EMBRYOLOGY: EARLY EMBRYO

Identify the three phases. What is capacitation? What does the process of capacitation involve? What is acrosome reaction?

This picture shows the three (3) phases of fertilization

The nucleus of the oocyte will form a female pronucleus while the sperm nucleus will form the male proncleus.

What will the two pronuclei form?

The picture shows the oocyte completing its second meiotic division in preparation for fertilization

What is the name of the process by which the zygote divides? What are the cells resulting from this division called?

The above pictures show the formation of the morula from a two-celled zygote.

The outer cell mass cells have differentiated into the inner cytotrophoblast and an outer syncytiotrophoblast.

What is the significance of the syncytiotrophoblast layer?

The picture shows the differentiation of the inner cell mass cells into the epiblast and hypoblast layers

What results in the formation of the blastocyst cavity? By implanting, what type of nutrition is the embryo seeking?

The picture shows the formation of the blastocyst cavity and the implantation of the blastocyst

What is the significance of this layer? What is found within the amniotic cavity?

The picture shows the formation of lacunae in the syntrophoblast layer as well as the formation of the exocoelomic membrane

What is the significance of this layer? What stage of development is depicted on this picture?

The picture shows the formation of the extra-embryonic mesoderm

What causes the maternal blood to flow into these lacunae? What is the significance of this utero-placenta circulation? What is an exocoelomic cyst?

The picture shows the flow of blood maternal into the lacunae

What is the name given to the new layer that is going to be formed?

This picture shows the process of gastrulation (primitive streak formation) in the embryo

What results in the formation of the primitive streak? On what day does the primitive streak form?

This picture shows the dorsal view of the embryo in the third week of development

What will the notochordal process form?

This picture shows the dorsal view of the embryo in the third week of development

Which structure induces the formation of the neural tube? What will the neural tube form in the adult?

The picture shows the process of neurulation

Which structure induces the condensation of this mesoderm?

The picture shows the condensation of intraembryonic mesoderm into the paraxial, intermediate and lateral plate mesoderm

What are the derivatives of the neural tube, notochord, intermediate and lateral plate mesoderm?

The picture shows the arrangement of the three germ layers in the embryo

Short essay questions Describe the embryonic formation of the morula. (6 marks) Describe the process of neurulation. (8 marks) Draw a schematic diagram showing the arrangement of the intra-embryonic

mesoderm following induction by the notochord. (6 marks)

Multiple choice questions The intraembryonic coelom forms

a) The secondary yolk sac. b) The exocoelomic cavity. c) The amniotic cavity. d) The pericardial cavity. e) The extraembryonic coelom.

The main results of fertilization are

a) Initiation of cleavage. b) Formation of the neural tube. c) Determination of a sex of an individual. d) Restoration of the diploid number of chromosomes. e) Formation of a blastocyst cavity.