Chapter - 3 PRENATAL DEVELOPMENT AND BIRTH Flashcards
How does Conception occurs
Single sperm cell from the male unites with an ovum (egg) in the female’s fallopian tube in a process called fertilization
Duration of Prenatal period
9.5 - 10 months / 266-288 days / 38-40 weeks
What is a prenatal period
Period starting from fertilization and ending with birth
3 stages of Prenatal period
1- Germinal
2- Embryonic
3-Fetal
How long Germinal Period lasts
2 weeks. The germinal period (about 14 days in length) lasts from conception to implantation of the zygote (fertilized egg) in the lining of the uterus.
What happens in Germinal period?
1) Creation of fertilized egg (Zygote)
2) Attachment of Zygote to a uterine wall, side of Uterus
3) Zygote goes through rapid cell division through a process called mitosis.
4) Cell division create specialized cells for different tasks. Blastocysts - Inner mass of cells that develop in to embryo and Trophoblast - outer cells that provide nutrition to embryo
The Embryonic Period duration
2 weeks - 8 weeks after the conception and begins when blastocyst attaches to uterine wall
What is blastocyst called after attaching to uterine wall
Embryo
What is Blastocyst
Three days after fertilization, a normally developing embryo will contain about six to 10 cells. By the fifth or sixth day, the fertilized egg is known as a blastocyst — a rapidly dividing ball of cells
Name 3 layers of Embryo
1.Endoderm - Inner layer
2. Mesoderm - Middle layer
3. Ectoderm - outer layer
endoderm
Inner layer of embryo develops in to digestive and reproductive system
Mesoderm
Middle layer of embryo develops in to respiratory system, bones, muscles, excretory system and reproductive system.
Ectoderm
Outer layer of Embryo- Develops in to nervous system - brain and CNS, skin parts such as hair, nails and also sensory receptors such as eyes, nose, ears
2 Life support systems in Embryo that develop out of fertilized egg
1 - Umbilical chord
2- Amnion
amnion
Bag containing clear fluid in which embryo floats . This protects embryo from shocks, provides environment where temp. humidity is controlled .etc.
umbilical cord
A tube like structure containing contains two arteries and one vein - connects baby to placenta
placenta
consists of a disk-shaped group of tissues in which small blood vessels from the mother and the off spring intertwine but do not join.
material that passes between embryo and mother
Oxygen, CO2, water, salt, digestive waste
how placenta protects baby
Large molecules can not pass through placenta, such as most bacteria, maternal waste, hormones. Complex mechanism that governs the transfer of material to baby through placenta is still not understood
organogenesis
name given to the process of organ formation during the first two months of prenatal development.
Neural tube
a tubular structure which eventually becomes a spinal chord in 3 weeks after conception
When does eyes begin form in germination stage
21 days
when does heart begins to form
24 days after conception
The Fetal Period
period between two months after conception and birth in typical pregnancies. Fetal period if about 7 months
neurons,
nerve cells, which handle information processing at the cellular level in the brain
when is the basic architecture is formed
first 2 trimesters of prenatal development
After the basic architecture is formed when does the connectivity of brain and functioning of brain happens
third trimester of prenatal development and the first two years of postnatal life are characterized by connectivity and functioning of neurons
defects that occur due to not closing of neural tube after 24 days of conception
anencephaly - Top portion of tube not closed
spina bifida - Bottom part of neural tube remains open
anencephaly
when the head end of the neural tube fails to close, e highest regions of the brain fail to develop.
Such infants die in the womb, during childbirth, or shortly after birth
Spina bifida
Results in varying degrees of paralysis of the lower limbs.
Ways to prevent neural tube defects
- take adequate amounts of the B vitamin & folic acid
- Avoid maternal diabetes and obesity
neurogenesis
The generation of new neurons after 5th week when the neural tube is closed naturally
neuronal migration
involves cells moving outward from their point of origin to their appropriate locations and creating the different levels, structures, and regions of the brain
TE-RA-TO-LOGY
The field of study that investigates the causes of birth defects is called teratology
teratogen
any agent that can potentially cause a birth defect or negatively alter cognitive and behavioral outcomes. (The word comes from the Greek word tera, meaning “monster.”).
When is the impact of Teratogens are highest
embryonic period between 3 - 8 weeks after conception. This can cause structural abnormalities
Effects of teratogens in Fetal period (9-36 weeks)
Instead of structural abnormalities it causes growth issues
behavioral teratology
Some teratogens cause defects in developing brain leading to issues in cognitive and behavioural functioning. This field is called behavioral teratology .