Term
| What is the relation between gametogenesis, spermatogenesis and oogenesis? |
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Definition
Gametogenesis is the creation of gametes, it can be specified further into:
1. Spermatogenesis - The creation of sperm
2. Oogenesis - The creation of eggs (ovum) |
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Term
Describe the process of sperm creation and development. What are sperm cells called:
1) Before meiosis
2) At the beginning of meiosis
3. After meiosis 1
4. After meiosis 2? |
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Definition
Spermatogonium (diploid cells) start in the outer layer of testes and move inward as they undergo meiosis.
Sperm starts out as spermatogonium, which turns into primary spermatocyte during Prophase I. After meiosis I, it becomes two secondary spermatocyte. After meiosis II it becomes four spermatid. They mature into sperm cells. |
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Term
| How do follicles relate to ovaries? How are eggs released into the oviduct? |
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Definition
| Follicles surround each egg in the ovaries. Once a month, one follicle bursts and is released into the oviduct. |
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Term
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Definition
| An oogonium diploid cell is turned into a primary oocyte (A DIPLOID CELL) before birth, during Prophase I. Once per month, Meiosis I occurs and ONE secondary oocyte is created (the other cell is a polar body and dies). After a second meiotic division, an ovum (egg) (A HAPLOID CELL) is produced and the other cell becomes a polar body and dies. |
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Term
| How does a sperm cell fuse with an egg? |
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Definition
The sperm stops outside a jelly like coating around the egg. The sperm's acrosome (cavity in head) releases enzymes that break down the jelly coat. This is called an acrosome reaction.
The sperm and egg membranes fuse, followed by their nuclei fusing. |
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Term
| What problem do cortical reactions eactions prevent? How do they do this? |
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Definition
Cortical reactions prevent polyspermy (more than one sperm binding with the egg).
In the reaction, cortical granuals (vesicles) in the egg fuse with the egg membrane and release their contents. This causes a hard, non-permeable exterior, called a fertilization envelope, to form around the egg. |
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Term
| What are the names for the poles at the top and bottom of a zygote? |
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Definition
| Top = animal, bottom = vegetal |
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Term
| Cleavage is the first step of development after the zygote is formed. What happens during this step? What is the relationship between blastomeres and morulas? |
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Definition
| During cleavage, the cell rapidly divides, but there is no net growth in embryo size. The new cells are called blastomeres. The new mass of cells together is called a morula. |
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Term
| What is a blastula? How does it relate to a morula? What is a blastocoel? |
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Definition
| A morula changed conformation to create a hollow ball with an outer layer of cells called a blastula (also called a blastosphere). The hollow part is called the blastocoel. |
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Term
| How does gastrulation and a gastrula relate to the previously formed blastula? |
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Definition
| A blastula undergoes gastrulation to form a gastrula. A gastrula has an ectoderm (outside), endoderm (inner, hollow tube) and mesoderm (middle, inside the gastrula). |
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Term
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Definition
1. One side of the blastula is indented to form a blastopore.
2. After more pushing in, an archenteron develops (crevice). This becomes the endoderm once its pushes all the way through the cell.
The gastrula that forms can be thought of as an orange that has a hole poked through it with a straw. |
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Term
| What is meroblastic and holoblastic cleavage? |
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Definition
Meroblastic cleavage is an off-center cleavage of the blastoceal.
Holoblastic cleavage is when the egg completely divides. |
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Term
In humans, a blastula is called a ___, and cleavage (endoderm development) occurs in the ___.
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Definition
| In humans, a blastula is called a blastocyst, and cleavage (endoderm development) occurs in the oviduct. |
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Term
| In humans, the outside layer of the blastocyst is called a ___. |
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Definition
| In humans, the outside layer of the blastocyst is called a trophoblast. |
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Term
| What is a placenta? What is its purpose? |
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Definition
| A placenta is a combination of blood cells fromt he mother and the embryo. It supplies nutrients to the embryo. |
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