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52 Cards in this Set
- Front
- Back
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Which stage of human development is a zygote? |
Days 1-3 |
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What stage of human development is a morula? |
Days 4-7
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What stage of human development is a blastocyst? |
Days 8-14 |
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What stage of human development is em embryo? |
Weeks 3-8 |
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What stage of human development is a fetus? |
Week 9 to birth. |
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What does the follicle become? |
Corpus luteum |
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Which hormones does the corpus luteum secrete? |
Progesterone and some oestrogen |
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What is the function of uterine milk? |
Nourishes the morula before implantation and prepares the endometrium for implantation. |
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How many sperm are in an average ejaculate? |
200-600 million |
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How many sperm on average reach the fertilisation site? |
~200 |
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Where are sperm deposited by ejaculation? |
Around the external os of the uterus and in the fornix of the vagina. |
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How fast can sperm travel? |
2-3mm/min |
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What is the average concentration of sperm? |
100 million/ml |
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What is the lower limit of male fertility in terms of sperm concentration, motility at 2 hours and 24 hours? |
20-50 million/ml, at least 40% at 2 hours and some should be motile at 24 hours |
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What proportion of semen does sperm make up and where are they produced? |
2-3%, testes |
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Which component of semen is made in seminal vesicles, (makes up 65-75% of semen) and what does it do? |
Seminal plasma, energy source for sperm |
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List the components of semen made in the prostate and the % of semen they made up |
Acid phosphatase Citric acid Fibrinolysis Prostate specific antigen Proteolytic enzymes Zinc 25-30% |
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What is the function of galactose and mucose in the semen, what proportion of the semen do they make up and where are they produced? |
Increase the mobility of sperm cells in the vagina and cervix, <1% and bulbourethral glands |
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How long is an oocyte viable for fertilisation after ovulation? |
Up to 24 hours |
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How long can sperm remain viable in the reproductive tract? |
Up to 48 hours |
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Which stage of meiosis do eggs exist in until fertilisation? |
Arrested metaphase? |
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Why are eggs more vulnerable than sperm? |
They are in suspended animation so vulnerable to environmental factors which could affect them. |
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When does the egg complete the second stage of meiosis? |
After the sperm has entered the egg |
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What is the name of the reaction which sperm undergo in the female reproductive tract? |
Capacitation |
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What does capacitation do? |
Removes proteins from the plasma membrane overlying the acrosomal region |
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How long does capacitation take? |
~7 hours |
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Why do sperm have to undergo capacitation? |
Only capacitated sperm can pass through corona cells and undergo the acrosome reaction. |
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Where does fertilisation occur in the uterine tube? |
The ampullary region |
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What would happen to a triploid gamete? |
It would spontaneously abort |
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What kind of reactions occur to prevent other sperm from entering the egg? |
Cortical reactions |
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What are the three consequences of fertilisation? |
Restoration of diploid number (2n) Sex determination (X/Y) Induction of cleavage |
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What is cleavage |
Rapid cell division which occurs once the sperm has released its DNA and lost its tail etc. |
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How is cleavage orchestrated? |
Swap between the S & M phase, no G phase. |
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Do maternal or paternal factors help stimulate fast cell division? |
Maternal (mitochondria etc.) |
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How does the morula develop into the blastocyst? |
Formation of an inner cavity |
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What does the inner cell mass become? |
Embryo |
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What do the trophoblast cell become? |
The fetal part of the embryo. |
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What must the blastocyst do before it can enter the uterus wall? |
Leave the Zona Pellucida (hatch) |
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Describe the lumen of the uterine tubes |
Muscular |
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Describe the body of the uterus |
Fluid-filled |
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How do trophoblast cells implant themselves in the endometrial wall? |
They are very invasive so they pull the blastocyst into the wall and break into arteries and glands |
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How is primitive circulation set up? |
Blood vessels in the endometrial wall leak (can cause bleeding) |
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Why might some women think they are not pregnant at the stage of implantation? |
The endometrial blood vessels lead, causing bleeding and the woman might think this is a period. |
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What happens once the blastocyst is implanted? |
The cells become packed with glycogen and puff up, ready for the blastocyst to sit comfortably in the environment. |
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Where are the normal sites for implantation? |
The posterior or anterior wall of the body of the uterus |
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What is the most common site for abnormal implantation? |
Uterine tube (95%) |
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What are the four sites of abnormal implantation? |
Uterine tubes Recto-uterine pouch Ovary Around the internal os |
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What is it called when implantation occurs around the internal os? |
Placenta previa |
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When does the decidual reaction occur? |
When the uterine mucosa reacts to implantation. |
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What happens in the decidual reaction? |
Stromal cells enlarge and fill with glycogen to provide nourishment for the embryo until the placenta becomes vascularised. |
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About when is implantation complete? |
Day 12 after fertilisation |
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When is the definitive placenta fully formed by? |
The end of the first trimester. |
