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Unformatted text preview: tion of
the membrane that forms a fast block to further
(d) Cortical reaction: A permanent change in the
egg surface that provides a slow (permanent)
block to sperm entry. Involves the release of
cortical granules into the perivitelline space,
followed by the release of substances from the
granules that raise and harden the vitelline layer.
(e) Fusion of egg and sperm nuclei: Results in the
formation of a diploid zygote and initiates the
rapid cell division that follows fertilization. (e) Urethra
(g) Scrotal sac (scrotum) (a) Spermatogenesis (gametogenesis is also correct).
(b) FSH and testosterone (reference to ICSH
which controls testosterone secretion is also
(c) Seminiferous tubules of the testes.
(d) Process completed in the epididymis.
Sperm cannot move easily in an acid environment.
The alkaline prostate secretions neutralize the acidity
of the vaginal secretions providing conditions suitable
for the sperm to move.
About 100-400 million sperm are produced because
only a very small percentage of them eventually reach
the ovum (remember that the sperm must negotiate
the cervix and then find their way into the fallopian
tube). Note: Although only one sperm is needed to
fertilize the egg, the combined action of the enzymes
from a large number of sperm is needed in order to
help digest the jelly-like barrier around the egg. 2. It is necessary to prevent fertilization of the egg by
more than one sperm because this would result in
too many chromosomes in the zygote (making the
zygote non-viable or unable to survive). Triploidy (a
condition resulting from two sperm fertilizing an egg)
is frequently found among spontaneous miscarriages. 3. (a) Oocyte is arrested in metaphase of meiosis II
after it has already undergone the first meiotic
(b) Meiotic division proceeds to completion if the egg
is fertilized (i.e. fertilization triggers completion). 4. (a) Zygote nucleus: sperm: 50%, egg: 50%
(b) Zygote cytoplasm: sperm: 0%, egg: 100% 5...
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This document was uploaded on 01/28/2014.
- Winter '13