Formation of Germ Layers and Fertilization

Fertilization of an ovum occurs in the ampulla of the uterine tube.

The fertilized ovum undergoes cell divisions (cleavage), and when it has 16 cells, it's a morula.

A morula develops into a blastocyst, containing an inner cell mass and trophoblast.

An embryonic disc with ectoderm, endoderm, and mesoderm arises from the inner cell mass, forming the three germ layers.

A cavity develops on the ectodermal side of the embryonic disc, forming the amniotic cavity.

A cavity forms on the endodermal side of the disc, called the yolk sac.

The trophoblast and underlying mesoderm create the chorion membrane.

Cells from the primitive streak differentiate into mesoderm, the middle germ layer between the ectoderm and endoderm.

DNA replication creates a second chromatid, making each chromosome double-stranded, ready for division.

The full set of chromosomes, restored to 46 after fertilization of egg and sperm.

The sex of a child is decided at fertilization. X-bearing sperm leads to a girl; Y-bearing, to a boy.

Human cells have 23 pairs of chromosomes. One chromosome from each pair comes from each parent.

The process where each chromosome splits into two, each containing identical genetic material

The spindle is a structure that forms in the cell during division to help move chromosomes.

The fertilized egg dividing into multiple cells. This is a key step after fertilization.

Sperm containing an X chromosome resulting in female offspring.

Cells produced after a parent cell divides.

A protective layer surrounding the oocyte or the embryo in the early stages of development.

A solid ball of cells formed during early embryonic development, resembling a mulberry.

Fertilization of an egg outside the body.

The inner cell mass of the blastocyst, which will develop into the embryo.

The outer layer of cells in a blastocyst that will form the placenta and other extra-embryonic tissues.

A baby conceived using in vitro fertilization (IVF).

The environment where fertilization and early embryo development occur.

Embryo placed inside the uterus after reaching this eight-celled stage during development.

Only about 20% of embryo transfers result in successful implantation.

Each egg cell (ovum) contains 22 chromosomes plus an X chromosome.

Sperm cells are categorized into two types based on their chromosome content (22+X or 22+Y).

The blastocyst has an embryonic (animal) pole where the inner cell mass attaches, and an abembryonic pole.

The zona pellucida prevents the embryo from sticking to uterine tissues while it travels to the uterus.

A thickened band of cells that forms on the dorsal surface of the embryonic disc during gastrulation. It is crucial for establishing the body axis and initiating development of the mesoderm.

The middle germ layer that arises from the primitive streak during gastrulation. It will give rise to various tissues and organs in the developing embryo, including muscle, bone, and blood.

Mesoderm that arises outside the embryo, specifically from the connecting stalk. It contributes to the development of structures like the amnion and chorion, supporting the growing embryo.

A structure attaching the embryo to the placenta. It contains blood vessels and serves as a conduit for nutrient exchange and waste removal.

The cavity that forms within the extra-embryonic mesoderm, surrounding the amnion and yolk sac. It plays a role in separation and protection of these structures.

A technique where the nucleus of a patient's cell is introduced into an embryonic stem cell, creating cells genetically identical to the patient. These cells can then differentiate into various cell types for treating diseases.

The process where stem cells, with potential to become various cell types, develop into specific types of cells like neurons, muscle cells, or blood cells, depending on the environmental factors.

Stem cells found in some adult tissues like bone marrow, brain, and skeletal muscle, with limited potential to differentiate into different cell types, compared to embryonic stem cells.

The first two weeks of pregnancy where the embryo develops but no organs are formed.

The embryo starts as a flat, two-layered structure with an outer ectoderm layer and an inner endoderm layer.

The process where the bilaminar disc transforms into a three-layered structure called the trilaminar disc.

The three-layered embryo structure formed during gastrulation, consisting of ectoderm, mesoderm, and endoderm.

The outer layer of the trilaminar disc that forms the skin, hair, and nervous system.

The middle layer of the trilaminar disc that forms muscles, bones, and the circulatory system.

The inner layer of the trilaminar disc that forms the lining of the digestive tract and lungs.

Birth defects that occur during embryonic development, often due to teratogens.