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  • 11

    Lecture 15: Pregnancy Lecture 15: Pregnancy

    •• Gestational DevelopmentGestational Development

    •• Early development and the Early development and the placentaplacenta

    •• Maternal/fetal conflictMaternal/fetal conflict

    •• The Physiology of The Physiology of PregnancyPregnancy

    •• Pica eatingPica eating

    •• Pregnancy SicknessPregnancy Sickness

    The Behavioral Biology of Women-2006

  • 22

    Exercise during Pregnancy Exercise during Pregnancy

    and Miscarriageand Miscarriage

    0

    4

    8

    12

    16

    20

    F re q u en cy o f M is ca rr ia g e

    Exercise Non-Exercise

    (Clapp, 2002)

    Stages of DevelopmentStages of Development

    •• Conceptus Conceptus (morula & blastocyte)(morula & blastocyte)

    •• EmbryoEmbryo •• FetusFetus

    •• EmbryogenesisEmbryogenesis

    •• Embryonic PhaseEmbryonic Phase •• Fetal PhaseFetal Phase

    •• Weeks 0Weeks 0--22

    •• Weeks 3Weeks 3--88 •• Weeks 9Weeks 9--3838

    EmbryogenesisEmbryogenesis

    •• Conceptus Conceptus (morulla & blastocyte) (morulla & blastocyte)

    •• First 14First 14--16 days = 16 days = formation of an embryoformation of an embryo

    EmbryogenesisEmbryogenesis

    •• Conceptus Conceptus (morulla & blastocyte) (morulla & blastocyte)

    •• First 14First 14--16 days = 16 days = formation of an embryoformation of an embryo

    •• Histiotropic nutritionHistiotropic nutrition -- relies on uterine secretions relies on uterine secretions for oxygen and metabolic for oxygen and metabolic substratessubstrates

    EmbryogenesisEmbryogenesis

    •• ConceptusConceptus •• First 14First 14--16 days = 16 days = formation of an embryoformation of an embryo

    •• Histiotropic nutrition Histiotropic nutrition -- relies on uterine secretions relies on uterine secretions for oxygen and metabolic for oxygen and metabolic substratessubstrates

    •• Differentiation into Differentiation into embryonic (inner cell embryonic (inner cell mass) and extramass) and extra--embryonic embryonic tissue (trophoblast)tissue (trophoblast)

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    Implantation: Actions of BlastocyteImplantation: Actions of Blastocyte

    •• (1) Blastocyte establishes physical and (1) Blastocyte establishes physical and nutritional contact with maternal nutritional contact with maternal

    endometriumendometrium

    Blastocyte Embedded in Uterine Lining

    Haemotrophic Nutrition =

    Nutrition from the maternal

    blood supply

    Establishment of the PlacentaEstablishment of the Placenta

    •• Digestion of Digestion of maternal tissue to maternal tissue to

    release metabolic release metabolic

    substratessubstrates

    •• Primary Primary Decidualization Decidualization

    ReactionReaction

    Species Differences in PlacentasSpecies Differences in Placentas

    Human (discoid) Mouse, rabbit, bat Cat, seal, elephant ,bear (zonary)

    Cow, sheep, giraffe (cotyledonary) Horse, whale, kangaroo (diffuse)

    •• (2) Trophoblast (2) Trophoblast starts to produce starts to produce

    HCG (Human HCG (Human

    Chorionic Chorionic

    Gonadotrophin) Gonadotrophin)

    to keep corpus to keep corpus

    luteum aliveluteum alive

    Implantation: Actions of Implantation: Actions of

    BlastocyteBlastocyte

    Expression of HCG during human pregnancyExpression of HCG during human pregnancy

  • 44

    Embryonic PhaseEmbryonic Phase

    (Weeks 3(Weeks 3--8)8)

    •• Formation of basic body planFormation of basic body plan •• Development of all major organ systemsDevelopment of all major organ systems

    5 Weeks

    6 Weeks

    7 Weeks

    Fetal PhaseFetal Phase

    (Weeks 9(Weeks 9--38)38)

    •• Growth and further development of body Growth and further development of body tissues and organs.tissues and organs.

  • 55

    9 Weeks

    13 Weeks

    21 Weeks

    Russell at 3 monthsRussell at 3 months

    THE PHYSIOLOGY OF THE PHYSIOLOGY OF

    PREGNANCYPREGNANCY

    Corpus Luteum

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    Corpus LuteumCorpus Luteum

    •• Produces increasing amounts of Produces increasing amounts of progesteroneprogesterone

    •• Synthesizes estrogenSynthesizes estrogen

    •• Important for production until 6Important for production until 6-- 7 weeks of pregnancy7 weeks of pregnancy

    •• If embryo canIf embryo can’’t maintain hormone t maintain hormone production often results in miscarriage at production often results in miscarriage at

    this time.this time.

    •• Helps maintain early pregnancyHelps maintain early pregnancy

    The Role of the FetusThe Role of the Fetus

    The Placenta The Placenta -- ““baby sidebaby side”” The Placenta The Placenta -- ““mother sidemother side””

    Human Haemomonochorial Human Haemomonochorial

    PlacentaPlacenta

    •• ExtraExtra--embryonic embryonic tissue, containing fetal tissue, containing fetal

    blood vessels, blood vessels,

    penetrates deep into penetrates deep into

    maternal tissuematernal tissue

  • 77

    Human Haemomonochorial Human Haemomonochorial

    Placenta Placenta -- Terminal villusTerminal villus

    •• Tips of capillaries Tips of capillaries form tortuous loops form tortuous loops ----

    slowing blood flow slowing blood flow

    and allowing for and allowing for

    exchange of exchange of

    metabolites with metabolites with

    maternal blood.maternal blood.

    Human Haemomonochorial Human Haemomonochorial

    PlacentaPlacenta

    •• Maternal spiral artery Maternal spiral artery ejects blood into ejects blood into

    ‘‘maternal blood maternal blood

    spacespace’’

    Pregnancy ConflictsPregnancy Conflicts HamiltonHamilton’’s Rules Rule

    You are related to yourself by 100%, You are related to yourself by 100%,

    to your children your siblings and to your children your siblings and

    your parents by 50%, etc.your parents by 50%, etc.

  • 88

    Pregnancy Pregnancy ““ConflictsConflicts””

    •• Paternal genes will be Paternal genes will be selected to increase the selected to increase the

    transfer of nutrients to transfer of nutrients to

    the fetusthe fetus

    •• Maternal genes will be Maternal genes will be selected to limit selected to limit

    transfers in excess of transfers in excess of

    some maternal some maternal

    optimumoptimum

    Haig, 1993

    Monogenetic Mouse Embryos

    Control Gynogenetic Androgenetic

    Embryo

    Yolk Sac

    Trophoblast

    Supporting EvidenceSupporting Evidence •• Trophoblast invades maternal Trophoblast invades maternal endometrium and remodels the endometrium and remodels the

    spiral arteries so they are spiral arteries so they are

    unable to constrictunable to constrict

    Supporting EvidenceSupporting Evidence •• Trophoblast invades maternal Trophoblast invades maternal

    endometrium and remodels the endometrium and remodels the

    spiral arteries so they are spiral arteries so they are

    unable to constrictunable to constrict

    –– Fetus gains access to motherFetus gains access to mother’’s s

    arterial blood & mother canarterial blood & mother can’’t t

    change nutrient content of bloodchange nutrient content of blood

    Supporting EvidenceSupporting Evidence •• Trophoblast invades maternal Trophoblast invades maternal

    endometrium and remodels the endometrium and remodels the

    spiral arteries so they are spiral arteries so they are

    unable to constrictunable to constrict

    –– Fetus gains access to motherFetus gains access to mother’’s s

    arterial blood & mother canarterial blood & mother can’’t t

    change nutrient content of bloodchange nutrient content of blood

    –– Volume of blood reaching Volume of blood reaching

    placenta not under maternal placenta not under maternal

    controlcontrol

    Supporting EvidenceSupporting Evidence •• Trophoblast invades maternal Trophoblast invades maternal

    endometrium and remodels the endometrium and remodels the

    spiral arteries so they are spiral arteries so they are

    unable to constrictunable to constrict

    –– Fetus gains access to motherFetus gains access to mother’’s s

    arterial blood & mother canarterial blood & mother can’’t t

    change nutrient content of bloodchange nutrient content of blood

    –– Volume of blood reaching Volume of blood reaching

    placenta not under maternal placenta not under maternal

    controlcontrol

    –– Placenta is able to release Placenta is able to release

    hormones directly into maternal hormones directly into maternal

    circulationcirculation

  • 99

    Supporting EvidenceSupporting Evidence •• Trophoblast invades maternal Trophoblast invades maternal

    endometrium and remodels the endometrium and remodels the

    spiral arteries so they are spiral arteries so they are

    unable to constrictun