unit 13 development
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what is differentiation?
the process whereby all diffrent cell types are produced through selective changes in the genetic activity
what are the 4 major phases of development?
- fertilization: fusion of the male and female gametes
- embryological development: firdt 2 months after fertilization
- fetal development: from the begining of the 9th week until birth
- postnatal development: commences at birth
what does fertilization invlove?
where does it occur?
involves the fusion of 2 haploid gametes with 23 chromosomes each to produce a zygote that contains 46 chromosomes
occurs in the uterine tube within one day
what is the corona radiata?
the protective layer of cells
of the 200 million sperm ejaculated how many enter the uterine tube, how many reach the egg?
- 10,000 enter the tube
- less than 100 reach the egg
what does the acrosomal cap contain?
contains the hylurondase which breaks down the bonds between the cells of the corona radiata
steps to accomplish fertilization?
- single sperm makes contact with the oocyte membrane
- it is activated and completes meiosis II which results in teh production of the second polar body. the oocyte has a single set of 23 chromosomes
- the sperm is absorbed into the oocyte cytoplasm
- a male pronucleus and female pronucleus form the fuse
- the result is the formation of a zygote with 2 pairs of 23 chromosomes (46 in all)
time spent in prenatal development
embryological development and early fetal development this trimester begins with fertilization the structure of all major organs systems appear
ddevelopment of the organs and organ systems. by the end of this trimester the fetus looks human
characterized by rapid fetal growth. early this trimester most of the organ systems become fully functional this trimester ends in birth
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