Life's Greatest Miracle Flashcards
How many babies get made around the world every day?
About 365,000
From a single cell, you build a body that has how many cells?
100 trillion
How many new sperm does the average man churn out every second, day, and over a lifetime?
1,000; 100 million; > 2 trillion
How are sperm and egg cells made?
Meiosis
In almost every cell in our body, how many different genes do we have spread out on chromosomes?
30,000
When is the only time that the 23 chromosomes from each parent come together?
Meiosis
What is the process of mitosis?
1) Each chromosome makes an exact copy of itself keeping it attached at one point
2) Condense creating an X-shape
3) Chromosome partners come together and cling so closely that big chunks carrying whole branches of genes get exchanged between them
4) Cell divides twice, each time pulling the pairs apart
5) Results in sperm or egg with 23 chromosomes
When do women create several million eggs?
Within a couple months of being a fetus in the whom
What happens to an immature egg cell every month?
1) Woman’s two ovaries selects an immature egg cell
2) Egg and support cells ooze out of the ovary
3) Goes through the fallopian tube into the uterus where tentacles capture the egg and pull it inside
4) Egg is swept along by muscular contractions of the tube as well as the constant swaying of tiny cilia
Why must a prepared egg be fertilized within a few hours?
It will die
How does sperm get into the vagina?
1) Hormones cue blood vessels to relax allowing spongy tissue in the penis to fill with blood
2) At the height of sexual excitement, millions of sperm are squeezed out of storage and swept up by fluid gushing from several glands including the prostate
3) The flood carries them into a 15-inch long tube looping into the abdomen and then out through the penis
What is the sperm’s first obstacle?
The cervix (passageway to the uterus) - Most of the time, it’s locked out and plugged with mucus that keeps bacteria and sperm out, but just a few days a month around ovulation, the mucus becomes watery and forms tiny channels that guide the sperm through
What propels the sperm into the fallopian tube?
Undulations of the uterine muscles
What sperm may have a better chance at joining with the egg?
The ones caught up in the cilia lining of the tube
Further up the fallopian tube the sperm will find the egg heavily chaperoned by what?
Support cells
What is the egg itself encased in?
A think protein shell called the zona
What must the sperm do to fertilize the egg?
Break through the zona by using proteins that protrude from the sperms cap to hoop up with precise set of proteins on the eggs surface, and if they match, the sperm is held fast and undergoes a dramatic transformation. It sheds its outer coating, releasing powerful enzymes that dissolve a hole in the zona allowing the sperm to push its way through. The membranes of the two cells fuse and the egg draws the entire contents of the sperm inside
How many fertilized eggs fail to develop?
Over 50%
In order for a fertilized cell to survive, what must it do?
- Order the zona to lock out all other sperm
- Finish meiosis, expelling half of its chromosomes into a tiny pouch called a polar body
Since the sperm entered the egg, how much time has passed and what has the fertilized egg been doing?
24 hours; moving down the fallopian tube toward the uterus
Why do the cells divide every few hours?
To create the building blocks needed to construct an embryo
How many days after fertilization does the egg arrive in the uterus?
5
What must the now called blastocyst do?
Break out of the zona and find a source of nourishment
At the beginning of the 6th day, how does the blastocyst orchestrate an escape?
Releases an enzyme that eats through the zona and the ball of cells squeezes it out onto the blood-rich lining of the uterus
What might happen now that the blastocyst has been striped of its protective coating?
Could be seen as a foreign invader and attacked by the mother’s immune system - white blood cells could swarm to devour it
How does the striped blastocyst try and prevent being seen as a foreign invader?
Produces several chemicals that suppress the mother’s immune system so that it is free to search for food and oxygen
What is gastrulation?
The process in which cells start to organize themselves into an embryo
Where does gastrulation occur?
Mother’s uterine lining
What occurs during gastulation?
1) Blastocyst creates 2 oblong bubbles one on top of the other with a thin layers of cells between them
2) Some cells begin moving toward the centre, then they dive downwards, creating a new lower level
3) More cells plunge through squeezing in between to form a third level
What is the lower level destined to form?
Structures like the lungs, liver, and the lining for the digestive tract
What will the middle layer form?
Heart, muscles, bones, and blood
What will the top layer create?
The nervous system, including the spinal cord and the brain, as well as an outer covering of skin, and eventually hair
How long is a human embryo 3 weeks after fertilization? What is happening during this time?
Less than a tenth of an inch; Beginning of the nervous system is in place, primitive brain cells exposed, cells multiplying, forming blood vessels, heart begins to beat
How long is a human embryo 4 weeks after fertilization? What is happening during this time?
A fifth of an inch; primitive backbone curls into a tail which will disappear in a few weeks, large brain and eyes develops
How do different cells do different jobs in different areas of the body?
Each cell has different groups of genes that are turned on or off when constructing a particular protein
What is collagen?
A fiber that makes up much of your skin, tendons, and bones
What is crystallin?
A protein that helps make the lens of your eye clear
What proteins move muscle fibers?
Actin and myosin
What does hemoglobin do?
Carries oxygen from the lungs to the rest of the body
How does a cell turn on the right set of genes to create the right protein?
Part of the answer seems to be location. Chemicals in one cell can trigger a reaction in the cell next door that can spread to the cell’s nucleus and turn genes on or off.
