Definition

1. Noun:
   • The inner membrane of embryos in higher vertebrates: A thin, protective tissue layer that surrounds the embryo during development. It is particularly noted for sometimes covering the head of a newborn at birth, a condition known as a caul.

Usage

• This is a specialized biological and medical term. It is used in scientific contexts to describe a specific anatomical structure in developmental biology, embryology, and sometimes in discussions of childbirth.
• It is a countable noun (e.g., ).

Examples

• Noun:
  • The doctor explained that the thin, translucent covering on the baby's head was the remnants of the embryonic membrane.
  • In their research, scientists studied the role of the embryonic membrane in nutrient exchange.

Advanced Usage

• "To be born with/in a caul": This idiom refers to being born with the embryonic membrane (or a piece of it) covering the head. Historically, this was sometimes considered a sign of good luck or a special destiny.
  • The midwife said the child was born in a caul, which was considered an auspicious sign.

Variants and Related Words

• Amnion (n): A specific type of embryonic membrane; the innermost membrane that encloses the embryo of a mammal, bird, or reptile. The amniotic sac is filled with amniotic fluid.
  • The fetus floats within the amnion.
• Chorion (n): The outermost membrane surrounding an embryo of a reptile, bird, or mammal. In mammals, it contributes to the formation of the placenta.
  • The chorion is vital for implantation in the uterine wall.
• Caul (n): A piece of the amnion (embryonic membrane) that can cover a baby's head and face at birth.
  • The caul was carefully removed by the obstetrician.

Synonyms

• Fetal membrane: A more general term for any of the membranes surrounding the fetus, including the amnion and chorion.
• Amniotic sac: The sac formed by the amnion, containing the embryo and amniotic fluid.

Noun

1. the inner membrane of embryos in higher vertebrates (especially when covering the head at birth)