Egg yolk

When the yolk or the (Greek λέκιθος Lekithos, lat vitellum ) is defined as:

• The formation of yolk -called cytoplasm of the egg cell, which produces the embryo and
• The food-yolk, a fatty structure in the egg which nutrients to the structure of the plasma formation and nutrition of the embryo holds. The food yolk from birds' eggs ( chicken eggs, and in particular ) is also referred to as egg yolk, as it is colored yellow by fat soluble carotenoids.

Food-yolk

The cytoplasm of the yolk contains, inter alia, proteins, fats, vitamins and minerals.

The yolk may be in the form of individual yolk granules, or as in the egg yolk as a whole. When bird and reptile area of the ovum from which the embryo develops, the germinal disc on the yolk surface is.

The egg yolk has a diameter of about three to four centimeters. The special thing is it's the yolk consists of only a single cell, making it the largest known biological cell. In chickens, it can also lead to eggs with double yolks.

In the center of the yolk to the yolk is bed, which makes up about 0.6 percent of the egg yolk substance. This part is much smoother than the rest of the egg yolk and solidifies itself not with boiled eggs. The whole egg also contains almost all vitamins (eg, D, B12, K and biotin), trace elements and proteins as well as many minerals such as calcium, selenium and iron.

Distribution types of the yolk in the egg:

• Isolecithal: uniform
• Anisolecithal: uneven
• Zentrolecithal: Collection in the center
• Telolecithal: predominantly yolk at the vegetal pole

In addition, the yolk endolecithal can be created ( from the inside ) or ektolecithal ( outward).

Eggs may be distinguished according to yolk content and its distribution.

Subdivision yolk content:

• Oligolecithal: little (eg the spawning of bony fish and amphibians)
• Mesolecithal: medium
• Polylecithal: a lot (eg bird's egg )

• Egg ( Developmental Biology)