This preview shows page 1. Sign up to view the full content.
Unformatted text preview: PSY 350 Child Psychology Child
Prenatal Period 9/15/10 Outline Outline
Periods of Prenatal Development 1. Germinal Period 2. Embryonic Period 3. Fetal Period Why study prenatal development? development?
To understand the changes in size, To form, & behavior that take place form, The developing organism can be The positively or adversely affected by positively mother’s nutritional status, health, & habits habits Zygote: single cell formed at Zygote conception from the union of the sperm & the ovum About the size of a period on a page Weighs approx. 15 millionths of a gram To compare: at birth, we consist of about 2 To billion cells & weigh (on average) 7 pounds billion 1: Germinal Period 1:
Begins at conception & lasts until developing lasts organism becomes attached to the wall of the uterus (8-10 days later) the 24 hours after conception, as zygote travels 24 zygote down fallopian tube, cleavage begins--begins--zygote divides by mitosis into two cells, zygote which then also divide, & so on… which Cells existing at any given time do not all divide at Cells do the same time; instead cells are dividing at different rates different Heterochrony—different parts of the Heterochrony—different organism develop at different rates (“variability in time”) (“variability Heterogeneity—variability in the levels —variability of dev. of different parts of the organism at a given time organism Heterogeneity continues throughout Heterogeneity child’s dev. child’s E.g., newborn’s hearing is more advanced E.g., than its ability to see than At this stage of prenatal dev., all cells are totipotent stem cells--each has totipotent -each potential to grow into an embryo & ultimately into a normal, healthy baby ultimately Identical twins develop when this single Identical mass of totipotent stem cells separate into two cell masses, which then develop into two which two individual but genetically identical human beings. human Implantation—process by which Implantation—process developing organism becomes attached to the uterus attached As developing cell mass is moving farther As into the uterus, outer cells are putting out tiny branches that burrow into the spongy wall of the uterus until they come into contact with the mother’s blood vessels contact 2: Embryonic Period 2:
Extends from time organism becomes Extends attached to the uterus until end of 8th until week of pregnancy, when all major week when organs have taken primitive shape organs Rapid growth facilitated by mother’s Rapid nutritional intake & protection from environmental influences environmental Sources of Nutrition & Protection
Embryo is surrounded by the amnion— amnion tough, thin membrane that cushions tough, the organism, provides liquid support for weak muscles & soft bones, & gives it a medium to move around it Amnion is surrounded by the chorion, Amnion chorion which later becomes the fetal component of the placenta component Sources of Nutrition & Protection Sources
Placenta—organ made up of tissue —organ from the mother & embryo; linked to the embryo by the umbilical cord the Acts as a filter that allows nutrients & Acts oxygen to be exchanged between mother & infant infant Converts nutrients carried by mother’s Converts blood into food for the embryo blood Enables embryo’s waste products to be Enables absorbed by the mother’s bloodstream (will eventually by extracted by her kidneys) kidneys) Embryonic Growth Embryonic
Growing number of cells in the inner Growing cell mass begin to differentiate into various kinds of cells that will eventually become all the organs of the body body Separation of inner cell mass into two layers: layers: Ectoderm, outer layer, gives rise to outer outer surface of the skin, the nails, part of the teeth, lens of the eye, inner ear, & nervous system (brain, spinal cord, & nerves) system Endoderm, inner layer, develops into the inner digestive system & lungs digestive Mesoderm, middle layer, develops last, will middle eventually become the muscles, bones, circulatory system, & inner layers of skin circulatory Embryo grows at rapid rate (refer to Table 3.1, pg. 88 in textbook) Table Two patterns of body development are Two maintained until adolescence: maintained Cephalocaudal pattern: development development proceeds from the head down proceeds
E.g., arm buds appear before leg buds Proximodistal pattern: dev. proceeds from dev. middle of organism out to the periphery middle
E.g., spinal cord develops before arm buds; E.g., upper arm develops before the forearm upper Sexual Differentiation Sexual
Genes that influence sexual Genes determination located on X and Y chromosomes inherited at conception chromosomes Zygotes w/ one X & one Y chromosome are Zygotes one genetically male; two X chromosomes, genetically two genetically female genetically For 1st 6 weeks after conception, no structural differences between these embryos embryos Both males & females have two ridges of Both tissue, called gonadal ridges, from which gonadal from male & female sex organs (gonads) will male will develop develop If embryo is genetically male (XY), process of sexual differentiation begins during 7th week of life, when gonadal during ridges begin to form testes ridges If embryo is genetically female (XX), no If changes apparent until several weeks later, when ovaries begin to form later, Fetal Period Fetal
Begins 9th week after conception, with Begins with the first signs of the hardening of the bones, and continues until birth bones, By the end of 16 weeks: head is erect; head lower limbs are developed; ears migrate from neck to sides of the head migrate th End of 7th month: lungs capable of End lungs breathing air; eyes open & can respond to light to th End of 8th month: many folds of the many brain are present (p. 91 in textbook) brain Fetus is becoming even more Fetus responsive to the uterine environment responsive Mother’s digestive system & heart sources Mother’s of noise; her movements provide motion stimuli stimuli Sensory Capacities Sensory
Sensing Fetus capable of sensing changes in mother’s Fetus posture & orienting itself as its floats inside the amniotic sac amniotic Response to sound 5-6 mos. after conception Also responds to change in sounds at 6-7 mos. Also (changes in heart rate) (changes Mother’s voice heard best, transmitted as Mother’s vibrations through her body vibrations 26 weeks after conception, fetus responds to light 26 (causes them to move, heart rate changes) (causes Hearing Seeing Fetal Activity Fetal
Movements become increasingly varied Movements & coordinated coordinated By 15 weeks, fetus capable of all the By movements observable in infants: movements Head turning Leg flexing Stretching Jaw opening Hand-face contact Yawning ...
View Full Document
This note was uploaded on 04/04/2011 for the course PSYCH 350 taught by Professor J.mojica during the Fall '10 term at CSU Dominguez Hills.
- Fall '10