FERTILIZATION Begins with 46 pair of chromosomes, splits off to 23 then combine for a unique new 46 pair.
Stages and Time Frames BlastocystGerminal Stage EmbryoEmbryonic Stage FetusFetal Stage OvumBefore fertilization Blastocyst0-2 weeks Embryo2-8 weeks Fetus8-40 weeks
IMPLANTATION First weeks of human development: Blastocyst embedded in endometrium.
GESTATIONAL AGE Gestational age=Time since last menstrual period (LNMP -Last Normal Menstrual Period) Fertilization LNMP Days280 Weeks40 Calendar Months9 Lunar Months10
TRIMESTERS Trimester 1st= weeks nd= weeks rd= weeks 27 and on (38-40 WEEKS)
STAGES OF DEVELOPMENT
1 Month Baby Center Video: Weeks 1-9Baby Center Video: Weeks 1-9 First Trimester At the end of four weeks: Baby is 1/4 inch in length Heart, digestive system, backbone and spinal cord begin to form Placenta (sometimes called "afterbirth") begins to develop The single fertilized egg is now 10,000 times larger than size at conception
Month 2 First Trimester At the end of 8 weeks: Baby is 1-1/8 inches long Heart is functioning Eyes, nose, lips, tongue, ears and teeth are forming Penis begins to appear in boys Baby is moving, although the mother can not yet feel movement
Month 3 Baby Center Video: Weeks Baby Center Video: Weeks First Trimester At the end of 12 weeks: Baby is 2 1/2 to 3 inches long Weight is about 1/2 to 1 ounce Baby develops recognizable form. Nails start to develop and earlobes are formed Arms, hands, fingers, legs, feet and toes are fully formed Eyes are almost fully developed Baby has developed most of his/her organs and tissues Baby's heart rate can be heard at 10 weeks with a special instrument called a Doppler
Month 4 Baby Center Video: Weeks Second Trimester At the end of 4 months: Baby is 6 1/2 to 7 inches long Weight is about 6 to 7 ounces Baby is developing reflexes, such as sucking and swallowing and may begin sucking his/her thumb Tooth buds are developing Sweat glands are forming on palms and soles Fingers and toes are well defined Sex is identifiable Skin is bright pink, transparent and covered with soft, downy hair Although recognizably human in appearance, the baby would not be able to survive outside the mother's body
Month 5 Baby Center Video: Weeks 21-27Baby Center Video: Weeks Second Trimester At the end of 5 months: Baby is 8 to 10 inches long Weight is about 1 pound Hair begins to grow on baby's head Soft woolly hair called lanugo will cover its body. Some may remain until a week after birth, when it is shed. Mother begins to feel fetal movement Internal organs are maturing Eyebrows, eyelids and eyelashes appear
Month 6 Second Trimester At the end of 6 months: Baby is 11 to 14 inches long Weight is about 1 3/4 to 2 pounds Eyelids begin to part and eyes open sometimes for short periods of time Skin is covered with protective coating called vernix Baby is able to hiccup
Month 7 Baby Center Video: Weeks 28-37Baby Center Video: Weeks Third Trimester At the end of 7 months: Baby is 14 to 16 inches long Weight is about 2 1/2 to 3 1/2 pounds Taste buds have developed Fat layers are forming Organs are maturing Skin is still wrinkled and red If born at this time, baby will be considered a premature baby and require special care
Month 8 Third Trimester At the end of 8 months: Baby is 16 1/2 to 18 inches long Weight is about 4 to 6 pounds Overall growth is rapid this month Tremendous brain growth occurs at this time Most body organs are now developed with the exception of the lungs Movements or "kicks" are strong enough to be visible from the outside Kidneys are mature Skin is less wrinkled Fingernails now extend beyond fingertips
Month 9 Third Trimester At the end of 9 months: Baby is 19 to 20 inches long Weight is about 7 to 7 1/2 pounds The lungs are mature Baby is now fully developed and can survive outside the mother's body Skin is pink and smooth Baby settles down lower in the abdomen in preparation for birth and may seem less active
AMNIOTIC FLUID Protects Fetus Controls Temperature Supports Symmetrical Growth Prevents Adherence to amnion Allows Movement Source of oral fluid Acts as a excretion-collection repository Clear, yellowish fluid surrounding the developing fetus. Average amount 1000 ml.
UMBILICAL CORD Connecting link between fetus and placenta. Transports oxygen and nutrients to fetus from the placenta and returns waste products from the fetus to the placenta. Contains: 2 arteries and 1 vein supported by mucoid material (wharton’s jelly) to prevent kinking and knotting. Contains NO pain receptors.
PLACENTA MOM Baby Schematic drawing of placenta: how it supplies oxygen and nutrition to embryo and removes waste products. Deoxygenated blood leaves fetus through the umbilical arteries and enters placenta, where it is oxygenated. Oxygenated blood leaves placenta through the umbilical vein, which enters the fetus via the umbilical cord Baby mom
PLACENTA Produces protein hormones: Human chorionic gonadotrophin (HCG) days past conception, is basis for pregnancy test Progesterone Estrogen Human Placental Lactogen
PLACENTA Sieve/filter – allows smaller particles through and holds back larger molecules. Passage of materials in either direction is effected by: –Diffusion: gases, water, electrolytes –Facilitated transfer: glucose, amino acids, minerals. –Pinocytosis: movement of minute particles
PLACENTA Mother transmits immunoglobulin G (IgG) to fetus providing limited passive immunity. Leakage: caused by membrane defect: may allow maternal and fetal blood mixing.
VIABILITY Capability of fetus to survive outside uterus at the earliest gestational age weeks Survival depends on: –Maturity of fetal central nervous system –Maturity of lungs
NEUROLOGICAL SYSTEM Formed during the 3 rd week Respiratory effort18 1/2 WKS Swallowing 12 1/2 WKS Fetal movement felt16-20 WKS (Quickening) Sucking29 WKS
IMMUNE SYSTEM Passive immunity - FROM MOM Active immunity - FROM FETUS
What Now? Using your notes for support, work with a partner to fill out the activity handout entitled “When’s That”? Be prepared to discuss your answers with the class.