The distal tubule of the nephron is responsible for reabsorbing sodium and calcium and secreting potassium, hydrogen, and bicarbonate. Remember that aldosterone is responsible for increasing reabsorption of sodium and increasing excretion of potassium.

The glomerulus is the capillary bed of the afferent arterioles, which filter the blood and allows the nephron to concentrate waste into urine. Glucose is a sugar is filtered into the glomerular capsule. It is, however, quickly reabsorbed back into the bloodstream in the proximal convoluted tubule, and returned to the efferent arterioles. In a healthy individual, the nephron will be able to reabsorb all the glucose that gets filtered into the glomerular capsule.

The main function of the Loop of Henle is to establish a concentration gradient so that water can be reabsorbed from the collecting duct and avoid being lost as urine. Although the ascending limb does absorb water, this water would be lost as urine if it were not for the concentration gradient established in the medulla of the kidney. Neither sodium nor potassium is absorbed in the Loop of Henle.

The correct path of filtrate through a nephron starts in the renal corpuscle, which is comprised of the glomerulus and Bowman's capsule. Filtrate then passes through the proximal convoluted tubule, where the majority of reabsorption takes place. It then travels through the descending and ascending limbs of the Loop of Henle, creating the counter current multiplier gradient that will allow urine to be concentration in the collecting duct. From the Loop of Henle, filtrate enters the distal convoluted tubule for final reabsorption before entering the collecting duct and being trasported to the bladder.

The renal artery is used to carry blood into the kidneys. Filtrate originates from the renal artery, but it is not a part of the nephrons.

The Loop of Henle creates a countercurrent multiplier system. As the filtrate descends through the Loop of Henle, water leaves the filtrate and is reabsorbed, making the filtrate very concentrated. When the Loop of Henle ascends, salt ions leave the filtrate and are reabsorbed making the filtrate less concentrated. This creates a strong concentration of ions in the interstitial fluid toward the bottom of the loop, as compared to the concentration at the top. When filtrate flows down the collecting duct, this gradient helps concentrate the urine by removing water.

A renal afferent arteriole is directed toward the glomerulus, while a renal efferent arteriole is directed away from the glomerlus. If the radius of the afferent arteriole is increased, there is more flow through it toward the glomerulus, and if there is a smaller radius in the efferent arteriole, there is a resultant back pressure in the glomerulus. This is can be imagined as trying to squeeze a high-pressure hose through a small pipe. This pressure increases the force within the glomerulus to increase filtration, and subsequently increase reabsorption.

Antidiuretic hormone (ADH) secretion has a neglible effect on the radius of renal arterioles. Blood flow to the kidney is increased when afferent arteriole radius is increased (this also increases the arteriole flow).

It is important to understand how urine is concentrated as it travels through the nephron. The proximal convoluted tubule does not alter the osmolarity of the filtrate, the loop of Henle increases the osmolarity of the filtrate, and the distal convoluted tubule lowers the osmolarity of the filtrate. In the absence of antidiuretic hormone, the collecting duct will be impermeable to water, preventing it from leaving the filtrate and resulting in more dilute urine. With the collecting duct impermeable to water, the filtrate will be most concentrated at the bottom of the loop of Henle.

The proximal tubule is the primary site of solute reabsorption and secretion, modifying the urine after its initial filtration in the glomerulus.

Concentration of the filtrate primarily occurs in the collecting duct, and the distal convoluted tubule transports urine from the loop of Henle to the collecting duct. Filtration occurs in the glomerulus and Bowman's capsule, know together as the renal corpuscle.

Bowman's capsule collects fluid filtered from the glomerulus and serves as a site of entry into the proximal tubule. The glomerulus is a convoluted capillary bed adjacent to Bowman's capsule. Osmotic and oncotic pressure gradients work to filter the blood from the glomerulus into Bowman's capsule. The nature of the epithelial cells that line the glomerulus determines the permeability of the filtration, and prevents unwanted content in the urine.

Filtrate moves from Bowman's capsule to the proximal tubule and into the loop of Henle, which dives into the renal medulla before returning to the renal cortex. From the loop of Henle, filtrate is transferred to the distal tubule and into the collecting duct, where it travels into the renal medulla for collection.

The main purpose of the glomerulus is filtration; thus, it is mainly composed of the thinnest walled-blood vessels (capillaries), and specifically those with pores (fenestrations) to facilitate filtration.