Chalaza
Chalaza
Chalaza (/kəˈleɪzə/; from Ancient Greek χάλαζα, meaning 'hailstone') is a structure inside bird eggs and plant ovules. In bird eggs, it serves to anchor the yolk within the egg and enables the exchange of nutrients and waste products. In plant ovules, it is the region where the nucellus is joined to the integuments.
Etymology
The term 'chalaza' originates from the Ancient Greek word χάλαζα (chalaza), which translates to 'hailstone'. This term was chosen due to the similarity in appearance between a chalaza and a hailstone.
In Bird Eggs
In bird eggs, the chalaza is a twisted, rope-like structure that serves to anchor the yolk in the center of the egg. It is made of protein and is attached to the yolk at one end and the lining of the eggshell at the other. The chalaza also allows for the exchange of nutrients and waste products between the yolk and the albumen (egg white).
In Plant Ovules
In plant ovules, the chalaza is the region where the nucellus (central part of the ovule) is joined to the integuments (outer layers of the ovule). It is often the site of nutrient intake for the developing seed.
Related Terms
- Albumen: The white of an egg, which surrounds the yolk and chalaza.
- Nucellus: The central part of a plant ovule, to which the chalaza is attached.
- Integument: The outer layers of a plant ovule, which are joined to the nucellus by the chalaza.
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