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PREGNANCY

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Title: PREGNANCY


1
PREGNANCY HUMAN DEVELOPMENT
  • Mutiara Budi Azhar
  • Faculty of Medicine Sriwijaya University

2
Embryology
  • Embryology is a science that studies the normal
    development as well as birth defects of a human
    being in the maternal uterus.

3
Historical gleanings
Hippocrates, Father of Medicine, first recorded
embryological studies bird embryo can be likened
to that of man.
Aristotle studied chick and other embryos, which
resulted from union of semen with menstrual
blood.
4
From Egg to Fetus
  • Pregnancy events that occur from fertilization
    (conception, conceptio) until the infant is born.
  • Conceptus the developing offspring.
  • Gestation period from the last menstrual period
    until birth.
  • Preembryo conceptus from fertilization until it
    is two weeks old.
  • Embryo conceptus during the third through the
    eighth week.
  • Fetus conceptus from the ninth week through
    birth

5
Relative Size of Human Conceptus
6
Gametes and Gametogenesis
7
Gamete
  • A gamete (from Ancient Greek ?aµet?? translated
    gamete wife, gametes husband) is a cell that
    fuses with another gamete during fertilization
    (conception) in organism that reproduce sexually.
  • In species which produce two morphologically
    distinct types of gametes, and in which each
    individual produces only one type, a female is
    any individual which produces the larger type of
    gametecalled an ovum (or egg)and a male
    produces the smaller tadpole-like typecalled a
    sperm.

8
Gamete. Cont
  • Anisogamy or heterogamy the condition wherein
    females and males produce gametes of different
    sizes in humans, the human ovum is approximately
    20 times larger than the human sperm cell.
  • Isogamy is the state of gametes from both sexes
    being the same size.

9
Gamete. Cont
  • The name gamete was introduced by the Austrian
    biologist biologist Gregor Mendel
  • Gametes carry half the genetic information of an
    individual, one chromosome of each type.
  • In human an ovum can only carry X chromosom (of
    the X and Y chromosom)
  • As a sperm can carry either an X or a Y, males
    have the control of the gender of any resulting
    zygote as the genotype of the sex-determining
    chromosomes of a male must be XY and a female XX.

10
The Human Life Cycle
  • Haploid pertaining to a single set of unpaired
    chromosomes or an organism or cell that comprises
    of a single set of chromosomes
  • Diploid Contain two homologous sets of
    chromosomes

11
Gametogenesis
12
Spermatogenesis
13
Ooogenesis
14
Spermatogenesis
15
Oogenesis
16
Sperm Meiosis
17
Spermatozoa
Spermatozoa
18
Oocyte
19
hypothalamus
GnRH
anterioir pituitary
FSH
LH
Mid-cycle peak of LH (triggers ovulation)
hypothalamus
Blood levels of FSH (purple) and LH (lavender)
anterior lobe of pituitary gland
FSH
LH
LH
growth of follicle
ovulation
corpus luteum
estrogens
progesterone, estrogen
Blood levels of estrogens (light blue) and
progesterone (dark blue)
estrogens
progesterone, estrogen
endometrium of uterus
menstruation
Days of one menstrual cycle (using 28 days as the
average duration)
FOLLICULAR PHASE OF MENSTRUAL CYCLE
LUTEAL PHASE OF MENSTRUAL CYCLE
20
Fertilization
21
Accomplishing Fertilization
  • The oocyte is viable for 12 to 24 hours
  • Sperm is viable 24 to 72 hours
  • For fertilization to occur, coitus must occur no
    more than
  • Three days before ovulation
  • 24 hours after ovulation
  • Fertilization when a sperm fuses with an egg to
    form a zygote

22
Sperm Transport and Capacitation
  • Fates of ejaculated sperm
  • Leak out of the vagina immediately after
    deposition
  • Destroyed by the acidic vaginal environment
  • Fail to make it through the cervix
  • Dispersed in the uterine cavity or destroyed by
    phagocytic leukocytes
  • Reach the uterine tubes
  • Sperm must undergo capacitation before they can
    penetrate the oocyte

23
Acrosomal Reaction and Sperm Penetration
  • An ovulated oocyte is encapsulated by
  • The corona radiata and zona pellucida
  • Extracellular matrix
  • Sperm binds to the zona pellucida and undergoes
    the acrosomal reaction
  • Enzymes are released near the oocyte
  • Hundreds of acrosomes release their enzymes to
    digest the zona pellucida

24
Acrosomal Reaction and Sperm Penetration. Cont.
  • Once a sperm makes contact with the oocytes
    membrane
  • Beta protein finds and binds to receptors on the
    oocyte membrane
  • Alpha protein causes it to insert into the
    membrane

25
Acrosomal Reaction and Sperm Penetration. Cont.
26
Blocks to Polyspermy
  • Only one sperm is allowed to penetrate the oocyte
  • Two mechanisms ensure monospermy
  • Fast block to polyspermy membrane
    depolarization prevents sperm from fusing with
    the oocyte membrane
  • Slow block to polyspermy zonal inhibiting
    proteins (ZIPs)
  • Destroy sperm receptors
  • Cause sperm already bound to receptors to detach

27
Completion of Meiosis II and Fertilization
  • Upon entry of sperm, the secondary oocyte
  • Completes meiosis II
  • Casts out the second polar body
  • The ovum nucleus swells, and the two nuclei
    approach each other
  • When fully swollen, the two nuclei are called
    pronuclei
  • Fertilization when the pronuclei come together

28
Events Immediately Following Sperm Penetration
29
Preembryonic Development
30
Preembryonic Development
  • The first cleavage produces two daughter cells
    called blastomeres
  • Morula the 16 or more cell stage (72 hours old)
  • By the fourth or fifth day the preembryo consists
    of 100 or so cells (blastocyst)

31
Preembryonic Development. Cont.
  • Blastocyst a fluid-filled hollow sphere
    composed of
  • A single layer of trophoblasts
  • An inner cell mass
  • Trophoblasts take part in placenta formation
  • The inner cell mass becomes the embryonic disc

32
The Period of the Zygote
  • Zygote ? blastocyst
  • Cell differentiation
  • of blastocysts that fail to implant?

33
The Period of the Zygote. Cont.
  • Outer layer of blastocyst develops into
  • Amnion
  • Chorion
  • Placenta
  • Umbilical cord
  • note that these structures actually develop
    during the period of the embryo

34
Implantation
35
Implantation
  • Begins six to seven days after ovulation when the
    trophoblasts adhere to a properly prepared
    endometrium
  • The trophoblasts then proliferate and form two
    distinct layers
  • Cytotrophoblast cells of the inner layer that
    retain their cell boundaries
  • Syncytiotrophoblast cells in the outer layer
    that lose their plasma membranes and invade the
    endometrium

36
Implantation. Cont.
  • The implanted blastocyst is covered over by
    endometrial cells
  • Implantation is completed by the fourteenth day
    after ovulation

37
Implantation of the Blastocyst
38
Implantation of the Blastocyst. Cont.
39
Implantation of the Blastocyst
40
Implantation of the Blastocyst. Cont.
41
Implantation of the Blastocyst. Cont.
42
Implantation of the Blastocyst. Cont.
  • Viability of the corpus luteum is maintained by
    human chorionic gonadotropin (hCG) secreted by
    the trophoblasts
  • hCG prompts the corpus luteum to continue to
    secrete progesterone and estrogen
  • Chorion developed from trophoblasts after
    implantation, continues this hormonal stimulus
  • Between the second and third month, the placenta
  • Assumes the role of progesterone and estrogen
    production
  • Is providing nutrients and removing wastes

43
Hormonal Changes During Pregnancy
44
Placentation
45
Placental Development
46
Placentation
  • Formation of the placenta from
  • Embryonic trophoblastic tissues
  • Maternal endometrial tissues

47
Placentation. Cont.
  • The chorion develops fingerlike villi, which
  • Become vascularized
  • Extend to the embryo as umbilical arteries and
    veins
  • Lie immersed in maternal blood
  • Decidua basalis part of the endometrium that
    lies between the chorionic villi and the stratum
    basalis

48
Placentation. Cont.
  • Decidua capsularis part of the endometrium
    surrounding the uterine cavity face of the
    implanted embryo.
  • The placenta is fully formed and functional by
    the end of the third month.
  • Embryonic placental barriers include
  • The chorionic villi
  • The endothelium of embryonic capillaries

49
Placenta
  • Permits the exchange of materials between the
    bloodstream of the fetus and that of the mother
  • Produces progesteron gradually take over the
    role of corpus luteum.
  • The placenta also secretes other hormones human
    placental lactogen, human chorionic thyrotropin,
    and relaxin.

50
Placentation. Cont.
Figure 28.7a-c
51
Placentation. Cont.
Figure 28.7d
52
Placentation. Cont.
Figure 28.7f
53
Germ Layers
54
Gastrulation
  • During the 3rd week, the two-layered embryonic
    disc becomes a three-layered embryo
  • The primary germ layers are ectoderm, mesoderm,
    and endoderm
  • Primitive streak raised dorsal groove that
    establishes the longitudinal axis of the embryo

55
Germ Layers
  • The blastocyst develops into a gastrula with
    three primary germ layers ectoderm, endoderm,
    and mesoderm.
  • Before becoming three-layered, the inner cell
    mass subdivides into the upper epiblast and lower
    hypoblast these layers form two of the four
    embryonic membranes

56
Gastrulation. Cont.
  • As cells begin to migrate
  • The first cells that enter the groove form the
    endoderm
  • The cells that follow push laterally between the
    cells forming the mesoderm
  • The cells that remain on the embryos dorsal
    surface form the ectoderm
  • Notochord rod of mesodermal cells that serves
    as axial support

57
Three Germ Layers
  • Endoderm formed from migrating cells that
    replace the hypoblast
  • Mesoderm formed between epiblast and endoderm
  • Ectoderm formed from epiblast cells that stay
    on dorsal surface
  • All layers derive from epiblast cells!

58
Primary Germ Layers
  • Serve as primitive tissues from which all body
    organs will derive.
  • Ectoderm nervous system, skin, hair, sensory
    receptors.
  • Endoderm digestive system, lungs, urinary
    tract, other internal organs.
  • Mesoderm muscles, bones, circulatory system,
    reproductive system, excretory system.
  • Endoderm and ectoderm are securely joined and are
    considered epithelia.

59
Derivatives of Germ Layers
60
Embryonic Membranes
  • Amnion epiblast cells form a transparent
    membrane filled with amniotic fluid
  • Provides a buoyant environment that protects the
    embryo
  • Helps maintain a constant homeostatic temperature
  • Amniotic fluid comes from maternal blood, and
    later, fetal urine

61
Embryonic Membranes. Cont.
  • Yolk sac hypoblast cells that form a sac on the
    ventral surface of the embryo
  • Forms part of the digestive tube
  • Produces earliest blood cells and vessels
  • Is the source of primordial germ cells

62
Embryonic Membranes. Cont.
  • Allantois a small outpocketing at the caudal
    end of the yolk sac
  • Structural base for the umbilical cord
  • Becomes part of the urinary bladder
  • Chorion helps form the placenta
  • Encloses the embryonic body and all other
    membranes

63
Embryonic Period
64
Embryonic Period
65
Embryo at 4 Weeks
66
Face Development from 5½ to 8 Weeks
67
The Period of the Embryo. Cont.
  • By 4th week, heart has formed and begun to beat
  • Becomes more human in appearance during 2nd month
  • Sexual differentiation during 7th 8th weeks

68
The Period of the Fetus
69
The Period of the Fetus
  • Final 7 months of pregnancy
  • Fetus
  • Digestive and excretory systems functional
  • Sex detected by ultrasound by end of 3rd month
  • Kicks and movements strong enough to be felt
  • Organ systems mature rapidly during final 3 months

70
The Period of the Fetus. Cont.
71
Fetus at 9 Weeks
72
Fetus at 11 Weeks
73
Fetus at 16 Weeks
74
Fetus at 18 Weeks
75
Fetus at 20 Weeks
76
Fetus at 28 Weeks
77
Fetal development
78
Twins
79
The Period of the Fetus. Cont.
  • Viable between 22-28 weeks
  • Receives antibodies
  • Assume upside-down position in final weeks
  • Weight of head
  • Shape of uterus

80
A Brief View of Prenatal Development
81
A Brief View of Prenatal Development. Cont.
82
Developmental Events of the Fetal Period
83
Developmental Events of the Fetal Period
Table 3.1 (2 of 3)
84
Developmental Events of the Fetal Period
Table 3.1 (3 of 3)
85
Trends in Development
  • Cephalocaudal Trend
  • Proximodistal Trend

86
Teratogens
87
Susceptible period
88
Teratogens
  • Root word means formation of monsters
  • Harm isnt always simple or straightforward
  • Amount and length of exposure
  • Genetic makeup of mother/baby
  • Presence of several negative factors

89
Teratogens. Cont.
  • Same defect ? different teratogens
  • One teratogen ? different defects
  • Some effects seen later
  • Age of baby
  • Sensitive period

90
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91
Teratogens. Cont.
  • Paternal influences often overlooked
  • Direct and indirect effects
  • Second hand smoke
  • Chemicals
  • Cocaine can hitchhike
  • Smoking, alcohol, drug use ? sperm
  • Diets low in vitamin C

92
Other Factors Teratogens. Cont.
  • Exercise
  • Nutrition
  • Emotional stress
  • Rh blood incompatibility
  • Maternal/Paternal age
  • Older ? less fertile, more risk of disorders
  • Younger ? increased risk of prematurity, infant
    death

93
Other Factors Teratogens. Cont.
  • Infectious diseases
  • Prenatal care
  • Previous births

94
Congenital malformations (Birth defects)
95
Chemical nitrite, benzol lead, arsenic,
cadmium, mercury, etc. Drugs thalidomide
(amelia and meromelia),
96
Drugs aminopterin (anencephaly, hydrocephalus,
cleft lip) streptomycin
(deafness). Hormones estrogens, progestins
Social drugs cigarettes (small babies) alcohol
(fetal alcohol syndrome).
97
Perinatal Environment
  • Environment surrounding birth
  • Stages of childbirth
  • Contractions
  • Delivery
  • Afterbirth
  • Newborn appearance

98
Birth
  • Labor
  • Oxytocin
  • Uterine contractions

99
Perinatal Environment
  • Assessing the Newborn
  • Apgar scale
  • 1 minute and 5 minutes after birth

100
The Apgar Test
101
Perinatal Environment
  • Assessing the Newborn
  • Neonatal Behavioral Assessment Scale (NBAS)
  • Several days after birth
  • 20 inborn reflexes
  • Reactions to comforting and social stimuli
  • Unresponsiveness may indicate neurological
    problems
  • Can be a parent teaching tool

102
Perinatal Environment
  • Complications
  • Anoxia
  • Severe ? cerebral palsy, mental retardation
  • Mild ? irritability, motor/cognitive delays
  • Chances have been reduced with fetal monitoring
  • Respiratory distress syndrome
  • Complicated delivery
  • Forceps
  • Cesarean
  • Medications

103
Preterm and Small-for-Date
  • Preterm born more than 3 weeks early, but
    appropriate weight for time in womb
  • Small-for-Date underweight due to slow fetal
    growth
  • Greater risk than preterm
  • Causes include smoking, drug use, stress, lack of
    prenatal care, multiple births, social support
  • Postterm born after 42 weeks

104
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