Ovulation Occurs in Two Phases
The first phase of the ovulation cycle is the follicular phase. It begins the first day of the last menstrual period (LMP) and stops at the next ovulation. This phase varies greatly for each woman.
The second phase is the luteal phase. It begins the day of ovulation and lasts until the next menstrual cycle begins. Governed by hormone release, it follows a more regular timeline of between 12 to 16 days following ovulation.
The day of ovulation determines the length of a menstrual cycle. The common belief that stress can affect the timing of a period is half true. Stress can affect ovulation which then affects hormone release which begins the next menstrual period ; but, stress around the time of an expected period will not make it late - that date was decided 12-16 days earlier.
What Is Going On Here?
Fertilization begins in the fallopian tube. An egg is fertilized and divides into a morula or "mulberry like" cluster or cells and then into a blastocyst - where the first cavity appears pushing cells to either the outside or inside. As the blastocyst falls, floating through the fallopian tube, about 70 - 75% will implant. Only upon implanting in the uterine wall will 58% have a chance of continuing on to a normal pregnancy.
Where are the Stem Cells?
The blastocyst embryo with its two cell types: the inner cells that can initiate all cells of the body, and the outer cells destined to become the placenta, is the source of embryonic stem cells (esc).
Embryonic Stem Cells (esc) have the potential to become any type of human body cell. Stem cells are the only cells of the body which divide into two unique entities. Typically when cells divide they produce an identical cell or "sister" cell. But stem cells make a new stem cell AND a new body type cell. This property makes them extremely unique.
Blastocysts only become available for use as stem cells when donated by couples using in-vitro fertilization (IVF) techniques. A woman in an IVF program who has multiple eggs fertilized in a petri dish, can choose to donate extra blastocysts to research. These stem cells are useful to children and adults needing interventions beyond conventional medicine.
When stem cells divide, one becomes a specialised cell,
while the other remains a stem cell. Specialised cells are
all the different cells in our body that perform a function.
They are all the cells we see on us and in us,
such as lung cells, skin cells, hair cells, and kidney cells."
When stem cells divide, one becomes a specialised cell,
while the other remains a stem cell. Specialised cells are
all the different cells in our body that perform a function.
They are all the cells we see on us and in us,
such as lung cells, skin cells, hair cells, and kidney cells." Roger Pedersen,Ph.D.
Professor of Regenerative Medicine,
Embryonic Stem Cells And Stem Cell Technology,
The Naked Scientists Interviews
Roger Pedersen PhD, Professor of Regenerative Medicine,
Embryonic Stem Cells And Stem Cell Technology,
The Naked Scientists Interviews
Egg being fertilized - 
