Which of the following is an organ of the respiratory system?

Correct Answer: B

Rationale: The larynx is an essential organ of the respiratory system. It plays a crucial role in producing sound, protecting the trachea from food aspiration, and regulating the airflow to and from the lungs. The brain is part of the nervous system, the urethra is part of the urinary system, and the pancreas is part of the digestive system. Therefore, they are not directly related to the respiratory system's functions.

Correct Answer: B

Rationale: The correct answer is B. The thymus is not a principal organ of the nervous system; it is part of the immune system. The brain, spinal cord, and ganglia are principal organs of the nervous system. The brain is responsible for processing information, the spinal cord helps transmit signals between the brain and the rest of the body, and ganglia are clusters of nerve cells that support the nervous system's functions. Therefore, the thymus is the correct answer as it is not directly involved in nervous system functions.

Correct Answer: B

Rationale: The adrenal cortex is the organ responsible for producing stress hormones like cortisol and aldosterone, which play a crucial role in the body's stress response. During stress, the adrenal cortex releases cortisol, a hormone that helps the body deal with stress by increasing blood sugar, suppressing the immune system, and aiding in metabolism. Parathyroid gland is responsible for calcium regulation, the posterior pituitary gland secretes hormones like oxytocin and vasopressin which are not directly related to the stress response, and the hypothalamus plays a role in regulating hormonal balance and various bodily functions but is not primarily responsible for producing stress hormones.

Correct Answer: A

Rationale: The primary function of the hypothalamus is to regulate body balance and thermoregulation. It plays a crucial role in maintaining overall body equilibrium by controlling functions such as body temperature and water balance. While the hypothalamus is also involved in hunger and thirst regulation, its main role is to ensure homeostasis by monitoring and adjusting body balance and temperature. Choices B, C, and D are incorrect because hunger and thirst regulation, sleep and circadian rhythm regulation, and control of voluntary movements are secondary functions of the hypothalamus compared to its primary role in maintaining body balance and thermoregulation.

Correct Answer: B

Rationale: Digestion begins in the mouth. Mechanical digestion through chewing and chemical digestion through saliva initiate the breakdown of food. Enzymes in saliva start breaking down carbohydrates, marking the beginning of the digestive process. The stomach primarily functions in further breaking down food and mixing it with gastric juices. The small intestine is where most of the digestion and absorption of nutrients occur. The esophagus is a muscular tube that helps move food from the mouth to the stomach, but digestion does not begin there.