Oocyte sperm-binding
membrane receptors
Sperm
nucleus
Microtubules
from sperm
flagellum
Mitochondria
Cortical
granules
Zona pellucida
sperm-binding
receptors
2
Acrosomal reaction.
Binding of the sperm to
sperm-binding receptors in
the zona pellucida causes the
Ca
2
H
levels within the sperm
to rise, triggering the
acrosomal reaction. Acrosomal
enzymes from many sperm
digest holes through the zona
pellucida, clearing a path to
the oocyte membrane.
3
Binding.
The sperm’s
membrane binds to the
oocyte’s sperm-binding
receptors.
4
Fusion.
The sperm and
oocyte plasma membranes
fuse, allowing sperm contents
to enter the oocyte.
5
Block of polyspermy.
Entry
of the sperm’s contents causes
Ca
2
H
levels in the oocyte’s
cytoplasm to rise, triggering
the cortical reaction
(exocytosis of cortical
granules). As a result, the
zona pellucida hardens and
the sperm receptors are
clipped off (slow block to
polyspermy).
1069
previous page 1103 Human Anatomy and Physiology (9th ed ) 2012 read online next page 1105 Human Anatomy and Physiology (9th ed ) 2012 read online Home Toggle text on/off