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Lecture 3

BIOB33H3 Lecture Notes - Lecture 3: Allantois, Umbilical Cord, Syncytium

Biological Sciences
Course Code
Connie Potroff

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Lecture 3
based on Chapter 28
The Reproductive System: Embryology and Human Development
Development involves:
Differentiation of cells
Reorganization of cells
Development can be characterized by different periods of time
Prenatal development – fertilization/conception to delivery
Involves Embryology – prenatal development focussing on the first two months after
Postnatal development – development from birth to maturity
Fertilization is the joining of two haploid cells to create a diploid cell
Function of the haploid cells:
Spermatozoon (see p.723)
Delivers the paternal chromosomes to the ovum
osperm has head, midsection and tail
ohead has an acrosome and a nucleus containing 22 haploid chromosomes (autosomes)
and one (X or Y) [sex] chromosome
omidsection has mitochondria to provide energy to move flagellum
oflagellum (tail) moves to allow sperm to swim
oOutermost layer has loosely defined cells called corona radiata (protective layer)
oDeep to corona radiata is another protective layer the jelly-like zona pellucida
oContains a polar body which is a non-functioning cell that eventually degrades
Provides the maternal chromosomes (secondary oocyte that has 23 haploid
chromosomes, 22 autosomes and a second X chromosome, suspended in
metaphase of meiosis II)
Note: oocyte is a cell in an ovary that may undergo meiotic division to form an ovum
*Ovum provides nourishment for embryonic development
An ovum is produced in one of the ovaries once a month and travels along the uterine tube to the
uterus (cilia in the tube move the egg along and it takes about 4-5 days for the egg to get to
the uterus)
Fertilization usually occurs in the ampulla of the uterine tube
200 million sperm cells enter the vaginal canal
Only about 10,000 make it to the uterine tubes
Less than 100 actually contact the egg
Only one will fertilize the egg
Fertilization details(zygote formation)
Oocyte at Ovulation: Ovulation releases a secondary oocyte and the first polar body; both
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