Difference between revisions of "Blastocyst Embryonic Development - Anatomy & Physiology"
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(New page: * In the Ootid, male and female pronuclei along with the first and second polar bodies are present. * Fusion of male and female pronuclei to form a single diploid nucleus ('''Syngamy''') *...) |
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| − | * In the Ootid, male and female pronuclei along with the first and second polar bodies are present. | + | * In the Ootid, male and female '''pronuclei''' along with the first and second '''polar bodies''' are present. |
| − | * Fusion of male and female pronuclei to form a single diploid nucleus ('''Syngamy''') | + | * Fusion of male and female pronuclei to form a single '''diploid nucleus''' ('''Syngamy''') |
| − | * Zygote (diploid) undergoes mitotic divisions ('''cleavage'''). | + | * '''Zygote''' (diploid) undergoes mitotic divisions ('''cleavage'''). |
* Cleavage gives rise to daughter cells called '''Blastomeres'''. | * Cleavage gives rise to daughter cells called '''Blastomeres'''. | ||
| Line 7: | Line 7: | ||
* Cleavage divisions continue and the 4-celled Embryo gives rise to an 8-celled Embryo. | * Cleavage divisions continue and the 4-celled Embryo gives rise to an 8-celled Embryo. | ||
* After the 8-celled stage, a ball of cells is formed. This stage is referred to as a '''Morula'''. | * After the 8-celled stage, a ball of cells is formed. This stage is referred to as a '''Morula'''. | ||
| + | * '''Tight junctions''' form between outer cells of the Morula. | ||
| + | * '''Gap junctions''' form between inner cells of the Morula. | ||
| + | * Thus, two groups of cells are created within the Morula. | ||
| + | * Outer cells pump Sodium into the intracellular spaces and water follows osmotically. | ||
| + | * Fluid begins to accumulate within the Morula. | ||
| − | + | * Cells of the Morula continue to divide and a '''Blastocyst''' develops, consisting of: | |
| − | * Cells of the Morula continue to | ||
** '''Inner Cell Mass''' (ICM) | ** '''Inner Cell Mass''' (ICM) | ||
** '''Blastocoele''' cavity | ** '''Blastocoele''' cavity | ||
** Single layer of '''Trophoblast''' cells | ** Single layer of '''Trophoblast''' cells | ||
| + | * As fluid accumulates, the outer cells become flattened and a cavity known as the Blastocoele is formed. | ||
| + | * Gap junctions connecting the inner cells of the Morula enable them to polarise as a group. | ||
| + | * As a result, two separate cellular components emerge - the Inner Cell Mass and the Trophoblasts. | ||
| + | |||
| − | * Blastocyst ''''hatches'''' from the ''' | + | * Blastocyst continues mitosis. |
| − | * Blastocyst free-floating within the Uterus. | + | * Fluid accumulates to fill the Blastocoele and pressure within the embryo increases. |
| + | * Concurrent with growth and fluid accumulation is the production of '''proteolytic enzymes''' by '''Trophoblastic''' cells. | ||
| + | * Enzymes weaken the '''Zona Pellucida'''. | ||
| + | * Blastocyst begins to contract and relax causing intermittent pressure pulses on the Zona Pellucida. | ||
| + | * Zona Pellucida ruptures with the development of a small fissure just large enough for the Blastocyst to squeeze out. | ||
| + | * Blastocyst ''''hatches'''' from the Zona Pellucida. | ||
| + | ** '''Rodent,Dog,Cat,Primate''': 8 days after fertilization | ||
| + | ** '''Ungulates''': 12 days after fertilization. | ||
| + | * Blastocyst free-floating within the Uterus, totally dependent on the Uterine environment for survival. | ||
Revision as of 14:06, 3 July 2008
- In the Ootid, male and female pronuclei along with the first and second polar bodies are present.
- Fusion of male and female pronuclei to form a single diploid nucleus (Syngamy)
- Zygote (diploid) undergoes mitotic divisions (cleavage).
- Cleavage gives rise to daughter cells called Blastomeres.
- Cleavage divisions continue and the 4-celled Embryo gives rise to an 8-celled Embryo.
- After the 8-celled stage, a ball of cells is formed. This stage is referred to as a Morula.
- Tight junctions form between outer cells of the Morula.
- Gap junctions form between inner cells of the Morula.
- Thus, two groups of cells are created within the Morula.
- Outer cells pump Sodium into the intracellular spaces and water follows osmotically.
- Fluid begins to accumulate within the Morula.
- Cells of the Morula continue to divide and a Blastocyst develops, consisting of:
- Inner Cell Mass (ICM)
- Blastocoele cavity
- Single layer of Trophoblast cells
- As fluid accumulates, the outer cells become flattened and a cavity known as the Blastocoele is formed.
- Gap junctions connecting the inner cells of the Morula enable them to polarise as a group.
- As a result, two separate cellular components emerge - the Inner Cell Mass and the Trophoblasts.
- Blastocyst continues mitosis.
- Fluid accumulates to fill the Blastocoele and pressure within the embryo increases.
- Concurrent with growth and fluid accumulation is the production of proteolytic enzymes by Trophoblastic cells.
- Enzymes weaken the Zona Pellucida.
- Blastocyst begins to contract and relax causing intermittent pressure pulses on the Zona Pellucida.
- Zona Pellucida ruptures with the development of a small fissure just large enough for the Blastocyst to squeeze out.
- Blastocyst 'hatches' from the Zona Pellucida.
- Rodent,Dog,Cat,Primate: 8 days after fertilization
- Ungulates: 12 days after fertilization.
- Blastocyst free-floating within the Uterus, totally dependent on the Uterine environment for survival.