Presentation on theme: "Prenatal Development Chapter 2. Biological Beginnings: Conception Ova are released from the ovaries and travel down the fallopian tubes, where conception."— Presentation transcript:
Prenatal Development Chapter 2
Biological Beginnings: Conception Ova are released from the ovaries and travel down the fallopian tubes, where conception occurs. Development begins at conception. Males produce an average of 300 million sperm per day. Only 300-500 reach the ovum. Sperm can live for 6 days and ova for one.
The Three Periods of Pregnancy Germinal (Period of the Zygote) –First two weeks, ends with implantation Embryonic Period –2-8 weeks, organogenesis Fetal Period –9 weeks – birth (all trimesters)
Period of the Zygote (Germinal) 4 th day – blastocyst, hollow, fluid filled ball (60-70 cells) –Inside, embryonic disk will become new organism –Outside, troboblast, protective covering
Period of the Zygote (Germinal) Within about 1 week of conception, cell differentiation begins Implants (attaches to the uterine wall) on the 10 th to 14 th day
Troboblast will form the amnion (fluid sac which regulates temperature and forms a cushion) Will also form the chorion, from which fingerlike villi or blood vessels emerge and the placenta forms as they burrow into the uterine lining. Period of the Zygote (Germinal)
Umbilical cord connects the growing organism to the placenta It has one vein and two arteries The mother’s and embryo’s blood will not mix directly (red blood cells, bacteria, hormones, maternal waste are filtered) Embryonic Period – 3 rd week after conception
Embryonic disk forms: –Ectoderm – skin and nervous system –Mesoderm – muscles, skeleton, circulatory system –Endoderm – digestive system, lungs, urinary tract, glands Embryonic Period – 3 rd week after conception
Embryonic Period (2-8 weeks) - Organogenesis Neural tube develops first, will become brain and spinal cord Next, heart begins to pump blood The basic structure of all the organ systems grows Eyes, ears, nose, jaw, neck, arms legs, fingers & toes form At the end of this period, it weighs less than one ounce, about one inch long.
–The fetus can kick, bend its arms, form a fist, curl its toes, open its mouth, suck its thumb, smile & swallow –By 12 th week external genitals well formed, also fingernails, toenails, tooth buds, eyelids –Heartbeat can be heard with a special stethoscope –End of 3 months, 3 inches, 3 ounces Period of the Fetus – Growth and Finishing Phase – 3 rd Month
Called a fetus from the 8 th week until birth Fetus means fully-formed human being because all organ systems are now in place During the 3 rd month (12-16 weeks) it will have coordinated movements, be able to roll over in the amniotic fluid Hair, eyelashes, eyebrows will grow Period of the Fetus – Growth and Finishing Phase
–Mother can feel movements –Can hear heartbeat with ordinary stethoscope –Neurogenesis proceeds rapidly (250,000 neurons per minute) –At 20-weeks can be stimulated/irritated by sound; will shield eyes during fetoscopy Period of the Fetus – Growth and Finishing Phase – 2 nd Trimester
–Age at which the fetus can survive outside the mother (38-40 weeks is full term) –5% survive at 22 weeks –50% survive at 26 weeks (6 months) –95% survive at 28 weeks Period of the Fetus – Growth and Finishing Phase-Age of Viability
–Depends upon gestational age at birth –Breathing Hyaline membrane disease –Regulating blood oxygen levels –Apnea –Temperature regulation –Feeding –Parenting – 40% faster weight gain & brain development with touch Kangaroo care Problems with Preemies
–Begins sleep-wake pattern –Responsiveness, can feel pain after 24 weeks –React to sounds –Prefer mother’s voice –Adds fat (5 pounds) –Receives antibodies –Assumes birth position (head down) Fetal Period – 3 rd Trimester
–Any environmental agent that causes prenatal damage (leading to birth defects) –Types – drugs, diseases, radiation, environmental pollutants –Factors – dose, resilience (heredity), number of teratogens, gestational age at exposure (embryonic period worst) Teratogens (Monsters)
Examples –Thalidomide – 7000 infants affected Limbs, heart, ears, kidneys, genitals –DES (diethylstilbestrol) – reproductive problems in adult children (cancer; abnormalities in reproductive organs) Teratogens - Drugs
–Don’t take anything without consulting your obstetrician Examples –Aspirin – may be associated with LBW, infant death, lower IQ, poor motor development –Caffeine – LBW, miscarriage, irritable infants Teratogens - Drugs
–Cocaine –Heroin/methodone Prematurity, LBW, breathing difficulties, physical defects, infant death, stressed and drug addicted –Marijuana Smaller head size, disturbed sleep, inattention in infancy Teratogens – Illegal Drugs
Nicotine constricts blood vessels and lessens blood flow to the uterus, causes the placenta to grow abnormally, reduces the transfer of nutrients, raises the carbon monoxide concentration in the blood stream which may damage the central nervous system Smoking during pregnancy is associated with LBW and increased frequency of prematurity, impaired breathing during sleep, infant death and childhood cancer. Teratogens - tobacco
Fetal Alcohol Syndrome (FAS/FAE) is the leading preventable cause of mental retardation. Other symptoms include impaired motor coordination, attention, memory & language; slow physical growth & overactivity. Facial abnormalities include widely spaced eyes, short eyelid openings, thin upper lip, small head, small upturned nose. Teratogens - Alcohol
Lesson – Women should avoid alcohol during pregnancy. Alcohol inteferes with brain development – causing abnormalities in structure and function. Oxygen needed for cell growth is taken from the fetus to metabolize alcohol. Teratogens - Alcohol
Environmental Teratogens Radiation (Hiroshima, Nagasaki, Chernobyl) – Miscarriages, babies with underdeveloped brains, physical deformities, slow growth Mercury – 1950s Minamata, Japan – resulting brain damage in children Lead – prematurity, LBW, brain damage, physical defects PCBs (insulators for electrical equipment) – lower intelligence
Nutrition Emotional stress Maternal age & previous births Other Maternal Factors
18% of women in the U.S. wait until the second trimester, and 4% until the end to get care Many of these are unmarried, adolescent, or poverty stricken. Reasons include lack of insurance, ambivalent feelings, high risk behaviors, and lack of transportation. Prenatal Health Care
Approaches to Childbirth How much medical care/availability? Should it be natural or prepared? How about the epidural? How about a midwife (or a doula)?
The Birth Process –Dilation and effacement (of the cervix)(Labor) At transition a clear channel from the uterus to the vagina is formed (birth canal) –Birth of the baby (Delivery) 20-50 minutes –Delivery of the placenta (afterbirth) (5-10 minutes)
Birth Complications and Medical Interventions –Anoxia –Breech position –Cerebral palsy –Fetal monitors –Medication (90-95% of births) Analgesics, anesthetics –Cesarean delivery (30% of births)
Low Birthweight Infants (LBW) (Low)Birthweight is the best available predictor of infant survival & healthy development. Low Birthweight Babies weigh less than 5.5 pounds. –1 of 14 American infants –More problems with inattention, overactivity, language delays, low IQ scores, and motor deficits
Low Birthweight Infants (LBW) –Preterm babies – born early (35 or fewer weeks) may be weight appropriate –Small-for-date babies have more serious problems.
Apgar (1 & 5 minutes after birth) 5 characteristics –Heart rate, respiratory effort, reflex irritability, muscle tone, color) –0,1,or 2 points on each Total score –7+, good physical condition –4-6, baby requires assistance –3-, infant in serious danger, requires emergency attention
The Newborn - Arousal Sleep 18-20 hours per day 50% is REM sleep SIDS (Sudden Infant Death Syndrome)