Fertilization and Embryonic Development Human Development: From Conception to Birth

What are we learning today? Benchmark Objectives SC.912.L.16.13 …Describe the process of human development from fertilization to birth and major changes that occur in each trimester of pregnancy. I will describe the process of human development from the zygotic stage to the end of the third trimester and birth.

What is the essential question? Summarize that changes that occur each trimester during the development of the embryo or fetus. Answer: First trimester Organ systems begin to form (cell differentiation) Nervous system begins forming Heart begins beating Embryo begins to move Ears, eyelids, and teeth buds are formed Second trimester Mostly growth Fetal skeleton forms Mother can feel the fetus moves Fetus can now hear. Hair forms on the body Third trimester Fetus turn into a head-down position. Fat is deposited beneath the skin A greasy substance forms on the fetus skin. Lungs mature Fetus can see light and react to sounds.

Occurs in upper third of Fallopian tube What is fertilization? Fertilization is the union of a sperm cell and an egg cell to form a zygote. Occurs in upper third of Fallopian tube Only 1 sperm can fertilize an egg To the Teacher:

What cellular processes make it all happen? Growth or the increase in the number of cells. Differentiation or the specialization of cells to perform specific tasks and functions. Development or the arrangement of the cells into specific organs. To the Teacher: Use the frog diagram to explain cellular processes.

What is implantation? Zygote divides several times to form a solid ball of cells called a morula. More cellular divisions result in a blastocyst, a ball of cells with a large fluid cavity. Blastocyst burrows into the lining of the uterus during implantation. Describe the process of fertilization and implantation?

What happens after implantation? Implanted blastocyst gradually sorts itself into three layers forming a gastrula. All the organs and tissues of the embryo will be formed from these three layers by cell differentiation.

What is neurulation? Neurulation is the development of the nervous system. Neural folds create neural tube. One end of the neural tube will develop into the brain, the other end develops into the spinal cord.

What are some important extraembryonic structures? Placenta is the structure through which the mother nourishes the embryo Umbilical cord contains arteries and veins that carry blood between the embryo and the placenta C Amniotic sac is a membrane that surrounds the embryo Amniotic fluid cushions the embryo keeping it from injury and keeps it moist

What are the major milestones of the first trimester? All organ systems begin to form (cell differentiation) Nervous system begins forming Heart begins beating Embryo begins to move Ears, eyelids, and teeth buds are formed

What are the major milestones of the second trimester? Mostly growth Fetal skeleton forms Mother can feel the fetus moves Fetus can now hear. Hair forms on the body

What are the major milestones of the third trimester? Fetus turn into a head-down position. Fat is deposited beneath the skin A greasy substance forms on the fetus skin. Lungs mature Fetus can see light and react to sounds.

Muscles in the vagina and cervix relax allowing them to enlarge What is birth? Takes place about 38 weeks after fertilization Muscles in the vagina and cervix relax allowing them to enlarge Uterine contractions force fetus through birth canal Once umbilical cord is cut, baby functions independently

The Miracle of Life

What is the essential question? Summarize that changes that occur each trimester during the development of the embryo or fetus. Answer: First trimester Organ systems begin to form (cell differentiation) Nervous system begins forming Heart begins beating Embryo begins to move Ears, eyelids, and teeth buds are formed Second trimester Mostly growth Fetal skeleton forms Mother can feel the fetus moves Fetus can now hear. Hair forms on the body Third trimester Fetus turn into a head-down position. Fat is deposited beneath the skin A greasy substance forms on the fetus skin. Lungs mature Fetus can see light and react to sounds.