Embryology 1 Flashcards
What are the different phases of embryology?
Pre-embryonic phase (0-3 weeks)
Embryonic phase (4-8 weeks)
Foetal phase (9-40 weeks)
Postnatal
What does the pre-embryonic phase last between?
0-3 weeks
What does the embryonic phase last between?
4-8 weeks
What does the foetal phase last between?
9-40 weeks
What is spermatogenesis?
Process by which a haploid spermatozoa develops from germ cells in the seminiferous tubules of the testis
What is the process by which a haploid spermatozoa develops from germ cells in the seminiferous tubules of the testis called?
Spermatogenesis
What is oogenesis?
Process of development of ova that takes place in the ovaries
What is the process of development of ova that takes place in the ovaries known as?
Oogenesis
What is produced during spermatogenesis?
4 spermatozoa (sperm) are produced from one spermatogonium
What is produced during oogenesis?
1 ova and 3 polar bodies are produced from one oogonium
What is spermatogonium?
Cell produced at an early stage in the formation of spermatozoa
What is the precurser for spermatogenesis?
Spermatogonium
What is oogonium?
Immature female reproductive cell that gives rise to primary oocytes by mitosis which go on to produce ova by meiosis
What is the precruser of oogenesis?
Oogonium
How many chromosomes do spermatogonium and oogonium have?
46 chromosomes
How does each sperm and ova compared to other sperm and ova?
Each one is genetically unique
What happens during fertilisation?
Several sperm surrounds the ovum, where one penetrates and its nucleus enters and fuses with the nucleus of the ovum to give a diploid cell called the zygote
What is a zygote?
Fertilised ovum
What happens during week 1 of the pre-embryonic phase?
Zygote is formed and divides to form a blastocyst
Blastocyst moves through uterine tube to reach uterine cavity
During what week is the zygote formed and divides to form a blastocyst?
Week 1
During what week does the blastocyst move through the uterine tube to reach the uterine cavity?
Week 1
How many chromosomes does a zygote have?
46 (diploid)
Why is each zygote genetically unique?
23 of mothers chromosomes and 23 of fathers chromosomes
Where does a zygotes mitochondria and cell organelles originate from?
Mother
What does a zygote divide to form?
Morula by dividing by mitosis
What is a morula?
Solid ball of cells
What does mitochondria being inherited from the mother mean in terms of genetic disease?
Mitochondrial genetic diseases cannot be inherited from the father
What is an example of a mitochondrial disease?
Leber’s disease
Hereditary optic neuropathy which leads to blindness
What is Leber’s disease?
Hereditary optic neuropathy which leads to blindness
What occurs during the development of the blastocyst from the morula?
1) As the number and size of cells increase getting nutrition to the central core of the cells becomes difficult
2) Cavity develops called the blastocystic cavity
3) Cells accumulate at one end to form an inner cell mast
4) Outer lining of cells is called the trophoblast
What is the cavity in a blastocyst called?
Blastocystic cavity
What is the outer lining of a blastocyst called?
Trophoblast
What does the zygote do once it is formed?
Moves through the uterine tube to the uterine cavity
Where is the ovum released from?
Ovary
Where does fertilisation occur?
Fallopian tube
Where does development from zygote to morula to blastocyst occur?
As it travels through the uterine tube to the uterine cavity
How long does the first cell division of the zygote take?
36 hours
What happens to the time of each cell division after the first?
Successive cell division takes lesser and lesser time
By what day does the blastocyst form?
5 or 6 where it has reached the uterine cavity and is ready to be implanted into it
What does the zygote/morula/blastocyst require in the fallopian tube to move down it and reach the uterine cavity?
Healthy ciliated epithelium
What could occur if cilia function of the fallopian tube is abnormal?
Ectopic pregnancy
What is ectopic pregnancy?
When the fertilised egg implants itself outside of the womb, usually in the fallopian tube
What is it called when the fertilised egg implants itself outside of the womb?
Ectopic pregnancy
What happens during week 2 of pre-embryonic pregnancy?
Implantation in the uterine endometrial layer and placenta begins to develop
Cells that later form the embryo form the bilaminar disc
Sacs, membranes and cord to nourish the human conceptus (baby) start to form
When does implantation in the uterine tube and the placenta begin to form?
Week 2
When do cells that later form the embryo form the bilaminar disc?
Week 2
When do sacs, membranes and cords to nourish the human conceptus start to form?
Week 2
What does the blastocyst burrow into during implantation?
Uterine wall (endometrium)
What plays an important role in the blastocyst burrowing?
Chorion
What happens to the trophoblast of the blastocyst?
Divides to form 2 laters and ultimately forms chorion
What are the finger like processes on chorion called?
Chorionic villi
What are the functions of chorion?
Helps with implantation (chorionic villi)
Forms part of the placenta
Secretes human chorionic gondotropin (HGT) which is used to detect pregnancy
What chemical is secreted by chorion?
Human chorionic gonadotropin (HCG)
What is human chorionic gonadotropin (HCG) secreted by?
Chorion
What chemical is used to detect pregnancy?
Human chorionic gonadotropin (HCG)
What maintains the endometrium after implantation has occured?
Human chorionic gonadotropin
For how long do maternal and urine levels of human chorionic gonadotropin (HCG) increase for?
Increase until 12 weeks gestation
What is gestation?
Period of developing inside the womb between conception and birth
What is the period of developing inside the womb between conceptiona and birth called?
Gestation
What is A?
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Myometrium
What is B?
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Endometrium (decidua)
What is C?
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Decidua basalis (with maternal blood vessels)
What is the decidua basalis?
Part of the endometrium deep to the inplanted conceptus
What happens to the inner mast cells of the blastocyst?
Forms a 2 layered flat disc called the bilaminar disc, forming 2 cavities
Is this picuture before or after formation of bilaminar disc?
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Before formation
Is this picture before or after formation of the bilaminar disc?
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After formation
What is A?
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Inner cell mass
What is B?
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Blastocyst cavity
What is A?
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Epiblast
What is B?
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Hypoblast
What is C?
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Amniotic cavity
What is D?
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Yolk sac
What are the 2 layers of the bilaminar disc called?
Epiblast
Hypoblast
What are the 2 cavities present after the formation of the bilaminar disc called?
Amniotic cavity
Yolk sac
What is A?
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Chorion
What is B?
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Embryo
What is C?
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Umbilical cord
What is D?
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Maternal blood vessels
What is E?
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Placenta
What is F?
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Fetal blood vessels
What are the main functions of the placenta?
Foetal nutrition
Transport of waste and gases
Immunity
What are the 2 parts of the placenta?
Foetal part
Maternal part
How can the foetal part of the placenta be described?
Smooth with foetal blood vessels and end of umbilical cord
How can the maternal part of the placenta be described?
Decidua basalis of endomatrium, rough and has maternal blood vessels
What week does the placenta mature by?
18-20 weeks
How does the weight of the placenta compare to that of the foetus?
1/6 of the foetus
What is A?
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Umbilical vein
What is B?
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Endometrial arteries
What is C?
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Endometrial veins
What is D?
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Myometrium
What is E?
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Chorionic villi
What is F?
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Umbilical cord
What is G?
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Umbilical arteries
What are the 2 kinds of multiple births/twins?
Fraternal/dizygotic
Identical/monozygotic
What causes fraternal/dizygotic twins?
2 ova released and 2 sperms creates 2 seperate zygotes
Different genetic make up
2 placentae
What causes identical/monozygotic twins?
1 ovum and 1 sperm creates 1 zygote initially, which divides into 2 and each develops into a different embryo
Same genetic makeup
Share one placenta, might share amniotic and chorionic sac
What is a summary of the stages of the first 2 weeks?
1) Fertilisation
2) Zygotes
3) Morula
4) Blastocyst with inner cell mass
5) Bilaminar disc with amniotic cavity above and yolk sac below