Formation of Extra-Embryonic Membranes

Formation of Extra-Embryonic Membrane

• Extra-embryonic membranes arise from the peripheral germ layer, providing protection and nutrition from maternal blood.
• These membranes are not integrated into the embryo, allowing them to be discarded at birth.

Classification of Extra-Embryonic Membranes

• Yolk Sac:

  • Originates from splanchnopleure.
  • Part of the primitive gut; does not include the embryo's body.
  • Directly covers the yolk, absorbing nutrients for the embryo.

• Amnion:

  • Derived from somatopleure.
  • Attached where the body wall opens ventrally to the yolk stalk.
  • Protects the embryo from mechanical injury through the amniotic sac.

• Chorion:

  • The outer layer of somatopleure.
  • Rapidly expands, closely apposing the inner shell membrane by 7-8 days of incubation in chicks.
  • Works with the allantois for gas and water exchange.

• Allantois:

  • Develops from the hindgut of the embryo as a diverticulum.
  • Takes over metabolic functions from the yolk sac for maternal-fetal nutrient exchange.
  • Grows larger as the yolk sac diminishes throughout development.

Formation of Extra-Embryonic Membranes

• Extra-embryonic membranes protect the embryo and secure nutrients from the maternal blood.
• Classified as extra-embryonic because they are not part of the embryo and are discarded at birth.

Types of Extra-Embryonic Membranes

• Yolk Sac

  • Derived from splanchnopleure.
  • Part of the primitive gut, not part of the embryo's body.
  • Absorbs nutrients from the uterus and covers the yolk.
  • Acts as a nutritive organ for the embryo.

• Amnion

  • Derived from somatopleure.
  • Attached to the embryo's body where it opens ventrally to the yolk stalk.
  • The opening reduces during development to form the umbilical ring.
  • Provides protection against mechanical injuries through the amniotic sac.

• Chorion

  • The outer layer of somatopleure.
  • Expands rapidly, closely opposing the inner shell membrane by 7-8 days into incubation in chicks.
  • Works with the allantois to facilitate gas and water exchange.

• Allantois

  • A diverticulum emerging with the establishment of the embryo's hindgut.
  • Takes over the yolk sac functions for metabolic interchange between fetus and mother.
  • The yolk sac shrinks while the allantois enlarges as development progresses.

This quiz examines the formation and function of extra-embryonic membranes, which play crucial roles in protection and nutrition of the embryo. Key membranes such as the yolk sac and amnion are discussed, highlighting their origins and significance during development. Test your knowledge on these important concepts and their classifications.