The nephron is the structural unit of the human

Correct Answer: C

Rationale: The correct answer is C: kidney. The nephron is the structural unit of the kidney responsible for filtering and processing blood to produce urine. The kidney's primary function is to regulate water and electrolyte balance in the body. Choices A, B, and D are incorrect because the nephron is not found in the lung, liver, or intestine. Each of these organs has its own specialized structures and functions unrelated to the nephron's role in kidney function.

Correct Answer: C

Rationale: The correct answer is C: Proton pump inhibitors (PPIs). PPIs are commonly used to reduce stomach acid in the treatment of peptic ulcer disease by inhibiting the proton pump in the gastric parietal cells. This reduces the production of stomach acid, allowing the ulcer to heal. Aspirin and ibuprofen can actually worsen peptic ulcers by irritating the stomach lining. Acetaminophen is not used to reduce stomach acid and does not directly treat peptic ulcers.

Correct Answer: D

Rationale: The correct answer is D because every mucosa consists of a surface epithelial layer, with or without glands, along with an underlying layer of loose connective tissue. This structure allows for protection, secretion, and absorption functions of mucosal surfaces. A simple epithelium (choice A) and a stratified epithelium (choice B) alone do not adequately support these functions. Choice C is incorrect because not all mucosas have associated glands, and the presence of loose connective tissue is crucial for proper mucosal function.

Correct Answer: B

Rationale: The correct answer is B because the submucosa of the GI tract typically contains the nerves and parasympathetic ganglia of the submucosal (Meissner's) plexus. This plexus regulates gastrointestinal secretion and blood flow. Choice A is incorrect because smooth muscle layers are found in the muscularis externa, not the submucosa. Choice C is incorrect as the myenteric plexus is located between the circular and longitudinal muscle layers of the muscularis externa. Choice D is incorrect because the submucosa contains a rich network of blood vessels for nutrient absorption and immune function.

Correct Answer: D

Rationale: The correct answer is D because tonsils are composed of lymphatic connective tissue with epithelially lined crypts. Tonsils play a crucial role in the immune system, containing lymphocytes to help fight infections. The other choices are incorrect. A, ordinary connective tissue with vascular sinusoids, does not accurately describe tonsils. B, adipose tissue, is not the main component of tonsils. C, serous glandular tissue, is not the primary constituent of tonsils. Hence, choice D is the correct answer based on the specific structure and function of tonsils.