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Repro > 8.1 Reproductive system (embryology) 2 > Flashcards

8.1 Reproductive system (embryology) 2 Flashcards

1
Q

where are the villi found in early embryonic development?

A

ALL along chorion (chorionic membrane)

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2
Q

where are villi found in week 12?

A

final disc shape achieved

chorion looses villi on one side (opposite decidua basalis side) - smooth chorion (chorion laeve)

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3
Q

what happens to the chorion and amnion at week 22?

A

amnion and chorion become a composite membrane
(fuse to form decidua parietalis, decidua basalis still present)
forms: amniochorionic membrane = decidua parietalis

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4
Q

what is the desidual basalis?

A

The area of ENDOMETRIUM between the implanted chorionic vesicle (amniochorionic membrane) and the myometrium, which becomes the MATERNAL part of the placenta

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5
Q

what is the degree to which membranes are shared in monozygotic twins?

A

varies:

  1. 2 amnions and 2 chorions (one of each)
  2. 2 amnions (inner), but 1 chorion (outer)
  3. 1 amnion and chorion (both shared)
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6
Q

what is the amnion continuous with?

A

umbilical cord

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7
Q

how do monozygotic twins with 2 amnions and 2 chorions come about?

A

originally 1 zygote, but during travel along fallopian tube to implantation, the zygote divided into 2 and 2 implantations result

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8
Q

how do monozygotic twins with 2 amnions but chorion come about?

A

1 morula, but the embryoblast (inner cell mass) forms 2 separate bilaminar disks

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9
Q

how do monozygotic twins with 1 amnion and chorion come about? (both shared)

A

1 blastocyst cavity and 1 bilaminar disk

BUT 2 primitive streaks (therefore 2 grooves, 2 notochords etc.)

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10
Q

what is the gross morphology of the placenta? (foetal aspect)

A

shiny outer - covered by amniotic membrane (enclosing foetus and amniotic fluid)
AM over umbilical cord as well
(extremely vascular organ)

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11
Q

what is the gross morphology of the placenta? (maternal aspect)

A

amniochorion membrane surrounding outer

within are cotyledons

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12
Q

what are cotyledons?

A

separations of the decidua basalis of the placenta (implantation side, maternal endometrium), separated by placental septa

(a unit on maternal side separated villus projections from foetal side, villus separated by placental septa on maternal side, which marks the beginning and end of each cotyledon)

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13
Q

what does each cotyledon consist of?

A

a main stem of a chorionic villus as well as its branches and subbranches etc.

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14
Q

describe a 1st trimester placenta

A

placenta established in first trimester
placental ‘barrier’ still relatively thick
cytotrophoblast layer under syncytiotrophoblast

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15
Q

what is term placenta?

A

SA of placenta for exchange INCREASES dramatically
placental ‘barrier’ now THIN
ONLY syncytiotrophoblast layer, cytotrophoblast lost

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16
Q

what happens as the placental ‘barrier’ becomes thinner throughout pregnancy?

A

the diffusion distnce from maternal blood to foetal blood via foetal endothelium and syncytiotrophoblast decreases
(with lost of cytotrophoblast)

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17
Q

what do umbilical vein and artery carry?

A

umbilical vein: oxygenated blood to foetus from placenta

umbilical artery: deoxygenated blood form foetus to placenta

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18
Q

where is the maternal blood delivered from?

A

endometrial spiral arteries and veins

branch to form spiral arteries

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19
Q

what does the cytotrophoblast shell contain?

A

the maternal blood bathing the foetal chorionic villus from spiral arteries, but the maternal blood doesn’t flow freely past the cytotrophoblastic shell

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20
Q

what happens to the main stem villus form foetus?

A

it branches continuous towards maternal direction

the end point (tip) is the anchoring villus, attached to the cytotrophoblastic shell on maternal side

21
Q

how many umbilical arteries and veins do foetus’ have?

A

2 umbilical arteries: deoxy blood (foetus –> placenta)

1 umbilical vein: oxy blood (placenta –> foetus)

22
Q

what does the placenta synthesise? (metab)

A

glycogen
cholesterol
fatty acid

23
Q

why is cholesterol synthesised by the placenta?

A

cholesterol is a pre-cursor for oestrogen and progesterone

both are hormones for supporting pregnancy

24
Q

what are the 2 classes of hormones produced by the placenta? (endocrine)

A

protein

steroid

25
Q

what are the steroid hormones produced by the placenta?

A

progesterone

oestrogen

26
Q

what are the protein hormones produced by the placenta?

A

human chorionic gonadotrophin (hCG)
human chorionic somatomammotrophin (hCS)
human chorionic thyrotrophin (hCT)
human chorionic corticotrophin (hCC)

27
Q

when is hCG produced?

A

during first 2 months of pregnancy

28
Q

what is the function of hCG?

A

supports the secretory function of corpus luteum

acts like LH, so CL produce oestrogen and progesterone to support pregnancy - until placenta take over

29
Q

what is hCG produced by specifically?

A

syncytiotrophoblast layer
therefore is pregnancy SPECIFIC
(aside from pathological e.g. testicular tumour)

30
Q

where is hCG excreted?

A

in urine

used as basis for pregnancy testing

31
Q

what are trophoblast diseases?

A

molar pregnancy

choriocarcinoma - malignant cancer of uterus (womb)

32
Q

what do trophoblast diseases lead to?

A

massive overgrowth of placenta tissue, there mass over production of hCG (indication of abnormal pregnancy)

33
Q

what is molar pregnancy?

A

non-viable fertilised egg implants in the uterus and will fail to come to term

34
Q

what are placental steroid hormones responsible for?

A

(progesterone + oestrogen)

responsible: maintaining pregnant state

35
Q

when does placenta production of steroid hormones take over form CL?

A

by the 11th week

36
Q

which placental hormones influence maternal metabolism?

A

progesterone

hCS / hPL

37
Q

how does progesterone influence maternal metabolism?

A

increases appetite - increase fat store for 2nd half of pregnancy, as baby can only use glucose (BBB), so fat store used by mum to reserve glucose for foetus

38
Q

how does hCS / hPL influence maternal metabolism?

A

increases glucose availability to foetus

39
Q

what are the different types of transports used in pregnancy?

A

simple diffusion (gas exchange)
facilitated diffusion
active transport
pino-endocytosis

40
Q

how does simple diffusion work and which molecules utilise this mode of transport?

A 
molecules moving down a concentration gradient
- water
- electrolytes
- urea + uric acid
- gases
(molecules small enough with no charge)
41
Q

which molecule uses facilitated diffusion?

A

glucose
(GI: GLUT 1 from intestine, GLUT 2 into blood,
GLUT 5 then GLUT 2 for fructose)

42
Q

what limits gas exchange in uteroplacental circulation?

A

simple diffusion, so FLOW limited, NOT diffusion limited

high flow, low resistance

43
Q

why is it necessary to maintain an adequate uteroplacental circulation flow?

A

foetal O2 stores are small

rely heavily on HIGH flow gas exchange (via simple diffusion)

44
Q

which molecules undergo active transport?

A

amino acids
iron
vitamins

45
Q

how does active transport occur across maternal to foetus?

A

specific ‘transporters’ expressed by the SYNcytiotrophoblast

46
Q

describe the foetal immune system

A

immature

47
Q

how does the foetus gets its immunity?

A

passive immunity

receptor-mediated process, maturing as pregnancy progresses

48
Q

which immunoglobulins crosses the placenta ‘barrier’ to be received by the foetus?

A

IgG only

49
Q

what type of process is passive immunity in foetus? why?

A

ACTIVE process

as the IgG concentrations in foetal plasma EXCEEDS those in maternal circulation

Repro (78 decks)

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