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REB > 14. Pregnancy > Flashcards

14. Pregnancy Flashcards

1
Q

What is fertilisation?

A

Fusion of male and female gametes

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2
Q

What are the layers surrounding the oocyte?

A

Corona radiata

Zona pellucida

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3
Q

Describe the process of fertilisation

A
  1. Sperm penetrates the corona radiata using the enzymes in its head
    Binds to ZP3 receptors on zona pellucida
  2. Binding triggers an acrosome reaction
    Hydrolytic enzymes in the acrosome are released onto the zona pellucida
  3. Acrosomal enzymes digest the zona pellucida, creating a pathway to the plasma membrane of the ovum
    Plasma membranes of the 2 cells fuse
  4. Sperm nucleus enters ovum cytoplasm
  5. Sperm stimulates release of Ca++ stored in cortical granules in ovum
    Inactivates ZP3 receptors to prevent polyspermy
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4
Q

What happens within the hour after fertilisation?

A

Sperm and egg nuclei fuse

Zygote is formed

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5
Q

What happens within 3-4 days after fertilisation?

A

Zygote remains in ampulla
Mitosis: becomes a morula
Increased levels of progesterone from new corpus luteum
Endometrium releases glycogen which is used as energy by embryo
this allows the morula to enter the uterus

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6
Q

What happens within 6-7 days after fertilisation?

A

Uterine lining still preparing for implantation due to luteal phase progesterone

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7
Q

Describe the process of implantation

A
  1. Trophoblastic cells release enzymes
    Permits cords of trophoblast to penetrate endometrium
  2. Plasma membranes of advancing trophoblastic cells degenerate
    Eventually become the foetal portion of the placenta
  3. After the blastocyst burrows into the decidua a layer of endometrial cells covers over the hole
    Blastocyst is buried within the lining
  4. Trophoblastic layer continues to digest surrounding decidua
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8
Q

What is the 2 cell thick trophoblast called?

A

Chorion

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9
Q

How is the placenta formed?

A

Chorion releases enzymes, expands and vascularises
Maternal blood leaks from capillaries and fills cavities
Projections of chorionic tissue extend into pools of maternal blood

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10
Q

What are the functions of the placenta?

A

Works as digestive system, respiratory system and kidneys for embryo
Nutrient and oxygen delivery
CO2 and water removal
Temporary endocrine organ

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11
Q

Where is hCG produced?

A

Developing chorion, then placenta

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12
Q

What are the functions of hCG?

A

Stimulates and maintains corpus luteum (progesterone production)
Increases progesterone production by the trophoblast
Stimulates precursor leydig cells in foetal testes to secrete testosterone in a male foetus

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13
Q

Where is HPL produced?

A

Initially by trophoblast, then placenta

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14
Q

What are the functions of HPL?

A

Promotes cell specialisation in mammary gland

Ensures adequate fuel supply for foetus

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15
Q

Where is progesterone produced?

A

Initially corpus luteum, then placenta

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16
Q

What are the functions of progesterone?

A

Maintain uterus and early embryo
Prevents miscarriage
Formation of a mucus plug
Suppress maternal immunological responses
Precursor for steroid production by foetal adrenal glands
Development of milk glands in breasts
Onset of labour

17
Q

What type of estrogen does the placenta produce?

A

Estriol

Levels can be used to determine the viability of the foetus

18
Q

Where is oestrogen produced?

A

Corpus luteum, then placenta

19
Q

What are the functions of oestrogen?

A

Stimulate growth of the myometrium
Increase uterine blood flow
Important for timing of implantation
Increase uterine receptors for progesterone and oxytocin
Enhance foetal organ development
Development of ducts within mammary glands

20
Q

What does the amount of progesterone secreted by the placenta depend on?

A

Placental weight

21
Q

What are the stages of labour?

A 
Cervical dilation (up to 24 hrs)
Delivery (30-90 mins)
Placenta delivery (15-30 mins)
22
Q

What is involution?

A

Shrinking of the placenta back to its original size

23
Q

What happens with progesterone before parturition?

A

Increase in placental progesterone-binding protein

Decrease in myometrial progesterone receptors

24
Q

What are the results of high oestrogen before parturition?

A

Causes uterine smooth muscle to contract
Increases myometrial receptors for oxytocin
Increases the production of prostaglandins

25
Q

What is the function of oxytocin in parturition?

A

Induces labour

26
Q

What is the function of relaxin in parturition?

A

Softens cervix

Increases oxytocin receptors

27
Q

What is the Furguson Reflex?

A

positive feedback in labour
Head of foetus pushing against cervix releases oxytocin
Oxytocin increases prostaglandin production by the decidua which softens cervix

REB (29 decks)

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