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Questions and Answers
What is the main difference between reproductive cloning and therapeutic cloning?
What is the main difference between reproductive cloning and therapeutic cloning?
Which primary germ layer arises from the yolk sac?
Which primary germ layer arises from the yolk sac?
What congenital defects are associated with the entoderm germ layer?
What congenital defects are associated with the entoderm germ layer?
Which of the following is a correct implication related to the primary germ layers?
Which of the following is a correct implication related to the primary germ layers?
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Why is rubella infection serious during pregnancy?
Why is rubella infection serious during pregnancy?
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During which stage does the developing entity transition from being called a zygote to an embryo?
During which stage does the developing entity transition from being called a zygote to an embryo?
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What is the maximum lifespan of an ovum after being released for fertilization?
What is the maximum lifespan of an ovum after being released for fertilization?
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What role does the corona radiata play in relation to the ovum?
What role does the corona radiata play in relation to the ovum?
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What physical action helps propel the sperm through the female reproductive tract?
What physical action helps propel the sperm through the female reproductive tract?
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What is the critical time span for successful fertilization?
What is the critical time span for successful fertilization?
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What is the typical amount of sperm per ejaculation?
What is the typical amount of sperm per ejaculation?
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Which structure increases the bulk of the ovum and protects it from injury?
Which structure increases the bulk of the ovum and protects it from injury?
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In how much time can sperm generally reach the outer fallopian tube after ejaculation?
In how much time can sperm generally reach the outer fallopian tube after ejaculation?
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What primary role does the smooth chorion play once it is formed?
What primary role does the smooth chorion play once it is formed?
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Which statement is true regarding the amniotic fluid's absorption?
Which statement is true regarding the amniotic fluid's absorption?
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What condition is indicated by a significant increase in amniotic fluid volume?
What condition is indicated by a significant increase in amniotic fluid volume?
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How does the amniotic fluid protect the fetus?
How does the amniotic fluid protect the fetus?
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What initiates uterine contractions before labor?
What initiates uterine contractions before labor?
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What is a common cause of oligohydramnios?
What is a common cause of oligohydramnios?
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What is the typical pH level of amniotic fluid?
What is the typical pH level of amniotic fluid?
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Which statement about the amnion is incorrect?
Which statement about the amnion is incorrect?
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What is the primary function of the umbilical cord?
What is the primary function of the umbilical cord?
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Which characteristic describes the structure of the umbilical cord?
Which characteristic describes the structure of the umbilical cord?
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What does the presence of Wharton’s jelly in the umbilical cord do?
What does the presence of Wharton’s jelly in the umbilical cord do?
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Which statement about the umbilical arteries is true?
Which statement about the umbilical arteries is true?
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What percentage of births present a nuchal cord condition?
What percentage of births present a nuchal cord condition?
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Which type of stem cells occurs during the first 4 days of life?
Which type of stem cells occurs during the first 4 days of life?
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At what stage does a zygote begin to show differentiation and become an embryo?
At what stage does a zygote begin to show differentiation and become an embryo?
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Which characteristic does NOT describe the umbilical cord?
Which characteristic does NOT describe the umbilical cord?
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At what week can a baby start to grasp objects placed in its hand?
At what week can a baby start to grasp objects placed in its hand?
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What significant development occurs by the end of the fourth month?
What significant development occurs by the end of the fourth month?
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Which of the following abilities does a baby have by week 12 of development?
Which of the following abilities does a baby have by week 12 of development?
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What marks the onset of kidney secretion during fetal development?
What marks the onset of kidney secretion during fetal development?
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At which week can the baby's heartbeat be audibly detected using a Doppler?
At which week can the baby's heartbeat be audibly detected using a Doppler?
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What emerges by week 20 during fetal development?
What emerges by week 20 during fetal development?
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By what gestational week can a fetus potentially be saved if born prematurely?
By what gestational week can a fetus potentially be saved if born prematurely?
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During which week does the baby begin to have REM sleep?
During which week does the baby begin to have REM sleep?
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Study Notes
Fertilization
- The union of an ovum and a spermatozoon occurs in the outer third of a fallopian tube (ampullar portion)
- Fertilization must occur within 24 hours of ovulation, otherwise the ovum atrophies
- The critical time span for successful fertilization is about 72 hours
- Ovum is protected by the Zona Pellucida and Corona radiata
- The ovum is propelled into the fallopian tube by the fimbriae
- Normal amount of semen per ejaculation is 2.5 ml, containing 50-200 million sperm per ml (average 400 million per ejaculation)
- Sperms can fertilize for 3-4 days after ejaculation
- Normal life span of sperm is 7 days
- Sperms reach the cervix within 90 seconds after ejaculation and the fallopian tube within 5 minutes
- Spermatozoa move by flagella (tails) and uterine contractions
Amniotic Membranes
- Chorionic villi on the medial surface of the trophoblast thin, leaving the surface smooth (smooth chorion)
- Smooth chorion becomes the chorionic membrane - the outermost fetal membrane
- Amnion forms beneath the chorion and covers the fetal surface of the placenta
- Amniotic membrane lacks nerve supply and ruptures spontaneously at term
- Amniotic fluid is constantly being renewed and is slightly alkaline (pH 7.2)
- Amniotic fluid is absorbed by the fetus and through the fetal intestine
- Amount at term - 800-1,200 ml
- Hydramnios - excessive amniotic fluid (more than 2,000 ml), commonly due to esophageal atresia, anencephaly, or diabetes
- Oligohydramnios - reduction in amniotic fluid (less than 300 ml), due to disturbances in fetal kidney function
Functions of Amniotic Fluid
- Protection for the fetus
- Shields against pressure or blows to the mother's abdomen
- Regulates temperature
- Aids in muscular development
- Protects the umbilical cord from pressure
Umbilical Cord
- Formed from the fetal membranes (amnion and chorion)
- Provides circulatory pathway connecting the embryo to the chorionic villi of the placenta
- Transports oxygen and nutrients from the placenta to the fetus
- About 53 cm (21 in) in length at term
- 2 cm ( ¾ in ) thick
- Consists of gelatinous mucopolysaccharide "Wharton's jelly" for support
- Outer surface covered with the amniotic membrane
- Contains one vein (carrying blood from the placenta to the fetus) and two arteries (carrying blood from the fetus to the placenta)
- Number of veins and arteries is assessed at birth
- Blood can be withdrawn from the umbilical vein or transfused during intrauterine life for assessments or treatment
- Rate of blood flow is 350 ml/min at term
- Cord is unlikely to twist or knot due to rapid blood flow
- Nuchal cord (loop found around the fetal neck) is present in 20% of births
- Wall of umbilical cord arteries have smooth muscle for hemostasis
- Lacks nerve supply
Stem Cells
- Totipotent stem cells (zygote cells) present during the first 4 days of life, can form a complete human being
- Pluripotent stem cells present after 4 days of implantation, have the potential to become specific body cells
- Multipotent stem cells are specific and have a set path to become a particular body organ
Types of Cloning
- Reproductive cloning: nucleus of an adult cell is transferred into an oocyte, creating an embryo identical to the donor
- Therapeutic cloning: pluripotent stem cells are removed to grow in a laboratory, potentially supplying any body cell needed by the donor
Zygote Development
- Growth proceeds in a cephalocaudal direction
Primary Germ Layers
- Ectoderm: arises from the amniotic cavity, the largest
- Entoderm: arises from the yolk sac, a smaller cavity. Provides nourishment after implantation and produces red blood cells until the embryo's system matures.
- Mesoderm: the third layer
- Each germ layer develops into specific body systems
- Coexisting congenital defects usually arise from the same germ layer
Fetal Development Week-by-Week
- Week 9-10: Teeth begin to form, fingernails develop, baby can turn head and frown
- Week 10 - 11: Baby can breathe amniotic fluid and urinate
- Week 11: Baby can grasp objects, all organ systems function, has a skeletal structure, nerves, and circulation.
- Week 12: (First Trimester) all body parts needed for experiencing pain are developed, vocal cords are complete, baby can suck thumb
- Week 14: Heart pumps several quarts of blood daily
- Week 15: Baby has adult taste buds
- Month 4: Bone marrow development begins, heart pumps 25 quarts of blood daily, baby is 8-10 inches long and weighs half a pound
- Week 17: Baby can have dream-like sleep
- Week 19: Babies can be saved after 21-22 weeks, and sometimes earlier.
- Week 20: Earliest stage for Partial Birth Abortion, baby recognizes mother's voice
- Week 24: (Second Trimester End) Baby practices breathing by inhaling amniotic fluid. Most mothers feel increased fetal movement
- Month 7-9: Eyeteeth present, baby opens and closes eyes, baby can distinguish between waking and sleeping
- Month 9: Baby uses four senses (vision, hearing, taste, touch)
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Description
This quiz covers the critical processes of fertilization, including the journey of the sperm and ovum, as well as the formation of amniotic membranes. Learn about the timelines, protective structures, and physiological changes that occur during these stages. Test your knowledge on these essential aspects of human reproduction.
