25 Questions
What is the process by which the bilaminar embryo is converted into a trilaminar embryo?
Gastrulation
What is the name of the structure that forms on the surface of the epiblast during gastrulation?
Primitive streak
What is the name of the two cell layers that form the bilaminar embryo?
Hypoblast and Epiblast
What is the name of the process by which the blastocyst attaches to the uterine wall?
Implantation
What is the name of the structure that forms the fetal part of the placenta?
Trophoblast
What is the process by which the trilaminar embryo is formed?
Gastrulation
Which of the following is NOT a part of the process of gastrulation?
Formation of the placenta
What is the role of the primitive streak in gastrulation?
It establishes the left-right symmetry of the embryo
Which of the following structures is formed during neurulation?
Neural tube
What is the correct sequence of events during early embryonic development?
Formation of the primitive streak, gastrulation, formation of the trilaminar embryo, neurulation
What is the name of the cellular structure found in the ovary where immature eggs mature, leading to ovulation?
Corpus Luteum
Which hormone stimulates the development of ovarian follicles, leading to the production of estrogen?
Follicle Stimulating Hormone (FSH)
What is the name of the structure that releases an ovum and later becomes the Corpus Luteum?
Ovary
Which level of hormonal control involves the Ovary and during pregnancy, the Placenta?
3rd level
What term describes the structure that contains a single immature ovum and is initiated to grow periodically resulting in one competent oocyte in humans?
Follicle
What is the name given to each cell of the divided zygote?
Blastomere
What process occurs during the 'compaction' stage of embryo development?
The blastomeres reorganize and adhere to each other
What is the name given to the stage of embryo development where a cavity forms within the morula?
Blastocyst
What are the two main cell types that make up the blastocyst stage of the embryo?
Trophoblasts and Embryoblast
What is the property of blastomeres up to the 8-cell stage of development?
Totipotent
Which of the following accurately describes the zonal reaction?
Cortical granules within the plasma membrane of the egg diffuse into the zona pellucida and hydrolyze sperm receptor molecules like ZP3, preventing additional sperm binding.
Which of the following is the correct sequence of events in fertilization?
Capacitation and acrosomal reaction, passage through corona radiata, penetration of zona pellucida, fusion of sperm and oocyte membranes, zonal reaction, pronucleus formation, zygote formation.
What is the significance of the zygote being genetically unique?
It ensures that the offspring inherits traits from both parents, allowing for variation within the species.
What is the process that results in an increase in cell number from the zygote?
Cleavage
Which of the following accurately describes the formation of the bilaminar embryo?
The bilaminar embryo is formed when the zygote divides into two cell layers: the epiblast and the hypoblast.
Study Notes
Embryonic Development
- Primitive streak formation:
- Results from proliferation and migration of epiblast cells to the median of the embryonic disc
- Establishes caudal-cranial direction, left-right symmetry, and dorsal-ventral sides in the embryo
- Gastrulation:
- Begins with the formation of the primitive streak on the surface of the epiblast
- Process by which the bilaminar embryo is converted into a trilaminar embryo
- Formation of Trilaminar Embryo:
- Involves the formation of notochord, somites, and neurulation
- Notochord Formation:
- Establishes the dorsal-ventral axis of the embryo
- Somite Formation:
- Gives rise to muscles, bones, and connective tissue
- Neurulation:
- Involves the formation of the neural tube, which will develop into the central nervous system
Fertilization
- Phases of Fertilization:
- Capacitation and acrosomal reaction
- Passage of sperm through corona radiata surrounding the zona pellucida
- Penetration of zona pellucida surrounding the oocyte
- Fusion of plasma membrane of sperm and oocyte
- Zonal reaction
- Prevention of Polyspermy:
- Cortical granules release enzymes that hydrolyze sperm receptor molecules, preventing additional sperm binding
- Formation of Pronucleus and Zygote:
- Female nucleus undergoes decondensation to form a pronucleus
- Sperm nucleus undergoes decondensation to form a pronucleus
- Fusion of male and female pronucleus forms a zygote with diploid (46) chromosomes
Cleavage
- Definition:
- Repeated mitotic divisions of the zygote, resulting in an increased number of cells
- Properties of Cleaving Embryo (Blastomeres):
- Totipotency: up to 8-cell stage, removing or killing one blastomere still results in normal offspring
- Ability to form a mosaic offspring if a blastomere of a different strain is introduced
- Morula:
- Compacted 32-cell stage embryo with an outer layer of trophoblasts and an inner cell mass (embryoblast)
- Blastocyst:
- Consists of an outer trophectoderm and an inner cell mass
- Cavity forms between the trophectoderm and inner cell mass, called the blastocyst cavity
Implantation
- Definition:
- Attachment of the blastocyst to the uterine wall
- Formation of Bilaminar Embryo:
- Reorganization of cells into hypoblast and epiblast
- Placentation:
- Development of the placenta, which provides oxygen and nutrients to the embryo
Gastrulation
- Definition:
- Process by which the bilaminar embryo is converted into a trilaminar embryo
- Formation of Three Germinal Layers:
- Ectoderm (outer layer), mesoderm (middle layer), and endoderm (inner layer)
Test your knowledge on concepts such as mosaicism, blastomeres, blastocysts, and embryo development in lower animals like sea urchins and drosophila. Learn about the process of introducing blastomeres of different strains into a blastocyst and the resulting 'mosaic' offspring with color markings.
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