Definition

Noun: 1. The innermost membrane enclosing the developing embryo or fetus: The amniotic sac is a thin, fluid-filled membrane that forms a protective sac around the embryo or fetus during pregnancy in reptiles, birds, and mammals.

Usage

The term "amniotic sac" is used specifically in biological and medical contexts to describe a key anatomical structure in embryonic development. * It is typically used with verbs like rupture, break, form, or surround. * It is often modified by adjectives like intact, ruptured, or protective.

Examples

• Noun:
  • The developing fetus floats within the amniotic sac.
  • When the amniotic sac ruptures, it is often a sign that labor is beginning.
  • The amniotic sac provides a cushion against physical shocks.

Advanced Usage

• "Amniotic sac" vs. "Amnion": While closely related, "amniotic sac" often refers to the complete structure (the amnion and its fluid), whereas "amnion" can refer specifically to the membrane itself.
• "Bag of waters": This is a common informal or layman's term for the amniotic sac, referring to the fluid it contains.

Variants and Related Words

• Amnion (n): The innermost membrane that encloses the embryo of a reptile, bird, or mammal.
• Amniotic fluid (n): The liquid contained within the amniotic sac that cushions the fetus.
• Amniocentesis (n): A medical procedure involving the extraction of a small amount of amniotic fluid for testing.

Synonyms

• Amnion: (Technical synonym for the membrane)
• Bag of waters: (Informal synonym)

Related Phrases

• Rupture of membranes (ROM): The medical term for the breaking of the amniotic sac.
• Premature rupture of membranes (PROM): When the amniotic sac breaks before the onset of labor.

Noun

1. thin innermost membranous sac enclosing the developing embryo of higher vertebrates (reptiles, birds and mammals)