Fertilisation & Implantation HARD MCQ

Fertilization typically takes place in the ampullary region of the fallopian tube. This area has folds that slow down the egg's movement, providing a conducive environment for sperm to meet the egg.

Hyaluronidase, released by the acrosome of the spermatozoa, breaks down the hyaluronic acid in the corona radiata, allowing sperm to reach the zona pellucida.

The zona pellucida contains proteins, mainly ZP3, that are specific to a particular species. This prevents fertilization by sperm from different species.

The acrosome releases enzymes, like acrosin, that digest the zona pellucida, allowing the sperm to penetrate the egg.

The perivitelline space is between the zona pellucida and the egg's plasma membrane. Sperm can penetrate the zona pellucida and reach this space, but only one spermatozoa will attach to the egg's plasma membrane.

The sperm attaches to the microvilli of the oocyte's plasma membrane by binding to specific receptors on the oocyte's membrane using antigens present on its head.

Once the sperm's plasma membrane fuses with the egg's, the sperm's head, midpiece, and tail enter the cytoplasm of the egg but the mitochondria remain outside.

Polyspermy occurs when multiple sperm fertilize a single egg. This is prevented by the release of granules from the egg that create a barrier to other sperm.

The outer layer of cells in a blastocyst that contributes to the formation of the placenta. It is responsible for implantation in the uterine wall and helps establish communication with the mother.

The cluster of cells inside the blastocyst that will develop into the embryo proper. It is the source of all embryonic tissues.

The fluid-filled cavity that forms within the blastocyst. It is formed by the passage of fluids from the fallopian tube through the zona pellucida into the embryo.

An immunosuppressant protein produced by the trophoblast to prevent the mother's immune system from rejecting the embryo, which carries the father's genetic information.

The part of the inner cell mass that will give rise to the embryonic tissues, such as the organs and systems of the body.

The series of rapid cell divisions that occur after fertilization, resulting in an increase in the number of blastomeres but not an increase in the overall size of the embryo.

The shift in genetic control during embryonic development where the embryo gradually transitions from relying on maternal genetic material to its own genetic material.

A condition that occurs when a cell line in an embryo has a different number of chromosomes or genetic material leading to cells with different genetic makeup. This can occur during cleavage.

The process where the tightly packed genetic material in the male nucleus becomes decondensed, allowing for the formation of the male pronucleus. This involves increased nuclear membrane permeability, loss of protoamines, chromatin spreading, and demethylation of paternal DNA.

The fusion of the male and female pronuclei, resulting in a single cell with a complete set of chromosomes (23 from each parent). This marks the beginning of a new individual.

Fertilization triggers the oocyte to complete its second meiotic division, restores the diploid chromosome number, determines the genetic sex of the offspring, introduces genetic variation, and activates the egg's metabolism, initiating cleavage.

The zona pellucida is a protective layer surrounding the egg cell that plays various roles, including promoting oocyte maturation, preventing polyspermy, initiating the acrosomal reaction, acting as a filter during cleavage, serving as an immunological barrier, keeping blastomeres together, facilitating trophoblast differentiation, and preventing premature implantation.

The individual cells produced during cleavage are called blastomeres. When 16 blastomeres are formed, they arrange themselves into a compact ball called a morula.

A process during cleavage where blastomeres tightly adhere to each other, maximizing cell-cell contact. This is facilitated by adhesion molecules like E-cadherin-catenin complexes.

As blastomeres compact and multiply, some remain in contact with the zona pellucida and are called outer blastomeres. Those not in contact are called inner blastomeres.

The epiblast is the dorsal layer of the bilaminar germ disc. It forms the amniotic cavity and is responsible for the development of the embryo and amnion.

The hypoblast is the ventral layer of the bilaminar germ disc. It forms the yolk sac and contributes to the extraembryonic mesoderm.

The fluid-filled cavity formed within the epiblast, which will eventually surround the developing embryo.

A sac formed from the hypoblast, which provides early nourishment to the embryo in some species.

The parietal endoderm, formed by cells of the hypoblast lining the inner surface of the trophoblast.

A layer of mesoderm derived from the hypoblast, that supports the amnion, yolk sac, and chorion.

The outer wall of the blastocyst, composed of the extraembryonic mesoderm and cytotrophoblast.

A cavity formed within the chorion, eventually surrounding the amnion and yolk sac.

The outer, invasive layer of the trophoblast, formed by the fusion of trophoblast cells. It erodes the endometrium, allowing the blastocyst to burrow in.

The inner layer of the trophoblast, cells that haven't fused. It contributes to the formation of the placenta.

Spaces within the syncytiotrophoblast that fill with maternal blood, supplying the embryo.

Changes in the endometrium, involving the maternal cells, that create a supportive environment for the embryo.

A hormone produced by the trophoblast that maintains the corpus luteum, ensuring continued progesterone production.

Factors that promote the invasion of the trophoblast, allowing implantation.

Factors that limit trophoblast invasion, preventing it from reaching the myometrium (muscle layer).

The amniotic cavity is a fluid-filled sac that develops around the embryo, forming the amniotic membrane. This sac provides cushioning and protection for the developing embryo.

Tertiary villi are the final stage of villus development. They are formed when blood vessels from the extraembryonic mesoderm connect to the embryo's circulation. This allows for exchange of materials between the mother and the developing embryo.

The placenta is the organ responsible for nutrient and oxygen exchange between the mother and the embryo. It allows the embryo to receive essential nutrients and oxygen from the mother's blood and release waste products back into the maternal circulation.

Spontaneous abortion, or miscarriage, is the natural loss of a pregnancy before the 20th week of gestation. It commonly occurs in the first trimester.

Chromosomal abnormalities are the most common cause of spontaneous abortion, particularly in the first trimester. Other causes include failure of blastocyst implantation and maternal conditions.

Adhesion molecules are proteins on the surface of the blastocyst and the uterine lining. They help the blastocyst attach to the uterine wall, initiating the process of implantation.

Embryos with neural tube defects, cleft lip, and cleft palate have a higher risk of spontaneous abortion due to developmental abnormalities that may affect the embryo's survival.

After the 10th week of gestation, spontaneous abortion can be caused by fetal, placental, or maternal factors.