Dictionary > Chorion

Chorion

Definition
noun, plural: chorions
(embryology) An extraembryonic membrane surrounding the embryo or the fetus of amniotes
(entomology) The outer protective membrane of insect egg
(botany) The outer membrane of a seed
Supplement
In embryology, the chorion pertains to one of the extraembryonic membranes of a developing embryo (or fetus). In higher vertebrates such as humans, the chorion is part of the placenta. It is comprised of four layers: (1) cellular layer, (2) reticular layer, (3) basement membrane, and (4) trophoblast. The trophoblast is the outermost layer. The chorion together with the amnion forms the amniotic sac. The chorion has projections called chorionic villi involved in the transfer of nutrients from maternal blood to fetal blood. As the embryo develops into a fetus, the chorionic villi develop as well and become a part of the placenta. As a result, the placenta becomes comprised of the fetal placenta and maternal placenta. The fetal placenta is also referred to as the chorion frondosum.
In entomology, the chorion is the outer protective membrane of the egg of insects whereas in botany it pertains to the outer membrane of a seed.
Word origin: Latin chorion, Ancient Greek khorion (“membrane surrounding the fetus, afterbirth”)
See also:


You will also like...

The process of photosynthesis
Photosynthesis – Photolysis and Carbon Fixation

Photosynthesis is the process that plants undertake to create organic materials from carbon dioxide and water, with the ..

Biological Energy
ATP & ADP – Biological Energy

ATP is the energy source that is typically used by an organism in its daily activities. The name is based on its structu..

Bryophytes
Bryophytes

Bryophytes (nonvascular plants) are a plant group characterized by lacking vascular tissues. They include the mosses, th..

Biological Viruses
Biological Viruses

Viruses possess both living and non-living characteristics. This unique feature distinguishes them from other organisms...

Ecological Research Measuring & Analysis
Ecological Research: Measuring & Analysis

This lesson is about the methods used for ecological research, such as quadrat and transect sampling, canopy fogging, an..

Neurology of Illusions
Neurology of Illusions

Illusions are the perceptions and sensory data obtained from situations in which human error prevents us from seeing the..