roles of hormones

a) a) Explain the role of hormones duringExplain the role of hormones during pregnancy b) b) Explain the role of hormones duringExplain the role of hormones during parturition / birth

process c) Explain the role of hormones during lactation

Roles of HormonesRoles of Hormones

CHAPTER : REPRODUCTION AND DEVELOPMENT

THE ROLE OF HORMONES DURING PREGNANCYTHE ROLE OF HORMONES DURING PREGNANCY

Hormonal changes during Hormonal changes during 11stst trimester trimester• The The chorion secretes hCGchorion secretes hCG (human chorionic gonadotropin) which maintains (human chorionic gonadotropin) which maintains

the corpus luteum, ensuring secretion of progesterone & estrogens-absence the corpus luteum, ensuring secretion of progesterone & estrogens-absence of this hormonal override during pregnancy-resulting in menstruation & loss of of this hormonal override during pregnancy-resulting in menstruation & loss of the embryothe embryo

• HCG level is so high & some is excreted in urine-its presence is the basis of a HCG level is so high & some is excreted in urine-its presence is the basis of a

common early pregnancy testcommon early pregnancy test

• ProgesteroneProgesterone - initiates increased mucus in the cervix - initiates increased mucus in the cervix ( forming a protective plug ); ( forming a protective plug );- stimulates growth of the maternal portion of - stimulates growth of the maternal portion of

placenta; placenta; - maintains the endometrium; - maintains the endometrium; - prevents ovulation & menstrual cycling;- prevents ovulation & menstrual cycling;- stimulates breasts enlargement- stimulates breasts enlargement


……THE ROLE OF HORMONES DURING PREGNANCYTHE ROLE OF HORMONES DURING PREGNANCY

• EstrogensEstrogens are important for development of uterus, foetus & mammary are important for development of uterus, foetus & mammary glandsglands

• Starting at week 5, the chorion secretes Starting at week 5, the chorion secretes hCGhCG which stimulates: which stimulates:- secretion of estrogens & progesterone by corpus luteum;- secretion of estrogens & progesterone by corpus luteum;- entry of amino acids into cells of embryo ( for protein synthesis - entry of amino acids into cells of embryo ( for protein synthesis

););- development of mammary glands;- development of mammary glands;- glucose & lipid metabolisms in the mother- glucose & lipid metabolisms in the mother


……THE ROLE OF HORMONES DURING PREGNANCYTHE ROLE OF HORMONES DURING PREGNANCY

Hormonal changes during Hormonal changes during 22ndnd trimester trimester • hCG level declineshCG level declines & corpus luteum deteriorates & corpus luteum deteriorates• PlacentaPlacenta secretes own progesterone & estrogens ( maintaining secretes own progesterone & estrogens ( maintaining

pregnancy )pregnancy )

Hormonal changes during Hormonal changes during 33rdrd trimester trimester • Estrogens reach highest levelEstrogens reach highest level during last weeks of pregnancy during last weeks of pregnancy• This will induce the birth processThis will induce the birth process


THE ROLE OF HORMONES DURING PARTURITION / BIRTH PROCESSTHE ROLE OF HORMONES DURING PARTURITION / BIRTH PROCESS

• During pregnancy, progesterone & estrogens are secretedDuring pregnancy, progesterone & estrogens are secreted

• High level of High level of progesterone prevents contractions of uterus progesterone prevents contractions of uterus ( prevents birth of immature baby )( prevents birth of immature baby )

• But But estrogensestrogens reach highest level during last weeks of pregnancy reach highest level during last weeks of pregnancy

• This triggers This triggers formation of oxytocin receptorsformation of oxytocin receptors on uterus on uterus

• Oxytocin Oxytocin - secreted by foetus & mother’s posterior pituitary- secreted by foetus & mother’s posterior pituitary

- stimulates - stimulates contractionscontractions of uterus of uterus

- stimulates - stimulates placenta to secrete placenta to secrete prostaglandinsprostaglandins

• ProstaglandinsProstaglandins enhance contractions enhance contractions of uterus of uterus • The contractions stimulate The contractions stimulate release of more release of more oxytocinoxytocin & & prostaglandinsprostaglandins

( ( +ve feedback+ve feedback ) )• Contractions become stronger & more frequent Contractions become stronger & more frequent


……THE ROLE OF HORMONES DURING PARTURITION / BIRTH PROCESSTHE ROLE OF HORMONES DURING PARTURITION / BIRTH PROCESS

Feedback mechanismFeedback mechanism


PARTURITION / BIRTH PROCESSPARTURITION / BIRTH PROCESS

• Parturition ( birth process ) occurs Parturition ( birth process ) occurs as a result of the strong, rhythmic as a result of the strong, rhythmic contractions ( labour )contractions ( labour )

• 3 stages3 stages of parturition: of parturition:

i. i. dilation of cervixdilation of cervix

- opening up & thinning of - opening up & thinning of cervix cervix

- ending with complete - ending with complete dilation dilation

- amnion ruptures- amnion ruptures

- contractions get stronger- contractions get stronger


……PARTURITION / BIRTH PROCESSPARTURITION / BIRTH PROCESS

ii. ii. delivery of babydelivery of baby

- continuous strong - continuous strong contractions force foetus contractions force foetus down and out of the down and out of the

uterus uterus & vagina& vagina

- aided by mother’s - aided by mother’s pushingpushing

- the umbilical cord is - the umbilical cord is then then cut and cut and clampedclamped


……PARTURITION / BIRTH PROCESSPARTURITION / BIRTH PROCESS

iii. iii. delivery of placentadelivery of placenta

- continuing contraction expel - continuing contraction expel the the placenta & associated placenta & associated membranes membranes ( the afterbirth )( the afterbirth )


THE ROLE OF HORMONES DURING LACTATIONTHE ROLE OF HORMONES DURING LACTATION

• ‘‘Milk production Milk production that occurs in the mammary glands’that occurs in the mammary glands’

• An aspect of An aspect of postnatalpostnatal care unique to mammals care unique to mammals

• The breasts contain The breasts contain mammary glandsmammary glands

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

• During pregnancy, During pregnancy, progesteroneprogesterone stimulates development of stimulates development of mammary alveolimammary alveoliEstrogensEstrogens stimulate development of mammary ducts stimulate development of mammary ducts


……THE ROLE OF HORMONES DURING LACTATIONTHE ROLE OF HORMONES DURING LACTATION



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

• This allows mother’s anterior pituitary to secrete This allows mother’s anterior pituitary to secrete prolactinprolactin

{ no lactation during pregnancy since prolactin secretion is inhibited }{ no lactation during pregnancy since prolactin secretion is inhibited }

• ProlactinProlactin stimulates mammary alveoli to stimulates mammary alveoli to produce milkproduce milk ( ~ 2 days after ( ~ 2 days after birth )birth )

• Mammary secretion for first few days is the Mammary secretion for first few days is the colostrumcolostrum ( thick, ( thick, yellowish fluid with high protein content & rich in maternal antibodies-yellowish fluid with high protein content & rich in maternal antibodies-IgG)IgG)



• Suckling of baby stimulatesSuckling of baby stimulates the nerve endings in the nipples to send the nerve endings in the nipples to send signals which trigger anterior pituitary to signals which trigger anterior pituitary to release more prolactinrelease more prolactin

• The signals also trigger posterior pituitary to The signals also trigger posterior pituitary to release oxytocinrelease oxytocin

• OxytocinOxytocin stimulates contraction of smooth muscles surrounding stimulates contraction of smooth muscles surrounding mammary glands, thus mammary glands, thus controlling release of milkcontrolling release of milk

roles of hormones

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