Implantation, Cleavage, 2nd Week of Development

Flashcards reviewing the key concepts of implantation, cleavage, and the second week of development.

What are Blastomeres?

Mitotic division results in these cells which are present during cleavage.

What are Trophoblasts?

The outer layer of cells in the morula that eventually forms part of the placenta.

What is the embryo?

The inner cell mass of the morula will eventually form what structure?

What is day 5-6?

The zona pellucida disappears around this day, allowing implantation to begin.

What is the 8-cell stage?

Up to what cell stage are cells considered totipotent?

What is the posterior wall of the body of the uterus close to the fundus?

The normal site of implantation in the uterus.

What are Syncytiotrophoblasts?

The cells that secrete proteolytic enzymes and HCG.

What are Syncytiotrophoblasts and Cytotrophoblasts?

The two layers formed from the division of trophoblasts.

What are Syncytiotrophoblasts?

The layer of trophoblasts that erodes the endometrium.

What is between the 5th and 10th day?

The approximate time frame for the completion of implantation.

What is the ectoderm?

The embryonic germ layer from which the epiblast is derived.

What is the endoderm?

The embryonic germ layer from which the hypoblast is derived.

What is the amniotic cavity?

The cavity that appears within the epiblast.

What is the exocoelomic (Heuser) membrane?

The membrane which lines the inner surface of the cytotrophoblast.

What is the primary yolk sac?

Another name for the exocoelomic cavity.

What is the bilaminar embryonic disc?

The location where the amniotic cavity and the primary yolk sac contact, forming this structure.

What are the epiblast and hypoblast?

The two layers that make up the bilaminar embryonic disc.

What is the yolk sac endoderm?

The source of primary or extra-embryonic mesoderm.

What is the lacunar network?

A network that is formed when clefts appear in the extra-embryonic (primary) mesoderm.

What is the extraembryonic coelom or chorionic cavity?

The cavity formed by the fusion of clefts in the extraembryonic (primary) mesoderm.

What are the somatic and splanchnic layers?

The two layers into which the extraembryonic (primary) mesoderm splits.

What is the primary yolk sac?

The yolk sac which starts shrinking during the second week.

What is the secondary (definitive) yolk sac?

The yolk sac which is forming as the primary yolk sac shrinks.

What are syncytiotrophoblast, cytotrophoblast, and somatopleuric layer of extraembryonic mesoderm (EEM)?

The three components of the chorion.

What is the end of the 2nd week?

Structure found during the second week; marks the appearance of primary villi.

What are the outer syncytiotrophoblast and the central core of cytotrophoblast?

The two layers which compromise the primary chorionic villus.

What is a secondary chorionic villus?

This structure is characterized by developing blood vessels within the chorionic villi.

What is the syncytiotrophoblast?

The components of the tertiary chorionic villi include connective tissue, capillaries and this outer layer.

What is maternal blood?

What type of blood fills the intervillous space?

What is the amniochorionic membrane?

The combination of the amnion and chorion membranes is known as what?

What is the decidua basalis?

The decidua related to the chorion frondosum.

What is the smooth chorion?

The part of the chorion wall where the villi degenerate.

What is the chorion frondosum?

The structure covered with multiple villi and related to the decidua basalis.

What is the Zona Pellucida?

Cleavage results in an increase in the number of cells, but not the overall size. What feature ensures this?

What is HCG?

Syncytiotrophoblasts secrete this substance that sustains the corpus luteum, crucial for maintaining pregnancy in early stages.

What is the posterior wall of the uterus?

Implantation typically occurs where?

What is the primary mesoderm?

This fills the space between the cytotrophoblast and the amnion and primary yolk sac.

What is the Chorion frondosum?

This structure forms the placenta along with the decidua basalis.

What is the chorion?

The extraembryonic somatic mesoderm, the cytotrophoblast, and the syncytiotrophoblast combine to form this.

What is the secondary yolk sac?

As the primary yolk sac shrinks, this other yolk sac forms. What is it called?

What is totipotent?

The cells of the morula are considered this, meaning they can differentiate into any cell type.

What is the blastocyst cavity?

The cavity within the blastocyst.

What are proteolytic enzymes?

These enzymes are secreted by the syncytiotrophoblast to erode the endometrium during implantation.