Placentation and implantation

Question 1

what are the 3 stages of the mother foetus link

Answer 1

invasion
decidualisation
placentation

Question 2

what is decidaulisation

Answer 2

endometrial remodeling: secretory transformations of the uterine glands, influx of natural killer cells and vascular remodeling

Question 3

what is the embryoninc placenta formed from

Answer 3

outermost layer of trophoblast- the chorion

Question 4

what is the maternal placenta derived from

Answer 4

the endometrium underlying the chorion

Question 5

describe blood flow in the placenta

Answer 5

chorionic villi extend from the chorion to the endometrium. villi have cappiliaries
endometrium changes so that it forms a pool of maternal blood around each villi

Question 6

what is the blood supply of the placenta

Answer 6

uterine artery and vein from the mother

umbilical arteries and veins from the foetus

Question 7

what is the zona pellucida

Answer 7

the membrane surrounding the ovum before implantation

Question 8

when does the blastocyst leave the zona pellucida

Answer 8

day 7

is bathed in uterine secretions for 2 days

Question 9

what hormones are involved in attachment and implantation

Answer 9

progesterone prepares the uterine environment and increases glandular tissue
oestrodiol releases glandular secretions

Question 10

describe implantation

Answer 10

syncytiotrophoblast cells flow into the endometrium and erode the maternal capillaries which bleed into the spaces.
oedema, glycogen synthesis and increased vascularisation(decidualisation).

Question 11

what is the term for the pregnant endometrium

Answer 11

decidua

Question 12

what do the villi form from

Answer 12

syncytiotrophoblast

Question 13

describe the features of villi

Answer 13

contain a fetal capillary loop with a slow flow rate

villi become localised at the embryonic pole

Question 14

when is maternal circulation functional by

Answer 14

10-12 weeks

hence the first trimester embryo is dependent on uterine tissues

Question 15

what makes up the placental membrane

Answer 15

fetal capillary endothelium
basement membrane
cytotrophoblast
syncytiotrophoblast

Question 16

what might cause early pregnancy losses

Answer 16

lack of hormonal support (luteal deficit)

endometrium is too thin,

Question 17

what are the components of a secondary villi

Answer 17

an inner core of extraembryonic mesoderm
a middle cytotrophoblast layer
an outer syncytiotrophoblast

Question 18

what is the function of HCG

Answer 18

maintains progesterone secretions from the corpus luteum until the placenta can synthesise its own progesterone

Question 19

when is hCG secreted

Answer 19

when the embryo implants at 8-10 weeks by the syncytiotrophoblast

Question 20

when is hCG measurable

Answer 20

7-8 days post conception

by urine tests after 2 weeks

Question 21

what is the function of hCG

Answer 21

mimics LH
supports steroid synthesis of the CL
prevents menstruation and follicular development
prevents menstruation and follicular development
stimulates leydig cells to produce testosterone in male foetuses

Question 22

describe the development of the placenta

Answer 22

month 1- villus formation
month 2 - increasing surface area and circulation
month 3- grows

Question 23

when does the placenta thin

Answer 23

20 weeks with loss of the cytotrophoblast

Question 24

what is the renal function of the placenta

Answer 24

regulates fluid volume and disposes of waste metabolites

Question 25

what is the endocrine function of the placenta

Answer 25

synthesises steroids and proteins that affect both foetal and maternal metabolism

Question 26

what is the function of progesterone in pregnancy

Answer 26

increases throughout pregnancy
suppresses follicular growth and ovulation
suppresses the immune response
maintains the endometrium

Question 27

how long is the CL required for

Answer 27

5 weeks which is the point at which the placenta is able to secrete all steroid hormones

Question 28

what substance is the substrate for progesterone

Answer 28

maternal cholesterol

Question 29

what is the main type of oestrogen in pregnancy

Answer 29

oestriol

Question 30

what is the function of oestriol

Answer 30

stimulates growth of myometrium and breast ducts
along with relaxin, relaxes and softens maternal pelvic ligaments and pubic symphysis which allows uterine expansion
stimulates LDL cholesterol uptake and p450 enzymes which helps to synthesise progesterone
provides an indication of the function of the placenta

Question 31

how are nutrients exchanged across the placenta

Answer 31

water and electrolytes diffuse freely
glucose is via facilitated diffusion
amino acids are via active transport
lipids cross as free fatty acids

Question 32

describe gas exchange

Answer 32

foetal hb has a greater affinity for o2 than maternal

towards the end of pregancy placenta is less able to meet the demands

Question 33

what might cause ectopic pregnancies

Answer 33

pelvic inflammatory disease

endometriosis

Question 34

where are the vast majority of ectopics

Answer 34

ampulla/isthmus

Question 35

where does attachment normally occur

Answer 35

posterior wall of fundus of the uterus

Question 36

what are the features of ectopics

Answer 36

increasing in incidence - 1 in 150 approx
rupture of the uterine tube may cause fatal blood loss
symptoms may be confused with appendicitis