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Questions and Answers
What occurs after the merging of the ovum and sperm genetic material?
What occurs after the merging of the ovum and sperm genetic material?
- The separation of the genetic material into two distinct cells
- The formation of a 16-cell embryo
- The immediate growth of the embryo into a fetus
- The formation of a single cell with combined genetic material (correct)
What is the primary function of peristaltic contractions in the reproductive process?
What is the primary function of peristaltic contractions in the reproductive process?
- To transport the embryo to the uterus (correct)
- To regulate hormone production
- To facilitate fertilization
- To induce embryonic growth
What is the characteristic of the embryo during the cleavage stage?
What is the characteristic of the embryo during the cleavage stage?
- No cell division or growth
- Cell division without significant growth (correct)
- Rapid growth accompanied by cell division
- Cell growth without division
What is the approximate duration of time it takes for the embryo to reach the uterus after fertilization?
What is the approximate duration of time it takes for the embryo to reach the uterus after fertilization?
What is the primary factor controlling the contractions that transport the embryo to the uterus?
What is the primary factor controlling the contractions that transport the embryo to the uterus?
What is the consequence of the fluid collection inside the embryo during the cleavage stage?
What is the consequence of the fluid collection inside the embryo during the cleavage stage?
Where does the fertilized egg attach in the uterus?
Where does the fertilized egg attach in the uterus?
How many days after fertilization does implantation typically occur?
How many days after fertilization does implantation typically occur?
What hormone primarily controls the uterus during the period of cleavage?
What hormone primarily controls the uterus during the period of cleavage?
What is the primary function of the endometrium during embryonic development?
What is the primary function of the endometrium during embryonic development?
How long does it take for the embryo to implant in the uterus in bovine species?
How long does it take for the embryo to implant in the uterus in bovine species?
What is the term for the movement of the embryo from one horn of the uterus to the other in porcine species?
What is the term for the movement of the embryo from one horn of the uterus to the other in porcine species?
When does the embryo become fixed in its location in the uterus in ruminant species?
When does the embryo become fixed in its location in the uterus in ruminant species?
What is the term for the failure of the corpus luteum to regress, preventing pregnancy?
What is the term for the failure of the corpus luteum to regress, preventing pregnancy?
What is the primary function of the placenta during pregnancy?
What is the primary function of the placenta during pregnancy?
Which of the following extraembryonic membranes is responsible for bringing blood vessels to the chorion?
Which of the following extraembryonic membranes is responsible for bringing blood vessels to the chorion?
What is the term for the process by which the fertilized ovum migrates to the uterine horn?
What is the term for the process by which the fertilized ovum migrates to the uterine horn?
What is the main purpose of the yolk sac in mammals?
What is the main purpose of the yolk sac in mammals?
What is the term for the remnants of the placenta that are expelled from the mother's body after birth?
What is the term for the remnants of the placenta that are expelled from the mother's body after birth?
What is the name of the cavity that forms between the amnion and the chorion?
What is the name of the cavity that forms between the amnion and the chorion?
Which extraembryonic membrane is responsible for protecting the embryo from injury?
Which extraembryonic membrane is responsible for protecting the embryo from injury?
What is the term for the process by which the fertilized ovum becomes fixed in the uterine horn?
What is the term for the process by which the fertilized ovum becomes fixed in the uterine horn?
What is the primary function of the allantois in embryonic development?
What is the primary function of the allantois in embryonic development?
What is the term for the fluid-filled space between the amnion and the chorion?
What is the term for the fluid-filled space between the amnion and the chorion?
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Study Notes
Fertilization and Early Development
- After fertilization, the chromosomes of the ovum and sperm unfold and merge, determining the embryo's characteristics.
- The merged genetic material forms one cell, called a zygote.
- The zygote undergoes multiple divisions without significant growth, known as cleavage.
Cleavage and Implantation
- During cleavage, the embryo divides many times, forming a 2-cell, 4-cell, 8-cell, and 16-cell embryo.
- The embryo enters the uterus as a 16-cell embryo in 3-4 days.
- Peristaltic contractions transport the embryo to the uterus, controlled by a balance of estrogen and progesterone.
- The embryo attaches to the upper 1/3 of the uterus, and the female is said to be pregnant within 3 to 5 days of fertilization.
Early Stages of Development
- The embryo, now called a blastocyst, begins to elongate, ending the period of cleavage.
- The uterus changes in preparation for implantation, primarily under the control of progesterone.
- Progesterone decreases muscle tone and increases secretory capacity of the endometrium, supplying the embryo with carbohydrates and proteins.
Uterine Location and Elongation
- The blastocyst's uterine location varies by species: bovine (9-11 days), equine and ovine (7-8 days), and porcine (6 days).
- Intrauterine migration occurs, with fixation in the cow and ewe being rare, and transuterine migration in the mare beginning on day 10.
Placenta Development
- The placenta develops in the uterus during pregnancy, providing nourishment and oxygen to the growing baby and removing waste.
- The placenta is also referred to as the afterbirth, as it is excreted from the body following birth.
Extraembryonic Membranes
- Four extraembryonic membranes form during differentiation: amnion, allantois, chorion, and yolk sac.
- The amnion is a fluid-filled, non-vascular membrane that provides a protective cushion and ruptures at birth.
- The allantois fuses with the chorion, bringing blood vessels to the chorion.
- The chorion is the outermost membrane, attached to the mother and providing a site for gas and nutrient exchange.
Germ Layers and Organ Development
- Three primary germ layers form: ectoderm, mesoderm, and endoderm.
- Each germ layer gives rise to different organs and tissues, such as the central nervous system, sense organs, digestive system, and more.
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