Class 15: Human Development and Sex Determination Flashcards
Fertilization
One Oocyte (Female Gamete) + One Sperm (Male Gamete) = Fertilized Zygote
What happens after Fertilization?
Meiosis II. It creates a diploid zygote. This diploid zygote starts a very long series of cell divisions (mitosis).
Blastocyst
After the first 6-7 days, the zygote undergoes many divisions as it is floating in the uterus.
Zygote -> Blastocyst
Implantation & (When does it happen?)
The blastocyst gets attached to the endometrium/uterine wall in the uterus.
Blastocyst -> Embryo -> Fetus
Happens day 6-7
Blastocyst
The Blastocyst is an internal group of cell mass that will develop into the Embryo.
Trophoblast
Outer layer of cells of the blastocyst.
- Protective membranes surrounding the embryo. Will be part of the placenta.
Blastocoele
Cavity in the blastocyst filled with fluid.
3 main layers of cells, inner cell mass
Ectoderm (outer layer)
Mesoderm (middle layer)
Endoderm (inner layer)
Orchestrate the morphogenesis and development of the embryo.
First Trimester
Organs formation
Second Trimester
Organ maturation
Third Trimester
Rapid Growth
Teratogen
- Any physical or chemical agent that increases the risk of congenital malformations.
- Examples: Radiation (X rays), Viruses(HIV), Medications(Thalidomide), Alcohol
FAS
Fetal Alcohol Syndrome
- Birth defects caused by alcohol consumption from the mother during pregnancy.
- Effects: Miscarriage, growth retardation, facial abnormalities, mental retardation, learning disabilities.
Sex determination (in Humans and one other species)
In Humans:
Y Chromosome -> male sexual development
No Y Chromosome -> female development
In Alligators:
Environmental interactions control sex determination. The warmer the temperature is, the more males are born.
When is chromosomal sex defined?
Fertilization
