Chapter 23 Pregnancy, Growth, and Development Pregnancy is the presence of a developing offspring in...

Chapter 23Pregnancy, 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

23-31

Prenatal Heart

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• stage• 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