Early Embryonic Development

Flashcards covering early embryonic development, fertilization, cleavage, blastocyst formation, implantation, and stem cell differentiation.

Zygote

The single cell that results from the fertilisation of an egg by a sperm.

Mitosis in Early Cleavage

The cell division process by which a zygote divides into 2 identical cells, then 4, 8, 16, and so on as it travels down the uterine tube.

Blastocyst Arrival Time

By approximately 6 days after fertilisation, the zygote reaches the uterus and develops into a blastocyst.

Blastocyst

A hollow ball of cells that surrounds a fluid-filled cavity.

Inner Cell Mass

A group of approximately 30 stem cells within the blastocyst that will develop into the embryo.

Embryoblast

Another name for the inner cell mass of the blastocyst, composed of about 30 stem cells that develop into the embryo.

Free Blastocyst Stage Duration

The period of 2 to 3 days during which the blastocyst remains free in the uterus before implanting.

Implantation

The process where the blastocyst sinks into the endometrium to become firmly attached to the wall of the uterus.

Endometrium

The inner lining or wall of the uterus into which the blastocyst sinks during implantation.

Stem Cells

Cells capable of repeated division by mitosis that can differentiate into any specialised cell under the right conditions.

Proliferation

The process of repeated replication or division of stem cells.

Cell Differentiation

The process of unspecialised cells developing characteristics and functions of a particular cell.

Gene Activation in Stem Cells

The mechanism during stem cell proliferation where different genes become activated, resulting in differentiation into specialised cells.

Totipotent Stem Cells

Stem cells that can give rise to all the cell types that make up the human body and all the cell types that make up the membranes that surround the developing embryo (including the placenta).

Zygote Totipotency

The ability of the newly formed zygote to turn into any cell necessary for embryonic development.

Formation of Identical Twins

An event that occurs when two totipotent cells separate.

Pluripotent Stem Cells

Stem cells that can give rise to all the cell types that make up the body but not the cell types that make up the embryonic membranes.

Location of Pluripotent Stem Cells in Blastocyst

The inner cell mass of the blastocyst.

Multipotent Stem Cells

Stem cells that can develop into more than one of the cell types that make up the body but not all cell types.

Origin of Multipotent Stem Cells

Formed when pluripotent stem cells specialize.

Potency of Stem Cells Table

A summary classifying stem cells into Totipotent, Pluripotent, and Multipotent based on their cell-differentiation abilities.

Embryonic Period

The first 2 months of pregnancy.

Foetus

The developing individual after the second month of pregnancy.

Fertilisation

The union of an egg by a sperm to create a zygote.

Uterine Tube

The duct down which the zygote travels while dividing by mitosis toward the uterus.

Early Cleavage

The initial series of cell divisions of the zygote leading up to the 2-cell, 4-cell, and 8-cell stages.

Late Cleavage

The stage of repeated cell division following early cleavage prior to blastocyst formation.

Gelatinous Covering

The protective layer surrounding the egg that remains around the human embryo at the two-cell stage.

Two-Cell Stage Embryo

An early embryo formed after the first mitotic division of the zygote, still surrounded by the original gelatinous egg covering.

Embryonic Membranes

Membranes that surround the developing embryo, including the placenta, which totipotent stem cells can form but pluripotent stem cells cannot.

Placenta

An essential embryonic structure that can be formed from totipotent stem cells.

Ovulation

The release of an egg from the ovary.

Ovary

The female reproductive organ that releases the egg during ovulation.

Fertilisation to Implantation Pathway

The sequential process from egg ovulation in the ovary to fertilisation and cleavage in the uterine tube, ending with blastocyst implantation in the uterine endometrium.

Unspecialised Cells

Cells, such as stem cells, that have not yet developed specific characteristics or specialized functions.

Nerve Cell Differentiation

A specialized cell outcome of stem cell differentiation.

Cardiac Cell Differentiation

A specialized heart cell type produced from stem cell differentiation.

Liver Cell Differentiation

Specialized liver cell types produced when stem cells undergo differentiation.

Blood Cell Differentiation

Specialized blood cells produced through stem cell differentiation.

Blastocyst Cavity

The fluid-filled internal space enclosed by the hollow sphere of cells in a blastocyst.