zona pellucida

Examples of zona pellucida in the following topics:

• Fertilization

  • In mammals, the egg is protected by a layer of extracellular matrix consisting mainly of glycoproteins called the zona pellucida.
  • When a sperm binds to the zona pellucida, a series of biochemical events, called the acrosomal reaction, take place.

• Implantation

  • In preparation for implantation, the blastocyst sheds its outside layer, the zona pellucida, which binds sperm during fertilization.
  • The zona pellucida degenerates and decomposes, and is replaced by a layer of underlying cells called the trophoblast.

• Fertilization

  • By destabilizing the membrane, the sperm prepares for the acrosome reaction, the enzymatic penetration of the egg's tough membrane, the zona pellucida.

• Adrenal Cortex

  • The adrenal cortex comprises three zones, or layers: Zona glomerulosa (outer), Zona fasciculata and Zona reticularis.
  • Zona reticularis, is the inner most cortical layer; the zona reticularis produces androgens, mainly dehydroepiandrosterone (DHEA) DHEA sulfate (DHEA-S), and androstenedione (the precursor to testosterone) in humans.
  • They are produced in the zona glomerulosa.
  • They are produced in the zona fasciculata.
  • They are produced in the zona reticularis.

• Adrenal Glands

  • These layers form three distinct regions: an outer zona glomerulosa that produces mineralocorticoids; a middle zona fasciculata that produces glucocorticoids; and an inner zona reticularis that produces androgens, which are sex hormones that promote masculinity.

• Production of Dilute and Concentrated Urine

  • The system then stimulates zona glomerulosa of the adrenal cortex which, in turn, secretes the hormone aldosterone.