Chapter 2 Biological Beginings Part II (prenatal development and birth)-1.pptx

Chapter 2: Biological Beginnings

Part II: Prenatal Development

Overview of Prenatal Development

• Stages include conception, gestation, and birth.

Page 2: Conception

• Conception: The process of fertilization involves the sperm cell from the male penetrating the ovum (egg) from the female. This process typically occurs in the Fallopian Tube.

• Zygote: The initial single-cell stage after sperm fertilizes the ovum. This zygote undergoes multiple divisions, leading to the formation of a blastocyst, which eventually implants in the uterine wall.

• Ovary: Releases the ovum (egg) during ovulation, which is critical for conception.

Page 5: From Zygote to Newborn

• Germinal Period (1-2 weeks): During this period, implantation of the blastocyst in the uterine lining occurs. For example, if fertilization happens shortly after ovulation, the embryo will start developing within a week or two.

• Embryonic Period (3-8 weeks): Vital organs begin to develop. By the end of this period, basic structures like the heart and major organs are being formed.

• Fetal Period (9-birth): This phase involves continued growth and maturation. For instance, during this stage, a fetus can typically start responding to sound around 25 weeks.

Page 4: Prenatal Critical Thinking Questions

• How does the fetus breathe and eat?

  • Answer: The fetus receives oxygen and nutrients via the placenta and umbilical cord, without needing to breathe air.

• Can a fetus urinate; if yes, where does it go?

  • Answer: Yes, a fetus can urinate into the amniotic fluid surrounding it.

• Why can't a baby survive outside of the womb despite organ development by 8 weeks?

  • Answer: Though organs develop, they are not yet functional enough to sustain life outside the womb.

• Are fetuses aware of their environment?

  • Answer: Fetuses can hear external sounds and may react to light, indicating some level of awareness.

Page 8: Embryonic Period Development

• Neural Tube Formation: The neural tube, which will develop into the central nervous system, starts forming from the outer layer of the embryo.

• Differentiation of Three Layers:

  • Outer Layer (Ectoderm): Becomes the nervous system, including the brain and spinal cord.

  • Middle Layer (Mesoderm): Develops into muscles and skeletal structures, like bones.

  • Inner Layer (Endoderm): Forms vital organs such as the heart and lungs.

Page 10: Organ Development Timeline

• Weeks 4-8:

  • At 4 weeks, initial structures form, such as the heart and yolk sac.

  • Arms and legs begin to bud out from the body.

  • By 8 weeks, all major organs are now present, and the embryo is referred to as a fetus.

Page 14: Fetal Period Details

• Third Month (9-12 Weeks): Significant developments occur, including the formation of sex organs. By the 12th week, all body parts are formed, and fetal movements can be detected.

Page 17: Viability and Development

• 6 Months: At around this time, a fetal weight of about ½ lb is common. The brain remains immature, and the lungs are still developing.

• Viability begins around 22-26 weeks, representing the point where survival outside the womb is possible with medical assistance.

Page 19: Answers to Critical Questions

• Fetal Nutrition: Managed through the umbilical cord and placenta, where nutrients and oxygen are exchanged with the mother's blood.

• Fetal Urination: Yes, fetuses urinate, and the urine becomes part of the amniotic fluid.

• Organ Functionality: Even though organs develop, they are not fully operational until after birth. For instance, the lungs are filled with fluid and must clear out to breathe air at birth.

• Awareness of Environment: Fetuses are capable of hearing internal sounds and possibly sensing changes in light and temperature.

Page 21: Teratogens

• Definition: Teratogens are substances that can cause harm to the developing fetus during prenatal development.

Page 23: Birth Defects from Teratogens

• The effects of teratogens vary based on the timing of exposure and critical periods of fetal development:

  • For example, exposure to certain medications during the embryonic period can lead to significant birth defects, while exposure later on might have less severe effects.

  • During the germinal period, the central nervous system and eyes are most affected due to rapid development at this stage.

Page 24: Harm Factors

• Factors Influencing Teratogen Impact:

  • Dose: Some substances, such as Vitamin A, can be harmful at high levels, leading to defects.

  • Interaction Effects: Combination of multiple substances (like alcohol and tobacco) can amplify potential harm.

Page 26: Alcohol as a Teratogen

• The impact of alcohol on fetal development can be severe, leading to Fetal Alcohol Spectrum Disorders (FASD), which can include growth deficiencies and cognitive impairments. Alcohol causes oxygen deprivation, significantly affecting development.

Page 30: Tobacco Effects

• Nicotine & Carbon Monoxide: These chemicals can be transferred through the placenta. They are linked to low birth weight, increased risk of Sudden Infant Death Syndrome (SIDS), and developmental problems in children.

Page 34: Parental Factors in Prenatal Development

• Key maternal influences include nutrition, the intake of prenatal vitamins, and management of stress and emotional states. Poor maternal diet can lead to deficiencies affecting fetal development.

• Fathers also have a role; paternal health has been shown to influence sperm quality.

Page 41: Health Assessment at Birth

• The Apgar Scale is used to measure newborn health at 1 and 5 minutes after birth. Scores range from 0 to 10, with higher scores indicating better health; for example, a score of 7-10 is considered normal.

Page 44: Postpartum Period

• This period lasts approximately six weeks following birth, involving adjustments to physical health (fatigue, recovery from childbirth) and significant hormonal changes, which can affect emotional well-being. Postpartum depression is a potential concern that can occur during this period.