Getty/Jason Hosking. A niche is a term that is used in ecological biology to define an organism's role in an ecosystem. Not only does a niche include the environment a given organism lives in, it also includes the organism's job in that environment.
Perilymph (also known as Cotunnius' liquid, and liquor cotunnii) is an extracellular fluid located within the cochlea (part of the inner ear) in two of its three compartments: the scala tympani and scala vestibuli. The ionic composition of perilymph is comparable to that of plasma and cerebrospinal fluid. The major cation (positively charged ion) in perilymph is sodium: The values of sodium and potassium concentration in the perilymph are 138 mM and 6.9 mM, respectively.
Blood that has traveled through the body returns to the heart and enters the right atrium. This blood flows through the tricuspid valve into the right ventricle. The right ventricle pumps the blood to the lungs, where it absorbs oxygen.Oxygen-rich blood returns from the lungs and enters the heart through the left atrium. Blood passes from the left atrium through the mitral valve and into the left ventricle.The left ventricle, the largest and most muscular of the four chambers, is the main pumping chamber of the heart.When the left ventricle contracts, blood is pumped through the aortic valve into the main artery of the body (aorta).lood that has traveled through the body returns to the heart and enters the right atrium. This blood flows through the tricuspid valve into the right ventricle. The right ventricle pumps the blood to the lungs, where it absorbs oxygen.