The Life Cycle Your Life Began as a Single cell, smaller than this period at the end of this sentence . Now your body is made up of trillion of cells, forming the organs, and tissues in your body!! This microscopic cell formed by the union of an egg cell (Ovum), from the Female and a Sperm cell from the Male. This is called FERTILIZATION. Also known as CONCEPTION. The resulting cell is now called a Zygote.

How it all starts……..    Each woman is born with two ovaries that are positioned in her pelvis. These oval-shaped organs produce one egg per month in response to the woman’s monthly cycle of hormones. Generally, one ovary produces one egg one month and the other ovary produces an egg the next month. Picture on next slide

Within Days after the Zygote forms, it begins dividing as it travels down the Fallopian Tubes. By the Time it reaches the UTERUS, the Zygote has divided many times to form a cluster of cells with a hollow space in the center. Within a few days the Zygote attaches to the Uterine Wall in the Process called IMPLANTATION. Refer to Figure 19.1 pg.487

Implantation is when the Zygote attaches to the Uterine Wall. The Cluster of cells that was once called a Zygote is now called an Embryo during the third and eight weeks of pregnancy. From the eighth week of pregnancy until term , the developing cluster of cells is called the Fetus.

Zygote

Embryo 9 weeks

Fetus

Embryonic Growth As the embryo continues to divide , it forms 3 tissue layers that later become Various body systems. 1st layer becomes the Respiratory and Digestive system. 2nd Layer develops into Muscle, Bones, blood vessels, and skin. 3rd layer forms the nervous system, sense organs, and mouth. (After 3 layers)….. As this is going on inside the embryo, two important structures form outside the embryo The Amniotic Sac and the Umbilical cord and placenta

Amniotic Sac is a thin, fluid- filled membrane that surrounds and protects the developing embryo.

Stages of Birth 1st- Dilation 2nd- “Crowning” passing through the birth canal Contractions of the Uterus cause the Cervix( opening of the uterus) to dilate. Contractions can cause the Amniotic sac to break. “water broke”. 2nd stage- when then cervix is fully dilated 10cm the mother can begin to push and the baby passes through the canal. 3rd stage- the placenta is still attached to the baby by the umbilical cord, contractions continue until the afterbirth is delivered. The umbilical cord is not cut 3rd- Afterbirth

Placenta is a thick-rich tissue that lines the walls of the Uterus during pregnancy and nourishes the embryo.

Umbilical Cord A rope like structure that connects the embryo and the mother’s Placenta.

Fetal Development 9 months/ 3 month periods called TRIMESTERS Pg. 488 Figure 19.2 Review Trimesters From conception until birth there is nine full months

How do Twins Form?? Identical twins result when a Single Egg that has been

Identical twins result when a single egg has been fertilized by one sperm, it divides and forms two embryos. Being that they originated form the same zygote, identical twins have the same genetic make-up. Fraternal twins form when the ovaries release two egg’s. Therefore two sperm fertilize each egg and two embryos develop. The genetic make-up is different

Identical twins result when a single egg has been fertilized by one sperm, it divides and forms two embryos. Being that they originated form the same zygote, identical twins have the same genetic make-up. Fraternal twins form when the ovaries release two egg’s. Therefore two sperm fertilize each egg and two embryos develop. The genetic make-up is different

The Health of the Fetus Tobacco, alcohol, and other drugs used by the mother can enter the body of the developing fetus and have harmful effects. Tobacco and Pregnancy It is estimated that smoking accounts for up to ; 30 % of low birth weight babies 14% of premature births 10% of all infant deaths. Smoking during pregnancy is very harmful to the fetus…Studies also suggest that a pregnant female;s smoking may also afftect the growth, mental development, and behavior of her child until he or she is 11 years old! Pregnant females repeatedly exposed to secondhand smoke also have increased of have low birth weight babies!

Fetal Alcohol Syndrome(FAS) Alcohol & Pregnancy Any Alcohol consumed during pregnancy quickly passes through the umbilical cord to the Fetus. Fetal Alcohol Syndrome(FAS) A group pf alcohol-related birth defects that includes both physical & mental problems. Life Consequences: Mental retardation, learning disabilities Serious behavior problems, slowed growth Physical deformities; including a small skull, abnormal facial features, heart defects.

Common Physical effects of FAS

Medicines,other drugs, and Pregnancy Serious consequences using drugs, even over-the counter medicine are: -weakened mother’s immune system, resulting in improper care of the baby. -Hinder fetal development -birth defects,premature labor, miscarriage -The baby can be born addicted to the drugs the mother uses during pregnancy, causing the baby to go through withdrawl after birth.

Environmental Hazards Harm to the Fetus can result when the mother is exposed to some common substances in the environment Lead-exposure has been linked to miscarriages,low birth weight,mental disabilities & behavior problems in children. Smog- air pollution has been linked to birth defects, low birth weight,premature birth, stillbirths, & infant death. Greatest risk is during the second month when most organs & facial features develop. Radiation- Ionizing Radiaiton-type found in X-rays, can affect fetal growth & cause mental retardation. Cat Litter- Contains parasites that cause a disease that can result in miscarriage,premature labor,and health problems in newborns.

Complications during pregnancy Miscarriage = spontaneous expulsion of a fetus that occurs before the 20th week of a pregnancy. A dead fetus expelled from the body after the twentieth week is called a Stillbirth. 2. Ectopic pregnancy = pregnancies result when the zygote implants in the fallopian tube, the abdomen, the ovary,or the cervix. This can occur when the fertilized egg can’t pass to the uterus, sometimes b/c of inflammation or scar tissue that has developed as a result of a Sexual transmitted disease.

3. Preeclampsia = also called, toxmia, can prevent the placenta from getting enough blood, This may result in low birth weight and problems for the mother; such as high blood pressure, & swelling. 4. Gestational Diabetes = Gestational diabetes affects about 4% of all pregnant women . Gestational diabetes starts when your body is not able to make and use all the insulin it needs for pregnancy. Without enough insulin, glucose cannot leave the blood and be changed to energy. Glucose builds up in the blood to high levels. This is called hyperglycemia.