Human Reproduction, Sterility, Contraception, and STIs

Spermatogenesis

Occurs in the seminiferous tubules, which contain interstitial cells that secrete testosterone. The walls of the tubules contain germ cells. As they multiply, they move towards the end until they mature to become spermatozoa.

Oogenesis

Takes place in the ovaries and is divided into two stages:

1. Fetal Development: The female develops immature ova while still an embryo in the mother's womb. Each ovum is surrounded by cells to form structures called follicles. Follicles with immature ova inside stop developing until the woman reaches puberty.
2. Ovarian Cycle: Occurs in cycles of approximately 28 days. Follicles grow, and the ovum inside matures. The release of the mature ovum from the ovary is called ovulation. Typically, females ovulate once a month.

The Ovarian Cycle

Lasts approximately 28 days and is divided into two phases:

1. Follicular Phase: The follicle grows for around 14 days, after which ovulation occurs.
2. Luteal Phase: After ovulation, the rest of the follicle becomes the corpus luteum. If fertilization does not occur, it disintegrates, and a new cycle begins.

The Uterine Cycle

Involves the transformation of the endometrium, which thickens to provide a place for the embryo to develop. It also lasts approximately 28 days and consists of three phases:

1. Menstruation: The endometrium is shed and expelled through the vagina along with blood from capillaries.
2. Proliferative Phase: The endometrium regrows.
3. Secretory Phase: The endometrium thickens and becomes vascularized.

Hormonal Regulation of the Cycle

FSH (Follicle-Stimulating Hormone), secreted by the pituitary gland, stimulates the growth of the follicle and the production of estrogen in the ovary. Estrogen causes the endometrium to thicken and triggers the secretion of LH (Luteinizing Hormone) by the pituitary gland. LH triggers ovulation. After ovulation, the corpus luteum secretes estrogen and progesterone, which cause the endometrium to thicken further. If fertilization does not take place, the corpus luteum disintegrates, stops secreting hormones, and a new cycle begins.

Causes of Male Sterility

• Failure to produce a sufficient number of spermatozoa.
• Production of spermatozoa with reduced motility that are unable to fertilize the ovum.
• Obstruction in the vasa deferentia.

Causes of Female Sterility

• Obstruction in the fallopian tubes.
• Problems in the uterus.
• Ovulation disorders due to hormone imbalances.

Assisted Reproduction

A series of artificial techniques aimed at solving infertility problems.

1. Artificial Insemination: Consists of placing sperm from a donor directly in the woman's uterus. Fertilization occurs naturally. Used in cases of anatomical or functional alterations.
2. In Vitro Fertilization: A technique carried out in three stages:
   • Extraction of ova and semen.
   • Fertilization of the ova by the sperm in a laboratory.
   • Transfer of the resulting embryo(s) to the mother's uterus.

Contraception

Any mechanism used to prevent embryonic development.

Natural Methods

• Ogino Method
• Basal Temperature Method

Artificial Methods

• Barrier Methods
• Hormonal Methods
• Implantation Inhibitors
• Surgical Methods

Sexually Transmitted Infections (STIs)

Caused by fungi, bacteria, or viruses that are spread by sexual contact.

AIDS

Caused by the Human Immunodeficiency Virus (HIV). Its main symptom is severe weakening of the body's defenses against microorganisms. Treatment is available to alleviate symptoms.

Hepatitis B

Caused by the Hepatitis B virus. Symptoms include yellow skin and fever. Treatment may not be required in all cases.

Candidiasis

Caused by the Candida albicans fungus. Symptoms include intense itchiness and thick white discharge from the vagina. It is treated with antimycotics.

Gonorrhea

Caused by the Neisseria gonorrhoeae bacterium. In women, it causes pain and vaginal discharge, and in men, itching and pain. It is treated with antibiotics.

Syphilis

Caused by the Treponema pallidum bacterium, which may not cause any symptoms initially. It is treated with antibiotics.

Genital Herpes

Caused by the Herpes simplex virus, which produces periodic outbreaks. There is no cure, but treatments are available to manage symptoms.