Aim: How does an embryo develop inside the uterus?

How long are humans pregnant? Females are pregnant for nine months or 38 weeks

Embryonic Development: + SpermEgg Fertilization Zygote Mitosis Embryo- the stage in human development from the first division of the zygote until about nine weeks after fertilization.

Cleavage The rapid number of mitotic cell divisions after fertilization – Number of cells increase tremendously, but size of embryo does not

EARLY DEVELOPMENT

Embryo vs. Fetus Embryo Fetus (Up to 8 weeks) (8 weeks-Birth)

Where does the embryo develop? Embryo implants itself in the uterine wall once it reaches ~100 cells (6- 7days) Sonogram

Do all cells have the same DNA? Same genes? YES!! – Every cell (except sex cells) have the same 46 chromosomes

Why do they look different and perform different functions? Because each cell type uses different parts (genes) of the DNA

What is cell differentiation? When cells become specialized in structure and function due to the expression of different genes

What does a developing embryo need? 1. Nutrients for ATP & to build its own body parts 2. Oxygen for ATP

Embryonic Waste Products 2. Carbon Dioxide 1. Metabolic waste (from cells)

Umbilical Cord The umbilical cord is responsible for carrying nutrients and oxygen to the developing fetus, and waste away.

Placenta The placenta is the organ that allows for the exchange of Nutrients, wastes and gases

Fetal Blood Supply The blood from the baby and the embryo NEVER mix. Materials DIFFUSE between the mother’s blood & the babies blood.

The Placenta

Why is the fetus floating in a fluid? The fetus is surrounded by amniotic fluid and an amniotic sac which protects the fetus and it helps absorb shock

STRUCTURES BY 3 rd WEEK Placenta Nervous and endocrine system (starting) Vital organs forming Heart is beating

FIRST TRIMESTER Most major organs formed Umbilical cord formed Muscular system developed Reflexes Amnion formed

SECOND TRIMESTER Tissues become specialized Skeleton forms Strong fetal heartbeat At ~6 months the baby can live outside the mom with life support

3 rd Trimester Fetus doubles in size Lungs are forming Sleeps 90-95% of the time Dreams Premature if born before 8 months Sonogram #2

What happens at around 9 months? The fetus has developed all its organs and is ready to live in the outside world Secretion of Oxytocin causes the uterine muscles begin to contract and the baby is forced out of the mother. This process is called:Labor

Prenatal care Good nutrition Moderate exercise No smoking No drugs, prescription or illegal No alcohol

Don’t get morning sickness: Thalidomide (1950)

Fetal Alcohol Syndrome (FAS) Consuming alcohol during development can cause FAS which has disastrous affects on the CNS.

What trimester is the most dangerous? The first trimester, because all the organs are forming at this time. Dangerous chemicals can affect cell division.