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.
The right atrium pumps blood through the right atrioventricular (tricuspid) valve to the right ventricle. From the right ventricle, blood flows through the pulmonary valve to the lungs via the pulmonary arteries (deoxygenated blood).In the lungs the blood becomes more red in color as it is oxygenated.Blood returns to the heart via the pulmonary veins (oxygenated blood) to the left atrium.The left atrium pumps blood through the left atrioventricular (bicuspid or mitral) valve to the left ventricle.n the lungs the blood becomes more red in color as it is oxygenated. Blood returns to the heart via the pulmonary veins (oxygenated blood) to the left atrium. The left atrium pumps blood through the left atrioventricular (bicuspid or mitral) valve to the left ventricle.