Puberty Flashcards
At what stage does sexual dimorphism start?
Puberty
What brings on the onset of puberty?
Girls weight 47kg
Nutrition
Leptin = signal the presence of fat
Outline the appearance of secondary sexual characteristics in girls
9-13yrs
Breast bud
Oestrogen and testosterone
Pubic hair growth = in response to testosterone
Before boys
Discuss the role of oestrogen
Important in bone mass
Closing the ephiseal growth plates
What is the role of aromatase?
Enzymes in fatty tissue
Responsible for conversion of androgens to oestrogen’s
Outline the appearance of secondary sexual characteristics in boys
10-14yrs
Genital devel
Testosterone dependent
Pubic hair growth
Spermatogenesis
What is the tanner scale?
Physical measurements of development based on external primary and secondary sex characteristics, such as the size of the breasts, genitals, testicular volume and development of pubic hair
Chart the development of puberty
What is somatic growth?
Growth of the cells of the body in contrast to the germ line cells
Both sexes
Depends of growth hormone and sex steroids
Earlier and shorter in girls
Ended in both sexes by epiphyseal fusion
What axis switches on to activate puberty?
HPG axis
Gradual activation of GnRH (gonadotropin releasing hormone)
Increasing LH pulses
Gonadotropins stim release of sexual steroids
What hormones has a critical role in reproductive maturation being established?
GnRH
What does GnRH go onto stimulate?
AP gonadotrophs to prod =
1) luteinizing hormone (LH
(2) follicle-stimulating hormone (FSH)
Outline somatic growth in puberty
Leptin = GnRH = LH = oestrogen from the ovaries = stim increased GH pulse amplitude = increased IGF-1 = growth spurt
Outline leptin
Adipocyte-derived protein hormone
Pulsatile release
Reg function in puberty – in regards to fat levels
Reg release of GnRH
What changes could account for some of the early pubertal changes seen in males?
Sleep related LH increase = nocturnal rise in testosterone = early pubertal changes
Outline the HPG axis
Hypothalamus = pulsatile GnRH
Pituitary = LH and FSH
Gonad = androgens, oestrogen
What is precocious puberty?
Puberty too young
Tumour in pineal
Outline the control of the HPG axis in males?
High testosterone = -ve feedback on hypothalamus
Low testosterone = no -ve feedback = hypothalamus starts GnRH prod
LH goes on to stimulate what in males?
Leydig cells (in the interstitial tissue between the seminiferous tubules) = prod testosterone from cholesterol
What are sertoli cells?
Sensitive to FSH = increase sperm prod
Forming tight junctions = prevents sperm entering the blood
How are sertoli cells controlled?
High FSH = prod inhibin = -ve feedback on AP = lower FSH = lower prod of sperm
What is the target of FSH in females?
Granulose cells
What is the target of LH in females?
Theca interna
Where is progesterone prod?
Corpus luteum
What are the cell types in the ovary?
Oocyte = gamete
Zona pelucida = Surrounds ovum before implantation
Antrum (secondary follicle) = in the latter stage of folliculogenesis
Zona granulosa = Respond to FSH by converting testosterone to oestrogen by aromatase. Produce progesterone after ovulation.
Theca interna = Respond to LH by producing androgens
How do varying levels of oestrogen effect GnRH?
Low = -ve feedback = reduce GnRH
High = +ve feedback = promote GnRH = LH surge
How does progesterone work with oestrogen?
When oestrogen is low = progesterone increases its inhib effects
When oestrogen is high = progesterone prevents +ve feedback
Outline the role of inhibin
Prod from the granulosa cells of corpus luteum
Inhibits FSH
Small inhib of LH
