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Anatomy and physiology of the male reproductive system
Puberty and Tanner staging
Puberty and Tanner staging
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GH secretion in p. 340
GnRH and p. 334
Kallmann syndrome and p. 663
precocious p. 55, 338
Tanner stages p. 660
A long time ago, in an uterus far, far away, there was a sexually undifferentiated embryo, that could develop into either a male or a female according to its sex chromosomes.
During that time, most of its organs and systems took shape and started functioning.
But one system - the reproductive system - developed and then waited for a trigger to kick into action.
Sexual maturation is under the control of the hypothalamic-pituitary-gonadal axis.
The hypothalamic-pituitary-gonadal axis is a system of hormone signaling between the hypothalamus, pituitary gland, and gonads, either the testes or ovaries, to control sexual development and reproduction.
When gonadotropin-releasing hormone reach the anterior lobe of the pituitary gland, it stimulates cells called gonadotrophs, to release gonadotropin hormones: luteinizing hormone, or LH, and follicle-stimulating hormone, or FSH, into the blood.
Now, the amount of hormone that gets produced by this axis varies over a person’s lifetime, and that affects the development of the sex organs, as well as the appearance of secondary sexual characteristics.
Puberty is the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction. During puberty, the sex organs mature functionally and begin producing sex hormones and gametes. It begins when the hypothalamus and the pituitary switch from a linear pattern of GnRH, FSH, and LH secretion to a pulsatile pattern.
In addition, in females, there's also a 28-day cycle of gonadotropin secretion called the menstrual cycle. The increased production of sex hormones determines the development of primary and secondary sex characteristics in both sexes, and these characteristics can be evaluated with the Tanner staging. The Tanner staging system consists of five stages, with stage 1 being the "pre-pubertal" stage, and stage 5 being the fully mature adult stage. Each stage is defined by specific physical characteristics: Stage 1: Pre-pubertal, no secondary sexual characteristics Stage 2: Beginning of breast development or testicular enlargement Stage 3: Further breast or testicular development Stage 4: Nearly mature; breast or testicular size nearly adult Stage 5: Adult; breast or testicles are fully mature
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