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Obs & Gynae > Fertilisation and physiology of pregnancy > Flashcards

Fertilisation and physiology of pregnancy Flashcards

1
Q

Where does fertilisation occur?

A

Ampulla of uterine tube

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2
Q

What happens during day 3-5 post fertilisation?

A

Blastocyst transports into uterus

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3
Q

What happens during day 5-8 post fertilisation?

A

Blastocyst implat in uterine wall

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4
Q

What do the inner cells and outer cells of the blastocyst develop into respectively?

A

Inner - becomes the embryo

Outer - burrows into uterine wall and becomes placenta

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5
Q

What is the first step of implantation of the blastocyst?

A

The free-floating blastocyst adheres to the endometrial lining, cords of trophoblastic cells begin to penetrate the endometrium

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6
Q

What is the second step of implantation of the blastocyst?

A

Advancing cords of trophoblastic cells tunnel deeper into endometrium, carving out a hole for the blastocyst. The boundaries between cells in the advancing trophoblastic tissue disintegrate

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7
Q

When does the blastocyst become completely buried in the uterine lining?

A

Day 12

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8
Q

What is decidua?

A

Decidua is the term for the uterine lining (endometrium) during a pregnancy

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9
Q

What tissues is the placenta derived from?

A

Decidual tissue

Trophoblastic tissue

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10
Q

What are trophoblasts?

A

Cells forming the outer layer of a blastocyst, which provide nutrients to the embryo and develop into a large part of the placenta

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11
Q

What happens to trophoblasts to create the placenta?

A

They differentiate into multinucleate cells (syncytiotrophoblasts) which invade decidua and break down capillaries to form cavities filled with maternal blood

Developing embryo sends capillaries into the syncytiotrophoblast projections to form “placental villi”

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12
Q

How does the structure of the placental villi ensure there is no direct contact between maternal and feotal blood?

A

Each villus contains foetal capillaries separated from maternal blood by a thin layer of tissue – no direct contact between foetal & maternal blood

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13
Q

When are the placenta and foetal heart functional?

A

Week 5 of pregnancy

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14
Q

How does the placenta work as an arteriovenous shunt?

A

More villi are produced as the placenta develops, increasing surfact contact area between uterus and placenta, allowing more exchange

Only a thin membrane separates the embryo’s blood in the villi from mother’s blood in the intervillous space (ie. no direct contact between foetal & maternal blood).

Circulation within the intervillous space acts partly as an arteriovenous shunt

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15
Q

What three factors mean that sufficient oxygenation of the fetus is possible?

A
  1. Fetal Hb (increased ability to carry O2)
  2. Higher Hb concentration in fetal blood - more than mother (see graph)
  3. Bohr effect (Fetal Hb can carry more oxygen in low pCO2 than in high pCO2)
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16
Q

How does water cross the placenta?

A

Goes from mother to fetus along osmotic gradient

17
Q

How do electrolytes cross the placenta?

A

Follow water - use the same concentration gradient as water

18
Q

What is the main source of energy for the fetus?

A

Glucose transported across the placenta by simplified transport

19
Q

How do levels of human chorionic gonadotrophin (HCG) and human chronionic somatomammotrophin (HCS) change during pregnancy?

A

HCG - prevents involution of corpus luteum

HCS - begins production at week 5 of pregnancy, increases steadily

20
Q

What is the purpose of Human Chorionic Somatomammotropin?

A

Growth hormone-like effects: protein tissue formation

Decreases insulin sensitivity in mother: more glucose for the fetus

Involved in breast development and possibly lactation

21
Q

What role does progesterone play in pregnancy?

A

Development of decidual cells

Decreases uterus contractility

Preparation for lactation

22
Q

What role does estrogen play in pregnancy?

A

Enlargement of uterus

Breast development

Relaxation of ligaments

23
Q

What are estriol levels an indicator of?

A

Viability of fetus

24
Q

What effects does the production of corticotrophin releasing hormone from the placenta have on the mother?

A

Activates ACTH:

aldosterone production can result in hypertension

glucocorticoid production can cause oedema, insulin resistance and gestational diabetes

25
Q

What effects can the increase in cardiac output due to pregnancy have?

A

ECG changes

Heart sounds

Functional murmurs

26
Q

Why does cardiac output decrease during the last 8 weeks of pregnancy?

A

The uterus begins to compress the vena cava

27
Q

Why does blood pressure drop during the second trimester?

A

Uteroplacental circulation expands

Peripheral resistance decreases

28
Q

What cardiovascular and respiratory functions increase during pregnancy?

A

40% increase in cardiac output

40% increase in tidal volume

29
Q

What haematological changes occur during pregnancy?

A

40% increase in plasma volume by 32 weeks

20% increase in RBCs, however, concentration falls

Increased clotting risk: increased factor VII, VIII, X, and rise in fibrinogen

Increased RBC mass

30
Q

Why does RBC mass increase during pregnancy?

A

To protect against blood loss during labour

31
Q

How much does oxygen demand increase during pregnancy?

A

15%

32
Q

Why are pregnant women at higher risk of acute pyelonephritis?

A

Renal pelvis and ureters dilate

33
Q

By how much does GFR increase during pregnancy?

A

50%

34
Q

When does the morula become the blastocyst?

A

32 cell stage

35
Q

What does the cord contain?

A

2 arteries and one vein

36
Q

How do estrogen and progesterone contribute to breast growth during pregnancy?

A

Estrogen causes growth of ductile system

Progesterone development of lobule-alveolar system

37
Q

What effects do estrogen and progesterone have on lactation?

A

They both inhibit milk production

Levels drop significantly after birth

38
Q

Which hormone relaxes smooth muscle in the breast to allow release of milk?

A

Oxytocin

Obs & Gynae (20 decks)

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