The term "vitelline sphere" refers to a yolk-like mass that is found in the center of an egg. The spelling of this word can be explained using the International Phonetic Alphabet. The first syllable, "vit-", is pronounced as /vɪt/ with a short i sound followed by a t. The second syllable, "-el-", is pronounced as /ˈɪl/ with a short i sound followed by an l. The final syllable, "-ine", is pronounced as /aɪn/ with a long i sound followed by an n. Altogether, the word is pronounced as /ˈvɪtəlaɪn ˈsfɪr/.
The vitelline sphere refers to an essential structure found in the early developmental stages of many animal embryos. It is typically a prominent rounded or oval-shaped mass composed primarily of yolk, a nutrient-rich substance that nourishes the developing embryo. The vitelline sphere is primarily observed in specific groups of animals, including birds, reptiles, and egg-laying mammals like monotremes.
This structure plays a crucial role in providing the necessary nutrients for the developing embryo. The yolk contained within the vitelline sphere is a vital source of proteins, lipids, and other essential molecules that are important for the initial growth and survival of the embryo. As the embryo develops, it absorbs the nutrients from the yolk via a network of blood vessels that connect the vitelline sphere to the developing cardiovascular system.
In many species, particularly birds, the vitelline sphere serves as the primary nourishment for the embryo throughout early development. As the embryo grows and develops additional structures, such as the amniotic sac or chorion, the vitelline sphere gradually diminishes in size and is eventually depleted. By the time of hatching or birth, the yolk reserves within the vitelline sphere have been expended, and the animal is reliant on other sources of nutrition.
Overall, the vitelline sphere is a crucial structure during early embryonic development, providing the necessary nutrients for growth until alternative sources of nutrition can be established.
Morula.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.
The word "vitelline" is derived from the Latin term "vitellus", which means "yolk". It is combined with the word "sphere" referring to a round or spherical shape. When used together, "vitelline sphere" describes the yolk sac or the circular structure that contains the yolk of an egg or an embryo.