Summarize how the countercurrent multiplier system produces concentrated urine in juxtamedullary nephrons
What will be an ideal response?
NaCl is active transported from the filtrate in the thick ascending limb into the interstitial fluid, raising the osmolarity of the interstitial fluid. The NaCl pumped into the interstitial fluid draws water out of the filtrate in the thin descending limb into the interstitial fluid by osmosis. NaCl concentration continues to increase as filtrate reaches the bottom of the nephron loop due to the continued loss of water. Now, as the filtrate reaches the thick ascending limb, it has a high NaCl concentration. Symporters continue to pump NaCl into the interstitial fluid and thus, less NaCl is pumped into the interstitial fluid. Water is returned to the blood and less water leaves the kidney in the urine. Thus, concentrated urine is formed.
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Indicate whether the statement is true or false.
The prominent bulge just posterior and inferior to the external auditory meatus is the
A) mastoid process. B) styloid process. C) occipital condyle. D) condyloid process. E) temporal process.
A cell membrane that is selectively permeable
A) is impermeable to all substances but water. B) randomly chooses which substances will pass through. C) can change which substances pass through by changing its lipid and protein content. D) will only allow substances in or out if their concentration in the cell is above or below a certain point.
Which of the following is not a step in endochondral bone formation?
A. Hyaline cartilage develops into the shape of the future bone. B. Hyaline cartilage changes to adipose tissue. C. Osteoblasts deposit osseous tissue in place of disintegrating cartilage. D. Periosteum forms from connective tissue outside the developing bone.