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Part 1 MRCOG > Physiology > Flashcards

Physiology Flashcards

1
Q

Half life of LH

A

60 mins

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2
Q

Half life of FSH

A

170 minutes (3h)

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3
Q

Half life of hCG

A

24 hours

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4
Q

Structure of GnRH

A

Decapeptide (10x peptides)

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5
Q

Source of cholesterol in term foetus

A

De novo synthesis in their own liver

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6
Q

Post menopausal ratio of uterus:cervix

A

1:1 or cervix is bigger than uterus 1:2

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7
Q

Largest cell in human body

A

Oocyte

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8
Q

How is magnesium excreted by the body?

A

Kidneys and faeces

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9
Q

Haldane effect

A

The ability of deoxygenated hemoglobin to carry more carbon dioxide (CO2) than in the oxygenated state, reflecting a tendency for an increase in pO2 to diminish the affinity of Hb for CO2

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10
Q

Umbilicus: how many arteries/ veins?

A

2 arteries (deoxygenated blood)
1 vein (oxygenated blood

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11
Q

When can the quadruple test be done and what does it include?
What indicates Down’s syndrome?

A

Second trimester (14-20 weeks)
Beta hCG, inhibin A, AFP and estradiol

Raised bHcG, raised inhibin A
Low AFP and low estradiol

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12
Q

What does the combined test involve and when can it be done?

Results suggestive of downs/ patau/ Edwards?

A

Nuchal translucency & PAPP-A/ beta hCG
11+2 until 14+1 gestation

Downs: Raised NT, low PappA, raised bhCG
Edwards & Patau: Raised NT, low PappA and bhCG

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13
Q

What happens to 2,3 DPG in pregnancy?

A

Increased concentration (by 30%) –> decrease in maternal red cell O2 affinity, facilitating transport of oxygen across placenta

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14
Q

How much does total lung volume decrease by in pregnancy?

A

200ml

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15
Q

What happens to expiratory reserve volume in pregnancy? (therefore functional residual capacity)

A

It reduces

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16
Q

How does minute ventilation/ volume change in pregnancy?

A

It increases by 40%

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17
Q

Difference between fetal Hb and adult Hb

A

Fetal Hb has higher affinity for O2 and can resist denaturation by strong acid/ alkali more than adult Hb

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18
Q

Path of sperm penetration

A

Corona radiata
Zona pellucida
Perivitelline space
Plasma membrane

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19
Q

Face presentation diameter

A

9.5cm (when hyperextended)- submento-bregmatic

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20
Q

Coagulation factors that increase during pregnancy

A

all except XI and XIII

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21
Q

3 fold increase in cortisol in pregnancy. Mechanism?

A

Increased unopposed oestrogen

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22
Q

Prolactin levels in pregnancy compared to pre-pregnancy

A

10 fold increase

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23
Q

Changes in blood composition during pregnancy

A
  • Platelet count reduces
  • Increased coagulation factors (VII, VIII, IX, X, XII)
  • Increased fibrinogen
  • Increased ESR
  • Protein S levels reduce (physiological anticoagulant)
  • Reduced XI and XIII
  • Antithrombin III and protein C are unchanged
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24
Q

How much does renal blood flow increase by in pregnancy?

How much does eGFR increase by?

How much do kidneys increase in size?

A

50-60%

eGFR: 40% (by end of 1st trimester)

Around 1cm

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25
Q

Lung volume changes in pregnancy

A

Functional residual capacity reduced by term by approx 20%.

Total lung capacity reduced by approximately 5% (200ml)

Residual Volume reduced by approximately 20%- leading to reduction in IRV and ERV

Tidal volume is increased by approximately 50%.
Minute ventilation increase by about 50% during 1st trimester.
Oxygen Consumption increases by approx 20% (50ml/min)

FEV1 and FVC are unchanged
Tidal volume unchanged
RR unchanged

PCO2 decreases.
PO2 increases.
pH remains normal or increases slightly (renal compensation: HCO3- decreases)

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26
Q

Typical volume increase from a non-pregnant to term uterus?

A

10ml to 5000ml

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27
Q

Typical weight of a non-pregnant vs pregnant uterus

A

40-50g

1100-1200g

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28
Q

Calcitonin production causes what response

A

Inhibits calcium absorption by the intestines

Inhibits osteoclast resorption of bone

Stimulates osteoblast activity in bone to sequester calcium

Inhibits renal tubule resorption of calcium

Increases urinary calcium excretion

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29
Q

Primary form of fetal haemoglobin

A

<12 weeks, primary form is Embryonic Hb (Hb Gower 1)

> 12 weeks, fetal Hb

By 6 months, adult Hb is primary form >98%

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30
Q

What is reabsorbed in the PCT?

A

Glucose
Amino acids
Carboxylate
Bicarbinate
Phosphate
Potassium
Sodium
Urea
Calcium, magnesium, water

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31
Q

99% of body calcium is in what form?

A

Calcium phosphate (in bone- hydroxyapatite)

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32
Q

Cardiovascular changes in pregnancy

A

Blood volume increases by 30%: Plasma increases by 40-50% & red cell mass by 25-30%

Heart rate rises by 15 beats/min above baseline

Stroke volume increases by 25-30%

Cardiac output increases by approximately 30-50% (Increased by 1.5L at term, 30% of which goes to uterus- 400ml/min)

Systemic vascular resistance (SVR) decreases by 20-30%

Diastolic blood pressure consequently decreases between 12 and 26 weeks but increases again to pre-pregnancy levels by 36 weeks

A third heart sound after mid-pregnancy

Systolic flow murmurs

ECG changes:
- LAD (around 15 degrees)
- Inverted T wave in lead III
- a Q wave in leads III and aVF

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33
Q

Average lifespan of RBC/ platelet/ WBC

A

RBC: 120 days
Plt: 5-9 days
WBC: 2-5 days

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34
Q

At what stage of fetal development does fetal Hb replace embryonic Hb?

A

10-12 weeks

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35
Q

Effect of vasopressin (ADH)

A

Promotes water retention by:
- Insertion of aquaporins into collecting duct and DCT
- Increased activity of urea transport proteins in the collecting duct promoting urea flow out of the collecting duct and water via osmotic gradient
- Increased sodium reabsorption across the ascending loop of Henle

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36
Q

How is ADH/ vasopressin secreted?

A

Receptors in the hypothalamus detect increases in serum osmolality and stimulate the posterior pituitary to secrete ADH

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37
Q

During the inflammatory stage of wound healing, what is the predominant cell type found? (D3-4)

A

Macrophages

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38
Q

Typical oxygen consumption in a non-pregnant vs pregnant woman (75kg)

A

Non-pregnant: 250ml/min

Pregnant, increases by 20%: 300ml/min

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39
Q

Changes to biliary physiology in pregnancy

A

Due to increasing circulating oestrogen and progesterone:
- Inhibition of canalicular excretion leading to cholestasis and itching

  • increased cholesterol synthesis
  • Increased bile acid concentration (increased lithogenic index) and increased risk of gallstones
  • Increased spider naevi (50% patients)
  • Incomplete gallbladder emptying
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40
Q

How is the intrinsic/ extrinsic pathway activated in the clotting cascade?

A

Extrinsic: tissue factor

Intrinsic: damaged endothelium

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41
Q

Body composition

A

Intracellular fluid = 40% body weight, 60-70% of body water

ECF = 20% of body weight,
30-40% of body water
ECF = plasma & interstitial fluid

Plasma volume + around 3L (5% body weight)

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42
Q

Intracellular/ Extracellular anion/ cation

A

ICF cation: K+
ICF anion PO4-

ECF cation: Na+
ECF anion: Cl-

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43
Q

When does oocytogenesis complete?

A

Either at birth or shortly before (3rd trimester)

44
Q

When does ootidogenesis complete?

A

Comprises both meiotic divisions.

First meiotic division halts until puberty

Second meiotic division only completes at fertilisation

45
Q

Increase in oxygen consumption in pregnancy at term?

A

50ml/min

46
Q

At what gestation does the maximum physiology anaemia occur?

A

32 weeks

47
Q

How much does ALP increase in pregnancy?

A

May reach 3x upper limit of normal

48
Q

Average size of:
- Resting follicle
- Prenatal phase follicle
- Antral phase follicle
- Pre-ovulatory phase follicle

A

Resting follicle
0.02mm
Preantral phase follicle
0.2mm
Antral phase follicle
2mm
Pre-ovulatory phase follicle
20mm

49
Q

What is the name of the fluid filled space in a follicle?

A

Antrum

50
Q

What proportion of primordial follicles undergo atresia to create a primary follicle?

A

99%

51
Q

what is the structure between the theca cells and the mural granulosa?

A

Basal lamina

52
Q

Where are the cumulus granulosa cells?

A

They surround the oocyte

53
Q

Which part of spermatozoa has highest concentration of mitochondria?

A

Middle piece

54
Q

Summary of spermatogenesis

A

Spermatogonium (2n) undergoes mitotic division to produce daughter spermatogonium (2n).

Daughter spermatogonium undergo growth and differentiation to produce primary spermatocyte (2n)

Primary spermatocyte undergoes Meiosis I to produce 2x secondary spermatocytes (1n)

Secondary spermatocytes undergo meiosis II to produce 4x (1n) spermatids.

Spermatids undergo spermeogenesis to produce spermatozoa.

55
Q

Primary anions in blood

A

Bicarbonate and chloride

56
Q

When does the LH surge happen and when does ovulation occur in relation to this?

A

LH surge occurs 24h post oestrogen surge.

Ovulation occurs 16-18h post LH surge.

57
Q

Which hormone rises prior to onset of menses?

A

FSH

58
Q

Sources of inhibin

A

Granulosa cells
Corpus luteum

59
Q

Half life of prolactin

A

20 minutes

60
Q

What impact does estradiol have on prolactin?

A

It increases its production

61
Q

Lifespan of ovum and sperm

A

Ovum <72h
Sperm <5d

62
Q

Corpus luteum
- What hormones does it produce?
- What receptors/ cells does it have?
- How long does it persist for?
- When is it no longer essential to a pregnancy?

A

Produces
Progesterone, Oestrogen , Relaxin, Inhibin A, Inhibin B

Has LH receptors
Contains lipid laden cells

Persists for 6 months.
Placenta takes over function after 3/12

No longer essential to pregnancy at 6 weeks gestation

63
Q

When does regression of corpus luteum happen in relation to menses?

A

3-4 days prior, allowing levels of progesterone/ oestrogen and inhibin to fall

64
Q

Hormones of spermatogenesis

A

GnRH – starts age 10 (Testicular size increase is first sign of puberty)

FSH stimulates spermatogenesis in seminiferous tubules Sertoli cells

LH acts on leydig cells, stimulating testosterone production

Inhibin produced by Sertoli cells in response to too much spermatozoa inhibits FSH

65
Q

Definition of delayed puberty and causes

A

Delayed puberty: no increase in testicular volume (i.e. <4 ml) by the age of 14 years in boys and no breast development by the age of 13.5 years in girls.

Causes:
Constitutional (90%)
Low body weight (<50kg)

Hypogonadotrophic hypogonadism (Kallman’s syndrome, hypopituitarism)

Hypergonadotrophic hypogonadism (Klinefelter’s 47XXY, Turner’s 45X0, Gonadal damage)

66
Q

Precocious puberty definition and causes

A

The development of any secondary sexual characteristic before the age of 8 years in girls and 9 years in boys.

Constitutional
Cerebral tumour
Hypothyroidism
Sex steroid excess (CAH, leydig tumour male, granulosa tumour female, exogenous)

67
Q

What does cervical ripening depend on?

What biochemical changes happen during parturition?

A

PGE2
Cytokines (IL-8)
Neutrophils
Collagenases and elastase
Realignment of collagen

  • NO withdrawal
  • Progesterone withdrawal and switch to type 2 P receptors
  • Increase in placental release of CRH and oestrogen
  • Upregulation of oxytocin receptors
  • Increase in PG synthesis in the uterus and fetal membranes
  • Increase in IL-1 and IL-8
68
Q

What occurs in the foetus during parturition?

A

Increase in CRH, ACTH and Cortisol/DHEAS leads to fetal lung maturation and also labour

This causes increased maternal oestrogen and oxytocin receptors –>
Augments oxytocin and PG F2A

69
Q

What happens to myometrial cells in labour?

A

Formation of gap junctions (promoted by estradiol (E2), which rises relative to progesterone)

70
Q

Role of catecholamines in labour

A

B2 adrenergic agonists inhibit labour

A2 adrenergic agonists cause contraction

71
Q

What is the Ferguson reflex?

A

Pressure to cervix and vagina causes spurts of oxytocin release

72
Q

When do women return to menses post- delivery?

A

Breastfeeding women return to menses at 28 weeks PP

Non breastfeeding women return to menses at 9 weeks PP

73
Q

Lifecycle of a spermatazoa

A

64 days

74
Q

Summary of oogenesis

A

Oogonium undergo mitosis in utero to produce around 2 million at the time of birth.

They undergo growth and differentiation to become primary oocytes.

Primary oocytes (2n) undergo meiosis I to produce 1x secondary oocyte (1n) and 1x polar body (1n). Meiosis I is arrested at prophase until ovulation.

Secondary oocytes undergo meiosis II to produce a mature ovum (1n) and a second polar body (in).
Meiosis II is arrested at metaphase until fertilisation.

75
Q

What is secreted into the PCT?

A

When substances are removed from the blood and transported into the PCT

  • Organic acids & bases e.g. bile salts, oxalate, catecholamines
  • Hydrogen ions (to maintain acid-base balance)- exchanged for bicarbonate and sodium
  • Drugs/ toxins
76
Q

What acid-base disturbance does diarrhoea typically cause?

A

Metabolic acidoses with normal anion gap

77
Q

How is anion gap calculated?

A

[Na+] + [K+] - [HCO3-] - [Cl-]

78
Q

Coagulation cascade

A

Occurs via the intrinsic or extrinsic pathway
- Intrinsic pathway is initiated by exposure of blood to negatively charged surfaces such as collagen in vivo or glass in vitro
- Extrinsic pathway is initiated by tissue thromboplastin which is released after tissue damage (endothelial)

Both pathways result in the activation of factor X

Prothrombin is then converted to thrombin

Thrombin converts solute fibrinogen into insoluble fibrin

Apart from the first two steps of the intrinsic pathway, all steps require calcium.
CItrate and oxalate remove calcium and prevent clotting.

79
Q

Natural anticoagulants

A

Anti-thrombin III
Protein C
Protein S
Heparin

The smoothness of the endothelial surface is important in preventing intravascular coagulation

Tissue thromboplastin activates the extrinsic pathway while plasmin causes clot lysis but does not prevent clot formation

80
Q

Where are clotting factors synthesised?

A

Most are synthesised in the liver.

Factor VIII is synthesised by liver sinusoidal cells and other endothelial cells

81
Q

How are free fatty acids transported across cell membranes?

A

Passive diffusion

82
Q

How is glucose transported across the placenta?

A

Facilitated diffusion

83
Q

Examples of bile acids

Synthesised from

Function

A

Cholic acid
Chenodeoxycholic acid

Can then be conjugated with taurine or glycine to form glycol- or tauro- conjugates

Synthesised from cholesterol

Have an emulsifying effect on fat in the intestine (decreasing surface tension)

Play important role in fat absorption

84
Q

Calculating mean arterial pressure

A

Diastolic pressure + (1/3 of pulse pressure)

Pulse pressure = systolic - diastolic

85
Q

Where does potassium absorption occur in the nephron?

A

PCT
LoH
Collecting ducts

86
Q

Which enzyme in the renal tubular cells is responsible for production of ammonia?

A

Phosphate-dependent glutaminase

87
Q

Diameter of fetal skull:
- OA with complete flexion
- OA without complete flexion
- OP
- Face presentation with head extended
- Incompletely extended face presentation
- Brow presentation

Breech presentation
- Bi trochanteric diameter
- Bi acromial diameter

A

OA with complete flexion: 9.5cm
(suboccipito-bregmatic)

  • OA without complete flexion: 10cm +
    (suboccipito-frontal)
  • OP: 11.5cm
    (Occipital-frontal)
  • Face presentation with head extended: 9.5cm
    (Submento-bregmatic)
  • Incompletely extended face presentation: 11.5cm
    (Submento-vertical)
  • Brow presentation: 13.5cm
    (Mento-vertical)
  • Bi trochanteric diameter: 10cm
  • Bi acromial diameter:11cm
88
Q

Change in colloid osmotic pressure during pregnancy compared to pre-pregnancy

A

10% increase

89
Q

What happens to aldosterone secretion in pregnancy

A

Increases

90
Q

Sickle cell syndrome- Hb

A

Autosomal recessive

Single base mutation of adenine to thymine producing a substitution of valine for glutamine at the 6th codon of the beta-globing chain

Homozygous (Hb SS) = SCD

Heterozygous (HbAS)- trait. Levels of HbA2 increased.

91
Q

What is associated with increased fetal surfactant production?

Decreased?

A

Increased:
Hypertensive disorders of pregnancy, malnutrition, placenta praaevia, drug addiction, PROM, IUGR, females, haemoglobinopathy

Decreased:
DM, anaemia, polyhydramnios, hypothyroidism, males, twins, is-immune disease, cold stress

92
Q

How is fetal blood volume related to weight

Approx blood volume in a term newborn?

A

10-12% body weight

300ml

93
Q

Which is the most abundant carbohydrate in breast milk?

A

Lactose

94
Q

Change in maternal cardiac output in labour and post delivery

A

Increases by 40%

(First stage, increases by 10-25%, second stage by 25-50%)

Post delivery, increases by 10-20%

95
Q

When are phagocytic cells present in the foetus?

A

During the first trimester

96
Q

Most common solid tumour in the neonate?

A

Neuroblastoma

97
Q

Cells in proximal duodenum that secrete alkaline rich mucus

A

Brunner’s cells

98
Q

Protein absorption by the PCT is by

A

Pinocytosis

99
Q

How are amino acids transported across the placenta

A

Secondary active transport

100
Q

When does GFR reach its maximum during pregnancy

A

36 weeks

101
Q

At what gestation does fetal urine become the major contributor to Amniotic fluid volume

A

18 weeks

102
Q

At what gestation does the formation of definitive alveoli take place?

A

36 weeks

103
Q

How long does it take the placental bed to acquire a new endometrial layer?

A

Within 1 week the uterine cavity has a new endometrial layer, with the exception of the placental bed which takes around 3 weeks.

104
Q

Which subunits are found in HbF?

A

Alpha and gamma (2 of each)

105
Q

When are primordial follicles at their max number in a female foetus?

A

20 weeks

106
Q

JVP waveforms

A

X wave occurs at the end of atrial systole.

A wave = atrial systole

C wave = ventricular systole

V wave = atrial filling against closed tricuspid valve

Y descent occurs following tricuspid valve opening.

Part 1 MRCOG (13 decks)

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