Blastula

The blastula (from Greek βλαστός (blastos), meaning "sprout") is an early stage of embryo

Embryo

An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...

nic development in animal

Animal

Animals are a major group of mostly multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously...

s. It is also called blastosphere. It is produced by cleavage of a fertilized ovum

Ovum

An ovum is a haploid female reproductive cell or gamete. Both animals and embryophytes have ova. The term ovule is used for the young ovum of an animal, as well as the plant structure that carries the female gametophyte and egg cell and develops into a seed after fertilization...

 and consists of a spherical layer of around 128 cells with a large fluid filled space called the blastocoel in the animal pole of the embryo. The blastula follows the morula

Morula

A morula is an embryo at an early stage of embryonic development, consisting of cells in a solid ball contained within the zona pellucida.-Production:...

 and precedes the gastrula in the developmental sequence.

Research

A whitefish

Freshwater whitefish

The freshwater whitefish are fish of the subfamily Coregoninae in the salmon family Salmonidae. Along with the freshwater whitefish, the Salmonidae includes the freshwater and anadromous trout and salmon species as well as graylings .The freshwater whitefish subfamily includes the genera...

 blastula is often used to help study the processes of mitosis in animal cells. The blastula is prevented from multiplying during the nuclear-injection stage.

Blastula and blastocyst

In mammal

Mammal

Mammals are a class of vertebrate animals whose females are characterized by the possession of mammary glands while both males and females are characterized by sweat glands, hair, three middle ear bones used in hearing, and a neocortex region in the brain.Mammals are divided into three main...

s, blastulation leads to the formation of the blastocyst

Blastocyst

The blastocyst is a structure formed in the early embryogenesis of mammals, after the formation of the morula, but before implantation. It possesses an inner cell mass , or embryoblast, which subsequently forms the embryo, and an outer layer of cells, or trophoblast, which later forms the placenta...

, which must not be confused with the blastula; even though they are similar in structure, their cells have different fates. The blastocyst contains an embryoblast as well.