Conception to Birth PDF
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This document discusses human development from conception to birth, covering topics such as fertilization, genetics, dominant and recessive genes, sex-linked traits, and different developmental stages, such as germinal, embryonic, and fetal periods. It also explains the placenta's function, prematurity risks and complications, prenatal influences on development, and various screening and diagnostic tests associated with prenatal care.
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Human Development ----------------- The study of development begins at the moment of conception. Every human begins with the union of one sperm and one ovum (egg). ### Fertilization: Zygote Formation: Genetic material from each parent fuses to form a zygote. The zygote is the first living cell fo...
Human Development ----------------- The study of development begins at the moment of conception. Every human begins with the union of one sperm and one ovum (egg). ### Fertilization: Zygote Formation: Genetic material from each parent fuses to form a zygote. The zygote is the first living cell formed at conception. Human DNA consists of 23 pairs of chromosomes and 20,000 genes. Genetics: --------- Genotype: The genetic makeup of an organism. Phenotype: The observable physical traits. Single Nucleotide Polymorphism (SNP): A change in a single nucleotide, a type of genetic mutation. These are biomarkers. Independent Assortment: How genes independently separate during the development of reproductive cells. ### Dominant and Recessive Genes: Dominant genes: Always expressed if present. Recessive genes: Only expressed if paired with another recessive gene. Co-dominant genes: Expressed equally (e.g., blood type). ### Sex-Linked Traits: Traits linked to X or Y (sex) chromosomes. Typically recessive and carried on the X chromosome. Examples include color blindness, baldness, hemophilia, and Fragile X syndrome. Developmental Stages: --------------------- ### 1. Germinal Period: First 2 weeks post-fertilization (zygote to implantation). ### 2. Embryonic Period: Weeks 3 to 8 post-conception. Major organs and anatomical structures begin to form. Heartbeat visible at 6 weeks via ultrasound. ### 3. Fetal Period: From week 9 to birth. Rapid growth of organs. ### Neural Tube Formation: Begins at 22 days, eventually forming the central nervous system. ### Week-by-Week Development: 6 Weeks: Embryo is 2.5 cm long. Legs and webbed toes develop. 8 Weeks: Recognizable as human. All major organs present except sex organs. Placenta Formation: ------------------- The placenta develops by the end of the first trimester (12 weeks). Acts as a life-support system, connecting the fetal and maternal circulatory systems via the umbilical cord. Second Trimester (13-26 weeks): ------------------------------- Fetus develops a more distinct human appearance. Quickening: Baby starts to swallow and kick. 20-24 weeks: Hair, lashes, and brows form. Visual and auditory senses become functional. Third Trimester: ---------------- 28 weeks: Eyes open/close and respond to light. Better organized motor skills and sleep-wake cycles. 32 weeks: Brain reaches 25% of adult weight. 36-40 weeks: Brain development slows; fetal body systems prepare for life outside the womb. Prematurity Risks: ------------------ 23 weeks gestation: Considered viable (\~20-35% survival rate). 26 weeks and beyond: Up to 90% survival but with high risks of impairments. ### Short-Term Complications: Breathing: Apnea of prematurity, broncho-pulmonary dysplasia. Heart: Patent ductus arteriosus (PDA), hypotension. Brain: Intraventricular hemorrhage. Immune System: Underdeveloped. ### Long-Term Complications: Cerebral Palsy, Impaired cognitive skills, Vision and hearing problems, Chronic health issues (e.g., SUDI -- sudden unexpected death in infancy). Prenatal Influences on Development: ----------------------------------- Nutrition, Maternal Anxiety, Maternal Health, Teratogens (agents causing birth defects), Health conditions during pregnancy (e.g., anemia, hypertension, depression). ### Examples of Teratogens: Thalidomide: Causes limb malformations. Alcohol: Causes fetal alcohol spectrum disorders (FASD). Screening and Testing: ---------------------- ### Screening Tests: Nuchal Translucency Scan: Ultrasound at 12-13 weeks measuring fluid behind baby's neck. Maternal Serum Screening: Blood analysis for neural tube defects and trisomy 21. ### Diagnostic Testing: Chorionic Villus Sampling (CVS): Performed between 10-12 weeks. Small risk of miscarriage. Amniocentesis: Detects chromosomal abnormalities, performed at 15-16 weeks. APGAR Scoring: -------------- A quick test is performed on a newborn to evaluate physical condition post-birth. Additional Facts: ----------------- Fetuses respond to sounds and light from 25 weeks. 90% of fetal time in the womb is spent asleep. Viability: 23 weeks gestation marks the point where a fetus can potentially survive outside the womb.