Human Fetal Development - PowerPoint Presentation

Slide1

Human Fetal DevelopmentSlide2

Chicken

Pig

Turtle

HumanSlide3

Sperm and Egg

After sexual intercourse, the sperm unites with the egg. Slide4

Only one sperm

After one sperm fuses with the egg, it develops a protective coating so that other sperm cannot get inside.

Since normally only one egg is present at a time, this means that only one zygote (2n) can begin to develop. Slide5

Uterus

After fertilization, the newly formed zygote travels to the uterus and

implants

itself in the uterus

wall and begins to develop. Slide6

Fetus/Placenta/Umbilical Cord

The zygote develops into a

fetus

in the uterus. The walls of the uterus thicken and become a temporary organ called the

placenta.The umbilical cord connects the fetus

to the placenta to provide oxygen and nutrition for the fetus. Slide7

The Navel

After birth, the baby is still connected to the placenta by the umbilical cord.

The doctor will cut the cord. Eventually, the remainder of the cord falls off, leaving a scar that becomes the

navel

or belly button. Slide8

Twins

Fraternal

Identical

Co-joined or “Siamese”Slide9

Central Questions

How do fraternal twins occurs?

How do identical twins occur?

How do “Siamese” twins occur?

How similar are identical/fraternal/cojoined twins genetically?

How common is each type of twin?Slide10

The normal situation

Normally, the woman’s ovaries are coordinated so that the ovaries will only release one egg per month.

Therefore, at any intercourse, there is only one egg that is available to be fertilized.

If that egg is fertilized, the woman’s body stops releasing eggs until that baby is born.

This is why generally, one baby is born at a time and you cannot have siblings who are closer than 9 months apart. Slide11

Fraternal Twins

Fraternal

or

dizygotic

twins means that two eggs were released by the ovaries at the same time and both were fertilized by two different sperm. They are called dizygotic

because they form from two separate zygotes (fertilized eggs).This occurs in around 2.4% of births in the USA.

Rivka

Yosef

Slide12

Fraternal Twins

These both implant in the uterus in separate places and formed two separate placentas.

These twins are no more genetically related than any other siblings. They are basically siblings born at the same time. Slide13

Identical twins

Identical twins

, or

monozygotic twins occur when a single zygote splits into two separate organisms. (They are called monozygotic because they form from a single zygote).

Normally, the zygote will perform mitosis and remain as a single organism but in rare circumstances the zygote will split into two genetically identical fetuses that form two distinct organisms. This occurs in roughly .8% of births. Slide14

Identical Twins

These both implant in the uterus in the same place and form a single placenta.

Identical twins have

exactly

the same DNA (since they were formed from the same egg and sperm). Slide15

Comparison of Fraternal and Identical TwinsSlide16

Thinking Question- HW

Can you have fraternal twins that are a boy and a girl? If so, how? If not, why not?

Can you have identical twins that are a boy and a girl? If so, how? If not, why not?Slide17

Siamese Twins

Siamese

or

Cojoined twins are twins that are born connected to each other.

This occurs through an incomplete splitting of the zygote, resulting in two fetuses forming that are connected to each other. This is extraordinarily rare and is estimated to occur in roughly 1 out of every 100,000 births. The overwhelming majority of

cojoined twins do not both survive, depending on how much of their bodies they share. Slide18

What is the origin of the term “Siamese twins”?Slide19

The origin of the term "Siamese twins" is Chang and Eng Bunker, famous conjoined twins from who earned their living in the U.S. as a circus attraction in the Barnum and

Baily

Circus.

Upon termination of their contract with their discoverer, they settled in the United States, where they married two sisters and had nearly two dozen children. They were successful businessman and farmers in Wilkes County, North Carolina, where they lived until 1874. They were 63 years old when they died.Slide20

http://www.youtube.com/watch?v=BkKWApOAG2g

Abigail and Brittany

Hensel

Slide21

Review: Development

How many sperm can enter an egg?

Where does the zygote develop into a fetus?

How does the fetus get nutrients and oxygen?

The umbilical cord connects the baby to a particular organ in the mother’s body called the…? How does the belly button form? Did Adam and Chava have a belly button?

One

The uterus

Through the umbilical cord

The placenta

It is the scar from where the umbilical cord used to be

????Slide22

Twins: Review

Is it possible to have:

Male-Male fraternal twins?

Male-Female fraternal twins?Female-Female fraternal twins?

Male-Male identical twins?Male-Female identical twins?Female-Female identical twins?Male-Male cojoined

twins?Male-Female cojoined twins?Female-Female cojoined

twins?

Yes

Yes

Yes

Yes

Yes

Yes

Yes

No

NoSlide23

Review: Twins

In normal births, how many eggs are available to be fertilized at once?

A

dizygotic twin is the same as a…

Fraternal twins come from the same egg but two different sperm. True or false? How is it possible to have male-female fraternal twins?How do identical twins form?

How do cojoined twins form?What is the most common type of twin?

One

Fraternal

False. They are formed from two sperm fertilizing two separate eggs.

If one egg is fertilized by a sperm containing an X-chromosome and the other is fertilized by a sperm containing a y chromosome

A single zygote splits completely

A single zygote splits incompletely

FraternalSlide24

Short quiz Friday on development

Will give back and discuss final

on Monday