Session 3 Flashcards
- What is the normal range for puberty in boys and girls?
- When is it precocious puberty in boys and girls?
- Age of menarche?
- What is the average age for menopause?
- Boys: 9-14
Girls: 8-13
- Boys <9
Girls <8
<10 menarche
- 11-15 yrs / <16
- Average age 52
lasts 2-8 yrs
- What is the first sign of puberty in females? Males?
- State when puberty starts in males and females
- Females: breast buds
Males: testicular volume
- In an individual who has a genotype of XXY, will they have ovaries or testis? Explain your answer.
- Define puberty
- Which gender begins puberty first? Which gender ends puberty first?
- Klinefelters – underdeveloped testis
2. sexual maturation and growth are completed
ability to reproduce – Morphological physiological and behavioural development
- Girls begin and end puberty before boys
– Accelerated somatic growth
– Maturation of primary sexual characteristics (gonads and genitals)
– Appearance of secondary sexual characteristics (pubic and axillary hair, female breast development, male voice changes,…)
– Menstruation and spermatogenesis begin
What is an important factor for menstration?
Weight
- Leptin (adipocyte-derived protein hormone)
- Signals information about energy stores to CNS
- important role in regulating neuroendocrine function
– reproductive dysfunction associated with leptin deficiency
– leptin can accelerate the onset of reproductive function
- Leptin has pulsatile release pattern significantly associated with the variations in LH
- leptin can regulate GnRH levels, and its secretion may, in turn, be influenced by gonadal steroids but appears to be independent of LH control
State why boys are taller than girls
• Occurs in both sexes
– Depends on growth hormone and sex steroids in both sexes
– Earlier and shorter in girls
– Men larger because growth spurt longer and slightly faster
- Genital development in boys depends on testosterone
- Ended in both sexes by epiphyseal fusion
– Oestrogen closes epiphyses earlier in girls
How do we switch on the HPG axis?
- GnRH-1 gene is exclusively expressed in a discrete population of neurons in the hypothalamus
- Hormonal changes precede physical changes
– gradual activation of the GnRH (pulsatile release)
– increases frequency and amplitude of LH pulse
– gonadotropins stimulate secretion of sexual steroids (oestrogenes and androgenes)
– extragonadal hormonal changes (elevation of IGF-I, and adrenal steroids)
What is the function of GH in puberty?
What are the features of GnRH
10 amino acid peptide
release is pulsatile every 1-3 hrs
Intensity of GnRH stimulus is affected by
- Frequency of release
- Intensity of release – GnRH travels to pituitary in hypophysial portal system
What anterior pituitary hormone increases during sleep and what effect does this have?
Sleep dependent nocturnal rise in LH (adolescent boys)
- Androgen levels increase could account for some of the early pubertal changes seen in males
- Similar pattern seen in females with concomitant increase in oestrogen
What is the function of LH in males?
LH acts on Leydig cells
Leydig cells produce testosterone
Most testosterone from the testes
constant production (long term)
There is an effect of:
– Circadian rhythm ( Highest early morning)
– Effects of environmental stimuli (Both driven by brain)
Describe the histology/ structure of the testes
1- 4 seminiferous tubules (ST)
ST is 60cm
Interstitial cells -> Leydig -> testosterone
Seminiferous Tubule cells: supporting cells (sertoli cells) & spermatogenic/germ cells
Sertoli cells function:
– provide nutrition & hormonal support to germ cells allowing sperm formation
– Sensitive to FSH (increase sperm production)
– Secreted inhibin (-) feedback on AP FSH
- Which cells produce inhibin in males and females
- What is the function of FSH & LH in females
- Males: sertoli -> inhibin
Females: granulosa -> inhibin
- • Act primarily on gonads via Gαs PCR →adenylate cyclase
• Granulosa cells (FSH) -> oestrogen, inhibin
Theca interna (LH) -> androgens (for oestrogen), progesterone
How do different levels of oestrogen effect GnRH
what are the effects of progesterone on oestrogen and GnRH
low levels inhibition
high levels stimulation
– Progesterone increases inhibitory effects of moderate oestrogen
– Progesterone prevents positive feedback of high oestrogen
• No LH surge
– Oestrogen reduces GnRH per pulse, progesterone frequency of pulses
Inhibin is produced by? Function?
- From granulosa cells of corpus luteum
- Inhibits the secretion of FSH (same as male)
- Has a small inhibitory effect on LH
Describe spermatogenesis
Spermiogenesis
State the percentage and components of ejaculate produced by the different glands
State the structures in which the spermatozoa move through to reach the external urethral meatus
Semen (~2ml per ejaculate)
Seminal vesicle secretions (~70%):
Aa, citrate, fructose, prostaglandins
Secretions of Prostate (~25%)
Proteolytic enzymes, zinc
Sperm (via vas deferens) (2-5%)
~200-500 million per ejaculate
Bulbourethral gland/Cowper gland
Mucoproteins - lubricate and neutralise acidic urine in distal urethra (<1% total vol)
Complete the flow diagram
oogonia ->
1. Oogonia
2. primary oocytes
3. primary follicles (primary oocytes + follicular cells)
4. Preantral stage (follicular cells change from flat to cuboidal & proliferate to produce a stratified epithelium of granulosa cells)
Granulosa cells secrete layer of glycoprotein on oocyte forming the zona pellucida
5. Antral stage Fluid filled spaces between granulosa cells coalesce = antrum. Theca externa, theca interna, granulosa, cumulus oorphorus
- Graafian follicle (When ovulation occurs)
LH surge -> increases collagenase activity
Prostaglandins increase response to LH & cause local muscular contractions in ovarian wall
- Corpus luteum:
Remaining granulosa & theca interna cells become vascularized
Develop yellowish pigment and change into lutein cells
Secrete oestrogens & progesterone
- Stimulates uterine mucosa to enter secretory stage in preparation for embryo implantation
- Dies after 14 days if no fertilisation occurs
- Corpus Albicans (fibrotic scar tissue)
OR
Human chorionic gonadotropin (acts as LH), secreted by developing embryo
CL continues to grow (forms corpus luteum graviditatis)
Cells continue to secrete progesterone until ~ 4th month
Secretion of progesterone by placenta then becomes adequate
State the origin, insertion and innervation of muscles of the pelvic floor
