PRENATAL AND NEWBORN DEVELOPMENT RG 9c

CONCEPTION ● when male’s sperm fertilizes female’s egg o At this point, the egg blocks all other sperm o Women are born with all the eggs they will ever have (1/5000 actually mature) o Men begin producing sperm at puberty and produce it 24/7 for the rest of their life

GENETICS ● This new one-cell entity contains 23 pairs of chromosomes…one member of the pair from the mother and the other from the father o Each chromosome contains thousands of genes…either individually or in combination, genes produce the particular characteristics of each person

GENETICS ● Genes are composed of sequences of DNA (deoxyribonucleic acid) molecules ● Some genes are responsible for the development of systems common to all humans (heart, circulatory system, brain, lungs, etc.), while others control characteristics that make each human unique (like eye color, height, facial features, etc.) ● Sex is also determined by combination of genes (the 23 rd chromosome)

PRENATAL DEVELOPMENT ● Zygote – fertilized egg o Fewer than ½ survive the 1 st 2 weeks ● Embryonic stage (weeks 2-8) o At 2 weeks, zygote becomes an embryo o By 4 weeks, embryo has developed a rudimentary beating heart, brain and intestinal tract (these organs are very primitive…but can be recognized) o By 8 weeks, embryo is about an inch long…has arms, legs and face that are distinct

ZYGOTE TO EMBRYO 8 weeks4 weeks 6 days old

20 week fetus

PRENATAL DEVELOPMENT ● Fetal stage (from 8 weeks to birth) o At week 8, now called a fetus o By around 4 months, fetal movement strong enough to be detected by mother o At around 6 months, eye lids open and fetus has well-developed grasp and taste buds

PRENATAL DEVELOPMENT ● Fetus reaches age of viability or the point at which it can survive if born prematurely at 24 weeks (about 50% of premie babies survive at this age and % increase as each week passes) ● Fetus continues to grow and gain weight during the last two months…at the end of a normal 38 week (9 ½ month) pregnancy, fetus typically weighs around 7 lbs and is about 20 inches in length

PRENATAL INFLUENCES – GENETICS ● Genetic factors (major cause of genetic defects is faulty genes or chromosomes) o Phenylketonuria (PKU): protein builds up in the body. Digestive issues. o Tay-Sachs disease: body is unable to break down fat, which causes these substances to build up in and destroy brain and nerve cells, until the nervous system shuts down  babies usually start exhibiting signs of the disease around 4-6 months old  children usually die by age of 5  if parents both carry genetic defect, child has a 1 in 4 chance of being born with the disease  seems to occur most frequently in Central and Eastern European Jews (and descendants) o Down Syndrome

DOWN SYNDROME ● occurs when a zygote receives an extra chromosome at the moment of conception…causes mental retardation (usually in the mild to moderate range) o Often related to a mother’s age…more common in babies born to mothers over the age of 35 o Characteristic facial features…including upward slanted eyes, smaller noses, ears and mouth, and sometimes smaller hands and shorter necks o Often accompanied by other health problems…heart, vision and hearing

ENVIRONMENTAL FACTORS ● Teratogens: environmental agents such as drugs, chemicals, viruses or other factors that can produce birth defects o Mother’s illness  Rubella (german measles) can cause blindness, deafness, heart abnormalities and stillbirth  Syphilis can cause mental retardation, physical deformities and miscarriage for mother  AIDS can be passed on to child prior to birth

ENVIRONMENTAL FACTORS ● Teratogens continued… o Mother’s use of drugs  Illegal drugs like cocaine can result in baby being born addicted to the drug  Even some legal drugs can cause fetal abnormalities o Alcohol and nicotine use  Fetal alcohol syndrome: condition resulting in mental and growth retardation  Some physical features associated with FAS – abnormally small, small eyes and upturned nose, and small or abnormally formed brain  Most have some degree of mental retardation and many exhibit problems with attention span, learning, coordination and behavior  Smoking can lead to fewer nutrients received by the fetus which results in lower birth weight…heavy smoking may affect the brain

NEWBORNS ● All babies are born with a number of reflexes (unlearned, involuntary responses that occur automatically in the presence of certain stimuli  Rooting reflex – automatic turn of head when cheek is touched  Sucking reflex – suck anything that touches lips  Startle reflex – infant flings arms, fans fingers and arches back in response to sudden noise  Babinski reflex – toes fan out when out edge of sole of foot is stroked  These reflexes are lost after first few months of age and are replaced by more complex behaviors

NEWBORNS