Human Reproduction

Spermatogenesis

Diploid spermatogonia cells lining the seminiferous tubules inside the testes undergo meiosis under the influence of the hormone testosterone and FSH to form haploid spermatids. Each spermatid undergoes differentiation and matures to form haploid spermatozoa.

Oogenesis

Diploid oogonia lining the wall of the ovary divide by mitosis to form numerous diploid primary follicles.
At the onset of puberty FSH stimulates, one of the diploid cells inside the primary follicle to enlarge and undergo meiosis
resulting in the formation of: four haploid daughter cells.
Three daughter disintegrate.
The remaining haploid daughter cell develops into a haploid ovum.
The Primary follicle grows and develops into a mature Graafian follicle containing the fully-developed haploid ovum.

FHS in females

Stimulates the development of the primary follicle into a secondary follicle containing a mature ovum .

FHS in males

Stimulates sperm formation in the testes.

LH

Stimulates the release of the ovum.
Stimulates the formation of the Corpus luteum.

Prolactin

Stimulates milk production in the mammary glands.

Oestrogen

Stimulates the thickening of the endometrium

inhibits release of FSH

Progesterone

Stimulates thickening of the endometrium for implantation of embryo

Stimulates the formation of the corpus luteum

Inhibits the release of FSH

Stops the uterine from contracting during pregnancy

Stops the release of prolactin during pregnancy.

Testosterone

Stimulates maturation of sex organs and sex drive. Promotes muscle growth and increased density of bones.

Hormones

Chemical messengers produced by endocrine glands and have their effect on target cells/organs.
Act slowly with long lasting effects.

Days 1 - 5 of menstrual cycle

Menstruation is still occurring, endometrium is being shed.
FSH released by pituitary.

Days 6 - 13 of menstrual cycle

Oestrogen released by developing Graafian follicle, promotes the growth of new endometrium layer.
High conc. oestrogen stimulates release of LH.

Day 14 of menstrual cycle

Ovulation triggered by LH.
Oestrogen levels decrease.
LH stimulates formation of corpus luteum.

Days 15 - 26 of menstrual cycle

Corpus luteum produces progesterone and some oestrogen.

Days 27 - 28 of menstrual cycle (no fertilization)

Corpus luteum breaks down.
Mucous-membranes of endometrium disintegrate.
Menstruation begins.

Days 27 - 28 of menstrual cycle (fertilization)

Fertilized egg causes corpus luteum to remain active.
Once placenta forms it takes over progesterone and oestrogen production.

Placental previa

Placenta attached close to cervix.
Dangerous and leads to bleeding during pregnancy.
C-section compulsory.

Function of amniotic fluid

Supports developing foetus allows it to move freely and prevent malformation due to gravity.
Protects foetus from mechanical injury.
Holds urine of the foetus.
Protects foetus against drastic changes in temperature

Chorionic villi

Embeds in the placenta and nourishes the developing foetus.

Umbilical cord

Provides foetus with oxygen and necessary nutrients.
Allows carbon dioxide and waste products to travel to the placenta and diffuse out for excretion.

Functions of the placenta

Gaseous exchange organ.
Organ through which the foetus can be nourished.
Organ of excretion.
Prevents many pathogenic microorganisms and some drugs from entering the foetus.

Oxytocin

Released in large amounts and acts on the muscular wall as of the uterus, causing strong waves of muscular contraction and relaxation.