13.58: Female Reproductive Development
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What changes happen during puberty?
A lot changes during this time, including changes to reproductive organs and other physical changes.
Sexual Development in Females
Female reproductive organs form before birth. However, as in males, the organs do not mature until puberty.
Development Before Birth
Unlike males, females are not influenced by the male sex hormone testosterone during embryonic development. This is because they lack a Y chromosome. As a result, females do not develop male reproductive organs. By the third month of fetal development, most of the internal female organs have formed. Immature eggs also form in the ovary before birth. Whereas a mature male produces sperm throughout his life, a female produces all the eggs she will ever make before birth.
Changes of Puberty
Like baby boys, baby girls are born with all their reproductive organs present but immature and unable to function. Female reproductive organs also grow very little until puberty. Girls begin puberty a year or two earlier than boys, at an average age of 10 years. Girls also complete puberty sooner than boys, in about 4 years instead of 6.
Puberty in girls starts when the hypothalamus “tells” the pituitary gland to secrete hormones that target the ovaries. Two pituitary hormones are involved: luteinizing hormone (LH) and follicle-stimulating hormone (FSH). These hormones stimulate the ovary to produce estrogen. Estrogen, in turn, promotes growth and other physical changes of puberty. It stimulates growth and development of the internal reproductive organs, breasts, and pubic hair (see Figure below).
Adolescent Growth Spurt
Like boys, girls also go through an adolescent growth spurt. However, girls typically start their growth spurt a year or two earlier than boys (and therefore a couple of centimeters shorter, on average). Girls also have a shorter growth spurt. For example, they typically reach their adult height by about age 15. In addition, girls generally do not grow as fast as boys do during the growth spurt, even at their peak rate of growth. As a result, females are about 10 centimeters (about 4 inches) shorter, on average, than males by the time they reach their final height.
One of the most significant changes in females during puberty is menarche. Menarche is the beginning of menstruation, or monthly periods as the ovaries begin the cyclic release of an egg. In U.S. girls, the average age of menarche is 12.5 years, although there is a lot of variation in this age. The variation may be due to a combination of genetic factors and environmental factors, such as diet.
- Female reproductive organs form before birth. However, they do not mature until puberty.
- State two ways that puberty differs in girls and boys.
- Define menstruation. What is the first menstrual period called?
- Males and females are quite similar in height when they begin the adolescent growth spurt. Why are females about 10 centimeters shorter than males by adulthood?
|[Figure 1]||Credit: Spirit-Fire
License: CC BY
|[Figure 2]||Credit: Zachary Wilson
Source: CK-12 Foundation
License: CC BY-NC 3.0