Questions and Answers
What is primarily responsible for maternal recognition of pregnancy in mares?
The placenta is a temporary organ formed by fetal tissues only.
False
What is the primary function of the amnion in fetal membranes?
mechanical protection and hydration
The __________ is essential for the exchange of nutrients and oxygen between the mother and fetus.
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Which of the following is NOT a function of the placenta?
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Match the following fetal membranes with their functions:
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The umbilical cord contains two veins and one artery.
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What occurs during the post-implantation phase of placental development?
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Which of the following describes the type of placentation found in canines and felines?
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Chorionic gonadotrophin is responsible for the immune response during pregnancy.
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What is the primary source of progesterone during pregnancy in sheep?
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In ruminants, the type of placentation is referred to as __________.
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Match the following species with their primary source of progesterone during pregnancy:
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What role does relaxin play during pregnancy?
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Which component is primarily involved in feto-maternal exchanges?
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Feto-maternal exchanges are totally independent of the degree of connection between fetal and maternal components.
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Equine chorionic gonadotrophin is produced by the fetus.
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What is the source of vascular supply for the chorio-vitelline placenta?
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Name one hormone that regulates glucose metabolism during pregnancy.
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The type of tissue involvement in pregnancy for pigs is referred to as __________.
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The tissue layer number in the fetal and maternal components affects the __________ of tissues involved in pregnancy.
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What is the function of estrogens during pregnancy?
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Match the classification of placentation with their characteristics:
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Which type of placenta allows for no transfer of antibodies or immune cells to the fetus?
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In the syndesmo-chorial placenta, chorionic villi erode the uterine wall, allowing contact with maternal blood.
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Name an animal that has a haemo-chorial placenta.
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The _____ type of placenta is characterized by fetal capillaries lying freely in maternal blood.
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Match the type of placentation with its description:
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What feature distinguishes haemo-chorial placenta from other types?
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In endothelio-chorial placentation, 100% of maternal antibodies are transferred to the fetus.
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Which group of animals demonstrates the epithelio-chorial type of placentation?
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In _____ placenta, the yolk sac disappears, and the allantois fuses with the chorion.
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Which type of placentation is typical in dogs and cats?
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Study Notes
Maternal Recognition of Pregnancy
- Maternal recognition occurs by blocking luteolysis, essential for maintaining pregnancy.
- The initial cycle appears similar for pregnant and non-pregnant individuals within the first 14 days.
- Suppression of PGF2α is crucial for preventing luteal regression.
- Mechanisms for maternal recognition vary by species and involve factors such as embryo mobility, interferon tau (IFNT), estrogens, and chorionic gonadotropin.
Attachment and Implantation
- Placenta formation involves attachment (placentation) where the blastocyst hatches and adheres to the uterine wall.
- The placenta acts as a temporary organ formed by extraembryonic membranes, including the trophoblast, extraembryonic mesoderm, and extraembryonic ectoderm.
- Key functions of the placenta include protection, nutrition, respiration, excretion, and hormone production.
Fetal Membranes in Domestic Animals
- Yolk sac provides nutrition and plays a role in sex differentiation; its fusion with chorion forms a yolk-sac placenta.
- Amnion contains amniotic fluid crucial for mechanical protection and temperature regulation for the fetus.
- The umbilical cord comprises one vein and two arteries, providing essential nutrients and waste management for the embryo.
- Allantois facilitates gas exchange and collects secretions from the embryo.
Placenta Development Stages
- Pre-implantation phase involves differentiation of embryonic cells into the inner cell mass (ICM) and trophoblast.
- During implantation, the blastocyst hatches and trophoblast cells invade the endometrium.
- Post-implantation marks the establishment of blood circulation between mother and fetus.
- At pregnancy's end, exchange between maternal and fetal circulations reduces, leading to parturition.
Types of Placenta
- Chorio-allantoic placenta involves fusion of the allantois with chorion while the yolk sac disappears; typical in marsupials and eutherian mammals.
Degrees of Involvement of Fetal and Maternal Tissues
- Epithelio-chorial: Chorionic epithelium remains in contact with uterine epithelium; no transfer of antibodies. Present in pigs, horses, and camels.
- Syndesmo-chorial: Chorionic villi contact uterine wall connective tissue without direct antibody transfer; found in ruminants like sheep and cows.
- Endothelio-chorial: Erosion of uterine epithelium and connective tissue allows some antibody transfer; seen in dogs and cats.
- Haemo-chorial: Erosion allows chorionic villi to bathe in maternal blood, facilitating IgG transfer; noted in humans and rodents.
- Haemo-endothelial: Fetal capillaries lie freely in maternal blood, allowing full antibody transfer.
Endocrinology of the Placenta
- Progesterone is crucial for maintaining pregnancy and is produced by the placenta in some species, but the corpus luteum remains the main source in others.
- Estrogens trigger placenta development and fetal organ formation.
- Relaxin loosens pelvic muscles for delivery preparation.
- Placental lactogen regulates maternal metabolism for nutrient transport to the fetus.
- Chorionic gonadotropin assists in maternal recognition of pregnancy.
Progestogen Requirements
- Species-specific sources of progesterone during pregnancy include:
- Sheep: Placenta
- Goat, cow, dog, cat, pig, rat/mouse: Corpus luteum
- Mare, primate, guinea pig: Feto-placental unit
Feto-Maternal Exchanges
- Vascular supply originates from yolk sac or allantoic circulation; the connection between fetal and maternal tissues influences exchange efficiency.
Placental Classification
- Types of placentation vary by species regarding vascular supply, tissue involvement, and intimacy of attachment.
- Classification includes chorio-vitelline placenta in marsupials characterized by a highly vascular yolk sac that fuses with the chorion.
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Description
Explore the intricate details of maternal recognition of pregnancy, particularly in mares. This quiz covers key mechanisms like luteotropic actions and the role of interferon tau in embryo mobility. Test your knowledge on the differences between pregnant and non-pregnant cycles during the early stages of gestation.
