Human Life Cycle PDF

2/15/2024 Endocrine System & Reproduction Human Life Cycle What are the stages of human development that occur before birth? How is the developing embryo protected and nourished? What happens during childbirth? What changes occur from infancy to adulthood? 1 Fertilization of the Egg by the Sperm Spe...

2/15/2024 Endocrine System & Reproduction Human Life Cycle What are the stages of human development that occur before birth? How is the developing embryo protected and nourished? What happens during childbirth? What changes occur from infancy to adulthood? 1 Fertilization of the Egg by the Sperm Sperm can survive up to 5 days within a female’s body Egg is viable from 12 to 24 hours after ovulation Video of the sperm fertilizing the egg and development till birth https://www.youtube.com/watch?v=s-Xpa5UZAZs 2 1 2/15/2024 General Development Before Birth Zygote  Embryo  Fetus Zygote: fertilized egg Embryo: unborn offspring with developed heart and developing organs Fetus: when embryo has recognizable body parts 3 Zygote and Embryo Fertilization: Sperm + Egg  Zygote Happens in the fallopian tube Zygote takes about 3-4 days to travel to uterus. During which the zygote cell undergoes mitosis to form a hollow ball of cells called a blastocyst Blastocyst attaches to the lining of the uterus Embryo stage – from 2 cell stage to before 8-weeks of development After 8 weeks of development  Fetus 4 2 2/15/2024 Fetus - From 9 weeks until Birth From 9 weeks: Internal organs have developed Brain is developing rapidly Clear dark eye patches, fingers and toes Between 4-6 months: Bones become distinct Lanugo, fine soft hair all around fetus, develops Heartbeat can be heard Limbs are more completely developed Fetus moves  muscles are developing At the end of 9 weeks, it will be about 9 cm long and weigh about 26 g (about an olive) At the end of 6 months, it will be about 30 cm long and weigh about 700 g (about a melon) 5 Fetus - From 9 weeks until Birth From 6 to 9 months: Brain continues development  grows grooves and ridges Lungs become ready to perform gas exchange (by week 24 lungs are fully developed but not ready for gas exchange yet) Body develop reserves of body fat Eyelids open By week 36, body loses lanugo and has hair on its head At the end of 9 months, it will be about 60 cm in length and weight about 3 kg (about gallon bottle of water) 6 3 2/15/2024 Protection & Nourishment After attachment to the uterus, new membranes form to protect and nourish the developing embryo and fetus Amniotic sac  membrane surrounding embryos which develops into a fluid-filled sac called the amniotic sac. Amniotic sac cushions and protects the developing baby from external bumps from outside 7 Protection & Nourishment Placenta  organ linking the embryo to the mother Embryo’s blood vessels run next to the maternal blood vessels Blood do not mix Proximity allows for exchange of materials between blood of mother and embryo Nutrients, oxygen and other substances diffuse from mother’s blood to embryo’s blood Carbon dioxide and other waste diffuse from embryo’s blood to mother’s blood Barrier between embryo and maternal blood prevents some diseases from spreading to the embryo Unable to prevent chemicals e.g. alcohol and drugs from entering fetus’ blood stream 8 4 2/15/2024 Placenta https://www.stlouischildrens.org/health-resources/pulse/medicalanimations-fetal-circulation-placental-blood-supply-and-capillary 9 Protection & Nourishment Umbilical cord  ropelike structure between the fetus and the placenta Contains blood vessels of the embryo that reaches the placenta Does not contain maternal blood vessels Cord blood contain stem cells that can be grown into specific kinds of cells in the body Stem cells may be used to treat some diseases, like some forms of cancer and anemia 10 5 2/15/2024 Birth Birth of a baby takes place in 3 stages 1. Labor Strong muscular contractions in the uterus Contractions  labor Cervix widens due to contractions to allow baby to pass through May last from about 2 hours to more than 20 hours 11 Birth 2. Delivery In normal delivery, baby is pushed out of the uterus through the vagina Head of the baby usually comes out first Baby is still connected to the placenta by umbilical cord Lasts from a few minutes to about an hour After baby is delivered, umbilical cord is clamped and cut about 5 cm from the baby’s abdomen Umbilical cord will dry up and fall off, leaving a scar  belly button after 7 to 10 days 12 6 2/15/2024 Birth 3. Afterbirth About 15 minutes after delivery Uterus contracts to push the placenta and other membranes out of the uterus. Completes in less than 1 hour Video of normal delivery https://www.youtube.com/watch?v=dYu-0rOnLpA Video of c-section https://www.youtube.com/watch?v=xyN48VnRYUY 13 Birth and the Baby Stressful process to both mother and baby Baby is pushed and squeezed to move the baby out of the mother’s body Contractions put pressure on the placenta and umbilical cord and may reduce baby’s blood supply Baby’s endocrine system responds with adrenaline release Increases baby’s heart rate. Within seconds of delivery, baby starts breathing with a cry or cough Cry/cough helps remove fluid from lungs and fill lungs with air Blood travels to lungs allow blood to pick up oxygen from lungs Heart rate slows to steady rate 14 7 2/15/2024 Multiple Births More than one baby in a single pregnancy  multiple birth 2 babies  twins (more frequently, may be identical or non-identical) 3 babies  triplets (less frequently – usually artificial) 4 babies  quadruplets (less frequently – usually artificial) 15 Identical Twins (Monozygotic Twin) Occurs when a single sperm fertilizes a single egg Embryo splits and forms identical embryos early in its development. Contains identical genetic material and will have identical inherited traits. Depending on when the split occurs, the development within the uterus will differ. 16 8 2/15/2024 17 Fraternal Twins (Dizygotic Twins) Occurs when two single sperms fertilize two separate eggs released from the ovary Fraternal twins have different genetic make up and may not be of the same sex 18 9 2/15/2024 19 Fraternal Twins (Dizygotic Twins) Occurs when two single sperms fertilize two separate eggs released from the ovary Fraternal twins have different genetic make up and may not be of the same sex 20 10 2/15/2024 Growth & Development - Infancy First 2 years of life When baby is first born, head is ¼ size of the body Body of infant develops faster while head develops slower 3 months  infant holds head up & reaches for objects 7 months  crawls 10 to 16 months  starts walking 1 to 3 years  starts talking By end of 2 years  are relatively independent & understand speech 21 Growth & Development - Childhood Infancy ends at 2 years Childhood  continue growing (taller and heavier) due to development of bones and muscles Muscular coordination improves with practice of learnt behavior (e.g. walking, writing etc) Language ability improves with socialization Social interaction help teach social norms and appropriate behavior in a group setting  psychology 22 11 2/15/2024 Growth & Development - Adolescence Stage between childhood and adulthood when an individual is gradually developing to become an adult physical and mentally Mentally  start thinking like adults Physically  enter puberty Puberty is the period of physical development when the body starts acquiring the ability to reproduce Girls  Pituitary gland and ovaries control physical changes. Sex organs develop. Ovulation and menstruation starts. Hips widen, breasts develop. Boys  Pituitary gland and testes control physical changes. Sex organs develop. Sperm is produced. Voice deepens, facial hair appears. 23 Growth & Development - Adulthood Mental and emotion growth continues Hard to identify when puberty ends and adulthood starts By 30 years, aging starts Physical changes happen due to slow down of cell renewal and repair process - skin wrinkle and muscle strength decreases - eyes lose ability to focus on near objects (old-sightedness) - hair lose coloring (start becoming grey) - women stops menstruating (menopause) - men may continue producing sperm throughout their lives but number of sperms produced will decrease 24 12 2/15/2024 Growth & Development - Adulthood Effects of aging may reduce with good diet and exercise Mental acuity may be maintained with active social and mental engagement - interaction & sharing of wisdom with peers and younger people - continually seeking to learn and remain relevant 25 Pauline Moy Fertilization to 9 months https://www.youtube.com/watch?v=8BH7WFmRs-E 26 13