BIOL124 Lecture 10 - First Trimester of Pregnancy

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  • Created on: 12-03-16 13:46
After how many days is the early morula formed?
3
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After how many days is the advanced morula formed?
4
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After 6 days the early morula becomes a...
Blastocyst
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Where does fertilization occur?
In the oviduct
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After cleavage divisions occur in the oviduct, the pre-embryo is wafted towards the uterus by what?
Cilia
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After how many days does the morula enter the uterus?
5
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In the uterus, the pre-embryo is bathed in what?
Uterine fluid
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Uterine fluid is rich in what?
Glycogen secreted by endometrial glands
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What does the Syncytial trophoblast secrete?
Hyaluronidase
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What happens when, during implantation, the blastocyst, contact the endometrium via trophoblast?
This triggers trophoblast cells to divide rapidly forming thick layer. Trophoblast cells fuse to form a syncytium.
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What are the intact cells closest to the inner cell mass called?
Cellular trophoblast
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What does hyaluronidase do?
It breaks down hyaluronic acid between the endometrial cells.
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What is the benefit of having the maternal capillaries and uterine glands erode?
They release nutrients and oxygen into lacunae (cavities) in trophoblast.
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When is implantation complete?
When the blastocyst is completely embedded in the endometrium.
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What causes an ectopic pregnancy?
When implantation occurs in the oviduct or body cavity.
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What are the symptoms of an ectopic pregnancy?
Vaginal bleeding, abdominal pain, tubal rupture (serious internal bleeding)
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How is an ectopic pregnancy diagnosed?
By HCG levels and ultrasound - there is a slower than normal rise in serum HCG.
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How are ectopic pregnancies treated?
Surgery, Methotrexate (disrupts folate metabolism and kills rapidly dividing cells), expectant management (most end naturally).
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What is gestational trophoblastic neoplasia?
When there is uncontrolled proliferation of trophoblast.
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How is gestational trophoblastic neoplasia diagnosed?
By high levels of serum HCG
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How is the amnion formed, and after how many days?
9 days - Inner cell mass separates from the trophoblast, forming the amniotic cavity. Cells of the inner cell mass line this cavity, forming the amnion.
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After 10 days, the inner cell mass is now two layers, what are these called?
The epiblast (upper) and the hypoblast (lower).
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What happens to the cells of the hypoblast?
They migrate to form a hollow sphere which is the yolk yac.
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What happens to cells of the hypoblast during gastrulation?
They migrate through primitive streak to form mesoderm.
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Where do the mesoderm cells migrate to?
They migrate to line the outside of amnion and yolk sac and inside the blastocoel.
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Nutrients from where diffuse to the embryo?
From the lacunae
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What forms the chorion?
The mesoderm and cellular trophoblast - this lines the blastocoel.
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What changes to the haemoglobin from a foetus to an adult?
Adult haemoglobin contains more partial pressure of Oxygen than foetus.
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4 weeks from fertilisation, what is the size of the foetus?
5mm
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4 weeks from fertilisation, what are the features of the foetus?
Beating heart, trachea, lungs, liver, pancrease, no kidney - waste via allantois
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8 weeks after fertilisation, what are the features of the foetus?
28mm, nail beds, sweat gland, kidney (all major organ systems formed)
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After after 12 weeks of fertilisation, what are the features of of the embryo?
It is 78mm, has all the major organs and the central nervous system
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What could put the embryo at risk in the first trimester?
Drugs (teratogens), smoking, alcohol, spina bifida (failure of neural tube closure), rubella virus
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What is Spina bifidia and can it be cured?
It is when the neural tube doesn't close - it can be surgically fixed
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What does Congential Rubella syndrom effect?
It effects the eyes, ears, heary and may result in mental retardation.
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What can prevent Congenital Rubella syndrom?
The MMR vaccination of the mother.
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After how many days is the advanced morula formed?

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4

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After 6 days the early morula becomes a...

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Where does fertilization occur?

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After cleavage divisions occur in the oviduct, the pre-embryo is wafted towards the uterus by what?

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