PBA201H: The Biology of Prenatal Human Development

* Intro: close your eyes, imagine that you're in a small, dark, enclosed place, and you can only communicate with the outside world with a small cord.

• Not talking about being in the womb, but the Chilean miners crisis
• SLED

• Timeline ( visual)
  • zygote
  • blastocyst
  • embryo: until 8 weeks
  • fetus: 8 weeks until birth

• As we learned in PBA100Y, a new human being comes into existence at Fertilization.
  • description, DNA, hair colour, eye colour, etc.
  • Sperm-egg fusion: A mature egg will leave the ovary and the sperm that travels through the Fallopian tube will fuse with the egg; the first sperm that fuses, uses the enzymes to crack through the outer layer (zona pellucida) of the egg and fuse with the inner membrane; then, there's an outer barrier created that will prevent any other sperm from fusing with that egg.

• Four Principles: At fertilization, a unique, whole, living human being comes into existence.
  1. Unique:
     1. The genetic code of the zygote is unique–distinct from those of the mother and father. For instance, a pregnant woman could be pregnant with a male child.
  2. Whole:
     • Some may ask what makes a single-celled zygote different from a single cell of, say, human skin. Both are living, human, diploid cells. However, one is a human whole while the other is a human part. Give each cell time, nutrition, and safety, then wait 9 months or 15 years…which one continues developing into a toddler, or a teenager? A skin cell will always remain a skin cell, while a zygote will continue human development into an embryo, fetus, newborn, toddler, etc.
  3. Living:
     1. If something is growing, isn't it alive?
     2. We know from the law of biogenesis that living things come from other living things. After all, if the pre-born child isn't biologically alive, why would a woman need an abortion?
  4. Human:
     1. If someone has human parents, aren't they human offspring?
• Cellular biology and sperm/egg fusion: composition, behaviour
  • While the zygote is a very young individual composed of only one cell, that one cell is substantively different from the sperm cell or egg cell. We can see this by considering the criteria science uses to distinguish between different cell types: cell composition and behavior. In other words, what the cell is made up of, and what it does.
    • Composition: Whereas a sperm is composed of 23 chromosomes from the father and an egg is composed of 23 chromosomes from the mother, a zygote is composed of both. Sperm and egg, i.e. gametes, are haploid; the zygote is diploid. ( include technical language of haploid vs. diploid?)
    • Behaviour: And where the behavior of sperm and egg is to penetrate or be penetrated (respectively), the zygote’s behavior is to do neither. The zygote acts in a coordinated manner for the health of the whole, and she self-directs her own growth. And so, the zygote is fundamentally different from sperm or egg. No human can claim ever having been a sperm or an egg, but as Drs. Moore and Persaud explain, the formation of the zygote 'marks the beginning of each of us as a unique individual.'

• Using the definition of death to mark the beginning of life
  • cardio-pulmonary death is the legally recognized point
  • complete irreversible brain death (this specifically), when all coordinated functioning for the overall good of that human being ceases to exist, is how we can define death more accurately (most medically accurate)
  • fertilization is when we first gain that coordinating functioning

condense

• Implantation starts at the end of the first week after fertilization, and is complete at about two weeks²⁾. Some argue that this is where life begins. But implantation simply marks a change of location (from fallopian tube to uterus), rather than a change of nature. The human being prior to implantation is the same as the human being after implantation (just like before and after birth—another event marking a location change).
  • Admittedly, most pregnancy tests will only read positive after implantation; as a result, abortion advocates tend to argue that women only become pregnant after implantation. In fact, they’ve even redefined the word “conception” to mean implantation, arguing that’s when pregnancy begins.
  • But the fact that a pregnancy test doesn’t come back positive pre-implantation doesn’t mean life isn’t there—it just means the test's ability to detect that life isn’t there.
  • Take, for example, the commonly used hCG pregnancy test, one which looks for Human Chorionic Gonadotropin in a woman’s urine. hCG is a hormone that is secreted by the developing placenta, and this occurs at implantation.
  • The release of hCG indicates the presence of the pre-born child, but it doesn’t mean she didn’t exist prior to that. We know this intuitively, of course: Just imagine you enter your home and find a stray puppy hiding in your bedroom—but you only discover it after you’ve been home for 30 minutes. Clearly, the puppy did not enter your house when you first discovered it, but instead when it managed to crawl in.

• Likewise, one’s offspring first exists at fertilization even if we don’t discover her existence until implantation.

• At approximatly 14 days after fertilization³⁾, the primitve streak will form in the embryo.
• Before this point, it is possible for identical twinning to occur, as some embryos can split into two before the formation of the critical streak. This rare phenomenon is often raised to dispute the idea that life begins at fertilization. Instead, some argue, it exists at the point of twinning, or after the point where twinning can occur⁴⁾.
• Just because some humans have the ability to split into two, doesn’t mean that prior to the split one human didn’t exist.
• Take the case of the flatworm.⁵⁾ If a flatworm is cut in half, each half will regenerate into two separate, fully-functioning flatworms. But prior to this separation a flatworm nonetheless existed.
• Likewise, even though in rare situations one human splits into two, one human existed before that split happened, and the beginning of that one human still was at fertilization.

“Most significant developmental milestones occur long before birth during the first eight weeks following conception when most body parts and all body systems appear and begin to function. The main divisions of the body, such as the head, chest, abdomen and pelvis, and arms and legs are established by about four weeks after conception. Eight weeks after conception, except for the small size, the developing human’s overall appearance and many internal structures closely resemble the newborn.” ⁶⁾

The embryo's heart will begin to beat between 16 and 22 days after fertilization⁷⁾⁸⁾. Her heart will beat approximate 54 million times⁹⁾ before birth!

Determining precisely when the pre-born feel pain is largely dependent on technology to detect this. While it is an interesting topic, it has no bearing on the morality of abortion. After all, is it wrong to kill someone because she feels pain or because she’s human?

Consider Gabby Gingras, an American girl with a rare condition called hereditary sensory autonomic neuropathy, Type 5¹⁰⁾. In short, she cannot feel pain. As a baby, she poked and scratched her eyes, causing significant damage—she never felt pain to tell her to stop. May we kill her because of her inability to feel pain? Why then may we kill the pre-born because they don't feel pain at certain points during pregnancy?

To make the point even more simply: would it be permissible to kill a 3-year-old as long as we give him anaesthetic first?

http://www.ehd.org/prenatal-summary.php

“A fetus is just a blob of tissue, just a clump of cells.”

Terms like “blob of tissue”, “clump of cells” etc. are dehumanizing terms that are ultimately meaningless. It's true that a pre-born child is a “clump of cells” – but so is a born human being! Although pre-born children are obviously less developed than older humans, they are still human beings with human rights.

“It doesn't even look like a human being.”

Pre-born children also look different from born children; a zygote looks different from a 10-week fetus, who looks different from a toddler, etc. But how would we expect a human being of that specific age to look? For instance, we would not expect a toddler to undergo the same body changes that a teenager undergoes during puberty. Pre-born children look exactly the way they are supposed to look for their age and level of development.

Richard Stith offers the following analogy¹¹⁾: Consider a Polaroid picture. Once you click the camera and the card comes out, what initially appears is brown/black smudges. But within a few minutes the image appears with clarity. The image is captured in an instant but it does need time to develop. So it is with each of us—who we are as unique, unrepeatable individuals is captured in an instant (fertilization); we just need time to develop.

So many embryos miscarry anyway, so what's the big deal about abortion?

- high rate of miscarriage in 1st trimester - miscarriage is a tragedy - cause of death is different: one child dies naturally, we couldn't prevent it. Another child is purposefully killed. Ex. difference between 1 person dying of a heart attack and another person being stabbed in the heart.

“A fetus isn’t human, it’s just a parasite feeding off of a woman’s body!”

While a fetus does require nutrients from her mother via the umbilical cord in order to survive, it is unscientific to call the fetus a parasite. By definition, a parasite must be of a different species than the host organism–for example, a flea on a dog. Since a fetus and her mother are of the same species – human, it doesn’t make sense to call her a parasite.

“a tumour”

condensed version of the rest of Oriyana's presentation, such that anyone else could give it, in an hour-long discussion format

* Maybe introduce fetal origins (Annie Murphy Paul): TED Talk (but see also PBA401H)

Embryology presentation used by CCBR

• From Oriyana Hrycyshyn (can sub in name of any child for her sister Inessa)
• approx. 45 min, covers all the major milestones of prenatal development + leaves time for questions/practice
• Link to Google Doc of notes: https://docs.google.com/document/d/16o1oh6ClzosIVa1SHByPgNXtNkTKHv1m8rrZteoxnno/edit?usp=sharing
• https://prolifetraining.com/resources/five-minute-10/ | constructed vs developing