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64 Cards in this Set
- Front
- Back
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What are 3 trimesters of fetal development?
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Germinal stage, embryonic stage, and fetal stage
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When is an ovum considered an ovum?
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Fertilization to hatching
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When is an embryo considered an embryo?
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From hatching to implantation
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When is a fetus considered a fetus?
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From implantation to parturition
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Describe the germinal stage
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2 cell --> 4 cell --> 8 cell --> morula --> blastocyst
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What is a morula?
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A round mass of blastomeres
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Describe the embryonic stage
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Blastocyst hatches and leaves zona pellucida. It is then free-floating within the uterus. Embryo undergoes massive growth.
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What causes the blastocyst to hatch?
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Growth & fluid inside, production of enzymes of trophoblast, and contraction of the blastocyst
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What are the extraembryonic membranes formed during the embryonic stage?
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Amnion, yolk sac, chorion, and allantois
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Which membrane is a fluid-filled protective sac for developing fetus?
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Amnion
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Which membrane contributes to the formation of the umbilical cord?
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Yolk sac
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Which membrane is the source for placental attachment?
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Chorion
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Which membrane is a fluid-filled sac that collects liquid waste from embryo?
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Allantois
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What do the allantois and chorion merge to form?
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Allantochorion, which is the fetal contribution to placenta
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What becomes the embryo proper?
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Inner cell mass
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What are the 2 major cell types in the trophoblast?
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Syncytiotrophoblast cells and cytotrophoblast cells
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What does the hatched blastocyst look like in the cow, ewe, and sow?
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Thread-like free floating embryo
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What does the hatched blastocyst look like in the mare?
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Spherical free floating embryo
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Where is the inner cell mass found?
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In the blastocoele
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What gives rise to the yolk sac?
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An evagination in the ventral portion of the embryo proper gives rise to the yolk sac
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How is the chorion formed?
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By fusion of the trophoblast and the primitive endoderm
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Where does the allantois develop from?
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From the primitive gut
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What regresses as the allantois begins to expand?
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Yolk sac
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What results from the fusion of the chorion edges?
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Amnion and amniotic cavity
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What are the 4 types of placenta?
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Diffuse, zonary, discoid, and cotyledonary
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What characterizes the diffuse placenta?
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Covered by chorionic villi
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What species have diffuse placenta?
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Horse, pig, and donkeys
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What characterizes cotyledonary placenta?
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Placentome, cotyledons, and caruncles
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What species have cotyledonary placenta?
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Cow, ewe, and goat
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What characterizes the zonary placenta?
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Central aggregation of chorionic villi near conceptus
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Which species have zonary placentas?
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Dog and cat
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What characterizes discoid placenta?
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Discs of chorionic villi
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Which species have discoid placenta?
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Rodents and primates
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Describe epitheliochorial placenta
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Maternal and fetal epithelium are intact, large surface area.
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Which species have epitheliochorial placentas?
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Mares and sows
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Describe the syndesmochorial placenta
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Maternal epithelium eroded; binucleated giant cells.
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Which species has syndesmochorial placenta?
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Ruminants
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Describe the endotheliochorial placenta
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Endometrial epithelium absent. Maternal capillaries exposed.
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Which species have endotheliochorial placenta?
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Dogs and cats
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Describe hemochorial placenta
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Fetal epithelium surrounded by maternal blood, very intimate.
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Which species has hemochorial placenta?
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Primates
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Describe hemoendothelial placenta
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Fetal capillaries surrounded by maternal blood (no direct exchange), most intimate
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Which species have hemoendothelial placentas?
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Rabbits and rodents
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What kind of placenta does a cow have?
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Cotyledonary
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How many cotyledons does a cow placenta have?
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70-120
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What structure do the cotyledons on a cow placenta have?
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Convex
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How many layers of tissue separate the fetal and maternal blood?
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5
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Are cotyledons on the fetal or maternal side?
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Fetal
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Where do cotyledons originate from?
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Trophoblasts
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What are cotyledons made up of?
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Blood vessels and CT
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Where are caruncles located?
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On the endometrium on the maternal side
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Characteristic of caruncles?
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Highly vascular
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What type of placenta do sows have?
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Diffuse
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Describe the diffuse placenta
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Uniform distribution of chorionic villi that cover the entire surface of the chorion (regions of nutrient transport)
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How many layers separate fetal and maternal blood?
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6
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What kind of metabolic exchanges occur through placenta?
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Nutrient and gas exchange
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How does the placenta serve as a transient endocrine organ?
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Maintains pregnancy, stimulates ovarian function, influences fetal growth, and assists in parturition
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What are the 3 types of exchange that occur through the placenta?
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Simple diffusion, facilitated diffusion, and active transport
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What is simple diffusion in the placenta?
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Gases and water flow from high concentration to low concentration
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What is facilitated diffusion in the placenta?
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Using complex molecules such as glucose and AA to exchange nutrients
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What is active transport in placenta?
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Sodium/potassium pump and calcium pump
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What are some substances that can cross the placental barrier?
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Small hormones, water-soluble minerals and vitamins, antibiotics, opiate drugs, barbiturates, lead, viruses, LSD, amphetamines, lithium
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What substances can't cross the placental barrier?
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Maternal proteins, lipids, large peptide hormones, fat-soluble vitamins
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How does the placenta function as maternal recognition of pregnancy?
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Prevents luteolysis, prevents decrease in blood progesterone, and to maintain pregnancy
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