BIOL 260 Chapter Notes - Chapter 4.1: Fallopian Tube, Gametogenesis, Cervical Canal

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6 Feb 2017
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4.1 Gametogenesis and Fertilization:
Embryology: the study of prenatal development, embraces processes extending from the
production of sperm and eggs (gametogenesis) to fertilization, embryonic and fetal
development, and birth
Gametogenesis:
o The advantage of sexual reproduction is the genetic variation among the offspring that
allows species to survive and adapt to their environment
o The disadvantage is that only half of the cells from each parent are passed onto the
offspring
Uses gametes (sex cells) that are haploid
o Haploid: 23 chromosomes
o Diploid: 46 chromosomes
o Spermatogenesis (sperm production): meiosis I and II result in four equal-sized cells
called spermatids, which then grow tails and develop into sperm without further
division
o Oogenesis (egg production): each meiotic division produces one large cell and one much
smaller cell
Small cell is called a polar body and is the excess chromosomes to be disposed
of and dies off
Large cell goes on to become the egg
It has a lot of cytoplasm (the raw material for early development
Unfertilized eggs die after meiosis I
Meiosis II never occurs unless the egg is fertilized
Sperm Migration and Capacitation:
o Migration:
1 egg is released a monthswept into uterine (fallopian)takes a 3 day trip to
get to the uterusif not fertilized in 24 hours, it dies off
o Capacitation:
ay sper do’t ake it;
destroyed by vaginal acid or drain out of the vagina
fail to get through the cervical canal into the uterus
destroyed by leukocytes in the uterus
may go up the wrong uterine tube
freshly ejaculated sperm cannot immediately fertilize an egg, they must
undergo a process called capacitation, which takes about 10 hours and occurs
during their migration in the female reproductive tract.
1.) Plasma membrane is toughened by cholesterol
2.) Fluids of the female reproductive tract dilute inhibitory factors in the
semen head
3.) The membrane becomes more fragile so it breaks open more easily
upon contact with the egg
It also becomes more permeable to calcium ions, which diffuse into the
sperm and stimulate powerful lashing of the tail
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