Endocrinology of Pregnancy Flashcards

1
Q

Where is tubular fluid reabsorbed and what controls this process?

A

Tubular fluid reabsorbed in the efferent ducts (vasa efferentia)

  • This is induced by oestrogen
  • This acts to concentrate the sperm prior to entering the epididymis

NOTE:

The tubular fluid produced by the sertoli cells in the seminiferous tubules functions to:

  • Provide nutrition for the developing sperm
  • Provides a means of transport to carry the develpoing sperm to the epididymis
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2
Q

What takes place in the epididymis and what controls this process?

A

In the epididymis, nutrients (e.g. fructose) and glycoproteins are secreted into the epididymal fluid

  • This is stimulated by androgens

NOTE: Epididymis is where the sperm mature and attain their motility

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3
Q

What is ejaculation?

A

Ejection of semen from the body

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4
Q

What does semen consist of?

A
  • Spermatozoa (15-120 million/ml)
  • Seminal fluid (2-5ml)
  • Leucocytes
  • Potentially viruses e.g. hepatitis B, HIV (if the man is infected)
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5
Q

What are the proportions of sperm that reach different parts of the female reporoductive tract after ejaculation?

A
  • 1/100 of spermatozoa in ejaculate enter the cervix
  • 1/10,000 cervix to ovum
  • Overall 1/million reach ovum
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6
Q

Which structures contribute to the production of the seminal fluid?

A

Small contibution from:

  • Testis (seminiferous tubules, rete testis - essentially the part before the epididymis)
  • Epididymis

Mainly from accessory sex glands:

  • Seminal vesicles
  • Prostate gland
  • Bulbourethral glands
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7
Q

What is capacitation of sperm?

A

This is when sperm achieve fertilising capability

  • Takes place in the female reproductive tract
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8
Q

What 3 changes take place in capacitation?

A
  1. Loss of glycoprotein coat
  2. Change in surface membrane characteristics
    • This allows the acrosome reaction when in close proximity to the ovum
    • Change in membrane → increased permeability to Ca2+
  3. Whiplash movements of the tail
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9
Q

Where exactly does capacitation take place and what is it dependent on?

A

Takes place in ionic & proteolytic environment of the Fallopian tube

Dependent on:

  • Oestrogen
  • Calcium
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10
Q

Describe the acrosome reaction.

A
  • The capacitated sperm binds to ZP3 (sperm receptor)
  • Once bound to ZP3, progesterone stimulates calcium influx into the sperm
  • Hyaluronidase & proteolytic enzymes are released from acrosome
  • This allows the spermatozoon to penetrate the Zona Pellucida (glycoportein layer surrounding egg)
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11
Q

Where does fertilisation normally occur?

A

Fallopian tube

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12
Q

What does fertilisation result in the formation of?

A

Second meiotic division

  • There is unequal distribution of cytoplam
  • Cell with cytoplasm and chromosomes = ovum
  • Cell with just chromosomes = polar body
    • This polar body is then expelled
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13
Q

Describe the cortical reaction.

A

The cortical reaction is triggered by fertilisation

  • Cortical granules release molecules that degrade the zona pellucida (including ZP3 and ZP2)
  • This prevents further binding of other sperm
    • As ZP3 and ZP2 are sperm glycoprotein receptors present in the zona pellicuda
    • So their degradation prevents further sperm binding as there are no receptors
  • The nuclei fuse: haploid → diploid
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14
Q

Describe how the conceptus develops before implantation

A
  • Continues to divide as it moves down Fallopian tube to uterus (3-4 days)
  • Receives nutrients from uterine secretions
  • This free-living phase can last for approx. 9-10 days
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15
Q

Describe the process of implantation.

A

Attachment phase: outer trophoblast cells contact uterine surface epithelium

THEN

Decidualisation phase: changes in underlying uterine stromal tissue (within a few hours)

NOTES:

  • Stroma = the part of the tissue which has a structural or connective role (i.e. parts which are not specific to the function of the tissue = everything except parenchyma)
    • e.g. connective tissue, BVs, nerves etc.
  • Blatocyst:
    • Trophoblast → placenta
    • Inner cell mass → embryo
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16
Q

What hormone environment is required for implantation?

A

Progesterone dominance in the presence of oestrogen

17
Q

Describe the molecules involved in the attachment phase.

A

Leukaemia inhibitory factor (LIF):

  • From endometrial secretory glands (and maybe blastocyst)
  • Stimulates adhesion of blastocyst to endometrial cells

Interleukin-11 (IL11):

  • Also from endometrial cells is released into uterine fluid (i.e. released into uterine cavity)
  • May be involved
    • Leads to trophoblast migration and decidualisation

Many other molecules involved in process - e.g. HB-EGF (growth factor from endometrial cells which interact with receptors on trophoblast)

18
Q

What happens in the decidualisation phase?

A

Endometrial changes due to progesterone

  • Glandular epithelial secretion
  • Glycogen accumulation in stromal cell cytoplasm
    • Stromal cells - refers to connective tissue cells, i.e. fibroblasts
  • Growth of capillaries
  • Increased vascular permeability (→ oedema)

Factors involved:

  • Interleukin-11 (IL11)
  • Histamine
  • Certain prostaglandins
  • TGFβ - promotes angiogenesis

NOTE:

  • This process forms the decidua
  • Decidua = modified endometrium which lines the uterus during pregnancy and is shed with afterbirth
19
Q

Describe the hormone changes which take place during pregnancy.

A

NOTES:

  • Oestriol is E3 and synthesised by placenta
    • Different to oestradiol (E2) which is produced by the ovarian follicles in the menstrual cycle
  • Human placental lactogen = growth hormone that can have prolactin like effects but is important for the growth and development of the foetus
    • ↓ maternal insulin sensitivity, leading to an increase in maternal blood glucose levels
    • ↓ maternal glucose utilization, which helps ensure adequate fetal nutrition
    • ↑ lipolysis with the release of free fatty acids
20
Q

Describe progesterone and oestrogen production during pregancy initially.

A

First 40 days:

  • Produced in corpus luteum in maternal ovary
    • Stimulated by hCG which acts on LH receptors (i.e. mimics the effects of LH)
      • hCG produced by trophoblasts
  • Essential for developing fetoplacental unit
  • Inhibits maternal LH & FSH (-ve feedback)

From day 40:

  • Placenta starts to take over production
21
Q

Describe oestrogen and progesterone production over the course of pregancy, more at later stages.

A

NOTES:

  • Cholesterol → pregenolone → any steroid hormone
  • DHEAS = Dehydroepiandrosterone sulfate
    • DHEA is a steroid which can be converted to oestrogens
    • Conjugation/deconjugation refers to addition/removal of sulphate
22
Q

Describe how maternal hormones change in pregnancy.

A

NOTE:

Placental GH-variant:

  • Secreted from placenta during pregancy
  • Predominant form of GH is maternal circulation (over one secreted by somatotrophs in anterior pituitary)
  • Associated with foetal growth
23
Q

Explain what happens during partruition (childbirth).

A

You get contraction of the uterus via two main ways

DIRECT:

  • Intracellular Ca2+ concentration increases
    • i.e. calcium release from stores triggered by prostaglandins, influx from extracellular enviroment
  • This stimulates muscle contraction directly by acting on actin-myosin in uterine smooth muscle cells in the myometrium

INDIRECT:

  • Oxytoxin is release by posterior pituitary
  • It acts on the oxytocin receptor on cells making up the myometrium and endometrium
    • i.e. receptor expressed by smooth musle cells and epithelial cells
  • This stimulates uterine contraction

Additional:

  • Foetal cortisol and placental oestrogen bind to oxytocin receptor → indirect contraction
  • Placental oestrogen can increase release of Ca2+ from intracellular stores → direct contraction
24
Q

What does oxytocin stimulate?

A
  • Uterine contraction
  • Cervical dilation
  • Milk ejection
25
Q

How is lactation (breastfeeding) controlled?

A