Children Psychology: Chapter 3 Processes
Period of the Zygote
1. Blastocyst forms
a. Ball- like structure
b. Inner layer = embryo
c. Outer layer = tissues that protect and nourish embryo
2. Implantation
a. When blastocyst reaches uterine wall, tendrils burrow inward and tap in to woman’s blood supply
b. 48 Hours, 7 to 10 days after ovulation (finished by 10-14 days after ovulation)
c. Looks like small translucent blister
d. ½ are firmly implanted
e. As many as half are genetically abnormal and fail to develop or burrow into a site that is incapable of sustaining them and are miscarried
f. ¾ fail to survive
3. Development of Support Systems
a. Once implanted, blastocyst’s outer later rapidly forms 4 major support structures that protect and nourish developing organism
i. Amnion : water tight sac that fills with fluid from woman’s tissues – amniotic fluid cushions developing organism against blows, regulate temperature, and provide weightless environment that will make it easier for embryo to move
1. Yolk sac floating in fluid produces blood cells until embryo can produce its own ii. Chorion : Membrane that surrounds amnion and eventually becomes lining of the placenta iii. Placenta : Multipurpose organ; formed from the lining of the uterus and the Chorion that provides for respiration and nourishment of the unborn child and the elimination of its metabolic wastes iv. Umbilical Cord : soft tube containing blood vessels that connects the embryo to the placenta : allantois forms umbilical cord
Period of the Embryo
1. 3rd to 8th week of pregnancy
2. By 3rd week, embryonic disks rapidly differentiating into 3 layers
a. Ectoderm (outer): nervous sytem, skin, hair
b. Mesoderm (middle): muscles, bones, circulatory system
c. Endoderm (inner): Digestive system, lungs, urinary tract, pancreas, liver
3. 3rd Week: Portion of ectoderm folds to form neural tube that soon become brain and spinal cord
4. End of 4th week: heart has formed and begun to beat; eyes, ears, nose, and mouth are beginning to form, arm and leg buds form (1/4th of inch long but already 10000 times size of the zygote from which it developed)
5. During 2nd Month: Grows 1/30 of an inch per day; coccyx (tip of backbone) forms
6. By middle of 5th: eyes have corneas and lenses
7. By 7th: ears are formed, rudimentary skeleton; limbs developing from body outward, upper arms followed by forearms, hands, then fingers
8. Brain develops rapidly during 2nd months; directs first muscular contractions by end of embryonic period
9. 7th and 8th: sexual development beings with appearance of genital ridge (indifferent gonad). Circulatory system functions on its own (liver and spleen produce blood cells)
Period of the Fetus
• Time during which all major organ systems begin to function and the etus begins to move, sense, and behave
• Individuality emerges (patterns of movement and different facial expressions)
The Third Month
• Organ systems that were formed earlier continue rapid growth and become interconnected
• Swallow, digest nutrients, urinate
• Sexual differentiation progresses rapidly
• By end of 3rd month, sex of baby can be determined with ultrasound
Fourth through Sixth Months
• Simple movements of tongue, lips, pharynx, larynx – suck, swallow, munch, hiccup, breathe, cough, snort
• Kicking strong enough for mother to feel it
• Fetal heartbeat could be heard; amount of bone and cartilage increases as skeleton hardens
• During 5th and 6th months, nails harden, skin thickens, eyebrows, eyelashes, and scalp hair suddenly appear
• 20 weeks; sweat glands. Fetus covered by Vernix (white, cheesy substance that covers the fetus to protect the skin from chapping) and lanugo (fine hair covering the fetus’s body tat helps