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18 Cards in this Set
- Front
- Back
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first period of human development
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embryonic period
- fertilization to 8 weeks |
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First four weeks of embryonic period
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basic body plan of embryo is established and differentiation of some essential cell types commences
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remainder of first 8 weeks of embryonic period
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development of organ system
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fetal period
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after 8 weeks
- major process is growth - final shape and size of newborn and final shape and function of organs is established |
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granulosa cells
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secrete glycoproteins that form zone pellucida
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pre-antral follicle
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primary follicle
- before appearance of cavity |
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sertoli cells
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supporting cells in seminiferous tubules that surround the developing sperm cells and provide nutrients and protection
- also phagocytize most of mature sperm cytoplasm |
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major cause of infertility in males
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- absence of sperm
- reduction in sperm number (<15 million) - production of defective sperm |
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major cause of infertility in females
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- failure of oocyte maturation or release
- blockage of egg transport into fallopian tubes - Polycystic ovary syndrome (PCOS) |
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polycystic ovary syndrome
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increase in male hormone levels with corresponding inhibition of oocyte maturation and release
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Trisomies
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abnormal meiotic divisions produce extra copies of chromosomes
- other trisomies are embryonic lethal |
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Trisomy 21
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Down syndrome
~ 75% of concept die in embryonic or fetal life ~ 85% of those born survive to one year ~ 50% can be expected to age 50 years FISH detection of trisomies |
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Trisomy 13
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Patau's syndrome
- involves multiple abnormalities, many of which are not compatible with life - >80% of children with trisomy 13 die in first month - some live to teens |
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Trisomy 18
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50% of infants do not survive beyond first week of life
- some survive to teens but with serious medical and developmental problems |
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Turner syndrome
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XO
- single copy of X chromosome in females - most severe sex chromosome abnormality - sx: short stature, extended neck folds, reduced sexual development, sterility |
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Klinefelter syndrome
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XXY
additional copy of X in males - rather minor - severe cases sx; slightly enhanced female characteristics, such as higher voice and breast enlargement, sterility |
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Robertsonian translocations
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amongst the most common of all chromosomal abnormalities
- observed in acrocentric chromosomes 13, 14, 15, 21, 22 |
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how is it possible to lose the short arms of Ch13 and 14 and not show defects?
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- only tRNA genes are located on the short arms of Ch 13 and 14
- because tRNA genes are present in many copies throughout the genome, no consequences are observed |
