What are the steps of fertilization?
- Sperm meets egg and secretes acrosome
- Digestive enzymes of acrosome degrades protective zona pellucida layer
- Sperm penetrates and delivers nuclueus
- Zona pellucida instantly hardens becoming impermeable to any other sperm
- Meoisis 2 is completed
Cleavage begins immediately at _____ and consists of what 3 stages?
- 2-cell, 4-cell, and 8-cell stages.
Cleavage is the...
rapid mitosis/division of the zygote upon fertilization
Cells during the cleavage stage are _____.
If a cell is pleuripotent, it means...
that it has the potential to develop to be any cell in the body.
Cell pleuripotentcy is lost at what stage of cleavage?
What occurs during the 2-cell stage of cleavage?
- Proteins shift to one side
- Cell splits in two
- Protein per side may differ
What do the proteins in zygote regulate?
- Gene expression
- The ability of cells to make certian proteins
What are the characteristics of differentiation and determination?
- Fate of what cells will become is determined
- Some genes are turned off
- This gives cells identity and function
True or False
As rapid mitosis occurs, the zygote continues to grow.
It stays the same size
What are the three stages of prenatal development?
- Preembryonic stage
- Embryonic stage
- Fetal stage
The preembryonic stage is subdivided into what four parts?
A single diploid cell formed by the union of egg and sperm
- Mitotic division of the zygote into smaller, identical blastomeres
A speroidal stage consisting of 16 or more blastomeres
- Fluid filled, spheroidal stage with an outer mass of trophoblast cells and inner mass of embryoblast cells
- Becomes implanted nt he endometrium
- Inner cell mass forms embryonic disc and
- differentiates into three primary germ layers
- A stage in which the primary germ layers differentiate into organs and organ systems
- Ends when all organ systems are present
A stage in which organs grow and mature at a cellular level to the point of being capable of supporting life independently of the mother.
The morula cells secrete fluid to form a _____, which form __ to __ days after fertilization.
In a blastocyst, the inner layer is called the _____ and will become the ____. The outer cell layer consists of _____, which will become the _____.
inner cell mass, embryo, trophoblasts, embryonic membrane
What are the four extra embryonic membranes? Give description of each.
- Chorion; outermost layer which fuses with endometrium upon implantation and will become placenta
- Amnion; fluid filled sac around embryo
- Yolk sac; non-functional
- Allantois; non-functional
In its early development, the zygote gets its nutrients directly from the _____.
At what part of the preembryonic stage does implantation occur?
Around day 15, the embryonic disc forms a thickened cell layer called the _____ along the midline.
Cells migrate toward and into the primative streak to form...
three germ layers.
Name the 3 primary germ layers that form from the primative streak.
The ectoderm germ layer is the _____ layer and will become _____.
outer, skin and nervous system
The mesoderm germ layer is the _____ layer and will become _____.
middle, connective tissues and muscles
The endoderm germ layer is the _____ layer and will become _____.
inner, digestive system
The end of gastrulation is at __ days, and the zygote becomes ____.
16, an embryo