Physiology - Pregnancy

Question 1

Where does fertilisation usually occur?

Answer 1

Ampulla

Question 2

What does the fertilised ovum divide to form?

Answer 2

Blastocyst

Question 3

When does the blastocyst implant in the uterus?

Answer 3

Day 5-8

Question 4

What do the inner cells of the blastocyst form?

Answer 4

Embryo

Question 5

What do the outer cells of the blastocyst form?

Answer 5

Placenta

Question 6

What do the burrowing outer cells of blastocyst first form?

Cell type

Answer 6

cords of trophoblastic cells

Question 7

What is the maternal response to the cords of trophoblastic cells?

Answer 7

Capillary formation and growth of decidual layer

Question 8

From where is the placenta formed?

Answer 8

Trophoblast and decidual tissue

Question 9

Where does the embryo get its nutrition before the placenta is functional?

Answer 9

Invasion of trophoblastic cells into the decidua

Question 10

When does the placenta become functional?

Answer 10

Week 5

Question 11

How does HCG enable early nutrition of the embryo?

Answer 11

Stimulates Corpus Luteum to continue secreting progesterone, causing decidual cells to concentrate glucose, proteins and lipids

Question 12

Trophoblast cells at the Chorion differentiate into…

Answer 12

multinucleate syncytiotrophoblasts invading into decidua

Question 13

How are placental villi formed?

Answer 13

embryo sends capillaries into syncytiotrophoblast projections, creating villi covered in thin layer of tissue within intervillous space (which is filled with maternal blood)

Question 14

What is the respiratory function of the placenta?

Answer 14

Supply of oxygen and removal of CO2 to foetus, by exchange between O2 rich maternal blood and umbilical blood (mixed arterial and venous)

Question 15

How does O2 travel from maternal to foetal circulation?

Answer 15

Diffusion due to difference in PO2

Question 16

How does CO2 travel from foetal to maternal circulation?

Answer 16

Diffusion across reverse concentration gradient, partial pressure elevated in foetal blood

Question 17

Which vessel supplies the foetus with the oxygenated blood?

Answer 17

Umbilical vein

Question 18

Which vessels do the O2 poor maternal blood return to?

Answer 18

Uterine veins

Question 19

How does foetal Hb facilitate O2 supply to the foetus?

Answer 19

Foetal Hb is in a 50% higher concentration in foetal blood than in adults, and foetal Hb can carry more O2 in low PCO2 than in high PCO2

Question 20

How are the following transported between maternal and foetal circulation?

1. Water
2. Electrolytes
3. Glucose
4. Waste

Answer 20

1. diffusion along osmotic gradient
2. Follows water (NB iron and Ca2+ only move from mother to foetus)
3. Simplified transport
4. Diffusion based on concentration gradient

Question 21

What is the role of Human Chorionic Gonadotrophin (HCG)?

Answer 21

Prevents involution of Corpus Luteum

Also effects development of male sex organs

Question 22

If level of HCG has doubled, or increased > 60%, this is indicative of…

Answer 22

Ongoing viable pregnancy

Question 23

Falling levels of HCG is indicative of…

Answer 23

Failing pregnancy

Question 24

Static or slow rising HCG levels is indicative of…

Answer 24

Ectopic pregnancy

Question 25

High levels of HCG is also indicative of...

Answer 25

Multiple or molar pregnancy

Question 26

When do HCG levels normally fall?

Answer 26

12-14 weeks

Question 27

What is the role of Human Placental Lactogen?

Answer 27

Acts like Growth Hormone and causes protein tissue formation Decreases insulin sensitivity in the mother (to give more glucose to the foetus) Also involved in breast development

Question 28

What is the role of progesterone in pregnancy?

Answer 28

Development of decidual cells Decreases uterus contractility Preparation for lactation

Question 29

What is the role of Oestrogens in pregnancy?

Answer 29

Enlargement of uterus Breast development Relaxation of ligaments

Question 30

What are the maternal cardiovascular adaptations?

Answer 30

``` Increased CO (30-50%) Increased Hr (90/min) Decreased BP during 2nd trimester ```

Question 31

What are the maternal haematological changes?

Answer 31

Increased plasma volume Increased erythropoiesis (25%) Hb decreased by dilution which decreases viscosity Iron requirements increase to 6-7mg/day

Question 32

What changes are made to coagulation? And what are the benefit and risk?

Answer 32

Hypercoagulable state Benefit - reduces risk of haemorrhage during and after delivery Risk - increased risk of venous thrombosis

Question 33

What are the maternal respiratory changes?

Answer 33

Progesterone signals to lower CO2 levels and increase O2 consumption. This is done via: Increased RR Increased tidal and minute volume Slightly decreased PCO2

Question 34

What are the maternal urinary changes?

Answer 34

Increased GFR and plasma flow Increased reabsorption of ions and water due to placental steroids and aldosterone Slight increase in urine formation Postural changes

Question 35

Reference ranges in pregnancy (normal)

Answer 35

ALT < 30 uL (5-55) Urea <3.5 mmol/L 9(2.5-7.8) Creatinine <50 umol/L (44-80) Albumin 20-40 g/L (30-50)

Question 36

How many kcals extra is required by mother during pregnancy, and how many g of protein?

Answer 36

200 kcals | 30g protein

Question 37

What are the two phases of pregnancy regarding metabolism?

Answer 37

1. Week 1-20 - mothers anabolic phase where glycogen stores increased (lipogenesis) 2. Week 21-40 - high metabolic demands of the foetus (lipolysis)

Question 38

What are the special nutritional needs during pregnancy?

Answer 38

``` Folic acid (folate) Vitamin D High protein Iron B vitamins ```

Question 39

Why is folic acid important in pregnancy?

Answer 39

Reduces the risk of neural tube defects

Question 40

What influences uterine excitability?

Answer 40

Oestrogen:Progesterone ratio Prostaglandins from placental and decidua Oxytocin from maternal posterior pituitary Mechanical stretch of uterine muscles

Question 41

How does the Oestrogen:Progesterone ratio effect uterine excitability?

Answer 41

Progesterone inhibits contractility. Oestrogen increases contractility. Towards the end of pregnancy, increase of oestrogen from the ovaries induces oxytocin receptors on the uterus. Oxytocin from others posterior pituitary causes uterus to contract, and stimulates placenta to make prostaglandins, which stimulate more vigorous contractions.

Question 42

What is the pattern of contractions during the onset of labour?

Answer 42

1. Braxton Hicks increase towards the end of pregnancy 2. Cervical ripening occurs, stretch of cervix increased contractility and oxytocin release 2. Stronger contractions and pain from birth canal cause neurogenic reflexes to induce intense abdominal muscle contractions

Question 43

What are the three stages of labour, and how long does each roughly last?

Answer 43

1. Dilatation - 8-24 hours 2. Expulsion - passage of foetus through birth canal (up to 120 mins) 3. Placental

Question 44

What hormones influence lactation?

Answer 44

Oestrogen Progesterone Prolactin Oxytocin

Question 45

What are the roles of oestrogen and progesterone in lactation?

Answer 45

Oestrogen - growth of ductile system Progesterone - development of lobule alveolar system Both inhibit milk production - these suddenly drop at birth.

Question 46

What is the role of prolactin in lactation?

Answer 46

Stimulates milk production - steadily rises from week 5 until birth, and first 7 days after birth there is very high milk production. Also stimulates colostrum.

Question 47

What is the role of oxytocin in lactation?

Answer 47

Milk Let Down Reflex

Question 48

Describe the milk let down reflex

Answer 48

1. Receptors in nipple stimulated 2. Impulses propagated to spinal cord 3. Stimulation of hypothalamic nuclei 4. Oxytocin released 5. Milk ejected

Question 49

Describe the signalling pathways in lactation

Answer 49

1. Stimulus at higher brain centres (mechanical or sound of cry) 2. Oxytocin neurons activated and PIH cells inhibited at hypothalamus 3. Increased prolactin from anterior pituitary, and increased oxytocin released from posterior. 4. Milk secretion and smooth muscle contraction, respectively.