Term
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Definition
| The process by which prospective endodermal and mesodermal cells move from the outer surface of the embryo to inside the embryo. |
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Term
| What does the ectoderm give rise to? |
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Definition
| Epidermis related structures (skin, nails, hair), brain and nervous system. |
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Term
| What does the mesoderm give rise to? |
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Definition
| The notochord, mesenchyme (bones and cartillage, circulatory system) and somites (muscle, excretory system). |
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Term
| What does the endoderm turn into? |
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Definition
| The embryonic gut (lining of digestive and circulatory tracts and glands) |
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Term
| Describe the structure of the blastula in a sea urchin. |
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Definition
| Inside the centre of the cell is the blastocel, which is a fluid-filled hole. Next out we come to the basal lamina, which is a lining before we reach the hollow ball of cells. At the vegetal pole and in a small region are the mesoderm cells, surrounded by endoderm cells and then the ectoderm (take up 2/3). The ball is coated with cilia cells and the hyaline layer. |
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Term
| How do we get from a blastula to a gastrula in a sea urchin? |
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Definition
- Mesoderm buds off inside the blastula forming the primary mesenchyme.
- The endoderm invaginates and the primary mesenchyme forms a ring around the invaginated gut and a vegetal extension forms.
- Secondary mesenchyne is ontop of the invagination- as it moves in towards the animal pole, forming a clear archenton (a big invagination).
- Filopodia extents from the secondary mesenchyme and contact the mesoderm wall at the animal pole where it fuses to form the mouth (The other hole is the anus).
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Term
| How do cells change shape during gastrulation? |
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Definition
| Caused by changes in the cells cytoskeleton (actin microfilaments, microtubules and intermediate fillaments) and proteins. |
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Term
How would we get an apical construction whereby the cell elongates?
What does this form in D.melanogaster? |
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Definition
A contractile network forms at one end of the cell, causing the cells to bundle together like an arch. This produces the invagination of the endoderm during gastrulation.
It forms the cleavage furrow. |
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Term
| What is differential cell adhesion? |
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Definition
| Caused by specific interactions between proteins in cell surface called cell-adhesion molecules. They are also called Cadherins, Immunoglobulin superfamily proteins and integrins. These attach themselves to proteins on adjacent cell surfaces or even the extracellular matrix. |
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Term
| Explain cadherins and immunoglobulin superfamily proteins. |
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Definition
| In the presence of Ca2+ ions they adhere to cadherins on the surfaces of other cells. ISP are calcium independant binding molecules. |
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Term
| Explain the experiment by Townes and Holtfreter. |
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Definition
| The ectoderm from the presumptive epidermis and from the presumptive neural plate of amphibian embryos are disaggregated to single cells by treatment with alkaline solution. When these cells are mixed together the respective positions are formed with the epidermal tissues on the outside. |
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Term
| Explain the adhesive specifity via cadherins. |
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Definition
| When cells are lined with different amounts of N-cadherin on their surface the cells with the higher amount will attract eachother and diplace the cells with lower amounts. Thus the cells with more N-cadherin will centralise and the cells with less N-cadherin will externalise via selective affinity. |
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