What is the primary function of the liver in the digestive system?

Correct Answer: A

Rationale: The correct answer is A: 'To produce bile.' The liver's primary role in the digestive system is to produce bile. Bile is essential for emulsifying fats, aiding in their digestion and absorption in the small intestine. Choice B is incorrect because while the liver does secrete some digestive enzymes, its primary function is bile production. Choice C is incorrect because while the liver does store glucose, it is not its primary function in the digestive system. Choice D is incorrect because the liver produces bile, but it does not store it.

Correct Answer: A

Rationale: The correct answer is the Pineal gland. The pineal gland is responsible for producing melatonin, a hormone that helps regulate the sleep-wake cycle. Melatonin secretion is influenced by light exposure. Higher levels are observed at night to promote sleep, while lower levels during the day encourage wakefulness. Choices B, C, and D are incorrect as they are not associated with the production of melatonin. The thyroid gland produces hormones like thyroxine and triiodothyronine, the pituitary gland controls various other glands, and the adrenal gland produces hormones like adrenaline and cortisol.

Correct Answer: A

Rationale: The correct answer is A: Protecting the body from external damage. The primary function of the integumentary system, which includes the skin, hair, and nails, is to act as a physical barrier that protects the body from external damage such as pathogens, UV radiation, and mechanical injuries. While the integumentary system does play roles in regulating body temperature and producing vitamin D, its main and most crucial function is to provide a protective shield for the body. Choices B, C, and D are incorrect because although the integumentary system contributes to regulating body temperature and producing vitamin D, as well as housing cells involved in the immune response, its primary role is protection.

Correct Answer: B

Rationale: The alveoli in the lungs are tiny air sacs responsible for the exchange of oxygen and carbon dioxide during breathing. Oxygen from inhaled air diffuses into the bloodstream through the alveoli, while carbon dioxide produced by cells is removed from the blood and exhaled out of the body through the alveoli. This gas exchange process is essential for the body to obtain oxygen and get rid of carbon dioxide, supporting cellular functions and maintaining overall health. Choices A, C, and D are incorrect because the alveoli do not filter blood, transport nutrients, or store oxygen. Their main function is gas exchange.

Correct Answer: B

Rationale: The central nervous system comprises the brain and spinal cord, responsible for processing and transmitting information. The retina, though part of the eye, is an extension of the central nervous system. However, the heart is part of the circulatory system, responsible for pumping blood throughout the body. Therefore, the correct answer is the heart as it is not a component of the central nervous system.

Correct Answer: A

Rationale: The correct answer is A: 'To produce bile.' The liver's primary role in the digestive system is to produce bile. Bile is essential for emulsifying fats, aiding in their digestion and absorption in the small intestine. Choice B is incorrect because while the liver does secrete some digestive enzymes, its primary function is bile production. Choice C is incorrect because while the liver does store glucose, it is not its primary function in the digestive system. Choice D is incorrect because the liver produces bile, but it does not store it.

Correct Answer: B

Rationale: Vitamin D is the correct answer. It is essential for the absorption of calcium in the intestines, facilitating the maintenance of strong bones and teeth. Vitamin D helps regulate calcium levels in the blood and promotes bone mineralization, making it crucial for overall bone health. Choices A, C, and D are incorrect because Vitamin C is not directly involved in calcium absorption, Vitamin A is more related to vision and immune function, and Vitamin K plays a role in blood clotting and bone mineralization but is not primarily responsible for calcium absorption.

Correct Answer: B

Rationale: The correct answer is B: Remove carbon dioxide from the body. The primary function of the lymphatic system is to return excess tissue fluid to the bloodstream and assist in the body's defense against infections by filtering out harmful pathogens and foreign particles. Choices A, C, and D are incorrect because transporting oxygen to cells is mainly done by the circulatory system, hormone production is primarily carried out by endocrine glands, and nutrient transport is also a function of the circulatory system and the digestive system, not the lymphatic system.

Correct Answer: A

Rationale: The correct answer is A: To secrete digestive enzymes. The pancreas is responsible for secreting digestive enzymes that aid in breaking down carbohydrates, fats, and proteins in the small intestine, facilitating the process of digestion. Choice B is incorrect because the pancreas does not store bile; that is primarily the function of the gallbladder. Choice C is incorrect as the absorption of nutrients mainly occurs in the small intestine, not the pancreas. Choice D is incorrect as the transport of glucose is primarily regulated by insulin produced in the pancreas, but this is not the main role of the pancreas in digestion.