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MRCOG - Part 1 > Physiology > Flashcards

Physiology Flashcards

1
Q

Where in the kidney is the main resorption site for all ions?

A

Proximal convoluted tubule

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2
Q

What activates the intrinsic pathway of the clotting cascade?

A

Damaged endothelium

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3
Q

What activates the extrinsic pathway of the clotting cascade?

A

Tissue factor

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4
Q

What activates thrombin?

A

Prothrombin

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5
Q

What is the action of thrombin?

A

Fibrinogen —> fibrin

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6
Q

What is the lifespan of a RBC?

A

120 days

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7
Q

What is the lifespan of a WBC?

A

2-5 days

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8
Q

What is the lifespan of platelets?

A

5-9 days

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9
Q

What LFT parameters are raised during pregnancy?

A

ALP; GGT

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10
Q

What LFT parameters are reduced during pregnancy?

A

AST; ALT; bilirubin; albumin

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11
Q

What is the trigger for ADH release?

A

High serum osmolality

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12
Q

What is the weight of the non-pregnant uterus?

A

40-50g

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13
Q

What is the weight of the pregnant uterus?

A

1200g

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14
Q

What holds platelets together in the 1st stage of wound healing?

A

Fibrin

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15
Q

By what proportion does oxygen consumption increase in pregnancy?

A

20%

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16
Q

By what proportion does tidal volume increase in pregnancy?

A

50%

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17
Q

By what proportion does minute ventilation increase in the first trimester of pregnancy?

A

50%

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18
Q

What are the cardiovascular changes that occur during pregnancy?

A

Blood volume slowly increases by 40-50%
Heart rate rises by 15 beats/min above baseline
Stroke volume increases by 25-30%
Cardiac output increases by approximately 30-50%
Systemic vascular resistance (SVR) decreases by 20-30%

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19
Q

What causes the increase minute ventilation during pregnancy?

A

Progesterone - it is known to directly stimulate ventilation by sensitizing the CNS respiratory centres to CO2

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20
Q

By what proportion does eGFR increase in pregnancy?

A

40%

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21
Q

In what ways does vasopressin/ADH promote water retention?

A

1) Insertion of water channel proteins called aquaporins into the collecting duct and DCT
2) Increased activity of urea transport proteins in the collecting duct promoting urea flow out of the collecting duct and water via increased osmotic gradient
3) Increased sodium reabsorption across the ascending loop of Henle

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22
Q

What lung parameters are unchanged in pregnancy?

A

FEV1 and FVC

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23
Q

At what point does fetal urine become a major contributor to amniotic fluid?

A

Week 18 - up until then the major contributors are placenta and fetal skin

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24
Q

What are the only vitamins whose daily requirements don’t increase in pregnancy?

A

Vitamin D and vitamin K

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25
Q

At what gestation do the definitive alveolar form?

A

Week 36

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26
Q

Which lung volume decreases in pregnancy?

A

Functional residual capacity

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27
Q

How is haemolytic disease of the newborn tested for?

A

Direct Coombs test

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28
Q

How does gestational diabetes affect free fatty acids and plasma ketones bodies?

A

Increased FFA and ketones bodies

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29
Q

By how many x is ALP increased in pregnancy?

A

x3

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30
Q

Oxygen consumptions increases by 20% in pregnancy, how much is this in ml/min?

A

50ml/min

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31
Q

By how much is total lung capacity decreased in pregnancy?

A

200ml decrease

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32
Q

What proportion of body calcium is stored in the skeletal system?

A

99%

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33
Q

At what gestation is dilutional anaemia at its greatest?

A

32/40

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34
Q

What is anuria?

A

<100ml produced in 24 hours

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35
Q

What is oliguria?

A

100-400ml or urine produced in 24 hours

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36
Q

What is normal urine output?

A

0.5-1ml/kg/hour, in infants 2ml/kg/hour

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37
Q

What is polyuria?

A

> 3000ml produced in 24 hours

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38
Q

How do LFTs change in pregnancy?

A

Albumin falls

ALP can be x3 higher (because the placenta also produces it)

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39
Q

Which layer of the ovarian follicle is vascular?

A

Theca layer

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40
Q

For how long do follicles have to grow before they can be recruited into the menstrual cycle?

A

65 days

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41
Q

Once follicles have reached the antral phase (resting — preantral — antral —- ovulatory phase) what hormone are they dependant upon for growth?

A

FSH

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42
Q

What drives cholesterol conversion to androgens, and in what cells?

A

LH drives

In Theca cells

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43
Q

What drives androgen conversion to estradiol, and in what cells?

A

FSH drives

Catalysed by aromatase in the granulosa cells

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44
Q

What are the features of a dominant follicle?

A

More FSH receptors
More granulosa cells
Higher intracellular cyclic adenosine monophosphate lvels

FSH causes the dominant follicle then induce LH receptors on the granulosa cells, allowing this dominant follicle to survive, whilst the FSH levels falls and so the other small follicles die by atresia

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45
Q

Which hormone causes the completion of the first meiotic division of the oocyte after ovulation?

A

LH

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46
Q

What induces the 2nd meiotic division of the oocyte?

A

Fertilisation

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47
Q

What is the thickness of the endometrium during the luteal/secretory phase?

A

6mm

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48
Q

What is normal testicular volume?

A

15-30ml

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49
Q

How much cooler are the testes compared to core body temperature?

A

1.5-2 degrees

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50
Q

What cells line the tubules of the testes?

A

Sertoli

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51
Q

What are the cell stages of spermatozoa?

A

Spermatogonia — primary spermatocytes — secondary spermatocytes — spermatids — spermatazoon

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52
Q

How long is the epididymis?

A

5m (highly coiled)

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53
Q

How long does it take for the spermatozoa to pass through the epididymis?

A

8-14 days

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54
Q

What is the combined length of the male and female reproductive tract that a sperm must traverse in order to fertilise an oocyte?

A

30-40cm

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55
Q

To what pH does ejaculate raise the vagina to, and why?

A

Rises it from 3-4 to 7.2

This is because the motility of the sperm is inhibited by acidic pH

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56
Q

Where does capacitation occur, and what is its purpose?

A

Occurs in the presence of uterine or uterine tube fluid, usually in the ampulla of the tube.
It alters the surface of the sperm head to make it more responsive to signals in the immediate area of the oocyte

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57
Q

By how many litres does cardiac output increase in pregnancy?

A

30-50%, from 4.5L/min to 6L/min

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58
Q

When does the rise in cardiac output plateau during pregnancy?

A

24-30/40

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59
Q

By what proportion does heart rate increase in pregnancy?

A

10%

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60
Q

By how many mmHg does BP fall in pregnancy?

A

From 8-36/40 SBP falls by 5mmHg and DBP falls by 10mmHg

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61
Q

How does the axis of the heart change in pregnancy and why?

A

The axis is shifted anteriorly and to the left as a result of the upward displacement of the diaphragm by the enlarging uterus

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62
Q

What are the ECG changes in pregnancy?

A

L axis deviation by approx. 15 degrees
Inverted T wave in lead III
Q waves in leads III and aVF

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63
Q

How does the increase in ventilation in pregnancy affect blood gases?

A

pCO2 falls to 4.1 (normal 4.7-6.0)

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64
Q

How does the slightly lower pCO2 effect bicarbonate?

A

PCO2 fall causes the blood to becomes slightly alkaline, in response the bicarbonate levels fall to 19-20 (normal 22-26)

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65
Q

How does residual volume change in pregnancy?

A

From 1500ml (non-pregnant) to 1300ml

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66
Q

How does total lung capacity change in pregnancy?

A

From 5L (non-pregnant) to 4.8L

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67
Q

By how many ml/minute does oxygen consumption increase in pregnancy? And how is that distributed?

A

Increased by 50ml/min

  • –> 20ml/min to fetus
  • –> 6ml/min to increased cardiac output
  • –> 6ml/min to increased renal work
  • –> 18ml/min to increase in metabolic rate
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68
Q

By how much do the kidneys increase in size in pregnancy?

A

1cm

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69
Q

What is the glomerular filtration rate during pregnancy?

A

140-170ml/minute

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70
Q

How does U&Es change during pregnancy?

A

Urea falls from 4.3 to 3.1

Serum creatinine falls from 73 to 47

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71
Q

Why does sickness occur in pregnancy?

A

Gastrointestinal tone and motility are reduced by progesterone, resulting in delayed gastric emptying

This reduced motility also increases stool transit time, allowing more time for colon reabsorption of water, making constipation more common

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72
Q

Why are pregnant women more prone to gallstone formation?

A

Due to reduced gallbladder contractility

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73
Q

By what proportion does plasma volume increase in pregnancy?

A

45% (2600ml —> 3800ml)

Expansion reaches its peak at 32/40

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74
Q

Which coagulation factors increase in concentration in pregnancy?

A

VII
VIII
X

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75
Q

Which coagulation factors are unchanged in pregnancy?

A

XI

XIII

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76
Q

What is the average milk production per day?

A

500-1000ml/day

Equilibrium in breastfeeding mothers is reached at approx. 3/52 whereby milk production is tailored to requirement

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77
Q

What is the energy content of 100ml breast milk?

A

75 kcal

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78
Q

Why is breast milk advantageous in babies with diarrhoea?

A

Because breastmilk has approx. 1/3rd to conc of sodium and chloride concentration compared to cows milk, and high solute load (as in cows milk) can exacerbate diarrhoea

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79
Q

What are the different types of lochia?

A

Lochia rubra - red
Lochia serosa - pink
Lochia alba - white

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80
Q

What promotes the formation of more myometrial gap junctions as labour approaches?

A

Oestrogen
increased myometrial gap junctions allow the transmission of chemical and electrical signal and so promote coordinated contraction

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81
Q

Which COX increases rapidly at the onset of labour?

A

COX-2 - this increases prostaglandin synthesis

82
Q

What brings about cervical ripening?

A

Prostaglandins and interleukin 8 cause neutrophils to be attached to the cervix where they release collagenase, leading to proteolysis of the collagen fibres of the cervix, making it softer and more stretchy

83
Q

What is the equation for cardiac output?

A

Cardiac output = stroke volume x heart rate

84
Q

How is cardiac output measured in a fetus and why?

A

Cardiac output ina fetus = combined ventricular output

Measured like this because int eh fetal circulation blood is shunted across the ductus venosus, foramen ovale and ductus arteriosus, meaning that the SV for each ventricle isn’t equal.

85
Q

What proportion of blood does the RV receive?

A

Two thirds

86
Q

What proportion of blood does the LV receive?

A

One third

87
Q

How does the fetal heart differ from the adult heart?

A

1) Smaller amount contractile tissue
2) Myofibrils are arranged in a less organised manner
3) Less compliant (i.e. more stiff) owing to the constraining effects of the lung and chest in teh absence of air

88
Q

What is the principle way in which a fetus can increase their cardiac output? And why?

A

Increased HR
Because of the factors that make the fetal heart different from the adult heart, it has very little functional reserve, and therefore limited capacity to increase stroke volume

89
Q

What is the main source of fuel of the cardiac fetus? Compared to adults?

A

Lactate and carbohydrates

In adults the main source is long chain fatty acids

90
Q

What is the definition of a deceleration?

A

A decrease of 15 beats/min for at least 15 seconds

91
Q

What is an early deceleration?

A

Deceleration that occurs during uterine contractions

92
Q

What is a variable deceleration?

A

Deceleration that occur without a regular pattern in terms of relation to contractions, length and depth

93
Q

What is a late deceleration?

A

Deceleration that starts before the peak of the contraction, and the nadir of the deceleration occuring AFTER the peak of contraction

94
Q

What does the ductus venosus shunt between?

A

Shunt from the umbilical vein to the IVC

95
Q

What does the foramen ovale shunt between?

A

From the RA to the LA

96
Q

What does the ductus arteriosus shunt between?

A

From the RV to the pulmonary artery to the aorta

97
Q

What happens when the mixed oxygenated blood enters the fetal RA?

A

It is divided into two streams - high velocity oxygenated blood is pushed towards the left side, the low velocity deoxygenated blood towards the right. This results in the more oxygenated blood be pushed across the foramen ovale, and so the blood in the LV being more highly oxygenated than the RV

98
Q

What is the purpose of the ductus arteriosus?

A

Allows blood to bypass the immature lungs

99
Q

What maintains the patency of the ductus arteriosus?

A

By the vasodilatory effects of prostaglandins - PGE1 and PGE2 - an dprostacyclin (PGI2)

100
Q

What causes the ductus arteriosus to close?

A

The fall in pulmonary pressure (resulting in there being less pressure to push blood from the pulmonary artery across the ductus arteriosus into the aorta it connects with)
The rise in systemic pressures

101
Q

When on average does the ductus arteriosus close?

A

2 days after birth

102
Q

When does the ductus venosus usually close?

A

1-3 weeks after birth in a term infant

103
Q

What are the 5 stages of lung development?

A
  1. Embryonic
  2. Pseudoglandular
  3. Canalicular
  4. Saccular
  5. Alveolar
104
Q

When does embryonic lung development occur, and what happens?

A

Conception to 7 weeks

Formation of main bronchi and bronchopulmonary segments

105
Q

When does pseudoglandular lung development occur, and what happens?

A

7-17 weeks

Branching of airways and vessels

106
Q

When does canalicular lung development occur, and what happens?

A

17-27 weeks

Formation of the acini - the gas-exchanging parts of the lung

107
Q

When does saccular lung development occur, and what happens?

A

28-36 weeks

Enlargement of the peripheral airways, formation of the terminal sacs

108
Q

When does alveolar lung development occur, and what happens?

A

36 weeks to 2 years post-birth

Formation of the definitive alveoli

109
Q

How many alveoli will form per acinus?

A

1000

110
Q

What is thought to be the purpose of fetal breathing movements?

A

To regulate lung growth by lung fluid regulation and lung cell growth

111
Q

Which types of cell produce surfactant?

A

Type II pneumocytes

112
Q

When does platelet production begin?

A

At week 6 in the yolk sac

At week 8 in the liver

113
Q

When does it switch from fetal Hb being the most predominant Hb to adult Hb?

A

Between birth and 12 weeks postnatally

114
Q

At what gestation are B cells seen in the circulation?

A

Week 12

115
Q

At what gestation are mature T cells seen in the circulation?

A

Week 14

116
Q

When do intestinal villi start to develop?

A

Week 7

117
Q

What is the swallowing rate at term?

A

250ml/day

118
Q

What is the volume of amniotic fluid in pregnancy?

A

Week 12 - 50ml
Week 16 - 150ml
Week 34 - 1000ml (having increased 50ml/week from week 16)
Term - 500ml

119
Q

What blood results are seen in DIC?

A

Thrombocytopenia
Prolonged APTT
Low fibrinogen

120
Q

Which equation is used for eGFR?

A

MDRD (modification of diet in renal disease) equation

121
Q

What factors are included in the eGFR equation?

A

Age
Creatinine
Gender
Ethnic group

122
Q

How does tidal volume change in pregnancy?

A

40% increase

123
Q

What is the equation for stroke volume?

A

SV = EDV - ESV

124
Q

What is the size of the dominant ovarian follicle at the time of ovulation?

A

20mm

125
Q

What is the equation for vital capacity?

A

Vital capacity = inspiratory capacity + expiratory reserve volume

126
Q

What is the function of bile salts?

A

Absorption of fats

127
Q

What is total blood volume?

A

5.6L

128
Q

What is the maintenance fluid volume requirement?

A

30ml/kg/day

129
Q

What is the anion gap?

A

The difference between the concentrations of the body’s cations and anions

130
Q

What causes an increase anion gap?

A

Lactic acidosis
Ketoacidosis
Hypoalbuminaemia

131
Q

What is the normal pH/base excess of fetus’?

A

Base excess in vein = -1-9
pH in vein = 7.17-7.48

Base excess in artery = -2.5-10
pH in artery = 7.05-7.38

132
Q

By how much does osmolarity decrease in pregnancy? And as a result of what?

A

10mOsm/L

As a result of progesterone

133
Q

On what type of receptors doe PTH act on?

A

G protein-coupled receptor

134
Q

Which hormone is important for placental Ca2+ transport?

A

PTHrP

135
Q

Where is calcitonin produced?

A

C cells in the thyroid

136
Q

What is the action of calcitonin?

A

Act to decrease circulating calcium by:

  1. Preventing osteoclast actions
  2. Decreased reabsorption of Ca2+ and phosphate from the PCT
  3. Decreased C2+ absorption from the GIT
137
Q

Where is vitamin D produced?

A

Skin, decidua, placenta

138
Q

What autosomal dominant traits put you at increased risk of parathyroid cancer?

A

MEN1

MEN2A

139
Q

What is the age of peak bone mineral density?

A

25

140
Q

What are the osteoblast modulators?

A

PTH
Oestrogen
Glucocorticoids
Thyroid hormone

141
Q

What are the osteoclast modulators?

A

TNF
IL-1/IL-6
GM-CSF

142
Q

When does ossification occur during pregnancy?

A

3rd trimester

143
Q

What is the A wave of the JVP?

A

Atrial systole

144
Q

What is the X wave of the JVP?

A

Occurs at the end of atrial systole

145
Q

What is the C wave of the JVP?

A

Ventricular systole

146
Q

What is the V wave of the JVP?

A

Atrial filling against closed tricuspid valve

147
Q

What is the Y descent of the JVP?

A

Occurs when tricuspid valve opens

148
Q

What is the 1st heart sound?

A

Atrioventricular valve closure (at the start of ventricular systole)

149
Q

What is the 2nd heart sound?

A

Semilunar valve closure (at the end of ventricular systole)

150
Q

What is the 3rd heart sound?

A

Occurs at the beginning of ventricular diastole, due to rapid ventricular filling.
Common in pregnancy

151
Q

What is the 4th heart sound?

A

Atrial systole

Absent in AF

152
Q

What does pre-load depend on?

A
  1. Intrathoracic pressure
  2. Total blood volume
  3. Gravity
  4. Calf muscle action
  5. Venous return
153
Q

What does after-load depend on?

A

Arterial resistance

154
Q

What is Starling’s Law?

A

1) Force of contraction proportional to fibre length
2) Fibre length is proportional to stretch of ventricular muscle
3) Ventricular dilatation is proportional to venous return

155
Q

Where are baroreceptors found?

A

Carotid sinus
Aortic body
Floor of 4th ventricle

156
Q

What are baroreceptors?

A

Sensitive to pressure, inhibitory in nature

157
Q

What chemical cause the vasodilation that occurs in pregnancy?

A
  1. Increased NO
  2. Decreased ADMA
  3. Increased prostacyclin(PGI2)
158
Q

What factors effect ventilation?

A

Airway compliance

Airway resistance

159
Q

What is minute volume (MV)?

A

The total volume of gas entering the lung per minute

TMV = TV x RR

160
Q

What is TV in ml/kg?

A

7ml/kg - i.e. approx. 500ml

161
Q

What does a left shift on an oxygen dissociation curve indicate?

A

Higher affinity for O2

162
Q

What factors cause a left shift on an oxygen dissociation curve?

A

CO
Fetal Hb
Decreased 2,3-DPG

163
Q

What does a right shift on an oxygen dissociation curve indicate?

A

Decreased affinity for O2

164
Q

What factors cause a right shift on an oxygen dissociation curve?

A

Hyperthermia
Acidosis
Hypercapnia

165
Q

How long does gastric and intestinal emptying take?

A

Gastric emptying - 2-6 hours

Intestinal emptying - 3-5 hours

166
Q

What is transit time through the large bowel?

A

24-150 hours

167
Q

What does the macula densa measure, and where is it found?

A

Measures sodium concentration

Macula densa found in the ascending loop of Henle

168
Q

What are the ascending impulses from bladder during bladder filling?

A

Bladder wall receptors —> pelvic splanchnic nerve —> sacral root S2-S4 —> lateral spinothalamic tract —> higher centres

169
Q

When do the primordial follicles appear in-utero?

A

At 6 months gestation

170
Q

What are the two phases of follicular growth?

A

Pre-antral - independant of FSH

Antral (Graafian) - dependant on FSH

171
Q

How long is the period between resting follicle and ovulation?

A

375 days

172
Q

How long in the period between pre-antral follicle and ovulation?

A

90 days

173
Q

Where do primordial germ cells originate?

A

Originate in the yolk sac, and then migrate into the ovaries

174
Q

What controls the proliferative phase of the menstrual cycle?

A

Oestrogen produced by the Graafian follicle

175
Q

What controls the secretory phase of the menstrual cycle/

A

Corpus luteum

176
Q

How long does the corpus luteum persist in pregnancy?

A

6 months (but its function is replaced by the placenta after 3 months)

177
Q

What body mass is required for menarche?

A

48kg, with 17% of it being fat

178
Q

What are the normal semen parameters?

A 
Volume = 1.5ml
Sperm count per ml >15million
Sperm per ejaculate >33 million
Vitality >55%
pH 7.2-7.6
Motility >38%
Progressive motility >31%
Normal morphology >3%
179
Q

What is the space between the pubic symphysis joint in pregnancy?

A

Up to 9mm

180
Q

In generating an action potential, what is depolarisation due to?

A

Rapid opening of voltage-gated Na+ channels

181
Q

In generating an action potential, wha is repolarisation due to?

A

Slow opening of the voltage-gated K+ channels

Closure of voltage-gated Na+ channels

182
Q

What MAP is required to maintain cerebral perfusion?

A

> 70mmHg

183
Q

Describe the pre-ganglionic/post-ganglionic fibres of the SNS and PNS?

A

SNS pre-ganglionic fibres - cholinergic
PNS pre-ganglionic fibres - cholinergic

SNS post-ganglionic - adrenergic (except sweat glands that are cholinergic)
PNS post-ganglionic - cholinergic

184
Q

What are the 4 cells types of the epidermis?

A

Keratinocytes
Melanocytes
Langerhans cells
Merkel cells

185
Q

What are the layers of the epidermis?

A

Stratum corneum
Stratum lucidum
Stratum granulosum
Stratum spinosum

186
Q

What changes occur to the skin during pregnancy?

A
  1. Striae gravidarum
  2. Chloasma
  3. Increased skin pigmentation
  4. Linea nigra
  5. Increased activity of the sebaceous and sweat glands
187
Q

What is the osmolality of amniotic fluid?

A

275mOsm/L

188
Q

At term how much urine does the fetus produce?

A

700-900ml/day

189
Q

How many ml is the first fetal breath?

A

10-60ml

190
Q

What do the first and second fetal inspiratory efforts require in terms of pressure?

A

1st inspiratory effort requires a transpulmonary pressure of 60cmH20
2nd inspiratory effort requires a transpulmonary pressure of 40cmH20

191
Q

What are the first fetal breaths triggered by?

A

Hypercapnia and hypoxia resulting fro partial occlusion of umbilical cord, and is promoted by 1) tactile stimulation; 2) decreased skin temperature

192
Q

What are the risk factors for RDS?

A
  1. Male
  2. C-section
  3. Perinatal asphyxia
  4. Maternal diabetes
  5. 2nd twin in an twin pregnancy
193
Q

What causes the ductus arteriosus to close?

A

Rapid rise in pO2 at birth causing smooth muscle contraction and fall in prostaglandin levels

194
Q

Where does foetal erythropoiesis take place?

A

3/40 - placenta and yolk sac
4/40 - liver and endothelium of blood vessels
End of first trimester - bone marrow and spleen

195
Q

When do primips/multips first begin to feel movement?

A

Primips - at 18 weeks

Multips - at 16 weeks

196
Q

How many lobules are there in each placenta?

A

40-60

197
Q

What are the pressures in the umbilical artery/umbilical vein/maternal spiral artery?

A

Umbilical artery = 50mmHg
Umbilical vein = 20mmHg
Maternal spinal artery = 70mmHg

198
Q

When do vernix and lanugo hair start to develop in the fetus?

A

Week 20

199
Q

At what gestation does the fetus shed lanugo?

A

Week 36

200
Q

What is avergae weight gain/week of the fetus?

A 
<28/40 = 100g/week
>28/40 = 200g/week
201
Q

Where a platelets produced?

A

Megakaryocytes

MRCOG - Part 1 (13 decks)

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