9.0 Reproduction

:

9.0 REPRODUCTION

AND

DEVELOPMENT

9.1 Asexual reproduction in plants and animals

9.2 Sexual reproduction in flowering plants

9.3 Human reproductive system

9.4 Fertilization and foetal development

9.5 Roles of hormones

9.0 REPRODUCTION AND DEVELOPMENT

9.5 Roles of hormones

a) Explain the role of hormones during pregnancy

i. progesterone

ii. estrogen

iii. human chorionic gonadotrophin (hCG)

b) Explain the role of hormones during parturition /

birth process

i. progesterone

ii. estrogen

iii. oxytocin

iv. prostaglandin

c) Explain the role of hormones during lactation

i. oxytocin

ii. prolactin

Learning outcomes :

(a) Explain the role of hormone during pregnancy

1st trimester

i. Progesterone

- initiates increased mucus in cervix (forming a protective plug)

- stimulates growth of the maternal portion of placenta

- maintains the thickness of endometrium

- prevents ovulation & menstrual cycle

- stimulates breasts enlargement

ii. Estrogen

• important for development of uterus, foetus & mammary glands

PREGNANCY & HORMONES INVOLVED

iii. hCG (human chorionic gonadotropin)

• The chorion secretes hCG

• Function: stimulate the corpus luteum to continue to secrete progesterone and estrogen

• hCG level is so high & some is excreted in urine

Learning outcomes :

(a) Explain the role of hormone during pregnancy

1st trimester

Learning outcomes :

(a) Explain the role of hormone during pregnancy

1st trimester

iv. hCS (human chorionic somatotropin )

• Starting at week 5, the placenta secretes hCS which stimulates:

– secretion of estrogens & progesterone by corpus luteum

– entry of amino acids into cells of embryo (for protein synthesis)

– development of mammary glands

– glucose & lipid metabolisms in the mother

Learning outcomes :

(a) Explain the role of hormone during pregnancy

2nd trimester

Learning outcomes :

(a) Explain the role of hormone during pregnancy

• hCG secrete by the placenta declines

• Corpus luteum degenerates, progesterone decrease

• Placenta takes over from corpus luteum by secreting progesterone & estrogen, (maintain pregnancy)

Learning outcomes :

(a) Explain the role of hormone during pregnancy

3rd trimester

• Level of estrogen & progesterone increase during pregnancy prevent from miscarriage

• And induce the birth

process

PARTURITION & HORMONES INVOLVED

During pregnancy, progesterone & estrogens are

secreted by placenta

i. Progesterone

High level of progesterone prevents contractions of

uterus (prevents birth of immature baby)

ii. Estrogen

- Estrogens reach highest level during last weeks

of pregnancy

- This triggers formation of oxytocin receptors on

uterus

Learning outcomes :

(b) Explain the role of hormone during parturition / birth process

PARTURITION & HORMONES INVOLVED

iii. Oxytocin

- secreted by foetus & mother’s posterior pituitary

- stimulates contractions of uterus

- stimulates placenta to secrete prostaglandins

iv. Prostaglandins

- Enhance contractions of uterus

- The contractions stimulate release of more oxytocin &

prostaglandins by positive feedback

- Contractions become stronger & more frequent

- that push the baby

Learning outcomes :

(b) Explain the role of hormone during parturition / birth process

• Parturition (birth process)

occurs as a result of the strong,

rhythmic contractions (labour)

• Induced and regulated by

estrogen, oxytocin, and

prostaglandins.

• 3 stages of parturition:

i. dilation of cervix

ii. delivery of baby

iii. delivery of placenta

PARTURITION

Learning outcomes :

(b) Explain the role of hormone during parturition / birth process

i. dilation of cervix

- opening up & thinning of

cervix

- ending with complete

dilation

- amnion ruptures releasing

amniotic fluid, which flows

out through the vagina.

- contractions get stronger

PARTURITION

Learning outcomes :

(b) Explain the role of hormone during parturition / birth process

ii. delivery of baby

- The expulsion of the fetus

- continuous strong

contractions force foetus

down and out of the uterus &

vagina

- aided by mother’s pushing

- the umbilical cord is then cut

and clamped

PARTURITION

Learning outcomes :

(b) Explain the role of hormone during parturition / birth process

iii. delivery of placenta

- The expulsion of the

placenta

- continuing contraction

expel the placenta &

associated membranes

(the afterbirth)

PARTURITION

Learning outcomes :

(b) Explain the role of hormone during parturition / birth process

LACTATION & HORMONES INVOLVED

• ‘Milk production that occurs in the mammary glands’

• An aspect of postnatal care

• The breasts contain mammary glands

• Alveoli of mammary glands will produce milk, that is secreted into mammary ducts which open at the nipple

Learning outcomes :

(c) Explain the role of hormone during lactation

LACTATION & HORMONES INVOLVED

• During pregnancy, progesterone stimulates development of mammary alveoli

• Estrogens stimulate development of mammary ducts

• When placenta is discharged after birth, levels of estrogens & progesterone decrease

• This allows mother’s anterior pituitary

to secrete prolactin

[no lactation during pregnancy since

prolactin secretion is inhibited]

Learning outcomes :

(c) Explain the role of hormone during lactation

LACTATION & HORMONES INVOLVED

• Prolactin stimulates mammary

alveoli to produce milk (~ 2

days after birth)

• Mammary secretion for first

few days is the colostrum

(thick, yellowish fluid with high

protein content & rich in

maternal antibodies)

• Oxytocin stimulates

contraction of smooth muscles

surrounding mammary glands,

thus controlling release of milk

Learning outcomes :

(c) Explain the role of hormone during lactation

• Nerve impulse will be sent

to the hypothalamus & sent

impulse to posterior

pituitary to release oxytocin

• Fx (oxytocin): Contraction

of the smooth muscle of

alveoli & force milk through

the duct & out of the nipple

• The anterior pituitary responds by releasing prolactin

• Fx (prolactin): Stimulate the production of milk

After birth, milk production is stimulated

by the sucking infant

Learning outcomes :

(c) Explain the role of hormone during lactation

9.1 Asexual reproduction in plants and animals

9.2 Sexual reproduction in flowering plants

9.3 Human reproductive system

9.4 Fertilization and foetal development

9.5 Roles of hormones

9.0 REPRODUCTION AND DEVELOPMENT

9.5 Roles of hormones

a) Explain the role of hormones during pregnancy

i. progesterone

ii. estrogen

iii. human chorionic gonadotrophin (hCG)

b) Explain the role of hormones during parturition /

birth process

i. progesterone

ii. estrogen

iii. oxytocin

iv. prostaglandin

c) Explain the role of hormones during lactation

i. oxytocin

ii. prolactin

Learning outcomes :

(a) Explain the role of hormone during pregnancy

1st trimester

i. Progesterone

- initiates increased mucus in cervix (forming a protective plug)

- stimulates growth of the maternal portion of placenta

- maintains the thickness of endometrium

- prevents ovulation & menstrual cycle

- stimulates breasts enlargement

ii. Estrogen

• important for development of uterus, foetus & mammary glands

PREGNANCY & HORMONES INVOLVED

iii. hCG (human chorionic gonadotropin)

• The chorion secretes hCG

• Function: stimulate the corpus luteum to continue to secrete progesterone and estrogen

• hCG level is so high & some is excreted in urine

Learning outcomes :

(a) Explain the role of hormone during pregnancy

1st trimester

Learning outcomes :

(a) Explain the role of hormone during pregnancy

1st trimester

iv. hCS (human chorionic somatotropin )

• Starting at week 5, the placenta secretes hCS which stimulates:

– secretion of estrogens & progesterone by corpus luteum

– entry of amino acids into cells of embryo (for protein synthesis)

– development of mammary glands

– glucose & lipid metabolisms in the mother

Learning outcomes :

(a) Explain the role of hormone during pregnancy

2nd trimester

Learning outcomes :

(a) Explain the role of hormone during pregnancy

• hCG secrete by the placenta declines

• Corpus luteum degenerates, progesterone decrease

• Placenta takes over from corpus luteum by secreting progesterone & estrogen, (maintain pregnancy)

Learning outcomes :

(a) Explain the role of hormone during pregnancy

3rd trimester

• Level of estrogen & progesterone increase during pregnancy prevent from miscarriage

• And induce the birth

process

PARTURITION & HORMONES INVOLVED

During pregnancy, progesterone & estrogens are

secreted by placenta

i. Progesterone

High level of progesterone prevents contractions of

uterus (prevents birth of immature baby)

ii. Estrogen

- Estrogens reach highest level during last weeks

of pregnancy

- This triggers formation of oxytocin receptors on

uterus

Learning outcomes :

(b) Explain the role of hormone during parturition / birth process

PARTURITION & HORMONES INVOLVED

iii. Oxytocin

- secreted by foetus & mother’s posterior pituitary

- stimulates contractions of uterus

- stimulates placenta to secrete prostaglandins

iv. Prostaglandins

- Enhance contractions of uterus

- The contractions stimulate release of more oxytocin &

prostaglandins by positive feedback

- Contractions become stronger & more frequent

- that push the baby

Learning outcomes :

(b) Explain the role of hormone during parturition / birth process

• Parturition (birth process)

occurs as a result of the strong,

rhythmic contractions (labour)

• Induced and regulated by

estrogen, oxytocin, and

prostaglandins.

• 3 stages of parturition:

i. dilation of cervix

ii. delivery of baby

iii. delivery of placenta

PARTURITION

Learning outcomes :

(b) Explain the role of hormone during parturition / birth process

i. dilation of cervix

- opening up & thinning of

cervix

- ending with complete

dilation

- amnion ruptures releasing

amniotic fluid, which flows

out through the vagina.

- contractions get stronger

PARTURITION

Learning outcomes :

(b) Explain the role of hormone during parturition / birth process

ii. delivery of baby

- The expulsion of the fetus

- continuous strong

contractions force foetus

down and out of the uterus &

vagina

- aided by mother’s pushing

- the umbilical cord is then cut

and clamped

PARTURITION

Learning outcomes :

(b) Explain the role of hormone during parturition / birth process

iii. delivery of placenta

- The expulsion of the

placenta

- continuing contraction

expel the placenta &

associated membranes

(the afterbirth)

PARTURITION

Learning outcomes :

(b) Explain the role of hormone during parturition / birth process

LACTATION & HORMONES INVOLVED

• ‘Milk production that occurs in the mammary glands’

• An aspect of postnatal care

• The breasts contain mammary glands

• Alveoli of mammary glands will produce milk, that is secreted into mammary ducts which open at the nipple

Learning outcomes :

(c) Explain the role of hormone during lactation

LACTATION & HORMONES INVOLVED

• During pregnancy, progesterone stimulates development of mammary alveoli

• Estrogens stimulate development of mammary ducts

• When placenta is discharged after birth, levels of estrogens & progesterone decrease

• This allows mother’s anterior pituitary

to secrete prolactin

[no lactation during pregnancy since

prolactin secretion is inhibited]

Learning outcomes :

(c) Explain the role of hormone during lactation

LACTATION & HORMONES INVOLVED

• Prolactin stimulates mammary

alveoli to produce milk (~ 2

days after birth)

• Mammary secretion for first

few days is the colostrum

(thick, yellowish fluid with high

protein content & rich in

maternal antibodies)

• Oxytocin stimulates

contraction of smooth muscles

surrounding mammary glands,

thus controlling release of milk

Learning outcomes :

(c) Explain the role of hormone during lactation

• Nerve impulse will be sent

to the hypothalamus & sent

impulse to posterior

pituitary to release oxytocin

• Fx (oxytocin): Contraction

of the smooth muscle of

alveoli & force milk through

the duct & out of the nipple

• The anterior pituitary responds by releasing prolactin

• Fx (prolactin): Stimulate the production of milk

After birth, milk production is stimulated

by the sucking infant

Learning outcomes :

(c) Explain the role of hormone during lactation