In girls of about 10-12 years old, the anterior pituitary hormones stimulate the ovarian development. They produce the female sex hormones, resulting

Puberty in girls [Female]

In girls of about 10-12 years old, the anterior pituitary hormones stimulate the ovarian development. They produce the female sex hormones, resulting in increased mammary gland, occurs skeletal growth and hair growth on the female type. At this time, ova begin to mature and the first menstruation (menarche) appears. It is a manifestation of the fact that the girl has become a woman. Although the ovum is already fertilized, the body of a very young girl is not ready for the full gestation.

The process of ova maturation is cyclical in nature and is called the menstrual cycle (diagram 122). Its duration is 24-30 (usually 28) days. Approximately in the middle of cycle occurs ovulation the ovulation, i.e. the release of an ovum from the follicle. Corpus luteum forms in the place of burst follicle. This is a temporary endocrine gland that produces the pregnancy hormone (progesterone). Its function is to delay the ripening of other follicles, uterus preparation for the adoption of a fertilized ovum (the thickness of its mucosa increases, it grows with a large number of congested vessels).

Fertilization normally occurs in the fallopian tube. If it does not, then after 5-6 days the ovum dies, yellow body destroys, stopping the production of its hormones, thickened uterine mucosa (endometrium) dies and peels off together with the newly formed blood vessels. There happens temporary uterine bleeding, or menstruation, that lasts 3-5 days. After it ends, endometrium restores and the cycle begins over again, but the ovum matures already in the second ovary. Taken from http://worldofschool.org

Diagram 122. The menstrual cycle

The first menstruation in girls is usually in 11-14 years. Approximately 1-1.5 years of menstruation may be irregular and inferior. If the girl has no menstruation at the age of 15-16 years or it’s accompanied by severe pain or bleeding, you should contact your doctor!

Questions:
  • Explain the physiological mechanisms of puberty in girls.

  • Explain the biological significance of the fallopian tubes.

  • Define the relationship between the menstrual cycle, ovulation and the function of corpus luteum.