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Reproduction > Week 3- physiology of pregnancy > Flashcards

Week 3- physiology of pregnancy Flashcards

1
Q

Describe what the ovum goes through from being fertilised to being implanted?

A

It progressively divides and differentiates into a blastocyst as it moves from the site of fertilisation to the site of implantation in the uterus.

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2
Q

Where does fertilisation occur?

What day does this occur on?

A

Ampulla of the Fallopian tube.

Day 1

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3
Q

Describe days 3-5 after fertilisation?

A

The blastocyst is transported into the uterus.

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4
Q

Describe days 5-8 after fertilisation?

A

The blastocyst implants in the uterus.

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5
Q

Describe the structure of the blastocyst?

A

The inner cells develop into the embryo

The outer cells burrow into the uterine wall and become the placenta.

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6
Q

What is the function of the placenta?

A

Produces several hormones to maintain pregnancy.

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7
Q

What is the trophoblast?

A

Surface layer of cells on the blastocyst.

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8
Q

What happens when the blastocyst adheres to the endometrium?

A

Cords of trophoblastic cells begin to penetrate the endometrium.
Then then tunnel deeper into the endometrium- carving out a hole for the blastocyst. The boundaries between the advancing trophoblast cells disintegrate.
When implantation is finished the blastocyst is completely buried in the endometrium.

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9
Q

By what day does the blastocyst become buried in the endometrium?

A

Day 12.

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10
Q

What is the placenta derived from?

A

Trophoblast cells and decidual (endometrium) tissue

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11
Q

How do the trophoblastic cells form the placenta?

A

They differentiate to form multinucleated cells (syncitiotrophoblasts) which invade decidua (endometrium ) and break down capillaries to form cavities filled with maternal blood.

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12
Q

How are placental villi formed?

A

The developing embryo sends capillaries into the syncitiotrophoblasts to form projections called placental villi.

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13
Q

What does each placental villus contain?

What occurs in the placental villi?

A

Contains foetal capillaries separated from maternal blood by a thin layer of tissue- there is no direct contact between foetal and maternal blood.

Exchange of gases, nutrients, metabolites etc

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14
Q

When is the placenta functional by? What else becomes functional at this point?

A

Functional by 5th week.

Feotal heart.

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15
Q

What is the function of HCG in relation to the placenta?

A

It stimulates the corpus luteum to keep releasing progesterone, this stimulates decidual (endometrial) cells to concentrate glycogen, proteins and lipids.

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16
Q

What does the placenta act as?

A

An arteriovenous shunt.

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17
Q

Why does the placenta form villi?

A

To increase the surface area for gas exchange.

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18
Q

Where is the interovillous space?

A

A thin membrane seperating the mother and foetal blood.

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19
Q

How does oxygen get into the foetus and how is carbon dioxide removed?

A

Oxygen moves down a partial pressure gradient from the mothers blood (high pp) to the foetal blood (low pp).
Carbon dioxide moves from a high partial pressure in the foetal blood to a low partial pressure in the mothers blood.

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20
Q

Which blood vessels does the exchange of oxygen and carbon dioxide take place between?

A

The maternal blood and the umbilical vein. The umbilical vein takes oxygenated blood to the foetus.

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21
Q

What factors increase the effectiveness of the foetus’s oxygen supply?

A

Feotal haemoglobin- has an increased ability to carry oxygen.
Higher concentration of haemoglobin in foetal blood.
The Bohr effect- fetal Hb can carry more oxygen in low partial pressures of Co2 than in high partial pressure of co2.

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22
Q

How does water get into the placenta?

A

Osmosis down its osmotic gradient.

23
Q

How do electrolytes get into the placenta?

A

They follow water down the diffusion gradient.

24
Q

How does glucose get into the placenta? What is its purpose?

A

By simple diffusion.

Its the fetus’s main source of energy.

25
Q

How do fatty acids get into the placenta?

A

Free diffusion

26
Q

What are drugs that can cross the placenta called?

A

Teratogens.

27
Q

During pregnancy, what cardiovascular maternal adaptations occur?

A

Cardiac output is increased by 30-50% due to demands of uteroplacental circulation. This occurs at week 6.
Heart rate increases up to 90bpm
Blood pressure drops during the second trimester.
Cardiac output decreases in the last 8 weeks.

28
Q

During pregnancy, what haematological maternal adaptions occur?

A

Plasma volume increases with cardiac output.
Erythropoeisis increases
Hb is decreased by dilution.
Iron requirement increases.

29
Q

During pregnancy, what respiratory maternal adaptions occur? Also why do lung changes occur?

A

They occur partly due to the increased progesterone and partly due to the enlarging uterus.
Progesterone signals the brain to lower Co2.
Oxygen consumption increases to meet metabolic needs

These all increase the RR, tidal volume increases, pCo2 decreases slightly.

30
Q

During pregnancy, what urinary maternal adaptions occur?

A

GFR and renal plasma flow increase.
Increased re-absorption of ions and water
Slight increase in urine formation

31
Q

True or false. Postural changes affect renal functions.

A

True:
Upright position decreases
Supine position increases
Lateral position during sleep increases.

32
Q

What is pre-eclampsia?

A

Pregnancy induced hypertension and proteinuria.

33
Q

What is eclampsia?

A

Extreme pre-eclampsia.

34
Q

What signs will someone with pre-eclampsia have?

A

Hypertensive
Oedema formation- especially on the hands and face. This is due to kidney function declining leading to salt and water retention.
Renal blood flow and GFR decrease.

35
Q

Who is most at risk of pre-eclampsia?

A

More common in women with pre-existing hypertension, diabetes, autoimmune diseases, renal disease, family history of pre-eclampsia, obesity.

36
Q

What causes pre-eclampsia?

A

Not sure- could be:
Extensive secretion of placental hormones?
Immune response to foetus?
Insufficient blood supply to the placenta?

37
Q

What signs would a patient with eclampsia have?

A

Vascular spasms
Extreme hypertension
Chronic seizures and coma

38
Q

Treatment of eclampsia?

A

Vasodilators and C section.

39
Q

How many extra calories a day should a mother consume during pregnancy?

A

250-300kcal.

85% of this is for fetal metabolism, 15% for maternal fat stores.

40
Q

How much extra protein should a mother ingest during pregnancy?

A

30g/day

41
Q

What are the two phases of metabolism during pregnancy? Describe each.

A

1st to 20th week- Mothers anabolic (synthesis of molecules) phase
-Anabolic metabolism of the mother
-quite small nutritional demands of the foetus
21st to 40th week- catabolic phase
High metabolic demands of the foetus
Accelerated starvation of the mother.

42
Q

Describe the levels of glucose, sensitivity to insulin, glycogen stores, and growth during the anabolic phase of the mother

A

Normal or increased sensitivity to insulin
Lower plasma glucose level
Glycogen stores increase, lipogenesis (fat build up) occurs
Growth of breasts, uterus, weight gain.

43
Q

Describe the sensitivity to insulin, fat stores and transport to the placenta during the catabolic phase.

A

Decreased sensitivity to insulin- maternal insulin resistance
Increased transport of nutrients
Lipolysis (fat breakdown)

44
Q

What hormones cause insulin resistance in the catabolic phase?

A

HCS, cortisol and growth hormone

45
Q

What supplements are needed during pregnancy?

A

Iron supplements- 300mg of ferrous sulphate
B-vitamins- for erythropoeisis
Folic acid- reduces risk of neural tube
Vitamin D3 and calcium supplements.

46
Q

What should you give to mothers before partuition (giving birth)?

A

Vitamin K.

Prevents intracranial bleeding during pregnancy.

47
Q

Describe the changes in hormones towards the end of pregnancy?

A

Estrogen:Progesterone ratio alters increasing excitability of the placenta. Progesterone inhibits contractility while estrogen increases it.
Oxytocin increases- increasing contractility and excitability

NOTE- also mechanical stretch of the uterine muscles increases the contractility. Stretch of the cervix also increases contraction.

48
Q

What sort of contractions occur during labour?

A

Braxton Hicks contraction- they increase towards the end of pregnancy.

49
Q

What aids contractions during labour?

A

Stretch of the cervix by the fetal head increases contractility.
Cervical stretching also causes oxytocin release.
Strong uterine contraction and pain from the birth canal cause neurogenic reflexes from the spinal cord that induce intense abdominal muscle contractions.

50
Q

How does estrogen initiate labour? Where is it released from?

A

Induces oxytocin receptors on the uterus.

Mothers ovaries.

51
Q

How does oxytocin initiate labour? Where is it released from?

A

Released from the fetus and mothers posterior pituitary.
This stimulates the uterus to contract and stimulates the placenta to make prostaglandins. (these stimulate more vigorous contractions)

52
Q

What are the three phases of labour?

A

1st -Cervical dilation (8-24 hours)
2nd -Expulsion stage- passage through birth canal (few mins to 30 mins)
3rd stage- placental delivery

53
Q

Which hormones aid lactation and what is their function?

A

Estrogen-growth of ductile system
Progesterone- Development of lobule-alveolar system
Both of these inhibit milk production. At birth you get a drop in these and a rise in prolactin.

54
Q

What is the function of human chorionic somatomammotrophin? When is it produced?

A

Produced from about week 5 in pregnancy
Has growth hormone like effects- protein tissue formation
Decreases insulin sensitivity in mother.
Involved in breast development.

Reproduction (34 decks)

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