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 region of the distal convoluted tubule in contact with the granular cells of the afferent arteriole is called the macula dense. 26. Within each kidney, the interlobar veins empty their blood into the renal vein. 27. In the female urinary system, the urethral orifice is situated posterior to the vaginal orifice.