fertilisation + implantation Flashcards by Amy Hollis

what do sperm infiltrate in feritlization?

zona pellucida

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what is the ovary called once sperm have fertilized it- day 1?

zygote

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is zygote haploid or diploid

diploid

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what occurs once a zygote is formed (day 1-day4)

cleavage
- cells within zona pellucida undergo meiosis, dividing and multiplying in number
-the cells increase in number but not in size

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what occurs on day 4 of fertilization?

Merula is formed

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how many cells is a merula

16 cells

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what days is the merula/ blastocyst transported into the uterine body?

days 3-4

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how many cells is a blastocyst?

32+ cells

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what days does a blastocyst implant in the uterus?

days 5-8

(think earliest can actually detect pregnancy is 1 week)

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describe process of fertilizartion and implantation from when sperm meets ovum - implantation in uterine wall

day 1- sperm infiltrates zona pellucida of ovum creating a ZYGOTE (diploid cell)

cleavage occurs causing increase in number of cella (meiosis within zona pellucida)

day 4- MORULA (16 cells)

BLASTOCYST- 32+ cells

days 3-5 the blastocyst is taken to uterine body
days 5-8 the blastocyst attaches to the uterine lining

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what are the cells on the outer layer of blastocyst called?

trophoblasts

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what are the trophoblasts (cells on outer later of blastocyst) destined to become?

placenta

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what are the inner cells of the blastocyst destined to become?

fetus

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what is syncytiotrophoblast?

-trophoblasts differentiate into syncytiotrophoblasts

-syncytiotrophoblasts invade decidua and break down capillaries to form cavities filled with maternal blood

-developing embryos send capillaries into the syncytiotrophoblast projections to form placental villi

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explain out blastocyst implants once it has reached the uterus body

blastocyst (32+ cells) reaches uterine body on days 5-8

-cells of trophoblast (outer layer of blastocyst) undergo adhesion to stroma of endometrium
-syncytiotrophoblast (outer later of trophoblast) forms progections into the stroma
-cells of stroma convert into a tissue called decidua (specialised in providing nutrients to trophoblast)
-when blastocyst implants, the syncytiotrophoblast starts to produce HCG

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what is decidua?

-specialised tissue that provides nutrients to the trophoblast (outer layer of the blastocyst)

-it is formed when the blastocyst implants and the synctiotrophoblast (outer layer of trophoblasts) forms prodjections into endometrial stroma

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explain the formation of placental villi

trophoblasts differentiate into syncytrophoblasts

-syncytrophoblasts invade decidua and break down capillaries to form cavities filled with maternal blood

-developing embryos send capillaries into these cavities of maternal blood (syncytiotrophoblast projections) to form placental villi

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what does each placental villi contain?

-fetal capillaries seperated from maternal blood by a thin layer of tissue

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is there any direct contact between fetal and maternal blood in the placental villi

-no direct contact between fetal and maternal blood

placental villi- contain fetal capillaries and maternal blood SEPERATED by a thin layer of tissue

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which way does gas exchange work in the placental villi?

2 way exchange
-of respiratory gases, nutrients, metabolites between mother and foetus

-largely down diffusion gradient

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what what week is the placenta functional?

5th week

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how is oxygen transported to the feotus?

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placental plays the role of ‘foetal lungs’

-oxygen diffuses from maternal blood (pool of blood within placental villi) and into the fetal circulation system

-oxygen saturated blood returns to the fetus via the UMBILICAL VEIN

-maternal oxygen poor blood flows black into the UTERINE VEIN

what transports fetal oxygen rich blood to fetus?

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Umbilical vein

what transports maternal oxygen poor blood back to the body?

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uterine vein

what factors facilitate O2 exchange from mother - foetus?

3 factors: -fetal Hb -Higher Hb concentration -Bohr affect (CADET right)

explain how water gets from mother to foetus?

water diffuses into placenta along its osmotic gradient -exchange increasing during pregnancy up to the 35th week

explain how electrolytes get from mother to foetus

electrolytes follow water down its osmotic gradient -iron and calcium can only go from mother to child -glucose passes placenta via simplified transport there is a free diffusion of fatty acids

explain how fatty acids are transported from mother to feotus

through free diffusion (do not need gradient)

what drugs can pass placental barrier

-Thalidomide (the one with all the birth defects a while ago) -Carbamazepine -Coumarins e.g. Warfarin -Tetracyclins -Aclohol, nicotine, heroin, cocaine + caffeine

can methotrexate be given in pregnancy?

no- can lead to skeletal abnormalities

can lithium be given in pregnancy?

no- can cause CVS defects

can ACEI/ARBs be given in pregnancy?

no- can cause renal hypoplasia (underdevelopment of kidneys)

what hormones are increased in anterior pituitary in pregnancy?

-ACTH increases -prolactin increases -melanocyte stimulating hormone increases

what does an increase in ACTH in pregnancy lead to

-increase in ACTH from anterior pituitary in pregnancy leads to increase in cortisol and aldosterone -this leads to increase risk of diabetes and infections

what does an increase in prolactin in pregnancy lead to?

-increase in prolactin from anterior pituitary in pregnancy leads to suppression of FSH and LH -reduced FSH and LH

what does an increase in melanocyte stimulating hormone lead to?

-increase in melanocyte stimulating hormone in pregnancy leads to increased pigmentation of skin, linea nigra and melasma

why might T3 and T4 increase in pregnancy?

HCG levels rise, doubling every 46 hours until around 3 months, then gradually start to fall -HCG can bind to TSH receptors stimulating release of T3 and T4 causing symptoms of hyperthyroidism

how long does the corpus luteum produce progesterone before the placenta takes over?

-until about 10 weeks in pregnancy

what occurs to plasma + blood volume during pregnancy?

during pregnancy plasma volume and blood volume increase

what occurs to cardiac output in pregnancy?

there is an increased cardiac output -increased HR -increased SV CO= HR x SV

what occurs to systemic vascular resistance in pregnancy?

-systemic vascular resistance decreases and so BP decreases in first + middle of pregnancy

what can occur due to vasodilation and decrease in systemic vascular resistance?

-varicose veins can occur due to peripheral vasodilation and obstruction of inferior vena cava (by the uterus) -peripheral vasodilation can cause hot flushes and sweats

explain what occurs to lung volumes in pregnancy?

Tidal volume increase to meet O2 needs -diaphragm is pushed up due to enlarged uterus -decrease in residual volume and functional residual capacity

what occurs to RR in pregnancy?

RR increases- to meet the new O2 needs

what are the renal changes that occuring during pregnancy?

-increase in blood volume to kidneys (makes sense because increase in blood volume, plasma volume + CO) -increase in GFR -increase in aldosterone -increase protein excretion from kidneys (also normal to have a trace of glucose) -dilatation of ureters and collecting system

why are pregnant women more likely to be iron, folate or B12 deficient?

-during pregnancy there is an increase RBC production leading to higher iron, folate and B12 requirements

why do pregnant women not seem to have a higher than normal Hb even though they are producing more RBC?

-there is an increase in RBC during pregnancy however -there is also increase in plasma volume plasma volume increases MORE than RBC volume, leading to a lower concentration of RBC

why are pregnant women hypercoagulable?

as there is an increase in clotting factors -fibrinogen -factor VII, VIII and X

what occurs to WBC in pregnancy

increase

what occurs to platelets in pregnancy?

decrease platelets

what occurs to ALP during pregnancy?

Increase ALP (secreted by placenta) 4x increase

what occurs to albumin in pregnancy?

-decrease in albumin because increase in GFR leads to more protein loss

what effect does a decrease in protein have when takin meds?

decrease in protein (albumin) means that theres a decrease in protein binding to drugs -increases the amount of free drug in the body

what occurs to calcium in pregnancy?

-calcium requirements increase but so does calcium absorption in the gut -so calcium remains stable

fertilisation + implantation Flashcards

(54 cards)