Pregnancy

Fertilization During intercourse, millions of sperm are released from the male and into

the female.

Only about 100 sperm will make its way to the fallopian tubes.

Those 100 sperm try to penetrate the outer egg. As soon as one makes it (success!!!!!), the egg releases a protein that prevents other sperm from entering the egg. (WOW the human body is so amazing.)

The cell membrane of the sperm will then fuse with the egg to produce the zygote. The zygote now has the DNA it needs to create the offspring.

Fertilization Upon a successful fertilization, the zygote grows for nine months (38 weeks)

inside the mother to be and ends with the birth of an offspring.

The nine months are divided into three trimesters (three months per trimester).

Image of a human sperm entering a human egg.

First Trimester The first trimester starts from fertilization and ends after three months.

The zygote – now an embryo – begins cell division in the fallopian tube and within one week will make its way to the uterus.

Once it gets to the uterus it will attach to the wall of the uterus. Here the embryo creates a sac that is filled with amniotic fluid and the umbilical cord is created to combine the mother to the embryo.

Amniotic fluid supports, protects, and maintains a warm environment for the embryo until birth.

Once the uterus realizes it has a zygote, and not an un-fertilized egg, the body releases hormones to prevent the menstruation cycle.

First Trimester Here is a labelled diagram of the fetus after it

attaches itself to the uterus wall. (Found on page 118 of textbook)

First Trimester All the cells are reading the DNA and starting to create

the offspring.

By the fourth week the brain and a nervous system have been developed and the heart is beating.

By the end of week 5 the eyes, ears and nose are noticeable; as are the limb buds (small little hands and feet) and the tail (which becomes the tailbone) are visible.

First Trimester By the end of the eighth week the embryo has started to develop the beginning of

all the organs and is now called a fetus.

The fetus looks like a human being, however it is only the size of a lima bean.

Through the umbilical cord the fetus and mother are able to share nutrients, oxygen, and the the fetus’ waste.

By the end of the third month, muscles and bones are starting to form. The heart is beating, blood is circulating through the fetus and sex organs are forming. It is at this point you can determine the sex of the baby.

The fetus is about 12 cm long and weighs approx. 50 grams

Second Trimester Through months four – six the fetus starts to really take shape.

It grows from 8 cm to 30 cm long.

The heartbeat can be heard by a stethoscope.

Movements can be felt by the mother – especially now that he abdomen is starting to swell as the fetus gets bigger.

By 24 weeks (or approx. 6 months) the fetus resembles a tiny infant. Fingers and toes have elongated. Facial features start to develop.

Oxygen is still being pumped through the umbilical cord.

Second Trimester Image of a fetus in the second trimester

Notice the hands, face, nose, ears, eyes and etc… as they are starting to become more developed.

Third Trimester During months seven - nine the fetus puts on more mass.

It starts to have sleeping and waking patterns, and it reacts to stimuli from the outside world (i.e. music, sound, movement and etc…)

The lungs continue to mature, and the final development of the body comes to an end just before delivery.

The fetus fills the capacity of the uterus, its body turns around with its head pointing towards the cervix and the birth canal in preparation for delivery.

At 37 weeks, the fetus is considered to be full term and ranges from 45 – 55 cm and can weigh up to 4.5 km (10 lbs)

Third Trimester In the thrid trimester, the fetus has fully formed, there is no room left for it

to grow in the uterus and is ready for delivery.

Growth Progression

Birth After 9 months of being pregnant, the muscles of the mothers uterus start

to contract regularly (like every 15 – 20 minutes and lasting for as long as 40 seconds). This is the body’s natural way to start delivery, it is at this point labour has begun.

During labour, hormones start to control the process of delivery, and while the mother is able to use her abdominal muscled to help with delivery, it is her body and the hormones that start and play an vital role in the delivery process.

There are four main parts to the birthing process.

Birth First – the cervix begins to dilate (open up). The membrane surrounding the

baby is forced into the birth canal (the Vagina)

Birth Second – the amniotic membrane breaks, and amniotic fluid lubricates the

birth canal. This is called the breaking of the water.

Birth Third – Once the cervix has widened to 10 cm, uterine contractions (this is

done via the hormones being released during labour) push the baby’s head into the birth canal.

Birth Fourth – When the head and shoulders are free of the birth canal, the rest

of the baby slips out easily – usually with the help of a nurse or doctor. After the baby is born, the placenta is pushed out of the uterus. Once the baby is able to breath on its own, the umbilical cord is cut and tied to prevent bleeding. The “belly – button” is the scar from the umbilical cord.

Stem Cells Stem Cells – are unspecialized cells that have the ability to reproduce

themselves. They have not yet reached the point where they divide into specialized cells (like our hair, ears, and etc…).

We can use these cells to help rebuild organs and other parts of the bodies that have been damaged. For example, they can be placed near the heart muscled of someone who had a heart attack. The stem cells are then able to read the person’s DNA, and at the same time rebuild a new heart muscle.

Stem Cells Problem, stem cells only survive in bone marrow, the umbilical cord and in an embryo.

Getting cells from bone marrow is EXTREMELY PAINFUL.

Keeping the umbilical cord frozen so it does not deteriorate is VERY EXPENSIVE.

But through in vitro fertilization, we can fertilize many eggs, and since only one of them is going to be used, what do you do with the other fertilized eggs? You could grow them to an embryo and then extract the stem cells from it, then destroy the embryo.

The last option is less expensive than freezing the umbilical cord, and is not as painful as getting bone marrow – but theoretically you are going to be killing a fertilized egg that could become an offspring…

Assignment Pg 121 – 3, 4, 5, 7, 11, 12, 19