PSYC20008 Lecture Notes - Lecture 13: Prenatal Development, Brain Structure And Function, Egg Cell
14 Jun 2018
School
Department
Course
Professor
Lecture 13 - Tuesday 11 April 2017
PSYC20006 - DEVELOPMENTAL PSYCHOLOGY
LECTURE 13
PRENATAL DEVELOPMENT
PHYLOGENETIC CONTINUITY
•We are just another type of animal.
•Due to our shared evolutionary history, we share many characteristics and developmental
processes with other living things.
BRAIN STRUCTURE & FUNCTION
•The size of human brain is markedly larger and more complex than other mammals.
•Scientists have a long-standing interest in the genetics underpinning development of the human
brain.
HOMO SAPIENS
•Principles of cortical development are similar in mouse, macaque and human brain
•Functions of neurotransmitters, receptors and ion channels do not change substantially over
phylogenetic scale
•Secret to success of human? Possibly increased number of neurons, more elaborate connections
and functional specialisation of cortical areas
GAMETES
•Sperm and ova are unique cells in the human body as they contain only
half the chromosomes of the somatic cells, via meiosis.
•Reduction to 23 chromosomes allows for the merging of the sperm and
ovum into one new being with 46 chromosomes. Happens during meiosis.
•The ovum is the largest cell in the human body and is released from one of
the ovaries into the fallopian tube.
•It releases a chemical signal to any awaiting sperm.
•During ejaculation, as many as 500 million sperm are produced.
•Each sperm has a pointed head packed with genetic information and a
long tail that whips the sperm along.
•The sperm must travel ~ 6 hours (6-7 inches) from the vagina through
uterus to the fallopian tube.
•Only about 200 ever get close to the ovum. Problems can
include;
•Tangling up of sperm with each other in the vagina.
•Going to the wrong fallopian tube, where there is no
ovum.
•Double-headed sperm and other genetic catastrophes.
•They believe at conception the ex ratio is 50/50 male/female.
The sex ratio among embryos however is different. Among
normal embryos it is female biased, and among abnormal
embryos it is male biased.
•Sex ratio may decrease in first week after conception due to
excess male morality, and then increases for at least 10-15
weeks due to female mortality and levels off after 20 weeks. It declines again due to excess male
mortality form 28-35 weeks. Therefore total female mortality during pregnancy exceeds total
male mortality.
•Higher rate of suicide, also boys do stupid things, more disorders.
Lecture 13 - Tuesday 11 April 2017
PSYC20006 - DEVELOPMENTAL PSYCHOLOGY
PERIODS OF PRENATAL DEVELOPMENT
•Prenatal development is often divided into three major
phases:
•Period of the zygote – 0 to 14 days
•From conception to implantation into the wall of the
uterus
•Period of the embryo
•3 to 8 weeks
•Virtually all the major organs are formed
•Period of the fetus
•9th week until birth
•All the major functions begin to function and the developing
organism grows
THE ZYGOTE
•The winning sperm penetrates the outer membrane of the ovum.
•A chemical reaction seals the membrane, preventing other sperm from
entering.
•Tail of sperm falls off, contents of head gush into ovum and within hours
the nuclei of the two gametes merge, producing the zygote.
•Within 12 hours of fertilisation, the zygote splits into two equal parts,
each containing a full set of genetic material. This process is called mitosis.
BLASTOCYST
•The two cells then divide into four, then eight, then sixteen and so on.
•Over the course of the next 38 weeks, the single celled organism will be
born as a person with trillions of cells.
•The blastocyst is a ball-like structure that contains 60-80 cells, within 4
days of conception.
•Implantation of the zygote into the uterine wall occurs between 8 and 14
days from conception.
•The zygote develops small, burr-like tendrils, that emerge from its outer
surface
•When the blastocyst reaches the uterine wall, these tendrils burrow inward,
tapping the woman’s blood supply (implantation).
WHAT CAN GO WRONG
•Only half of all fertilised ova are firmly implanted.
•Perhaps as many as half of all such implants are genetically abnormal or fail to develop, or
burrow into a site incapable of sustaining them.
•3⁄4 of zygotes fail to survive this initial phase of development.
THE EMBRYO
•The embedded balls of cells begin to differentiate.
•The inner cell mass will become the embryo and the rest of the
cells will become the amniotic sac and placenta.
4 MAJOR SUPPORT STRUCTURES
•Once implanted, the blastocyst’s outer layer forms four major
support structures that protect and nourish the developing
embryo.
•Amnion is a watertight sac that fills with fluid, acting as a
cushion, regulating temperature and providing a weightless
environment.
Document Summary
Phylogenetic continuity: we are just another type of animal, due to our shared evolutionary history, we share many characteristics and developmental processes with other living things. Brain structure & function: the size of human brain is markedly larger and more complex than other mammals, scientists have a long-standing interest in the genetics underpinning development of the human brain. Possibly increased number of neurons, more elaborate connections and functional specialisation of cortical areas. Problems can include: tangling up of sperm with each other in the vagina, going to the wrong fallopian tube, where there is no ovum, double-headed sperm and other genetic catastrophes, they believe at conception the ex ratio is 50/50 male/female. The sex ratio among embryos however is different. It declines again due to excess male mortality form 28-35 weeks. Therefore total female mortality during pregnancy exceeds total male mortality: higher rate of suicide, also boys do stupid things, more disorders.
