The signs and symptoms of large bowel obstruction are:

Choice A reason:
Loss of muscle tone at the lower esophageal sphincter (LES) is the primary cause of GERD. The LES normally prevents stomach contents from refluxing into the esophagus. When its tone is reduced, acidic gastric contents can flow back, leading to symptoms such as heartburn, regurgitation, and potential damage to the esophageal lining. Factors contributing to LES dysfunction include obesity, hiatal hernia, and certain dietary habits.
Choice B reason:
Sympathetic nerve stimulation is not a cause of GERD. The autonomic nervous system plays a role in regulating digestive functions, but GERD is primarily a mechanical issue involving the LES and is not directly related to sympathetic nervous activity.
Choice C reason:
Fibrosis of the lower third of the esophagus is typically associated with conditions such as scleroderma, which can lead to esophageal motility disorders. While fibrosis might contribute to esophageal dysfunction, it is not the primary cause of GERD.
Choice D reason:
Reverse peristalsis of the stomach is not a mechanism for GERD. GERD results from dysfunction of the LES, not from the backward movement of stomach contents due to altered motility.

Choice A reason:
Fatty acids are essential components of many lipids, but they are not the primary building blocks of bile salts. Bile salts are synthesized from cholesterol. Fatty acids mainly function as energy storage molecules and are involved in forming complex lipids, like triglycerides and phospholipids. They don't participate directly in the production of bile salts, which are crucial for digesting and absorbing dietary fats.

Choice B reason:
Testosterone is a steroid hormone that plays a vital role in male reproductive tissues and secondary sexual characteristics. It is not involved in the synthesis of bile salts. Bile salts are derived from cholesterol, not hormones. Testosterone’s primary function is related to endocrine activities rather than hepatic functions like bile salt synthesis.

Choice C reason:
Cholesterol is the correct answer. Bile salts are synthesized from cholesterol in the liver. This process involves the conversion of cholesterol into bile acids, which are then conjugated with amino acids to form bile salts. These bile salts are critical for the digestion and absorption of fats in the small intestine. The liver’s conversion of cholesterol to bile salts helps in maintaining cholesterol homeostasis in the body.

Choice D reason:
Lecithin is a type of phospholipid that plays a significant role in cell membrane structure and function. While it is an important component of bile, it is not the substance from which bile salts are synthesized. Lecithin helps in the emulsification of fats in the digestive process but is not a precursor to bile salts. The synthesis of bile salts specifically involves cholesterol.