Metamorphic grade is a general term for describing the relative temperature and pressure conditions under which metamorphic rocks form. As the temperature and/or pressure increases on a body of rock we say that the rock undergoes prograde metamorphism or that the grade of metamorphism increases.he original rock that has undergone metamorphism is called the protolith. Protolith can be any type of rock and sometimes the changes in texture and mineralogy are so dramatic that is difficult to distinguish what the protolith was. 1  Note that diagenesis and weathering are also a changes in form that occur in rocks.
Within the nephron (the functional unit of the kidneys), filtration occurs in the glomerolus. The filtered fluid is called filtrate. Reabsorption of filtrate occurs in a few places within the nephron, however, the majority of reabsorption takes place in the proximal convoluted tube.
Identify the parts and histology kidney nephrons. 1  The glomerulus is the site in the nephron where fluid and solutes are filtered out of the blood to form a glomerular filtrate.  The proximal and distal tubules, the loop of Henle, and the collecting ducts are sites of reabsorption of water and ions.