Chapter 23 Pregnancy, Growth, and Development Pregnancy is the presence of a developing offspring in the uterus Growth is an increase in size. Involves increases in cell numbers and cell sizes Development is the continuous process by which an individual changes from one life phase to another 23-2

Fertilization Paths of the egg and sperm cells through the female reproductive tract 23-3

Steps in Fertilization acrosome releases enzymes sperm cell penetrates zona pellucida sperm cell’s membrane fuses with egg cell’s membrane 23-4

Formation of Morula zygote blastomeres morula 23-5

Early Human Development 23-6

Implantation trophoblast will help form the placenta 23-7

Summary of Stages and Events of Early Human Prenatal Development fertilized ovum zygote forms cleavage mitosis increases cell number morula solid ball of cell blastocyst trophoblast and inner cell mass form gastrula primary germ layers form 23-8

Hormonal Changes During Pregnancy Mechanism that preserves uterine lining during early pregnancy 23-9

Hormonal Changes During Pregnancy Relative concentrations of three hormones in maternal blood during pregnancy 23-10

Hormonal Changes During Pregnancy secretion of maintains corpus luteum corpus luteum secretes estrogens and progesterone estrogens and progesterone stimulate and maintain uterine lining, inhibit FSH and LH, inhibit uterine contractions, and enlarge reproductive organs placental lactogen aldosterone promotes sodium retention PTH 23-11

Derivatives of Each Primary Germ Layer 23-13

Embryos three weeks; dorsal view three and a half weeks; lateral view four weeks; lateral view 23-14

Embryonic Development 23-15

Changes During Embryonic Development 23-16

Placenta Consists of an embryonic portion and a maternal portion 23-19

Placenta at Seventh Week 23-20

Embryo at Eight Weeks End of eighth week marks end of embryonic period 23-21

Teratogens structures in developing embryo are sensitive to teratogens at different times 23-22

Development body portions change considerably 23-23

Development of External Reproductive Organs 23-24

Position of Full-Term Fetus 23-25

Major Events of Fetal Development 9th –12th week ossification centers appear sex organs differentiate fetal limbs begin to move 13th – 16th week body grows rapidly ossification continues 23-26

Major Events of Fetal Development 17th – 20th week muscle movements stronger 21st – 38th week body gains weight subcutaneous fat deposited eyebrows and eyelashes appear eyelids open testes descend 23-27

Fetal Circulation oxygen and nutrients diffuse into the fetal blood from the maternal blood waste diffuses into the maternal blood from the fetal blood 23-28

Fetal Cardiovascular Adaptations fetal blood has greater oxygen-carrying capacity umbilical vein- ductus venosus – foramen ovale – ductus arteriosis umbilical arteries carry blood from internal iliac arteries to placenta 23-29

Fetal Circulation 23-30

Fetal Circulation Summary Prenatal Heart 23-31

Factors Contributing to the Labor Process as birth approaches, progesterone levels decrease prostaglandins synthesized which may initiate labor fetal head stretches uterus 23-32

Birth Process A positive feedback mechanism propels the birth process 23-33

Stages in Birth stage 23-34

Milk Production placental estrogens and progesterone stimulate further breast development estrogens cause ductile system to grow progesterone causes alveolar glands to develop placental lactogen also produces changes in breast prolactin is released about the 5th week of pregnancy breast production does not begin until after birth 23-35

Postnatal Period Neonatal period newborn begins to carry on respiration, obtain nutrients, digest nutrients, excrete wastes, regulate body temperature, and make cardiovascular adjustments Infancy teeth begin to erupt muscular and nervous systems mature communication begins 23-38

Major Changes in the Newborn’s Cardiovascular System 23-41

Causes of Death 23-43

Clinical Application Preimplantation Genetic Diagnosis Probes disease-causing genes in an eight-celled embryo 23-44