Back to AI Flashcard MakerBiology /Biology IB HL - 11.4 Sexual Reproduction Part 6
What does fetal growth cause?
In the case of childbirth, fetal growth eventually causes stretching of the uterine walls, which is detected by stretch receptors
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Term
Definition
What does fetal growth cause?
In the case of childbirth, fetal growth eventually causes stretching of the uterine walls, which is detected by stretch receptors
What does the stretching of uterine walls trigger?
This triggers the release of hormones (oxytocin) that induce uterine muscles to contract, further reducing space in the womb
What does oxytocin trigger?
This causes more stretching and hence more contraction until the origin stimulus (the foetus) is removed (i.e. birth)
What 4 hormones regulate the birthing process?
The chemical regulators of the birthing process include oxytocin, oestrogen, progesterone and prostaglandin
What happens to trigger the birth process after 9 months?
After 9 months, the baby is fully grown and stretches the walls of the uterus – placing a strain on both mother and infant
What does this stress induce?
This stress induces the release of chemicals which trigger a rise in the levels of estrogen (estriol in particular)
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| Term | Definition |
|---|---|
What does fetal growth cause? | In the case of childbirth, fetal growth eventually causes stretching of the uterine walls, which is detected by stretch receptors |
What does the stretching of uterine walls trigger? | This triggers the release of hormones (oxytocin) that induce uterine muscles to contract, further reducing space in the womb |
What does oxytocin trigger? | This causes more stretching and hence more contraction until the origin stimulus (the foetus) is removed (i.e. birth) |
What 4 hormones regulate the birthing process? | The chemical regulators of the birthing process include oxytocin, oestrogen, progesterone and prostaglandin |
What happens to trigger the birth process after 9 months? | After 9 months, the baby is fully grown and stretches the walls of the uterus – placing a strain on both mother and infant |
What does this stress induce? | This stress induces the release of chemicals which trigger a rise in the levels of estrogen (estriol in particular) |
What does estriol prepare? | Estriol prepares the smooth muscle of the uterus for hormonal stimulation by increasing its sensitivity to oxytocin |
What does estriol inhibit? | Estriol also inhibits progesterone, which was preventing uterine contractions from occurring while the foetus developed |
Once the uterus is prepared for childbirth, what is released? | Now that the uterus is primed for childbirth, the brain triggers the release of oxytocin from the posterior pituitary gland |
What is the role of oxytocin? (+what does it inhibit) | Oxytocin stimulates the uterine muscles to contract, initiating the birthing process (it also inhibits progesterone secretion) |
What does the foetus release in response to uterine contractions? | The foetus responds to this uterine contraction by releasing prostaglandins, which triggers further uterine contractions |
What loop is created due to the cycle of contractions? | As the uterine contractions trigger the release of chemicals that cause further contractions, a positive feedback loop ensues |
When will contractions stop? | Contractions will stop when labour is complete and the baby is birthed (no more stretching of the uterine wall) |
What is the gestation period (for mammals)? | For mammals, the gestation period is the time taken for a foetus to develop – beginning with fertilization and ending with birth |
Will the duration of the gestation period differ between species? | YES
The duration of the gestation period will differ markedly between different species of animal |
What are the two main factors that contribute to the length of the gestation period? | animal size/mass
level of development at birth |
How does animal size/mass affect the length of the gestation period? | Animal size / mass – larger animals tend to have longer gestation periods (as they tend to produce larger offspring) |
How does level of development at birth affect the length of the gestation period? | The level of development at birth – more developed infants will typically require a longer gestation period |
How can the level of development at birth be described for mammalian infants? | The level of development at birth for mammalian infants can be described as either atricial or precocial |
What does it mean if an infant is altricial? | Altricial mammals give birth to relatively helpless, undeveloped offspring that need extended rearing |
What does it mean if an infant is precocial? | Precocial mammals give birth to more developed offspring that are mobile and independent and require minimal rearing |
Do altricial or precocial mammals require shorter gestation periods? | Generally, altricial mammals (e.g. marsupials and rodents) require shorter gestation periods than precocial mammals (e.g. ungulates such as cows, pigs and rhinoceroses) |
Are size/mass and level of development the only factors affecting the gestation period? | While the length of a gestation period does appear to positively correlate with size and development, other factors also exist
Some mammal species may have similar gestation periods despite having significantly different body masses |