Human Growth and Development

Zygote When a sperm carrying ______ the necessary DNA combines with an egg containing _____ the necessary DNA combine a zygote forms. A zygote contains ____ of the genetic information (DNA) necessary to become a child. The zygote undergoes _______ until a ball of cells is formed.

Blastocyst In a few days a ball consisting of an inner group of cells and an outer shell is formed. This ball is called a blastocyst. The inner cells will become the ______. The outer shell will become the membranes that nourish and protect the fetus.

Embyro The cells begin to differentiate (take on specific ___________ – types of cells that make up a human being) some form blood cells, others form nerve, bone, etc. These first few weeks are when a developing child is most at _______ from what the mother takes into her system.

Embryo 1 st week Embryo has moved from the fallopian tubes to the __________ where it attaches to the uterine wall. The ________ and umbilical cord will grow and connect the fetus to the ________. This will be the fetus’s only source of food, water, and oxygen.

Embryo First 3 to 5 weeks The heart, brain and spinal cord have already begun to develop.

After about 8 weeks the embryo is considered a fetus Most of the organs and main body parts have begun to develop and can be clearly seen here.

10 to 32 weeks Eyes aren’t complete until about 24 weeks.

Were you paying attention? What is a fertilized egg called? ________________ In a ________________ the inner cells become the ____________ the outer layer of cells become the membranes (placenta/amniotic sack) that nourish and protect the fetus. At how many weeks is the embryo considered a fetus? _________ Where are eggs usually fertilized? ___________________

What two things connect the fetus and the mother providing food, water, and oxygen to the fetus? ________________ This is a thin but tough bag that surrounds the fetus protecting it and holding in the fluid that surrounds the fetus. ________________ When do the eyes finish forming? ___________