The initial filtration step in the glomerulus of the mammalian kidney occurs primarily by: A. passive flow due to a pressure difference. B. passive flow resulting from a countercurrent exchange system. C. active transport of water, followed by movement of electrolytes along a resulting concentration gradient. D. active transport of electrolytes, followed by passive flow of water along the resulting osmolarity gradient.

Answer is option "A"

Explanation:

The first phase in making urine is to isolate the liquid part of your blood (plasma), which contains all the dissolved solutes, from your platelets. Every nephron in your kidneys has a minuscule channel, considered a glomerulus that is continually separating your blood.  Blood that is going to be separated enters a glomerulus, which is a tuft of blood vessels (the littlest of veins). The glomerulus is settled inside a cup-like sac situated toward the finish of every nephron, called a glomerular case. Glomerular vessels have little pores in their dividers, much the same as an exceptionally fine work sifter.  Blood plasma enters the afferent arteriole and streams into the glomerulus, a bunch of entwined vessels. The Bowman's case (additionally called the glomerular container) encompasses the glomerulus and is made out of visceral (basic squamous epithelial cells—inward) and parietal (straightforward squamous epithelial cells—external) layers.  The visceral layer lies just underneath the thickened glomerular storm cellar film and is made of podocytes that structure little cuts where the liquid goes through into the nephron. The size of the filtration cuts confines the entry of enormous particles, (for example, egg whites) and cells, (for example, red platelets and platelets) that are the non-filterable segments of blood.Hence,the correct answer is option A "Passive flow due to a pressure difference".