Puberty Flashcards
What are primary and secondary sexual characteristics?
Primary- established before birth and directly involved in reproduction
Secondary- develop at puberty and not directly concerned with reproduction
E.g. pubic/ axillary hair, breasts, Male voice
What are the three stages of secondary sexual characteristic development in females and what occurs at each stage?
At what age does this take place?
thelarche:
Breast bud
Pubic hair growth
Adrenarche:
Growth spurt
Onset of menstrual
Menarche:
Pubic hair adult
Breasts adult
9-13yrs
What secondary sexual characteristics develop in boys and at what age?
Genital development Pubic hair growth Spermatogenesis Growth spurt Genitalia adult Pubic hair adult
What can be used to assess how developed a child is and how many stage are there?
The tanner scale
1-5
What does somatic growth depend on? How is it different in boys and girls and why?
Depends on growth hormone, Insulin like growth factor -1 and sex steroids
Earlier and shorter in girls
In men: testosterone is converted to oestrogen by aromatisation in peripheral tissues
Oestrogen is responsible for epiphyseal fusion so girls have more and quicker = they reach max height quicker and end up being shorter
Genital development in boys depends on testosterone
What might explain why puberty in Western countries is much earlier than it used to be?
C 1800 17yrs
Now <13yrs
Girls Critical weight = 47kg (weight to start puberty bc able to carry a child)
Leptins May be involved in signalling
How is the hypothalamus and pituitary unit involved in different aspects of puberty?
Controls: The reproductive glands Somatic growth Lactation Milk production
How does the hypothalamus and pituitary unit control puberty?
Years before puberty hypothalamus secretes nocturnal pulsatile gonadotropin-realising hormone (GnRH) (regulated light/ leptins)
-> portal system
-> anterior pituitary ->
Stored & new LH and FSH ->
Gonad ->
Androgens and oestrogen (-ve feedback on hypothalamus)
Most parts of reproductive system can work before puberty but don’t bc low hormone level due to low GnRH secretion
At puberty GnRH increases and steady rise in FSH and LH -> androgens/ oestrogen
Which gene is responsible for mammalian GnRH and where is it Expressed? What proves the critical role of GnRH in reproductive maturation?
GnRH-1 gene
Discrete population neurones hypothalamus
Treating prepubertal primates GnRH induces puberty
Lack of GnRH -> lack of reproductive development
Used to treat infertile mice -> spermatogenesis and ovarian maturation
What’s another name for the anterior pituitary gland? What 6 peptide hormones does it produce?
Adenohypophysis
Prolactin FSH LH GH ACTH TSH
What does LH specifically stimulate in males? What affects the levels of testosterone?
LH stimulated Leydig cells (adjacent to seminiferous tubules which need functioning Leydig) in testis to convert cholesterol to the steroid hormone testosterone
Greatest amount produced from testis (Some from adrenal cortex)
Peaks at 20yrs then slowly declines
Effect of circadian rhythms (highest early morning) and environmental stimuli
What are seminiferous tubules, which make up 90% of testicular volume, surrounded by?
Lined by epithelium made from:
- Supporting Sertoli cells (provide nutrition and hormonal support to germ cells and absorb XS cytoplasm from spermatozoa, activated by FSH. Produce inhibin-ve feedback FSH)
- Spermatogenic germ cells
Where do FSH and Lh in females act? What do they do?
Act via G protein coupled stimulators receptor-> adenylate cyclase
Act on Ovarian (FSH) granulosa and (Lh) theca interna cells
Stimulate steoidgenesis ->
Oestrogen, progesterone, inhibin
Control gamete production (folliculogenesis and ovulation)
Granulosa cells -> oestrogen and Inhibin
Theca interna -> androgens (precursor for oestrogen)
How do levels of oestrogen and progesterone affect GnRH secretion?
Moderate titres of oestrogen reduces GnRH (-ve) per pulse
High titres of oestrogen alone promote GnRH -> LH surge (+ve)
Progesterone reduces GnRH frequency of pulses and prevents LH surge (contraceptive). Increases inhibitory effects of moderate oestrogen
Where does inhibin come from and what’s its affect on FSH and LH?
From granulosa cells of corpus luteum
Inhibits FSH secretion (Some as males)
Small inhibitory effect on LH
