Gametes- cells that unite at conception (ova in females; sperm in males)
Every cell in the human body contains 23 pairs of chromosomes. However, sperm and ovum contain 23
single (unpaired) chromosomes.
Zygote- a single cell created when sperm and ovum unite
(22 pairs determine traits, called autosome, and 23 pair determines the sex, called sex choromosomes)
Assisted human reproduction (AHR)- “any activity undertaken for the purpose of facilitating human
reproduction” (Health Canada)
The act protects the health and safety of Canadians undergoing AHR treatment and the children born
from such procedures.
Cryopreservation- preserving cells or tissues through a freezing process that stops all biological activity
Vitrification- the use of cryoprotectants along with rapid cooling to prevent the fluid in biological tissues
(eg, eggs, semen, embryos) from forming ice crystals (that ct like glass shards on cell structures) and
from dehydrating. This tissue becomes an inact, non-crystalline, glass-like solid that can be preserved for
Prenatal development, or gestation, is the process that transforms a zygote into a newborn.
Prenatal care during the first trimester is critical to prevent congenital anomalies, because all the baby’s
organs form during the first 8 weeks.
Cephalocaudal pattern- growth that proceeds from the head downward
Proximodistal pattern- growth that proceeds from the middle of the body outward (ex. First rib cage,
Germinal stage- the first stage of prenatal development, beginning at conception and ending at
implantation (approximately 2 weeks)
Implantation- attachment of the blastocyst to the uterine wall
Placenta- specialized organ that allows substances to be transferred from mother to embryo and from
embryo to mother without their blood mixing
Umbilical cord- organ that connects the embryo to the placenta
Amnion- fluid-filled sac in which the fetus floats until just before it is born
By the 12 day, the cells that will become the embryo’s body are also formed
The embryonic stage- the second stage of prenatal development, from week 2 through week 8, during
which the embryo’s organ systems form
Neurons- specialized cells of the nervous system The cells of the nervous system, the neurons, form a structure called the neural tube, from which the
brain and spinal cord will develop. A primitive heart and forerunners of the kidney also develop during
week 3, long with 3 sacs that will become the digestive system.
Gonads- sex glands (ovaries in females; testes in males)
Organogenesis- process of organ growth. His is completed by the end of the 8 week
Fetal stage- the 3 stage of prenatal development, from week 9 to birth, during which growth and organ
refinement take place
Viability- ability of the fetus to survive outside the womb
By the end of the 23 week, a small number of babies have attained viability. But waiting until the end
of the 24 week greatly increases their chances of survival
Cell bodies- the part of a neuron that contains the cell body and is the site of vital cell functions
Synapses- tiny spaces across which neural impulses flow from one neuron to the next
Axons- tail-like extensions of neurons
Dendrites- branch-like protrusions from the cell bodies of neurons
Glial cells- specialized calls in the brain that support neurons (These cells are the glue that hold the
neurons together to give shape to the brain’s major structures)
Male fetuses, on average, re more physically active
Female fetuses appear to be more sensitive to external stimulation and to advance more rapidly in
Congenital anomaly- an abnormality present at birth
Many disorders appear to be transmitted through the operation of dominant and recessive genes
Autosomal disorders are caused by genes located on the autosomes (chromosomes other than sex
chromosome). The genes that cause sex-linked disorders are found on the X chromosome.
Some chromosomal errors: 1- trisomies: a condition in which a child has 3 copies of a specific autosome.
In down syndrome, the child has 3 copies of chromosome 21. This is greatest for mothers over 35 years
2- sex-chromosome anomalies: this is associated with the mother’s age. The most common is an XXY
Mothers who are heavy drinkers or alcoholics are at significant risk of delivering infants with fetal
alcohol syndrome (FAS) Teratogens- substances such as viruses and drugs that can cause birth defects