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Obstetrics and Gynaecology > Reproductive System and Physiology > Flashcards

Reproductive System and Physiology Flashcards

1
Q

What is the basis of the hypothalamic pituitary gonadal axis?

A

Hypothalamus releases GnRH
GnRH stimulates anterior pituitary to produce luteinising hormone (LH) and follicle stimulating hormone (FSH)

LH and FSH stimulate development of follicles in ovaries.
Theca granulosa cells around follicles - oestrogen.

Oestrogen has negative feedback effect on hypothalamus and anterior pituitary - suppresses GnRH, LH and FSH.

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2
Q

What is oestrogen and where does it act?

A

Steroid sex hormone
Produced by ovaries in response to LH and FSH
Acts on tissues with oestrogen receptors to promote female secondary sexual characteristics

Breast tissue development
Growth and development of female sex organs
Blood vessel development in the uterus
Development of endometrium

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3
Q

What is progesterone and where does it act?

A

Steroid sex hormone
Produced by corpus luteum after ovulation
Taken over by placenta from 10 weeks if pregnant
Acts on tissues previously stimulated by oestrogen

Thicken and maintain the endometrium
Thickens cervical mucus
Increases body temperature

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4
Q

When do girls tend to start puberty?

A

8-14

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5
Q

When do boys tend to start puberty?

A

9-15

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6
Q

Why do overweight children start puberty earlier?

A

Aromatase enzyme found in adipose tissue

More adipose tissue present, higher quantity of aromatase responsible for oestrogen creation

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7
Q

What is the tanner scale for females?

A

Stage I - under 10
No pubic hair, no breast development

Stage II - 10-11
Light and thin, breast buds behind areola

Stage III - 11-13
Course and curly
Breasts begin to elevate beyond areola

Stage IV - 13-14
Adult like, not reaching thigh
Areolar mounds form, project from surrounding breast

Stage V - above 14
Hair extends to medial thigh
Areolar mounds reduce, and adult breasts form

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8
Q

What is the tanner scale for males?

A

Tanner I
testicular volume less than 1.5 ml; small penis (prepubertal; typically age 9 and younger)

Tanner II
testicular volume between 1.6 and 6 ml; skin on scrotum thins, reddens and enlarges; penis length unchanged (9–11)

Tanner III
testicular volume between 6 and 12 ml; scrotum enlarges further; penis begins to lengthen (11–12.5)

Tanner IV
testicular volume between 12 and 20 ml; scrotum enlarges further and darkens; penis increases in length (12.5–14)

Tanner V
testicular volume greater than 20 ml; adult scrotum and penis (14+)

Same pubic hair scale applies

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9
Q

When are the two phases of the menstrual cycle?

A

Follicular phase from start of menstruation to ovulation Days 1-14 in a 28 day cycle

Luteal phase from ovulation to start of menstruation
Final 14 days of the cycle

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10
Q

What are follicles?

A

Ovaries have a finite number of cells - oocytes

Granulosa cells surround the oocytes forming follicles.

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11
Q

What are the four key stages of the development of follicles?

A

Primordial follicles
Primary follicles
Secondary follicles
Antral follicles - Graafian follicles

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12
Q

When does primordial follicle maturation occur?

A

Occurs independent of the menstrual cycle

Mature into primary and secondary follicles

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13
Q

What occurs during the follicular phase?

A

FSH stimulates further development of secondary follicle
Secondary follicles have FSH receptors
Follicles grow and granulosa cells surrounding them release oestradiol
Oestradiol has negative feedback on pituitary
Amount of FSH and LH reduces
Rise in oestrogen allows cervical mucus to be permeable for sperm to penetrate cervix at ovulation

One follicle becomes dominant
LH spikes just before ovulation
Causes dominant follicle to release ovum (unfertilised egg) approx 14 days before end of cycle

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14
Q

What occurs during the luteal phase?

A

Follicle that released the ovum collapses
Becomes the corpus luteum
Corpus luteum secretes progesterone maintaining endometrial lining

Progesterone causes cervical mucus to become thick and no longer penetrable
Corpus luteum also secretes small amount of oestrogen

If fertilisation - syncytiotrophoblast secretes HCG
HCG maintains corpus luteums

No fertilisation - no HCG, corpus luteum degenerates
Fall in oestrogen and progesterone causes endometrium to break down - menstruation
Stromal cells of endometrium release prostaglandins

Negative feedback from oestrogen and progesterone on hypothalamus and pituitary ceases, LH and FSH rise.

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15
Q

What are the levels of hormones during the cycle?

A

FSH maintains constant level, but peaks at Day 14
LH massive spike at Day 14

Oestrogen rises over the follicular phase then dramatically falls after Day 14
Progesterone rises during the luteal phase

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16
Q

Describe the journey of the zygote from fertilisation until a urinary pregnancy test becomes
positive.

A

23 chromosomes from the egg and 23 chromosomes from the sperm combine to form a fertilised egg called a zygote.
This then divides rapidly to form a morula. This mass of cells travels along the Fallopian tube towards the uterus.
Whilst travelling, a fluid filled cavity gathers within the group of cells and becomes a blastocyst, contains the embryoblast.
Alongside embryo blast is fluid filled cavity called blastocele. Surrounding this is the trophoblast.

Blastocyst arrives at the uterus 8-10 days after ovulation, and reaches endometrium.

Outer layer of the trophoblast known as the sycytiotrophoblast extends into the storm and mixes with the endometrium.

The cells of the storm convert into the decidua and provides nutrients to the trophoblast. The syncytiotrophoblast starts producing hCG which causes a positive pregnancy test.

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17
Q

What is the placenta formed from?

A

Trophoblast

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18
Q

What happens to the placenta at day 6 of gestation?

A

Trophoblast interact with endometrial decidual epithelia –> invasion into maternal uterine cells

Invasion is interstitial and on the anterior and posterior walls of the body of the uterus

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19
Q

What happens to the placenta at day 8 of gestation?

A

Differentiation into syncitiotrophoblast and cytotrophoblast

Syncitiotrophoblast send out projections to erode maternal tissue and produce HCG

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20
Q

What happens to the placenta at day 9 gestation?

A

Lacunae form within syncitiotrophoblast and maternal blood enter from spiral arteries

Cytotophoblast begin to form villi

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21
Q

What are the types of villi in the placenta?

A

Primary - projections of trophoblast
Secondary - invasion of a mesenchyme core

Tertiary - invasion of fetal vessels

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22
Q

What happens to the maternal circulation in the formation of the placenta?

A

Spiral arteries remodel forming low resistance, high flow circulation

Cytotrophoblast invade the spiral arteries and replace maternal endothelium - 1 less barrier

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23
Q

What are the key blood vessels in the fetus?

A

Umbilical vein - carry oxygenated blood

Umbilical artery - carry deoxygenated blood

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24
Q

How do nutrients exchange at the placenta?

A

Maternal O2 and nutrients exchange at terminal villi into intervillous space

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25
Q

What surrounds the fetal surface?

A

Chorionic membrane:

  • amnion
  • umbilical vessels
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26
Q

What is the decidua?

A

Name given to the endometrium which is modified by progesterone in preparation for pregnancy

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27
Q

What forms the placental barrier in the first trimester?

A

Syncitiotrophoblast resting on cytotrophoblast

Relatively thick

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28
Q

What is the placental barrier like in the third trimester?

A

Thin - cytotrophoblast lost

Huge SA

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29
Q

What happens to the placenta around month 4-5?

A

Decidua form septal which project into intervillous lacunae

Has core maternal tissue and covered by syncitial cells

Septa divide placenta into cotyledons

30
Q

What is the function of HCG and what secretes it?

A

Maintain corpus luteum until placenta can secrete the pregnancy hormones

Secreted by syncitiotrophoblast

31
Q

What causes most maternal adaptations in pregnancy?

A

Progesterone

Oestrogen has some effect

32
Q

What changes are seen in pregnancy?

A

GI
Haematological

MSK
Renal
Biochemical
Respiratory
Nutrient
CVS
33
Q

What GI changes are seen in pregnancy?

A

Visceral displacement - appendicitis present as RUQ pain

SM relaxation - heartburn + gall stones

Reduced GI motility - constipation

34
Q

What haematological changes are seen in pregnancy?

A

Plasma volume increase - dilution anaemia

Raised fibrinogen and clotting factors and decreased fibrinolysis - Pro-thrombotic state

Immunosuppression - risk of infection

35
Q

What MSK changes are seen in pregnancy?

A

Ligament laxity - Pubic symphysis dysfunction

Back pain

36
Q

What renal changes are seen in pregnancy?

A

Renal plasma flow and GFR increase - increased creatinine and clearance

SM relax - stasis = UTI

Large uterus - Risk of obstruction

Bicarb excretion (compensate for hyperventilation) - low bicarb reserve so acidosis risk

37
Q

What biochemical changes are seen in pregnancy?

A

Calcium req. increase - Increased renal excretion (stones) and more GI absorption

TBG increase - free T3/4 = same but overall T3/4 increase for fetal neural development

38
Q

What respiratory changes occur in pregnancy?

A

Diaphragm displaced up - AP and transverse diameter increase to compensate

Increased CO2 from fetus and increased respiratory drive - hyperventilation

39
Q

What nutrient changes are seen in pregnancy?

A

Raised lactogen, prolactin and cortisol - increased insulin resistance so maternal FA and glucose saved for fetus

Lipolysis to increase FA as metabolic substrate - risk of ketoacidosis

40
Q

What CVS changes occur in pregnancy?

A

Increased blood volume
Increased CO, SV. HR

Peripheral resistance and BP drop in 1st and 2nd trimester
IVC compressed if flat on back

41
Q

How is dyspepsia due to pregnancy managed?

A

Sleep propped up
Small frequent meals

Decrease spice, fruit, caffeine
Most antacids can be used

42
Q

How is constipation due to pregnancy managed?

A

Increase fluid intake
High fibre food

Plenty of exercise
Laxatives

43
Q

How is fatigue and insomnia due to pregnancy managed?

A

Rest and reassure
Avoid sleeping tablets

Peak in first trimester

44
Q

Explain what must be considered when a pregnant lady has pruritus

A

Look for rash
Exclude obstetric cholestasis - check LFT’s

Common in last 12 weeks

45
Q

How is back pain due to pregnancy managed?

A

Light exercise
Simple analgesia

Physio referral

46
Q

What happens in pubic symphysis dysfunction?

A

Pain in suprapubic and lower back area which radiates to thigh and perineum

47
Q

How is pubic symphysis dysfunction managed?

A

Education
Physiotherapy

Belts
Crutches

48
Q

Why do pregnant women get carpel tunnel syndrome and how is it managed?

A

Fluid retention compresses nerve

Wrist splints and steroid injections

49
Q

What changes are seen in blood results in pregnancy?

A

Raised - WCC, ALP, TSH (in 3rd trimester)

Lowered - Hb, Na+, K+, Urea, Creatinine, Ca2+, Albumin, Bilirubin, TSH (1st trimester)

50
Q

When is the uterus usually palpable in the abdomen?

A

12 weeks

51
Q

What could cause a large for date uterus?

A

Molar pregnancy
Multiple pregnancy

Polyhydramnios
Fibroids and Cysts

52
Q

When does the uterus normally reach the umbilicus?

A

20 weeks

53
Q

How long does labour usually last?

A

8 hours in first pregnancy

5 hours in subsequent pregnancies

54
Q

What happens to the myometrium in labour?

A

Pacemaker smooth muscle cells generate AP’s which spread across specialised gap junction –> co-ordinated contractions

55
Q

What movements does the baby do when being delivered?

A

Head flex
Head internally rotate

Head delivered
Head extend
Head externally rotate
Shoulders rotate and deliver

56
Q

What happens to the breasts during pregnancy?

A

Alveolar cells differentiate to be able to produce milk from mid gestation

Areolar enlarge and darken

Montgomery tubercles produce sebum and pheromones

57
Q

What is the purpose of sebum and pheromones?

A

Sebum - prevent cracking

Pheromones - Baby locate nipple

58
Q

Why is there little milk secretion in pregnancy?

A

High progesterone:oestrogen ratio

59
Q

What is the composition of breast milk?

A

Water - 88.1%
Fat - 3.8%

Protein - 0.9%
Lactose - 7%
Other - 0.2%

60
Q

What is colostrum?

A

First secretion from mammary glands

Low in water, fat and sugar
High in protein, IgA,M,G and white cells

61
Q

How much colostrum is produced?

A

40ml/day for first 3 days

62
Q

What are the benefits to breastfeeding?

A

Baby gets less infections
Bonding - oxytocin

Reduced risk ovarian and breast cancer
Further contract uterus
Weight loss

63
Q

How does milk production start post delivery?

A

Delivery of placenta remove large amount of progesterone

Alveoli respond to Prolactin and produce milk within 24-48hrs

64
Q

How is prolactin stimulated?

A

Suckling

Mechanical stimulation of receptors in nipple inhibit dopamine secretion in hypothalamus. Dopamine inhibit prolactin. Suckling also increase vasoactive intestinal protein which promotes prolactin.

65
Q

Why is some milk made in the first 24-48 hours?

A

Prolactin produced by decimal cells which aren’t inhibited by dopamine

66
Q

How is milk production regulated?

A

Suckling at one feed promote prolactin release which produces milk ready for next feed - it is a demand based production

67
Q

Describe the milk let down reflex

A

Oxytocin released from posterior pituitary in response to suckling

Myoepithelial cells stimulated and contract squeezing milk out of breast (Milk is ejected not sucked out)

68
Q

What can stimulate/inhibit oxytocin release?

A

Stimulate - Cry, sight of infant, fondling, anticipation

Inhibited - Pain, embarrassment, alcohol

69
Q

How does milk production stop?

A

If suckling stop, milk production gradually ceases

This can be due to:
Turgor induced damage to secretory cells
Low prolactin levels

70
Q

What drugs should be avoided while breastfeeding?

A

Antibiotics - cipro, tetracycline, chloramphenicol, sulphonamides
Lithium and Benzo’s

Aspirin
Carbimazole
Methotrexate
Sulfonylureas
Cytotoxics
Amiodarone
Clozapine

Obstetrics and Gynaecology (11 decks)

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