week 10 reproductive system

menopause

unique to humans

reproductive strategy to maximise survival and assisting on the birth of the next generation

factors of human reproductive success

• biological adaptation

• cognitive abilities

• social cooperation

• tool use and tech

• cultural evolution

• dietary flexibility

• adaptability

• domestication

• prolonged childhood

• delayed reproduction

• post reproductive life

• longevity

• global impact

biological adaptation

bipedalism, thumbs, brain, life stages

enhanced mobility and tool making, problem solving

prolonged childhood

extended learning and brain development, social and parental investment

survival and cultural skills, creativity

delayed reproduction

reproduction after physical and cognitive maturity

improved offspring survival and care

post reproductive life

grandmother hypothesis, transmission of knowledge

increased chance of survival, social cohesion, knowledge transmission

how do we become male or female?

5-6 weeks after conception is sexual differentiation

hormonal changes to switch genes on/off on gonads

positive feedback loffects XX chromosomes

main structures common in both males and females

• gonads

• gametes

• ducts to receive and transport gametes

• external genitalia

• urethra

spermatogenesis

a stage of mitosis, meiosis I and meiosis II

physical maturation of spermatocyte into spermatozoa

64-72 days long

hormonal regulation in males

hypothalamus releases GnRH, which stimulates release of LH and FSH

LH releases testosterone which inhibits the release of LH

FSH releases inhibin which inhibits the release of more FSH

female reproductive system

eggs defined at birth

depends on family diseases

the ovarian cycle

every 25-34 days an immature gamete is releases

consists of a follicular phase and a luteal phase

menses

destruction of the functional zone

increasing levels of estrogen and inhibin

proliferative phase

repair and regeneration of the functional zone

high levels of estrogen and inhibin

secretory phase

secretion of endometrial glands

high levels of progesterone, decreasing levels of estrogen and inhibin

hormonal regulation in females

GnRH released from the hypothalamus stimulates the production and release of FSH, and production of LH

FSH secretes inhibin, which inhibits the release of more FSH, and estrogens, which stimulate the release of more GnRH, as well as after 10 days stimulating the release of LH

LH and estrogen stimulate the release of progesterone, which inhibits the release of more GnRH

developmental stage at 0-4 weeks

germinal stage

developmental stage at 5-6 weeks

gonadal ridge formation

developmental stage at 7-8 weeks

differentiation begins

developmental stage at 9-12 weeks

ovarian development

developmental stage at 13-16 weeks

external genitalia differentiation

developmental stage at 17-20 weeks

rapid ovarian development

developmental stage at 21-28 weeks

regression of oogonia

developmental stage at 29-36 weeks

maturation and final positioning

developmental stage at 37-40 weeks

preparation for birth

intergenerational hypothesis

when the mother is affected by persistent environmental conditions, this affects the germ cells of the fetus

therefore maternal health, paternal health (quality of sperm) and epigenetic programming influences offspring fertility

growth of reproductive system

only after all other systems have developed

height

height velocity decreases with age

girls have a growth spurt around 14 years old, while boys have a larger growth spurt around 15 years old

development in girls

menarche after peak velocity decreases back to normal

before peak velocity, pubic hair and breasts develop

development in boys

genitals and pubic hair develop at the beginning of their growth spurt

associations

the relationship between age at menarche and age at menopause is uncertain

ag at menarche, parity and age at natural menopause is related to metabolic measures

sex spectrum

genetic variations

sex development disorders can cause ambiguous genitalia that don’t match sex chromosomes