Fertilization

• After ovulation, the ovum, which is around 0.15 mm in diameter, enters the uterine tube and proceeds towards the uterus.
• The cilia and the peristaltic muscle contraction of the tube transport the ovum through the tube.
• Under the influence of oestrogen, the cervix secretes a flow of alkaline mucus that attracts spermatozoa.
• During an intercourse, 60-120 million sperm are deposited in the vaginal posterior fornix.
• Those that reach the loose cervical mucus live to propel (drive forward) towards the uterine tubes, while the rest are killed by the vaginal acid medium. 
• More sperm perish on the passage via the uterus, and just thousands reach the tube, where they normally meet the ovum in the ampulla.
• As the sperm mature, they produce an enzyme called hyaluronidase, which helps them to penetrate the zona pellucida and the cell membrane surrounding the ovum.
• This requires a large number of sperm, yet only one will enter the ovum. Following that, the membrane is shut to prevent further sperm invasion. 
• The sperm’s tail is left behind. The two cells’ nuclei fuse, leading in the development of a zygote.
• The male and female gametes are sperm and ovum, respectively. 
• Because neither the sperm nor the ovum can survive for more than 2-3 days, fertilisation is most likely to occur when intercourse occurs between 48 hours before and 24 hours after ovulation.

Development of fertilized ovum:

• The fertilised ovum (zygote) travels via the fallopian tube and into the uterus in 3-4 days. It goes through segmentation or cell division during this stage to form blastomeres.
• The ovum divides into two cells, then four, eight, sixteen, and so on until a mulberry-like ball of cells known as the morula is created.
• The divisions happen slowly, about once every 12 hours.
• The blastocyst is formed as a result of the gradual accumulation of fluid in the morula. The inner cell mass is a dense mass of cells at one pole of the blastocyst.
• A single layer of cells known as the trophoblast surrounds it on all sides.
• The trophoblast will develop into the placenta and chorion, whereas the inner mass will develop into the foetus and amnion.
• The zygote is fed glycogen from the goblet cells of the uterine tubes and, later, the secretory glands of the uterus as it travels.

Implantation

• When a blastocyst enters the uterus, it is free for 2-3 days.
• The trophoblast that sits above the inner cell mass becomes extremely sticky and sticks to the endometrium.
• It then starts secreting enzymes that cause the epithelium (endometrial cells) to erode, allowing the blastocyst to sink into the endometrium.
• This is known as embedding or nidation (nesting), and it is usually finished by the 11th day after ovulation.
• The endometrium entirely covers it, leaving only a little bump on the surface to indicate the presence of the blastocyst.
• Implantation normally takes place on the posterior uterine wall, however it can also happen on the anterior wall of the fundus.

Application and implication in providing reproductive care

• Ovaries work normally until the age of 45-50, when menopause sets in. Menstruation occurs only between the ages of 12 and 50. The vaginal organ is a copulatory organ.
• Rape is a forced/unwilling coitus that causes a slew of issues. Females of all ages must be given extra care and protection to avoid rape, etc.
• Maintaining good hygiene during the menstrual cycle is essential.
• The breast is a reproductive auxiliary organ. Breast self-examination can detect breast cancer at an early stage. It is susceptible to cancer. Its lymphatic outflow is becoming increasingly important as cancer spreads via lymphatics.
• Per vaginal examination (P/V) is quite helpful in a variety of gynaecological and obstetrical conditions. Examine a pregnant woman for uterine height and advise her on hygiene, food, vaccination, and so on.
• Ultrasound is an extremely helpful tool throughout pregnancy.
• An episiotomy is performed during vaginal delivery to widen the vaginal opening.
• Contraception: The permanent technique of contraception is vasectomy/tubectomy. Females can also use the diaphragm, T tube, injectable, and tablet methods.
• Tubectomy: A woman can be sterilised for family planning purposes by removing a section of the uterine tube on both sides. This can be accomplished through laparoscopy or through an incision in the abdominal wall.