Human Development Week 2

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Questions and Answers

What is the primary focus of the second week of human development?

Implantation of the blastocyst (correct)

Development of the placenta

Cleavage of the zygote

Formation of the morula

Which term describes the solid sphere of cells formed at around sixteen divisions of the zygote?

Trophoblast

Embryoblast

Blastocyst

Morula (correct)

What triggers the formation of the blastocole within the developing embryo?

Fusion of the morula cells

Expansion of the trophoblast layer

Absorption of nutrients from the uterine wall

Fluids penetrating the zona pellucida (correct)

During which phase does the blastocyst establish weak interactions with the uterine wall?

Period of apposition Signup and view all the answers

What happens to the zona pellucida once the blastocyst enters the uterus?

It degenerates to expose the trophoblast Signup and view all the answers

How frequently does cleavage division occur after the zygote's first division?

Every 12-24 hours Signup and view all the answers

What is the ultimate purpose of implantation during the second week of development?

To establish a source of nutrition Signup and view all the answers

What term refers to the inner cell mass of the blastocyst that will develop into the embryo?

Embryoblast Signup and view all the answers

What structure does the inner cell mass of the blastocyst ultimately develop into?

Embryo Signup and view all the answers

What are the two sub-layers that the trophoblast develops into?

Cytotrophoblast and syncytiotrophoblast Signup and view all the answers

What is the primary function of human chorionic gonadotropin produced by the syncytiotrophoblast?

To stimulate release of progesterone Signup and view all the answers

During which stage does the syncytiotrophoblast create vacuoles filled with blood?

Lacunar stage Signup and view all the answers

What is the role of progesterone in the early stages of embryo development?

To enrich the uterus with a thick lining Signup and view all the answers

What forms the bilaminar disc during blastocyst development?

Epiblast and hypoblast Signup and view all the answers

What triggers the endometrial lining to become thickened and vascularized after ovulation?

Progesterone secretion Signup and view all the answers

What mechanism allows the blastocyst to hatch from the zona pellucida?

Expansion of the blastocoel Signup and view all the answers

Study Notes

Second Week of Development

The second week of human development focuses on implantation and differentiation of the blastocyst.
The morula forms from the zygote after rapid cell division.
The morula develops into a blastocyst.
The blastocyst contains the inner cell mass (ICM) which forms the embryo and outer cells called the trophoblast.

Implantation

Implantation happens within the uterus.
The blastocyst attaches to the endometrial lining.
The zona pellucida degenerates, exposing the trophoblast.
The trophoblast interacts with the uterine wall.
There are three phases of implantation: apposition, attachment, and invasion.

Blastulation (Blastocyst Formation)

The trophoblast differentiates into two sub-layers: cytotrophoblast and syncytiotrophoblast.
The embryoblast differentiates into two layers: epiblast and hypoblast.
The amniotic cavity and yolk sac develop around the bilaminar disc.
The syncytiotrophoblast invades the maternal capillaries, creating uteroplacental circulation.

Placenta Development

The syncytiotrophoblast produces human chorionic gonadotropin (hCG).
hCG supports the corpus luteum, which produces progesterone.
Progesterone thickens the endometrial lining for the embryo.

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Description

Explore the crucial processes during the second week of human development, including implantation and blastocyst formation. This quiz covers the transition from zygote to morula, and the subsequent stages of implantation involving the trophoblast and endometrial interaction.