicle is inside the follicle.
- The cumulus of force, or discus proligeras, is a small mound of cells on which the ovum is placed. The ovum is covered by a vitiligo membrane, zona pellucida, and corona radiata from the inside to the outside.
- The ovarian cortex also shows corpus luteum or a yellow body formed from the empty graphene follicle after ovulation. In the absence of pregnancy the corpus luteum is converted into corpus albicans or white body.
Menstruation (ovarian cycle)
Menstrual cycle | Menstrual cycle phases
Menstrual cycle class 12 | Menstrual cycle Class 12 Notes PDF
4 phases of Menstrual cycle | Menstrual cycle hormones and functions
- Menstruation involves cyclical, ovarian and uterine changes.
- Cyclic events are regulated by gonadotropin in the pituitary and hormones in the ovaries.
- Cyclic events in women recur within approximately 28 days.
- Menstruation is divided into the following stages, e.g.
A. Menstrual phase (Day 1-5)
B. Follicular phase (Day 5-14)
C. Ovulatory phase (Day 14-15)
D. Luteal phase (Day 16 to 28)
A. Menstrual phase (Day 1-5)
Menstruation occurs in the absence of conception.
During the menstrual cycle, the uterine endometrium leaks. At this stage the levels of progesterone and estrogen decrease and as a result prostaglandins are released which causes it to rupture.
About 45-100 ml of blood, tissue fluid, mucus, endometrial lining and unfertilized oocyte and other cellular debris is released from the vagina in the form of menstrual flow. The endometrial lining is about 1 mm thin.
Fibrinolicin does not allow blood to clot during this period.
The pituitary begins to secrete FSH, causing many primary follicles to develop into primary and some secondary follicles.
B. Follicular phase (Day 5-14)
The follicular phase of the ovary that coincides with the growth phase of the uterus. / Post Menstrual Stage:
In this stage of the ovary, the follicles develop and the endometrium begins to grow in the uterus. 6 to 12 secondary follicles begin to develop but the action of FSH usually results in only one of them forming a Graafian follicle.
Secondary follicles secrete the developing hormone estrogen.
Estrogen causes the endometrium to regenerate. Further proliferation of the endometrium results in the formation of a network of endothelial cells, endometrial or uterine glands, and blood vessels.
The thickness of the endometrium is 3-5 mm.
C. Ovulatory phase (Day 14-15)
D. Luteal phase (Day 16 to 28)
This phase is called ovarian luteal phase, as the empty graphene follicle converts itself to corpus luteum under the influence of LH. At the same time, the endometrium of the uterus thickens and becomes more secretive, which is why it is called the secretion phase in the uterus.
The corpus luteum secretes progesterone, some estrogen, and inhibin. These hormones stimulate the growth of endometrial glands which then start the secretion of uterus.
The endometrium becomes more vascular 8-1O mm. In thickness. If these changes occur during fertilization, the ovary is ready for transplantation.
In the absence of fertilization, the corpus luteum can live for only two weeks and then transforms into a non-secretory white spot called corpus albicans.
If the ovum is fertilized, the woman becomes pregnant and the hormone hCG (human)
Chorionic gonadotropin) is secreted by the chorionic membrane of the fetus which keeps the corpus luteum active until the formation of the placenta.
If the ovum is fertilized, the corpus luteum survives.
Once the embryo is implanted in the endometrium. It initiates the secretion of human --- chorionic gonadotropin (HCG) which prolongs the life of corpus luteum.
The presence of HCG in the mother's blood and urine is an indicator of pregnancy
If the ovum does not fertilize, the corpus luteum recedes and the corpus albicans is formed. Then the next menstrual period begins.
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