This external structure is often a feature of bacterial pathogens; it aids in allowing the bacterium to counteract the body's immune system cells, such as avoiding phagocytosis.

Bacteria capsule.

Explanation:

The bacteria capsule is a layer of polysaccharides that is around the bacteria membrane. Its principal function is to protect the bacteria from dehydration, destructive toxins,  and cells that can destruct the bacteria, such as phagosomes. As a result, the bacteria have a higher probability of surviving and colonizing.

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.