Early Human Development Quiz

Fertilization

• Acrosome reaction happens during the phase of fertilization when the sperm penetrates the oocyte.
• Penetration of the sperm through the corona radiata is known as canopus reaction.
• The event that occurs first in fertilization is the penetration of the sperm through the corona radiata.

Early Human Development

• On Day 3 of early human development, the fertilized ovum undergoes cleavage and forms a compact cluster of cells called a morula.

Polar Bodies

• The purpose of polar bodies in fertilization is to receive excess chromosomes, ensuring the fertilized ovum has the correct number of chromosomes.

Pronuclei

• After the pronuclei dissolve in fertilization, the genetic material from the sperm and oocyte combines to form a single nucleus.

Sex Determination

• The sex of the embryo in fertilization is determined by the sperm, which carries either an X or Y chromosome.

Pre-implantation Stages

• The correct sequence of events during the pre-implantation stages of human development is: fertilization, cleavage, morula, blastula, and blastocyst.

Blastocyst

• The blastocoele is a fluid-filled cavity within the blastocyst that provides a supportive environment for embryonic development.
• Blastomere cells in the blastocyst are specialized to form the embryoblast (inner cell mass) and trophoblast (outer cell layer).
• The embryoblast will form the embryonic tissues, while the trophoblast will form the placenta and other supporting tissues.

Bilaminar Embryo

• The bilaminar embryo consists of two layers: the epiblast and hypoblast.
• The epiblast will form the mesoderm and endoderm, while the hypoblast will form the amniotic sac and chorion.

Gastrulation

• During gastrulation, the primitive streak forms bilateral symmetry and is the site of future 'tail'.
• The primitive streak forms around day 14-15 of human development.
• The process by which the bilaminar disc elongates and forms the primitive streak is called gastrulation.
• The epiblast cells migrate through the primitive groove into the hypoblast during gastrulation, a process called ingression.
• The significance of gastrulation in development is the formation of the three primary germ layers: ectoderm, mesoderm, and endoderm.

Trilaminar Embryo

• The ectoderm gives rise to the nervous system, skin, and hair.
• The endoderm gives rise to the lining of the digestive tract and respiratory system.
• The mesoderm forms both embryonic tissues (notochord, bones, muscles) and extra-embryonic tissues (amnion, chorion).

Germ Layers

• The three primary germ layers formed during gastrulation are ectoderm, mesoderm, and endoderm.
• The mesoderm is NOT one of the primary germ layers formed during gastrulation (it is one of the three primary germ layers).