Repond to student...100-200words
Puberty In Girls-Principal Signs,3 Stages, Why Is Age Of Menarche Lowering?
Puberty In Girls
Puberty begins at ages 8 to 10 for most girls in the United States and Europe, but significantly later in many countries (Saladin K. 2015). A small part of the brain called the hypothalamus that secrete gonadaotroipn-releasing hormone (GnRH) is what starts the puberty. GnRH stimulates the pituitary gland, a pea- sized organ connected to the bottom of the hypothalamus, to emit two hormones: luteinizing hormone (LH) and follicle-stimulating hormone (FSH) (Jones & Lopez 2006). These two hormones stimulate development of the ovarian follicles, which in turn, secrete estrogen, progesterone, inhibin, and a small amount of androgen (Saladin K. 2015).
There are three signs that occur in puberty. The first stage is thelarche also known as the breast development. Breast development begins between 8 years of age and 13 years of age and continues through puberty. Estrogen, progesterone,and prolactin initially induce the formation of he lobules and ducts in the breast (Saladin K. 2015). Breast size varies from woman to woman, and there is no way to try to make your breast larger or smaller other than going through plastic surgery. Changes can occur in pregnancy as well.
Next, is pubarche which is known as the pubic and axillary hair, sebaceous glands , and axillary glands (Saladin K. 2015). Pubarche is stimulated by the androgens from the ovaries and the adrenal cortex. Women secrete about 0.5mg of androgen per day, compared with 6 to 8 mg/day in men (Saladin K.2015).
Finally, the menarche also known as a woman first menstrual cycle. Menstruation is the monthly shedding if the uterine wall.This stage has the biggest effect on girls because it can be exciting, scary, or embarrassing for some. It marks a physical change from adolescence to adulthood. Menarche cannot occur until a girl has attained about 17% body fat, and adult menstruation generally ceases if a woman drops below 22% fat (Saladin K. 2015). After a menarche, a womans body is able to become pregnant.
In my opinion the age of when girls get their menstrual has something to do with the amount of hormones that she has. Every girl is different yes, but today you see a lot of young girls with breast and already on their period at the age of 12. Why is this? I'm not sure why all I know that it can be apart of genetics as well as their own hormone and level of estradiol.
Reference:
Jones, R. E. & Lopez, K.H. (2006) Human Reproductive Biology, 3rd edition. Academic press
Saladin Kenneth S. 2015 Anatomy & Physiology The unity of Form and Function.