Pregnancy, parturition + lactation Flashcards

Semester 1 year 1

1
Q

What are oocytes surrounded by?

A

Granulosa cells

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2
Q

What must happen to allow the sperm to penetrate the egg?

A

-sperm undergo physiological changes to their membrane + increase mobility in the vagina
-smooth muscle contractions in uterus + fallopian tubes to aid sperm trajectory
-cervical mucus made into channels to help sperm be propelled

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3
Q

How does fertilisation occur?

A

-sperm undergo acrosomal reaction that allows penetration
-acrosome contains enzymes that break down the egg
-a cortical reaction activated the oocyte - increase in Ca2+, causing 2nd meiotic division + prevents polyploidy

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4
Q

Describe what happens to the fertilised egg pre-implantation

A

-it’s nourished by oviduct secretions as it moves along it for 3 days
-when it reaches uterus, it floats freely for another 3 days
-then forms a blastocyst (becomes lined by trophoectoderm layer)
-after 6 days, blastocyst is implanted

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5
Q

Why does it take 3 days for the fertilised egg to move along the fallopian tube?

A

-impeded by contractions of isthmus stopping it from reaching uterus
-allows womb lining to generate for implantation

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6
Q

Describe the process of implantation of the fertilised egg

A

-blastocyst received into endometrium supported by secretory phase, where there’s a low oestradiol to progesterone ratio
-blastocyst promotes transition of endometrial stromal cells into decidua cells (predecidualisation)
-blastocyst trophoblast cells used to gain nourishment from endometrium

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7
Q

Describe inner and outer cytotrophoblasts

A

-inner = single mitotic layer that differentiates into:
-outer = produces hormones

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8
Q

What are the stages of endometrial invasion?

A
  1. hatching
  2. apposition
  3. adhesion
  4. invasion
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9
Q

Describe the hatching stage of endometrial invasion

A

The zona pellucida surrounding the blastocyst begins to disintegrate

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10
Q

Describe the apposition stage of endometrial invasion

A

-trophoblastic + endometrial epithelium membranes meet
-complete degradation of zona pellucida

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11
Q

Describe the adhesion stage of endometrial invasion

A

-adhesion between maternal + developing trophoblast cells
-have intracellular + extracellular integrins

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12
Q

Describe the invasion stage of endometrial invasion

A

-trophoblastic cell proliferation + differentiation to syncytiotrophoblast
-syncytiotrophoblast penetrates the endometrium

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13
Q

Describe the structure of the placenta

A

-maternal spinal arteries bring food
-intervillous space reduces force + velocity to allow for exchange
-syncytiotrophoblast lacunae merge + fill with maternal blood
-cytotrophoblast + syncytiotrophoblast form villi/microvilli projecting into maternal blood

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14
Q

In a mature placenta, what separates maternal and foetal blood?

A

-foetal capillary endothelium
-mesenchyme
-cytotrophoblasts
-syncytiotrophoblast

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15
Q

What substances are transported between maternal and foetal blood and how?

A

-from M to F: glucose (F. diffusion), amino acids (2 active transport), vitamins (active transport)
-from F to M: waste urea + creatinine
-large molecules move by receptor-mediated endocytosis
-oxygen exchange facilitated by higher oxygen affinity of foetal haemoglobin

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16
Q

What hormonal changes occur during trimester 1?

A

-in trophoblasts (then placenta), human chorionic gonadotropin (HCG) ‘rescues’ the corpus luteum
-as a result, corpus luteum continues secretion of oestrogen + progesterone to support the endometrium

17
Q

What hormonal changes occur during trimester 2-3?

A

-placenta becomes primary hormone source, replacing corpus luteum
-human placental lactogens (group of hormones) are secreted

18
Q

What do the human placental lactogens do?

A

-coordinate fuel economy (what’s given to foetus + what remains with mum)
-control development of mammary glands

19
Q

What are the stages of partuition?

A

-stage 0 - quiescence
-stage 1 - activation/transformation
-stage 2 - stimulation/labour/birth
-stage 3 - involution recovery from birth

20
Q

Describe stage 0 of parturition

A

-from conception to initiation of parturition
-uterus is relaxed + insensitive to uterotonic hormones
-progesterone suppresses myometrial contractions

21
Q

Describe stage 1 of parturition

A

-preparation of birth
-foetal-hypothalamic pituitary adrenal axis increases cortisol production
-cortisol increases oestrogen-progesterone ratio to increase contractility
-oestrogen stimulates prostaglandin (PG) release - promotes gap junction formation, causes softening, thinning + dilation of cervix
-gene expression of contraction-associated proteins (CAPs), receptors for OT + PG, enzyme PG synthesis
-cervical gene expression of enzymes to hydrolyse collagen matrix

22
Q

Describe stage 2 of parturition

A

-increased PG levels cause myometrial contraction due to OT + cervical dilation
-increased myometrial connectivity due to gap junctions
-increased myometrial responsiveness due to PG + OT receptors
-+ive feedback leads to Ferguson reflex (neuroendocrine regulation of OT) + uterine contraction to stimulate PG
-stages of labour + delivery: dilation, expulsion, placental

23
Q

Describe stage 3 of parturition

A

-haemostasis
-decreased placental oestrogen causes: myometrial atrophy (myometrium muscle starts to regress - involution) + regression of uterine vasculature
-cervix remodelling
-reestablishment of endometrial cycle after 3-5 months

24
Q

What is haemostasis?

A

Vasoconstriction of spinal arteries to decrease risk of haemorrhage

25
Q

Where does lactation occur and what makes up the area?

A

-secretory unit of breast
-made up of: alveoli surrounded by contractile myoepithelial cells + adipose tissue

26
Q

Describe the hormonal effects of pregnancy on lactation

A

-oestrogen + progesterone stimulate breast growth + development
-oestrogen stimulates anterior pituitary gland to produce prolactin (PRL) for further development
-oestrogen + progesterone inhibit PRL lactogenic action on the breast

27
Q

Describe the postpartum hormone action on lactation

A

-oestrogen increases cell proliferation
-PRL initiates milk production
-OT increases myoepithelial contraction for ejection
-PRL + cortisol maintain milk production

28
Q

What must interact to enable lactation?

A

Neuronal + hormonal systems

29
Q

Why is PRL essential for production of milk?

A

-inhibits dopamine released
-OT from posterior pituitary
-downregulates release of GnRH to inhibit ovarian cycle