What happens to the mRNA before it comes to the ribosome?

The mRNA molecules are transported through the nuclear envelope into the cytoplasm, where they are translated by the rRNA of ribosomes (see translation). ... Messenger RNA (mRNA) then travels to the ribosomes in the cell cytoplasm, where protein synthesis occurs

The mRNA is end product of transcription that takes place in the nucleus and it is followed by translation or synthesis of proteins. So, the first important step is to transport the mRNA to the cytoplasm via nuclear pore complex.

Explanation:

The process of transcription is second step of the central dogma of molecular biology. This process is characterized by the creation of mRNA strand from the template pre-mRNA strand. This process involves three defined steps of initiation, elongation and termination. RNA polymerase is the associated enzyme that plays a critical role in the process.

The occurrence of this process in the nucleus illustrates the carrying away of the product formed that is the mRNA to the cytoplasm. The transport process takes place via nuclear pore complex. The ribosome in the cytoplasm reads the mRNA and forms the protein.

the oxygenated blood then leaves the lungs through pulmonary veins, which return it to the left heart, completing the pulmonary cycle. this blood then enters the left atrium, which pumps it through the mitral valve into the left ventricle. from the left ventricle, the blood passes through the aortic valve to the aorta.

deoxygenated blood leaves through the right ventricle through the pulmonary artery. from the right atrium, the blood is pumped through the tricuspid valve (or right atrioventricular valve), into the right ventricle.