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Lecture 3

Week 3 - Periods of Prenatal Development.docx

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PSYC 100
Jill L Atkinson

Week 3: Development Periods of Prenatal Development  Conception begins when sperm enters egg , matching chromosomes become one cell  Till two weeks, it is known as the zygote when it is implanted into the uterine wall, where rapid cell division occurs  From the 3 to 8 week, major development occurs when it is known as the embryo, where the major organ systems are built as well as cell differentiation and many other bodily functions  9 week to birth, it is known as the fetus where there is continued development and rapid growth of the body Developmental Processes  Cell division begins to divide in first 12 hours at an exponential rate  Cell migration occurs during the embryonic period  Cell differentiation – initially all the cells are stem cells but undergo differentiation, there are 350 types of cells and their location ultimately determines their type  Programmed cell death also happens which is called apoptosis  Eg. Our webbed fingers, tail  Hormonal Effects – all foetuses can go either way Period of the Zygote  Blastocyst, a hollow sphere with inner cell mass-less than 1mm in diameter  Identical twins are the cause of the splitting of the inner cell mass  Implantation end of first week occurs for about a week Period of the Embryo  Early development is mostly rapid  All development proceeds in a cephalocaudal and proximodistal manner (head to tail and inside to outside respectively)  Ectoderm – outer most layer, nervous system, nails, teeth, inner ear, eye lens and epidermis  Mesoderm – muscles, bones, circulatory system, skin  Endoderm – digestive system, lungs, urinary tract and glands  U shaped groove forms down center of top layer-neural tube where one end will swell to become brain and spinal cord  Placenta – blood doesn’t mix with mothers but allows nutrients to go in  Amniotic sac protects and provides a constant temperature and allows exercise for the baby Fetus at 16 Weeks  Mom begins to feel babies first kicks  Beginning of period of lower body growth Fetus at 20 weeks  More head down position, goes upside down  Should turn by 22 week  Less movement, cramped  Putting on weight  Facial expressions begin to occur, and will shield eyes from fetoscope  May be able to survive at 20-22 weeks with lots of intervention  Lungs aren’t developed, no fat on body etc Fetus at 28 weeks  Age of viability where brains and lungs are developed enough to survive without major medical intervention  Eyes open and move, auditory system is functional  In the last 3 months of pre-natal development, the fetus triples in weight in the form of fat under the skin Fetal Behaviour  Normal formation of organs and muscles depends on the baby being able to move even such as hiccups  By the age of 12 weeks the developing organism has all the newborn’s movements  Chest movements similar to breathing though its not constant, but can’t really breathe as it is in fluid  At first constant motion then moves into rest activity cycles that are similar to newborn Fetal Sensory Experience  Experiences tactile stimulation, hands touch and bang onto the wall of the uterus as well as suck thumb  Taste – amniotic fluid has a taste which the fetus prefers some to othe
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