2Pregnancy We have discussed the parts of the reproductive system. However, it’s not just enough to know the parts. It’s also important to understand how the system works, how pregnancy happens.
3The Components of A Cell Cell membrane - The thin membrane that surrounds every cell.Cytoplasm - The jelly-like material inside a cell’s membrane, and all the parts floating in it except the nucleus.Nucleus - The core of a cell, which contains the chromosomes.
4The Components of A Cell 1. DNA - Deoxyribonucleic acid. The hereditary chemical of which genes and chromosomes are made.1. Genes - The microscopic messenger codes inside each cell of our bodies. They carry the plans for many things about us; whether we are male or female; what color hair, skin, eyes we’ll have; how we’ll become, how our bodies will work, etc.2. You can think of genes as the “blue print” of our bodies.1. Chromosomes - A string of genes.
5The Components of A Cell An egg cell (Ovum) and a sperm cell each have 23 chromosomes.When the two have joined together at fertilization there are a total of 46 chromosomes. We all have 46 chromosomes.
6Process of Fertilization 1. Fertilization - When an ovum and sperm cell join.2. Sperm are released into the vagina during ejaculation.2. Sperm travel up through the cervix, into the uterus, and up into the fallopian tubes where the sperm cell will meet the egg cell.2. Only one sperm cell will enter an egg cell to cause fertilization.Fertilized Egg - What an ovum is called after the chromosomes from a sperm have mixed with the ovum’s chromosomes.
7Implantation1. Fertilized egg multiplies into a ball of cells as it travels through the fallopian tube into the uterus.1. Ball of cells “nests” in uterus2. Implantation - The ball of cells (that used to be a single fertilized egg) nesting in the wall of the uterus.
8Implantation Fertilization + Implantation = Conception Conception - The beginning of a pregnancy. Conception is fertilization of an ovum by a sperm, followed by implantation in the uterus.
9TwinsIdentical TwinsTwins that grew from one egg, fertilized by one sperm, that split into two balls of cells before it implanted in the uterus. They have the same genes, so they look exactly alike.
10TwinsFraternal TwinsTwins that grew from two eggs, each fertilized by a different sperm. They don’t look any more alike than any brothers and sisters because they have different genes.
11Gender Determination 1. Mother = xx chromosomes 1. Father = xy chromosomes1. One chromosome from each person joins together2. Baby Girl = xx chromosomes2. Baby Boy = xy chromosomesIt is the father’s chromosome which determines whether one will have a boy or a girl.
12PregnancyEmbryo - The developing baby from implantation to about 10 weeks. After 10 weeks it is called a “fetus”.Amniotic Fluid - The “water” in which a developing baby floats. It acts as a cushion.Amniotic Sac - The thin membrane that surrounds the amniotic fluid and the fetus.
13PregnancyPlacenta - An organ that grows inside the uterus during pregnancy to carry food and oxygen from the mother and waste from the embryo or fetus. It produces many hormones that affect both the mother and the baby. It develops from the original ball of cells that implanted in the uterus.Umbilical Cord - The tube leading from the navel of the embryo or fetus to the placenta. It carries food and oxygen to the developing baby, and waste from the developing baby.
14Reference Sheets Pregnancy Reference Sheets 1 - 4. Discuss Prenatal DevelopmentHow the fetus grows in the uterus before birth
15Reference SheetsReference Sheet 4Glossary and Resources
16Pregnancy Problems 1. Miscarriage 2. A pregnancy ending much too soon, before the embryo or fetus is able to live outside the uterus.1. Birth Defects2. A disability that a baby is born with (retardation, heart problems, blindness, cerebral palsy, Downs Syndrome, etc.
17Pregnancy Problems1. Premature Birth2. Born “too” soon...after fewer than 38 weeks of pregnancy. Depending on how early she or he is born, a premature baby may have serious birth defects or problems and die, minor birth defects or problems and do OK with help from the hospital, or no birth defects or problems and do just fine.
18Pregnancy Problems 1. Low Birth Weight 2. A baby that is “too” small...less than five and a half pounds at birth. A “low birth weight” baby is more likely to be sick or have birth defects; it is also likely to develop more slowly and to have more difficult in school. He/She may turn out healthy and do just fine.
19Pregnancy Problems Miscarriages and birth defects may be caused by: a chromosomal abnormality in the ovum or sperm (more than 23 or less than 23 chromosomes)Mother’s/Father’s consumption of drugs and/or alcoholMother’s illness, including STD’sRadiation and environmental pollution
20Pregnancy Problems Miscarriages and birth defects may be caused by: Mother’s age (the healthiest, safest time is in her 20’s and early 30‘sFather’s ageBirth trauma (Forceps delivery, Vacuum Delivery)Baby’s illnessUnknown factors
21Pregnancy ProblemsSome possible reasons for the especially high rate of birth defects, miscarriages, premature birth, and low birth weight in babies born to TEENS are:No/Poor prenatal careLate Prenatal carePoor NutritionConsumption of alcohol, cigarettes and other drugsHigh rates of STD’s among teens
22HomeworkBirth Information SheetDue: Next class period!