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Presentation on theme: "PREGNANCY & HUMAN DEVELOPMENT"— Presentation transcript:


2 Fertilization oocyte viable 12 - 24 after ovulation
sperm retain fertilizing power within female reproductive tract hours some “super sperm” viable for 72 hours about 5 days a month that pregnancy can occur

3 Sperm Transport acidity within the vagina is hostile to sperm & some leak from vagina or die almost immediately many cannot penetrate cervical mucus in uterus thousands are killed by leukocytes only a few thousand finally reach uterine tubes

4 Capacitation membranes must become fragile so that hydrolytic enzymes in their acrosomes can be released

5 Acrosomal Reaction acrosomal reaction: release of acrosomal enzymes that occurs in immediate vicinity of oocyte hundreds of acrosomes must rupture to break down intercellular cement of oocyte single sperm makes contact with oocyte

6 Sperm Penetration nucleus is pulled into oocyte cytoplasm
only one sperm is allowed to penetrate Fusion of nuclear material occurs to complete fertilization

7 Preembryonic Development
fertilized egg is now called a zygote

8 1. Cleavage & Blastocyst Formation
cleavage: period of rapid mitotic divisions following fertilization daughter cells become smaller & smaller results in a high surface-to-volume ratio for greater uptake of oxygen & nutrients

9 blastomeres: 2 identical cells by 36 hours 4 identical cells by 60 hours 8 identical cells by 72 hours morula: berry-shaped 100 cell 4-5 days

10 Implantation 6 days after ovulation implantation begins
completed by 14 day

11 Placentation formation of placenta highly vascular
fully functional as nutritive, respiratory, excretory, & endocrine organ by end of 2nd month of pregnancy some harmful substances can pass placental barriers

12 teratogens: may cause severe congenital abnormalities or even fetal death
alcohol, nicotine, drugs, infections

13 Events of Embryonic Development

14 Formation & Roles of Embryonic Membranes
amnion: sac that becomes filled with amniotic fluid which bathes cells provides buoyant environment & protection against physical trauma helps maintain temperature as kidneys develop urine is added to fluid water portion is exchanged 3 hours

15 yolk sac: blood cell formation & produce gonads
chorion: forms placenta allantois: constructs umbilical cord becomes part of bladder

16 Gastrulation: Germ Layer Formation
Ectoderm Mesoderm Endoderm

17 Ectoderm all nervous tissue
skin, hairs, sebaceous & sweat glands, & nails tooth enamel epithelium of: oral & nasal cavities, anal canal, pineal & pituitary glands

18 Mesoderm skeletal, smooth, & cardiac muscle cartilage, bone & other CT
blood, bone marrow, lymph tissue ureters, kidneys, gonads

19 Endoderm epithelium of digestive tract liver, pancreas
thyroid, parathyroid, & thymus glands

20 Effects of Pregnancy on Mother

21 Anatomical Changes breasts enlarge & areolae darken
“mask of pregnancy” pigmentation of facial skin uterus enlarges lordosis placenta produces the hormone relaxin, that causes ligaments to relax & become flexible for child birth weight gain about 25 lbs

22 Gastrointestinal System
excessive salivation morning sickness: increase of hormones heartburn: esophagus & stomach is crowded constipation: motility of digestive tract declines

23 Urinary System urination more frequent & sometimes uncontrollable
uterus compresses bladder kidneys also have to dispose of fetal wastes

24 Respiratory System lung volume decreases nasal stuffiness

25 Cardiovascular System
total body water rises as safeguard against blood lose during birth blood volume increases % blood pressure & pulse rise uterus presses on pelvic blood vessels, venous return from lower limbs may be impaired & result in varicose veins

26 Birth 280 days after conception
Parturition Birth 280 days after conception

27 Initiation of Labor last few weeks of pregnancy estrogen reaches highest levels myometrium becomes increasingly irritable & weak which may cause Braxton Hicks contractions or false labor oxytocin is released by posterior pituitary which causes expulsive contraction of true labor

28 Stages of Labor

29 Dilation time from labor’s onset until cervix is fully dilated (10 cm)
contractions begin in upper part of uterus & move downward toward vagina contractions minutes apart & last for sec. contractions become more vigorous & rapid

30 infant’s head is forced against cervix causing it to soften & become thinner
amniotic fluid breaks lasts 6-12 hours

31 Expulsion from full dilation to delivery
contraction every minutes & lasting 1 minute lasts 20 minutes to 2 hours crowning episiotomy may be performed to reduce tearing umbilical cord is clamped & cut

32 Placental delivery of placenta within 15 minutes of birth
important that all placental fragments be removed called afterbirth


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