Control of human reproduction

Female sex hormones

The Placenta

Female sex hormones

Understanding the menstrual cycle is key to understanding human reproduction.

You need to know in detail how the menstrual cycle is controlled and regulated by hormones.

The key hormones are : luteinising hormone, follicle-stimulating hormone, oestrogen and progesterone

Luteinizing hormone (LH) triggers the release of testosterone by the follicle which causes the release of enzymes which rupture the ovary wall allowing the release of the secondary oocyte. After ovulation promotes the transformation of the follicle into the corpus luteum.

Follicle-stimulating hormone (FSH) – stimulate the formation of several primary follicles – only one of which will eventually develop while the other disintegrate. Also FSH stimulates the enzymes that lead to the formation of oestrogen.

Luteinizing hormone (LH) triggers the release of testosterone by the follicle which causes the release of enzymes which rupture the ovary wall allowing the release of the secondary oocyte. After ovulation promotes the transformation of the follicle into the corpus luteum.

Progesterone secreted by corpus luteum:

•Prepares uterus wall (endometrium) for implantation of a fertilised egg

•Promotes growth of the mammary glands

•Inhibits FSH secretion

Follicle-stimulating hormone (FSH) – stimulate the formation of several primary follicles – only one of which will eventually develop while the other disintegrate. Also FSH stimulates the enzymes that lead to the formation of oestrogen.

Oestrogen produced by modification of the testosterone produced by the follicle. It:

•Stimulates further growth of the follicle

•Promotes repair of the endometrium

•Inhibits secretion of FSH

Luteinizing hormone (LH) triggers the release of testosterone by the follicle which causes the release of enzymes which rupture the ovary wall allowing the release of the secondary oocyte. After ovulation promotes the transformation of the follicle into the corpus luteum.

Progesterone secreted by corpus luteum:

•Prepares uterus wall (endometrium) for implantation of a fertilised egg

•Promotes growth of the mammary glands

•Inhibits FSH secretion

Body temperature rises by about 1oC at the time of ovulation

Follicle-stimulating hormone (FSH) – stimulate the formation of several primary follicles – only one of which will eventually develop while the other disintegrate. Also FSH stimulates the enzymes that lead to the formation of oestrogen.

Oestrogen produced by modification of the testosterone produced by the follicle. It:

•Stimulates further growth of the follicle

•Promotes repair of the endometrium

•Inhibits secretion of FSH

Development of follicle within the ovary is initiated by FSH but continued by LH. Eventually becomes the corpus luteum and inhibits LH

Luteinizing hormone (LH) triggers the release of testosterone by the follicle which causes the release of enzymes which rupture the ovary wall allowing the release of the secondary oocyte. After ovulation promotes the transformation of the follicle into the corpus luteum.

Progesterone secreted by corpus luteum:

•Prepares uterus wall (endometrium) for implantation of a fertilised egg

•Promotes growth of the mammary glands

•Inhibits FSH secretion

Body temperature rises by about 1oC at the time of ovulation

After ovulation the endometrium becomes thicker and highly vascularized.

Follicle-stimulating hormone (FSH) – stimulate the formation of several primary follicles – only one of which will eventually develop while the other disintegrate. Also FSH stimulates the enzymes that lead to the formation of oestrogen.

Oestrogen produced by modification of the testosterone produced by the follicle. It:

•Stimulates further growth of the follicle

•Promotes repair of the endometrium

•Inhibits secretion of FSH

Development of follicle within the ovary is initiated by FSH but continued by LH. Eventually becomes the corpus luteum and inhibits LH

The endometrium thickens under the influence of oestrogen.

Luteinizing hormone (LH) triggers the release of testosterone by the follicle which causes the release of enzymes which rupture the ovary wall allowing the release of the secondary oocyte. After ovulation promotes the transformation of the follicle into the corpus luteum.

Progesterone secreted by corpus luteum:

•Prepares uterus wall (endometrium) for implantation of a fertilised egg

•Promotes growth of the mammary glands

•Inhibits FSH secretion

Body temperature rises by about 1oC at the time of ovulation

After ovulation the endometrium becomes thicker and highly

vascularized.

Menstruation is initiated by falling levels of oestrogen and progesterone as the corpus luteum degenerates.

Luteinizing hormone (LH) triggers the release of testosterone by the follicle which causes the release of enzymes which rupture the ovary wall allowing the release of the secondary oocyte. After ovulation promotes the transformation of the follicle into the corpus luteum.

Progesterone secreted by corpus luteum:

•Prepares uterus wall (endometrium) for implantation of a fertilised egg

•Promotes growth of the mammary glands

•Inhibits FSH secretion

Body temperature rises by about 1oC at the time of ovulation

After ovulation the endometrium becomes thicker and highly

vascularized.

Menstruation is initiated by falling levels of oestrogen and progesterone as the corpus luteum degenerates.

The Placenta

The functions of the placenta

The functions of the placenta

Immune protection: protective molecules cover the surface of the early placenta “hiding” it from the maternal immune system so it is not rejected as ‘non-self’ due to the presence of the paternal genes.

The functions of the placenta

Barrier: limits the transfer of blood components from the maternal to foetal system. Cells of the maternal immune system do not cross so reducing risk of immune rejection. (The placenta is not a barrier to heavy metals, nicotine, HIV, heroin or other toxins)

The functions of the placentaImmune protection: protective molecules cover the surface of the early placenta “hiding” it from the maternal immune system so it is not rejected as ‘non-self’ due to the presence of the paternal genes.

Site of exchange of many solutes between maternal and foetal systems. Oxygen (aided by foetal haemoglobin), glucose, amino acids are all selective transported. CO2, urea and other waste materials diffuse the other way. Some antibodies pass from the mother during later pregnancy.

The functions of the placenta

Barrier: limits the transfer of blood components from the maternal to foetal system. Cells of the maternal immune system do not cross so reducing risk of immune rejection. (The placenta is not a barrier to heavy metals, nicotine, HIV, heroin or other toxins)

Endocrine function – the placenta takes over the production of oestrogen and progesterone as the corpus luteum degenerates ensuring the endometrium is maintained.

The functions of the placenta

Barrier: limits the transfer of blood components from the maternal to foetal system. Cells of the maternal immune system do not cross so reducing risk of immune rejection. (The placenta is not a barrier to heavy metals, nicotine, HIV, heroin or other toxins)

Endocrine function – the placenta takes over the production of oestrogen and progesterone as the corpus luteum degenerates ensuring the endometrium is maintained.

BIRTH

Read chapter 12.9, pages 260-261 of your text book and make detailed notes on the process of birth!

FINAL POINTS!!!

The pressure of the fetal head against the cervix causes the mothers brain to release the release the hormone oxytocin.This hormone causes the uterine wall muscles to start to contract.Levels of this hormone build up during labour.

FINAL POINTS!!!

Lactation depends on the action of the two hormones: prolactin and oxytocin.

Both of these are produced in the pituitary gland.

Progesterone inhibits the release of prolactin.

FINAL POINTS!!!

Prolactin promotes milk production in the glandular cells of the mammary glands.

Oxytocin stimulates the ejection of milk from the nipples.

Every time a baby suckles prolactin levels increase.

CONGRATULATIONS!

You’ve finished the course!