human egg cells

egg production

Egg production takes place in the ovaries. It takes several steps to make an egg: 1. Before birth, special cells in the ovaries go through mitosis (cell division), producing identical cells. 2. The daughter cells then start to divide by meiosis. But they only go through the first of the two cell divisions of meiosis at that time. They go through the second stage of cell division after the female goes through puberty. 3. In a mature female, an egg develops in an ovary about once a month. The drawing below shows how this happens ( Figure 1.1). As you can see from the figure, the egg rests in a nest of cells called a follicle. The follicle and egg grow larger and go through other changes. The follicle protects the egg as it matures in the ovary. After a couple of weeks, the egg bursts out of the follicle and through the wall of the ovary. This is called ovulation, which usually occurs at the midpoint of a monthly cycle. In a 28 day cycle, ovulation would occur around day 14. The moving fingers of the nearby fallopian tube then sweep the egg into the tube. At this time, if sperm are present the egg can be fertilized. Fertilization occurs if a sperm enters the egg while it is passing through the fallopian tube. When this happens, the egg finally completes meiosis. This results in two daughter cells that are different in size. The smaller cell is called a polar body. It contains very little cytoplasm. It soon breaks down and disappears. The larger cell is the egg. It contains most of the cytoplasm. This will develop into a child.

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eggs and egg production

When a baby girl is born, her ovaries contain all of the eggs they will ever produce. But these eggs are not fully developed. They develop only after she starts having menstrual periods at about age 12 or 13. Just one egg develops each month. A woman will release an egg once each month until she is in her 40s. A girl is born with over a million eggs. They die off and by puberty about 40,000 remain.

eggs

Eggs are very big cells. In fact, they are the biggest cells in the human female body. (How many egg cells are in the human male body?) An egg is about 30 times as wide as a sperm cell! You can even see an egg cell without a microscope. Like a sperm cell, the egg contains a nucleus with half the number of chromosomes as other body cells. Unlike a sperm cell, the egg contains a lot of cytoplasm, the contents of the cell, which is why it is so big. The egg also does not have a tail.

instructional diagrams

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questions

eggs are the biggest cells in the female and male body.

a. true

-->  b. false

the follicle protects the egg while it matures in the fallopian tube.

a. true

-->  b. false

in a 28 day cycle, ovulation would usually occur around day

a) 1.

b) 7.

-->  c) 14.

d) 21.

just prior to ovulation, the egg is inside the

a) immature follicle.

-->  b) mature follicle.

c) corpus luteum.

d) polar body.

after ovulation, an egg enters the

a) ovary.

-->  b) fallopian tube.

c) corpus luteum.

d) uterus.

if sperm are present, an egg will be fertilized while it is in the

a) ovary.

b) uterus.

-->  c) fallopian tube.

d) follicle.

a human body cell has 46 chromosomes. how many chromosomes are present in an egg cell?

a) 1

-->  b) 23

c) 46

d) 92

diagram questions

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