Saliva does not contain:

Correct Answer: D

Rationale: Saliva does not contain platelets because platelets are components of blood responsible for blood clotting, not found in saliva. Saliva does contain ABO blood group antigens, lysozymes for antibacterial activity, and immunoglobulins for immune function. Platelets are not a normal component of saliva, making option D the correct answer.

Correct Answer: D

Rationale: The correct answer is D because the oesophageal phase of swallowing starts when a bolus enters the oropharynx. This triggers the swallowing reflex, leading to the contraction of the upper oesophageal sphincter and relaxation of the lower sphincter to allow the bolus to move into the oesophagus. Choices A and B are incorrect because the oesophageal phase can proceed with the mouth open and is not primarily reflex-controlled by the myenteric plexus. Choice C is incorrect as the swallowing center in the brain coordinates and initiates the swallowing reflex but is not the primary control of the oesophageal phase.

Correct Answer: A

Rationale: Step-by-step rationale: 1. Hematemesis refers to vomiting blood, which typically originates from the upper gastrointestinal tract. 2. Blood from the lower gastrointestinal tract is usually passed through the rectum as melena or hematochezia. 3. Therefore, hematemesis is a clear indication of upper gastrointestinal bleeding. 4. Choice A is correct because hematemesis specifically points to upper GI bleeding. Summary: - Choice B is incorrect because lower GI bleeding does not typically present with vomiting blood. - Choice C is incorrect as hematemesis is specific to upper GI bleeding. - Choice D is incorrect as hematemesis indicates an issue in the upper GI tract.

Correct Answer: B

Rationale: The correct answer is B because esophageal carcinoma most frequently involves squamous cell carcinoma, not adenocarcinoma. Male predominance (A), patients over 50 years of age (C), and squamous cell type (D) are all accurate descriptors of esophageal carcinoma. Adenocarcinoma is more commonly associated with the lower esophagus and gastroesophageal junction, not the most frequent type in esophageal carcinoma overall.

Correct Answer: D

Rationale: Metabolic rate is high in pregnancy due to increased energy demands for fetal growth. After a heavy meal, metabolic rate increases to process and digest food. Hypothyroidism actually slows down metabolic rate. Option D is correct because both pregnancy and postprandial state increase metabolic rate, while hypothyroidism decreases it.