8. Placental function and dysfunction (workbook)

Question 1

what does the placenta contain?

Answer 1

both materal and fetal components

Question 2

what does a good placenta determine?

Answer 2

a good pregnancy

Question 3

what does the placenta represent?

Answer 3

the surface interface between the mother and developing child

Question 4

what is the function of the placenta?

Answer 4

the structure through which nutrients are supplied from the mother and waste is removed from the embryo / foetus

Question 5

when does development of the placenta begin?

Answer 5

soon after fertilisation at compaction

Question 6

from which cells does the placenta develop?

Answer 6

trophoblast

outer cell mass destined to develop into the structures that support the embryo / foetus during pregnancy

Question 7

what is the embryo / foetus enclosed by?

Answer 7

the amnion and chorion membranes in a protective sac

Question 8

what does the placenta develop as?

Answer 8

a specialisation of the outer membrane, the chorion

Question 9

when does the development of the placenta as the chorion begin? (specialised outer membrane)

Answer 9

begins as implantation gets underway

Question 10

what does the chorion take the form of? (post-fertilisation)

Answer 10

finger-like projections: chorionic villi

Question 11

what are chorionic villi?

Answer 11

functional units of the placenta

Question 12

what do chorionic villi represent?

Answer 12

point of exchange between the maternal and fetal circulations

Question 13

what do chorionic villi consist of?

Answer 13

a vascularised core covered by 2 epithelial layers

Question 14

how does materno-fetal exchange occur?

Answer 14

both simple and facilitated diffusion,
active transport,
receptor mediated endocytosis

Question 15

what ensures materno-fetal exchange is efficient and simply regulated?

Answer 15

combined utero-placenta and feto-placental circulations

represent a counter-current supply

Question 16

what does the placenta act as?

Answer 16

a selective barrier to the fetal circulation that regulates access to the fetal circulation
considerable protection from harmful agents

Question 17

what is a flaw of the placenta as a barrier?

Answer 17

not complete, can be breached

Question 18

how can the placental barrier be breached?

Answer 18

by simple ‘leakage’
Number of infectious agents may utilise existing transport systems e.g. HIV
Actively penetrate e.g. Treponema
Opportunistically exploit gaps in the epithelium

Question 19

how can the placental barrier be breached?

Answer 19

by simple ‘leakage’

number of infectious agents may utilise existing transport systems e.g. HIV

Question 20

what (else) is placenta responsible for?

Answer 20

Provision of passive immunity that affords immune protection in the neonatal period
Endocrine support of pregnancy
(nutrient supply + waste removal)

Question 21

why does the placenta mature?

Answer 21

to meet the increasing demands of the growing fetus

Question 22

what happens as the placenta matures?

Answer 22

it adapts by decreasing the interhaemal distance

Question 23

how is the interhaemal distance decreased?

Answer 23

by thinning of the trophoblast layer (s)
Margination of the fetal capillaries of the core of the villi
Increasing the SA for exchange

Question 24

how does the placenta increase the SA for exchange?

Answer 24

through increasing branch of villus tree

Question 25

when is decreasing of interhaemal distance exaggerated?

Answer 25

in situations where the demand for transported materials or restriction on the maternal side leads to a deficit

Question 26

when does the demand for transported materials or restriction on the maternal side lead to a deficit?

Answer 26

e.g. placentae from pregnancies in women who smoke / live at high altitude - have reduced interhaemal distances when compared to ‘normal’
(interhaemal distance decreased MORE than normal)

Question 27

is there a limit to the decrease of interhaemal distance?

Answer 27

yes, can have circumstances when the placenta’s power of compensation is exceeded

Question 28

what is placenta defect one of the major risk factors of?

Answer 28

intrauterine growth restriction

Question 29

what does impaired fetal growth link to?

Answer 29

long-term adult health problems

Question 30

what is impaired fetal growth linking to long-term adult health problems called?

Answer 30

Barker hypothesis

the fetal origins of adult disease

Question 31

when is the placenta shed?

Answer 31

at parturition (birth)

Question 32

what happens at parturition? (birth)

Answer 32

the massive blood supply to the implantation is shut down

Question 33

what happens if the placenta fragments during labour?

Answer 33

can result in retained placenta which impairs shut-down of the utero-placental circulation

Question 34

what happens if the shut-down of utero-placental circulation is impaired?

Answer 34

can cause serious post-partum haemorrhage

post birth