Fertilization and Embryonic Development

Flashcards covering Fertilization and Early Embryonic Development.

What is fertilization?

The fusion of two haploid gametes, resulting in the formation of a diploid cell.

What is the state of the egg before fertilization?

Not fully mature, in a state of suspended animation (Metaphase II).

What two layers surround the egg upon ovulation?

Corona radiata and zona pellucida.

What is contained within the acrosomal cap of sperm?

Hyaluronidase and acrosin.

What is the role of hyaluronidase and acrosin?

To allow sperm to penetrate the corona radiata and zona pellucida.

What are the three stages of fertilization?

Penetration, activation, and fusion of nuclei.

How does the sperm penetrate the egg?

Using acrosomal enzymes to move through the corona radiata and zona pellucida to get to the egg membrane.

What initiates the activation stage of fertilization?

The fusion of sperm and egg membrane.

What occurs upon membrane fusion during fertilization?

Egg membrane becomes depolarized, preventing polyspermy, completion of Meiosis II, and increase in cell's metabolic rate.

What is amphimixis?

Fusion of the egg and sperm nuclei.

What is a zygote?

The cell formed after the fusion of egg and sperm nuclei, containing a full complement of 46 chromosomes.

What is cleavage?

A series of cell divisions that continue until the pre-embryo comes in contact with the uterine wall.

What are blastomeres?

The cells produced by cleavage.

What is a morula?

A solid mass of cells at the 32 cell stage produced by cleavages.

What is a blastula?

A hollow ball of cells formed once fluid forms within the morula.

What is the trophoblast?

The outer layer of the blastula that will provide nutrients to the developing cells.

What is the embryoblast?

The inner cell mass of the blastula.

When does implantation begin?

When the blastula comes into contact with the uterine wall.

What does the trophoblast secrete during implantation, and for what purpose?

Hyaluronidase, which allows the blastula to penetrate into the uterine lining.

What is decidua?

The maternal part of the placenta that develops from the endometrium of the uterus during pregnancy.

Amniotic cavity

Fluid-filled space that forms during implantation, surrounds and protects the developing embryo.

What is gastrulation?

The formation of the three primary germ cell layers: ectoderm, mesoderm, and endoderm.

What does the ectoderm form?

Epidermis of skin, skin glands, nails, sensory receptors in skin, cornea and lens of eye, nervous system, tooth enamel.

What does the mesoderm form?

Skeletal system, muscular system, circulatory system, and lymphatic system.

What does the endoderm form?

Epithelial lining of digestive system (except mouth and anus), epithelium of respiratory system, liver, and pancreas.

What are the extraembryonic membranes?

Structures that develop outside the embryo but are crucial for its development: yolk sac, amnion, chorion and allantois

What is the role of the yolk sac?

Important in blood cell formation and blood circulation development

What is the amnion?

The innermost layer surrounding the embryo, containing the amniotic fluid. Allows the fetus to move in later pregnancy and provides protection.