18 Questions
Which hormone is primarily responsible for preparing the uterus for implantation of the fertilized egg?
Progesterone
How long does it typically take for the ovum to reach the uterus after ovulation?
3-4 days
What is the primary function of the zona pellucida, corona radiata, and sticky matrix that surround the freshly released ovum?
To guide the sperm towards the ovum during fertilization
What is the primary purpose of the fertilization process?
All of the above
What is the primary function of the corpus luteum during the ovarian cycle?
To secrete progesterone
What is the primary function of the placenta during pregnancy?
All of the above
What is the term for the process by which the bilaminar embryo is converted into a Trilaminar embryo?
Gastrulation
What occurs prior to the attachment of the blastocyst during implantation?
Shedding of zona pellucida
What type of eggs do birds and reptiles lay outside the body?
Eggs with large amount of yolk
Which marks the reorganization of cells of the morula into inner cell mass and outer Trophoblast?
Formation of blastocyst
What is the term for a ‘mosaic’ offspring resulting from the introduction of a blastomere from a different strain into a blastocyst?
Mosaicism
What is the term for the series of mitotic division resulting in blastomeres and morula formation?
Cleavage
What is the duration of the cleavage process in human development?
6 days
What is the term used to describe each of the divided cells of the zygote?
Blastomere
What is the stage of development where the blastomeres become 'compacted' and reorganized?
Morula
What is the term used to describe the cavity that forms within the morula as it migrates and uterine fluid moves in?
Blastocyst cavity
What is the name of the two distinct cell types that form in the blastocyst embryo as a result of 'segregation'?
Embryoblast and Trophoblast
What property do the blastomeres up to the 8-cell stage possess, according to the 'deletion experiment' described in the text?
Totipotent
Study Notes
Fertilization and Cleavage
- Mosaicism occurs when a blastomere of a different strain is introduced into a blastocyst, resulting in an offspring with color markings characteristic of the introduced strain.
- In mammals, eggs contain a small amount of yolk and depend on placental development for intrauterine growth.
Implantation
- Prior to attachment, the zona pellucida is shed.
- Formation of the bilaminar embryo consists of the hypoblast and epiblast.
Gastrulation
- Gastrulation is the beginning of morphogenesis, occurring during the 3rd week.
- It begins with the formation of the primitive streak on the surface of the epiblast.
- Gastrulation converts the bilaminar embryo into a trilaminar embryo.
Ovarian Cycle and Ovulation
- The ovarian cycle is a 28-day cycle with four phases of endometrial change: menstrual, proliferative, secretory, and pregnancy or gravid.
- Ovulation occurs at mid-cycle (day 14), and the freshly released ovum is surrounded by the zona pellucida, corona radiata, and a sticky matrix cover.
Fertilization
- Fertilization is a complex sequence of coordinated molecular events that restores the normal diploid number of chromosomes.
- It determines the chromosomal sex (XY or XX) of the embryo and results in a genetically unique product due to the mingling of maternal and paternal chromosomes.
Cleavage
- Cleavage is a slow 6-day process in humans as the zygote moves through the uterine tube.
- Each cell of the divided zygote is called a blastomere.
- Compaction occurs at the 8-cell stage, and the blastomeres become progressively smaller.
- The morula is a 32-cell stage compacted embryo (day 4).
Properties of Cleaving Embryo
- Deletion experiment: removing one blastomere or killing one still results in the development of normal offspring.
- Addition experiment: transferring one blastomere into a different color mother results in normal offspring of the original color mother.
Explore concepts such as blastomeres, mosaicism, implantation, and embryonic development in lower animals through this quiz. Learn about the transmission of traits and the development of 'mosaic' offspring with distinct characteristics.
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