Human ovum. The zona pellucida is seen as a thick clear girdle surrounded by the cells of the Corona radiata.
Anatomical terminology
[edit on Wikidata]
The cortical reaction is a process initiated during fertilization that prevents polyspermy, the fusion of multiple sperm with one egg. In contrast to the fast block of polyspermy which immediately but temporarily blocks additional sperm from fertilizing the egg, the cortical reaction gradually establishes a permanent barrier to sperm entry and functions as the main part of the slow block of polyspermy in many animals.
To create this barrier, cortical granules, specialized secretory vesicles located within the egg's cortex (the region directly below the plasma membrane), are fused with the egg's plasma membrane. This releases the contents of the cortical granules outside the cell, where they modify an existing extracellular matrix to make it impenetrable to sperm entry. The cortical granules contain proteases that clip perivitelline tether proteins, peroxidases that harden the vitelline envelope, and glycosaminoglycans that attract water into the perivitelline space, causing it to expand and form the hyaline layer. The trigger for the cortical granules to exocytose is the release of calcium ions from cortical smooth endoplasmic reticulum in response to sperm binding to the egg.
In most animals, the extracellular matrix present around the egg is the vitelline envelope which becomes the fertilization membrane following the cortical reaction. In mammals, however, the extracellular matrix modified by the cortical reaction is the zona pellucida. This modification of the zona pellucida is known as the zona reaction. Although highly conserved across the animal kingdom, the cortical reaction shows great diversity between species. While much has been learned about the identity and function of the contents of the cortical granules in the highly accessible sea urchin, little is known about the contents of cortical granules in mammals.
The cortical reaction within the egg is analogous to the acrosomal reaction within the sperm, where the acrosome, a specialized secretory vesicle that is homologous to cortical granules, is fused with the plasma membrane of the sperm cell to release its contents which degrade the egg's tough coating and allow the sperm to bind to and fuse with the egg.
the cortical granules in the highly accessible sea urchin, little is known about the contents of cortical granules in mammals. The corticalreaction within...
disintegrate. The fusion of sperm and oocyte membranes causes corticalreaction to occur. Cortical granules inside the secondary oocyte fuse with the plasma...
oocyte's extracellular matrix. This exocytosis of cortical granules is known as the corticalreaction. In mammals, the oocyte's extracellular matrix includes...
cascade. The cortical granules inside the oocyte then fuse to the outer membrane, and a quick fast block reaction occurs. Furthermore, the cortical granules...
and help to form the fertilization envelope from the cortical granules. The corticalreaction occurs due to calcium oscillations inside the oocyte. What...
cytoplasm. Activation of the ovum includes the following events: Corticalreaction to block against other sperm cells Activation of egg metabolism Reactivation...
triggers the corticalreaction, which results in depositing several substances onto the vitelline membrane through exocytosis of the cortical granules, transforming...
when the release of calcium causes the corticalreaction, in which various enzymes are released from cortical granules in the eggs plasma membrane, causing...
in 1951 by both Min Chueh Chang and Colin Russell Austin. Corticalreaction Acrosome reaction Johnson MH (2007). Essential reproduction (6th ed.). Malden...
protein. Hyalin is located in the cortical granules within an egg. Here, the protein is in a solated form. Cortical granules migrate to the inner plasma...
Nicholas D.; Holland, Linda Z. (1989). "Fine Structural Study of the CorticalReaction and Formation of the Egg Coats in a Lancelet". The Biological Bulletin...
negative to the exterior by approximately 70 to 90 millivolts. During corticalreaction in fertilisation[circular reference]of sperm with secondary oocyte...
processing speed or reaction time on cognitive tasks to infer the content, duration, and temporal sequencing of mental operations. Reaction time (RT; also...
of a cortical implant and neuroprosthetic in general is "to replace neural circuitry in the brain that no longer functions appropriately." Cortical implants...
cluster together as cortical columns. David Hubel and Torsten Wiesel proposed the classic ice-cube organization model of cortical columns for two tuning...
the coordinated activation of a multitude of cortical points, terminating at a final locus of motor cortical activity, which holds the limb at a spatial...
neural platforms for bodily expression configured before the advent of cortical circuits for speech. They consist of pre-configured pathways or networks...
called steroidogenesis, and involves a number of reactions and processes that take place in cortical cells. The medulla produces the catecholamines, which...
(as given below) suggest cortical involvement in postural control and maintenance of balance. An initial postural reaction on exposure to an external...
In organic chemistry, a homologation reaction, also known as homologization, is any chemical reaction that converts the reactant into the next member of...
a space underneath the capsule called the subcapsular sinus, then into cortical sinuses. After passing through the cortex, lymph then collects in medullary...
the blood creates a gradient for CO2 to move into the cell and push the reaction HCO3 + H ↔ H2CO3 ↔ CO2 + H2O to the left. On the luminal side of the cell...
schizophrenia. Evidence suggests that reduced numbers of astrocytes in deeper cortical layers are assocociated with a diminished expression of EAAT2, a glutamate...
involving not only cortico-basal ganglia-thalamo-cortical pathways, but the cortico-ponto-cerebello-thalamo-cortical loop as well. Even in the absence of traditional...
Immunosuppressive effects are mediated by suppressing delayed hypersensitivity reactions by direct action on T-lymphocytes. Anti-proliferative effects are mediated...
(February 6, 2020). "Breathing is coupled with voluntary action and the cortical readiness potential". Nature Communications. 11 (1). Nature Portfolio:...
status and limits of plasticity of the auditory cortical pathways is to study the latency of cortical auditory evoked potentials (CAEP). In particular...
of an oocyte or fertilized ovum. In the slow block to polyspermy, the cortical granules released from the ovum are deposited in the perivitelline space...
Global Information