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Gametes - Pregnancy Flashcards

1
Q

Cleavage of early embryo

A

Early division of zygote into multiple cells without increase in size, partitions contents

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2
Q

Proportion of fertilised eggs lost before a woman finds out she’s pregnant

A

50%

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3
Q

Function of amniotic fluid

A
  • Surrounds embryo
  • Helps maintain a constant body temp for foetus
  • Permits symmetric growth and development
  • Cushions foetus from trauma
  • Allows umbilical cord to be relatively free of compression
  • Promotes foetal movement to enhance musculoskeletal development
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4
Q

Describe placentation

A

Development of placenta from edges of blastocyst

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5
Q

What is the placenta

A

An organ that forms from the chorion and the endometrium and allow the embryo/foetus to exchange nutrients and waste

Chorionic villi provide surface area for exchange

Nutrient and gas exchange happens without actual blood exchange

Umbilical cord - contains 2 umbilical arteries and 1 umbilical vein

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6
Q

overview of 6 major placental functions

A

Respiratory

Excretory

Nutritive

Endocrine

Barrier function

Immunological function

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7
Q

How is transfer of materials carried out in the placenta

A

Transport is facilitated by the close approximation of maternal and foetal vascular systems within the placenta

There is normally no mixing of foetal and maternal blood within the placenta

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8
Q

What substances travel by simple diffusion

A

Water

O2

CO2

Na+

Cl-

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9
Q

What substances travel by facilitated transport across the placenta

A

Glucose

Galactose

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10
Q

Substances that travel by active transport across the placenta

A

AAs

Ca2+

Fe

Iodine

Vitamins

Glucose

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11
Q

Substances that travel by pinocytosis

A

Albumin

Gamma globulin

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12
Q

Substances that travel via endocrine system across the placenta

A

hCG

hPL

Oestrogen

Progesterone

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13
Q

2 main sites for the exchange of water

A

Placenta

Non-placental chorion

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14
Q

What impact could sever/over hydration have on the foetus

A

Major impact on foetal homeostasis and could lead to fatal consequences

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15
Q

Electrolytes that travel by simple diffusion

A

Na+

K+

Cl-

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16
Q

Electrolytes that travel by active transport

A

Ca2+

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17
Q

Location of additional body water in pregnant women at term

A
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18
Q

How does the mother’s total body water change during pregnancy

A

Increase in the mother’s total body water // 6-8L is needed for plasma vol expansion, constitution of amniotic fluid and for placenta

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19
Q

Amniotic fluid - what is it composed of and what is its volume

A

Mainly composed of water - 500-1200ml

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20
Q

How does plasma vol change during pregnancy

A

Increases up to 40-50% above pre-pregnancy level

Osmolality decreases from 290 to 280 mosm/kg compared to non pregnant women

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21
Q

Water content of placenta

rate of supply of water to foetus

A

85% water - 500ml of water

Major organ supplying water to the foetus

12 weeks - 100ml/hour

full term - 3600ml/hour

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22
Q

Regulation of water in pregnant women (same as non-pregnant)

A
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23
Q

Placental Ca2+ transport

A

Ca2+ enters from maternal circulation via facilitated transporters (CAT 1 and 2), crosses the cytosol bound to proteins such as calbindin and is then actively extruded into foetal circulation by Na+/Ca2+ exchanger and PMCA proteins (Plasma Membrane Calcium ATPases)

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24
Q

consequences of maternal fluid intake on foetal wellbeing

A

AMNIOTIC FLUID VOL

Recognised as a predictor of foetal wellbeing and subsequently of poor perinatal outcome

Can be evaluated using the amniotic fluid index - AFI

AFI = in pregnant women with low amniotic fluid vol, maternal fluid intake may influence AFI

** potential benefit of increased water intake on amniotic fluid vol in women with low amniotic fluid vol

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25
Effect of Ca2+ on foetus
26
How does intake of O2 and output of CO2 take place
By simple diffusion
27
O2 rate of supply cord flow rate
5 ml/kg/min 165-330 ml/min
28
How does O2 transfer efficiency of placenta compare to the lung What is O2 transfer dependent on
1/5 of O2 transfer efficiency of adult lung O2 transfer is dependent upon partial P
29
What is the major energy substrate to placenta and foetus How is it transported How is this substrate changed in the placenta
Glucose is the major energy substrate provided to the placenta and foetus Transported across placenta by facilitated diffusion via hexose transporters Although the foetus receives large amts of intact glucose, a large amt is oxidised within the placenta to lactate, which is used for foetal energy production
30
AA distribution between foetus and mother
AA conc in foetal blood is HIGHER than in maternal blood AAs are therefore transported to the foetus by ACTIVE TRANSPORT
31
Lipid distribution from mother to foetus
TGs and FAs are DIRECTLY TRANSPORTED from mother to foetus in early pregnancy but SYNTHESISED in foetus later in pregnancy Foetal fat has got dual origin
32
Excretory function of placenta
Waste products: urea, uric acid and creatinine are excreted to maternal blood by simple diffusion
33
Barrier function of placenta
Protective barrier to foetus against noxious agents circulating in maternal blood ## Footnote **high MW \> 500**
34
Relating to the father, what do the foetus and plcanta contain
Paternally determined antigens, foreign to the mother In spite of this, there is no evidence of graft rejection
35
How does the mother accept the foreign antigens of the father
1. Fibrinoid and sialomucin coating of trophoblast may suppress the trophoblastic antigen 2. Placental hormones, steroids, hCG have got weak immunosuppressive effect that may be responsible for producing sialomucin 3. Nitabuch's layer which intervenes between decidua basalis and cytotrophoblast may inactivate the antigenic property of tissue 4. There is little HLA and blood grp antigens om trophoblast surface - so weak antigenic stimulus 5. Production of block antibodies by mother protects foetus from rejection
36
Placental hormones
hCG human chorionic somammotropin (hCS) / placental lactogen (hPL) - affects maternal metabolism and stimulates pelvic ligament relaxation oestrogen progesterone
37
What is the integrated hormonal unit composed of
Foetal, placental and maternal compartments form an integrated hormonal unit
38
what does the feto-placental-maternal (FPM) unit create
The endocrine environment that maintains and drives the processes of pregnancy and pre-natal development
39
Hypothalamic-like releasing hormones
GnRH CRH cTRH GH-RH
40
Other hormones related to placenta
Chorionic adrenocorticotropin Chorionic thyrotropin Relaxin PTH-rP hGH-V
41
Placental Peptide hormones
Neuropeptide-Y Inhibin & activin ANP
42
What are the major hormones involved in the FPM
hCGn Progesterone Oestrogen Human Chorionic Somatomammotropin (hCS) - placental lactogen
43
How do the blood levels of hormones vary during gestation
44
Structure of Human Chorionic Gonadotrophin What is it produced by
Protein MW = 30,000 glycoprotein produced by trophoblastic cells α subunit - common (with FSH, TSH, LH) β - hormone specific
45
Secretion rate of hCG
Begins with implantation Detected in blood - day 8 Detected in urine - day 14 Peaks approx 2 months of gestation
46
Functions of hCG
* Produces effects similar to LH * Maintenance of CL until placenta functions * stimulates oestrogen and progesterone secretion * prevents ovulation * Stimulates continual growth of endometrium * Has thyroid-stimulating ability * Suppresses maternal immune function - prevents immunological rejection of implanted embryo * Stimulates testosterone production - development of foetal testes * BASIS OF PREGNANCY TEST
47
Structure of Human Chorionic Somatomammotrophin (hCS)
Protein - MW of 38000 similar to GH and prolactin - common progenitor
48
Where is hCS synthesised and when
placental secretion, week 5 post fertilisation directly proportional to placental size
49
Actions of hCS
* Increased maternal lipolysis - Increased FFA * Increased maternal protein synthesis * Increased maternal glucose usage - decreased insulin sensitivity Hence spares glucose for foetal development
50
Source of progesterone in the 1st trimester
Corpus luteum
51
Source of progesterone in 2nd and 3rd trimesters
Placenta
52
How is progesterone formed How do levels change throughout pregnancy what proportion is produced by placenta
formed from maternal precursors levels increase significantly throughout pregnancy 80-90% produced by placenta - secreted to BOTH foetus and mother
53
Maternal functions of progesterone
Decreases uterine contractility **Inhibits ovulation** - acting on GnRH, FSH and LH **Maintains uterine function** - placental secretion and function **Embryo nutrition** - increases decidual cells, increases uterine secretion
54
Embryonic functions of progesterone
Precursor for other hormones adrenal hormones - weak androgen (oestrogen) Cortisol - surfactant production Testicular hormones - testosterone, foetal differentiation
55
What proportion of oestrogens are produced by the placenta What oestrogen is produced in greatest amts
90% of oestrogens are produced by placenta oestrone, oestriol, 17B-oestradiol oestriol in greatest amts
56
what steroids come from the adrenal glands
C-19 steroids Dehydroepiandrostenedione (DHEA) 17-OH-DHEA
57
Foetal vs maternal contribution to precursors at term
58
Importance of oestrogens in pregnancy
* Essential for foetal survival - urinary oestrogens =\> decreased foetal death * Myometrial hypertrophy and gap junctions * Lacterous duct development * Increase uterine size * Increase external genitalia size * Relaxes pelvic ligament * Increases oxytocin receptors
59
Timeline of development of adrenal cortex - foetal adrenal gland
VITAL to organism survival Begins to develop @ 4th week of embryonic life Functional around 10th-12th week of embryonic life hCG may have a role in stimulating adrenocortical development
60
Influence of maternal, placental and foetal units on production of progesterones

GGE (33 decks)

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