Final answer:
The nephron functions to filter blood in the glomerulus and Bowman's capsule. Reabsorption of Na, glucose, water, and bicarbonate occurs in the proximal convoluted tubule. This process takes place at various locations in the nephron to maintain homeostasis and excrete potential toxins.
Step-by-step explanation:
Nephron Function
Within the nephron, the glomerulus and Bowman's capsule form the renal corpuscle, where filtration occurs. Blood enters the glomerulus through the afferent arteriole and is filtered into the Bowman's capsule. From there, the filtrate passes through the renal tubule, where reabsorption and secretion take place.
Reabsorption of Na, Glucose, Water, and Bicarbonate
In the proximal convoluted tubule (PCT), around 67% of the filtered sodium (Na) is reabsorbed. Along with Na, glucose and amino acids are actively transported out of the filtrate and into the capillaries. The reabsorption of most water occurs through the walls of the PCT and the loop of Henle. Bicarbonate (HCO3-) reabsorption takes place in the renal tubule, where filtered HCO3- combines with hydrogen ions (H+) to form bicarbonate ions.
Locations of Reabsorption and Secretion
The majority of Na and water reabsorption occurs in the PCT. Glucose, amino acids, and bicarbonate are also reabsorbed in the PCT. In the descending limb of the loop of Henle, water is reabsorbed, while sodium is reabsorbed in the ascending limb. Tubular secretion primarily occurs in the distal convoluted tubule (DCT) and the collecting duct, where hydrogen ions (H+), potassium ions (K+), and some medications are secreted into the tubular fluid.