Video Transcript
Complete the table to correctly
relate the structures of a nephron to their functions. (A) Encourages the diffusion of
glucose into the nephron. (B) Selectively reabsorbs ions and
water. (C) Forms urea and then urine from
waste amino acids. Or (D) transports blood back to the
glomerulus.
Nephrons are microscopic structures
found within the kidneys. The kidneys are incredibly
important organs that form part of our excretory systems. The primary functions of the
kidneys are to filter blood and remove the waste products as urine.
To answer this question, let’s
briefly recap how the thousands of nephrons found within the kidneys help the
kidneys function by producing urine. In the first stage, blood that
enters the kidneys via the renal artery is filtered. Substances like water, glucose,
urea, and salt move from the capillaries of the kidney and into the Bowman’s capsule
of the nephron. Then, selective reabsorption occurs
in the proximal, or first, convoluted tubule. This is where useful products, like
glucose, some ions, and water if needed, are reabsorbed back into the blood.
Finally, the waste products are
emptied into the collecting ducts of the nephron to form urine. The collecting ducts transport
urine to the ureter, which is the tube that connects the kidneys and the
bladder. Urine is stored in the bladder
until it is ready to be excreted.
Let’s look back at our
question. We are asked to complete the table
by giving the function of the proximal convoluted tubule. We now know this is where selective
reabsorption of useful products back into the bloodstream occurs. So our correct answer is given by
choice (B). The proximal convoluted tubule
selectively reabsorbs ions and water.
