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.
The process by which glomerular filtration occurs is called renal ultrafiltration. The force of hydrostatic pressure in the glomerulus (the force of pressure exerted from the pressure of the blood vessel itself) is the driving force that pushes filtrate out of the capillaries and into the slits in the nephron.