Embryonic Development and Fertilization Vocabulary

Vocabulary flashcards covering the key terms and cellular mechanisms of fertilization, cell differentiation, and blocks to polyspermy in sea urchin development.

Cell Differentiation

The divergence in cellular structure and function as cells become specialized during development.

Fertilization

The formation of a diploid zygote from the fusion of a haploid egg and haploid sperm nuclei.

Zygote

A fertilized diploid ($2n$) egg containing a complete set of paired chromosomes, with one set contributed by the egg and one set by the sperm.

Jelly Coat

The outer layer of a sea urchin egg that emits molecules to attract sperm and provides protection.

Vitelline Layer

The middle extracellular layer of a sea urchin egg situated between the outer jelly coat and the inner cell membrane.

Cytoplasmic Determinants (CDs)

Maternal substances, including mRNA, transcription factors, and other proteins, unevenly distributed in the unfertilized egg cytoplasm that direct early embryonic development and differentiation.

Acrosome

A membrane-bound vesicle at the tip of the sperm head containing hydrolytic enzymes that digest the egg's outer jelly coat.

Acrosomal Process

A structure protruding from the sperm head that penetrates the jelly coat, containing an actin filament and bindin proteins.

Bindin Proteins

Species-specific proteins located on the acrosomal process of the sperm that bind directly to specific receptor proteins on the egg's plasma membrane.

Polyspermy

The entry of multiple sperm nuclei into a single egg cell.

Fast Block to Polyspermy

A rapid depolarization across the egg cell membrane caused by the diffusion of sodium ($\text{Na}^+$) ions into the egg $1$ to $3$ seconds after sperm binding, lasting about $1$ minute.

Slow Block to Polyspermy

The cortical reaction in which cortical granules lift the vitelline layer away from the cell membrane and harden it into a protective fertilization envelope.

Cortical Granules

Vesicles in the egg cytoplasm that fuse with the plasma membrane during fertilization to break bonds, degrade remaining egg receptors, and form the fertilization envelope.

Calcium Wave

A signal originating at the sperm contact site that releases calcium ($\text{Ca}^{++}$) ions from the egg's endoplasmic reticulum, triggering cortical granule fusion and egg activation.

Egg Activation

The process stimulated by the calcium wave following fertilization that leads to an increased rate of cellular respiration and protein synthesis in the egg.

What are the 4 stages of embryonic development

Fertilization, Gastrulation, Cleavage, Organogenesis (Neurulation)