fertilisation + implantation Flashcards
what do sperm infiltrate in feritlization?
zona pellucida
what is the ovary called once sperm have fertilized it- day 1?
zygote
is zygote haploid or diploid
diploid
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
what occurs on day 4 of fertilization?
Merula is formed
how many cells is a merula
16 cells
what days is the merula/ blastocyst transported into the uterine body?
days 3-4
how many cells is a blastocyst?
32+ cells
what days does a blastocyst implant in the uterus?
days 5-8
(think earliest can actually detect pregnancy is 1 week)
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
what are the cells on the outer layer of blastocyst called?
trophoblasts
what are the trophoblasts (cells on outer later of blastocyst) destined to become?
placenta
what are the inner cells of the blastocyst destined to become?
fetus
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
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
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
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
what does each placental villi contain?
-fetal capillaries seperated from maternal blood by a thin layer of tissue
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
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
what what week is the placenta functional?
5th week
how is oxygen transported to the feotus?
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?
Umbilical vein
what transports maternal oxygen poor blood back to the body?
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
