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.

The sodium-potassium pump pumps three sodium ions out of the cytosol, and two potassium ions into the cytosol. It is electrogenic because each sodium and potassium ion have a charge of positive one, and the two ions are pumped in unequal quantities. The pump generates an electric gradient and current due to the directional flow of positive charge out of the cell.

When aldosterone is released, it increases the action of the sodium-potassium pump, causing excess sodium to be removed from the filtrate in the distal tubule, thus conserving sodium and drawing water out of the filtrate.

The glomerulus is the primary site of filtration in the kidney. Together, the glomerulus and Bowman's capsule for the renal corpuscle of the nephron and are responsible for collecting filtrate from the blood. Deposition and accumulation of immune complexes in the glomerulus would result in blockage of its filtering functions, impeding nephron function and preventing proper excretion of soluble wastes.

The sinoatrial node is the natural pacemaker region of the heart, located in the right atrium. Haversian canals are the central regions of osteons and often house nerves and blood vessels, facilitating cellular communication within bone. Neuromuscular junctions are the interface regions between a single neuron and the muscle fiber it innervates. The semicircular canals are located in the inner ear and function in the propagation an integration of sound vibrations. None of these structures are involved in filtration, and they would most likely be unaffected by the presence of immune complexes in the body.

Together, Bowman's capsule and the glomerulus make up the renal corpuscle. Blood flows through the glomerulus, where high hydrostatic pressures force plasma through the fenestrations of the glomerular endothelium into Bowman's capsule. The substance that ends up in the capsule is called the filtrate, which then moves to the proximal tubule. Proteins, glucose, and ions are secreted from the proximal tubule back into the blood.

The collecting duct is impermeable to water and is not particularly sensitive to aldosterone. Instead, aldosterone, a steroid hormone produced by the adrenal cortex, acts primarily at the distal tubule to increase sodium reabsorption, potassium secretion, and ultimately water reabsorption to increase blood pressure. The distal tubule absorbs Na⁺and Ca²⁺, not HCO_3.^-。

The loop of Henle is a U-shaped structure found in the nephron. Its main function is to reabsorb water and essential solutes. Reabsorption is the process by which nutrients and water are transported from the filtrate back into the body.

The loop of Henle contains two parts: the descending limb and the ascending limb. The descending limb functions to reabsorb water, whereas the ascending limb functions to reabsorb sodium and chloride ions. The question states that filtrate in location A has a higher solute concentration. This means that filtrate in location A has more solutes (or less water) than filtrate in location B. Since the descending limb only reabsorbs water, the filtrate concentration is higher in the descending loop; water is removed without solute being able to follow. Location A would be the descending limp of the loop of Henle because it reabsorbs water and increases the solute concentration of the filtrate.

Concentration decreases in the ascending limb when ions are pumped out of the filtrate, removing solute.

The adrenal gland is situated superior to the kidney, and is responsible for the production of several key hormones.

One such hormone is cortisol. Cortisol is often released when an individual is highly stressed over an extended period. It is a steroid hormone that functions to increase blood glucose levels by inducing gluconeogenesis, the process that converts glycogen stores in the liver to glucose. Cortisol is released from cells in the adrenal cortex. Recall that the adrenal cortex is the outer portion of the gland, whereas the adrenal medulla is the inner portion of the gland.

Aldosterone is another hormone that is released by cells in the adrenal cortex, and is essential for sodium reabsorption in the kidney. Epinephrine is released from the adrenal medulla in response to stimulation by the sympathetic nervous system.