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In the nephron, the fluid that immediately precedes urine is known as:

A.

renal filtrate

B.

tubular fluid

C.

plasma

D.

glomerular filtrate

Answer and Explanation

The Correct Answer is B

A. Renal filtrate refers to the fluid filtered from the blood in the glomerulus, which is the initial stage of urine formation. It does not immediately precede urine. 

 

B. Tubular fluid is the filtrate as it passes through the nephron tubules, undergoing various processes like reabsorption and secretion. This fluid eventually becomes urine, after the final adjustments in the collecting duct.

 

C. Plasma is the liquid component of blood that is filtered by the glomerulus, but it is not the direct precursor to urine. 

 

D. Glomerular filtrate is the fluid filtered out of the blood in the glomerulus and is the precursor to tubular fluid, not directly to urine.


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Correct Answer is C

Explanation

A. Esophageal glands secrete mucus to lubricate the esophagus, but they do not cause acid reflux.

B. Pharyngeal constrictors are muscles that help in the swallowing process, not in preventing acid reflux.

C. The lower esophageal sphincter (LES) is a ring of muscle that controls the passage of food from the esophagus to the stomach. If the LES is weakened or relaxes inappropriately, stomach acid can flow back into the esophagus, causing acid reflux or "heartburn."

D. The upper esophageal sphincter controls the passage of food from the pharynx into the esophagus, but it is not involved in preventing acid reflux.

Correct Answer is B

Explanation

A. Chief cells secrete pepsinogen, not HCl.

B. Parietal cells in the stomach lining are responsible for secreting hydrochloric acid (HCl). This acid is crucial for digestion and killing pathogens.

C. Mucous cells secrete mucus, which protects the stomach lining from the acidic environment. They do not secrete HCl.

D. Regenerative (stem) cells are involved in the renewal of the stomach lining, but they do not secrete HCl.