Which structure in the eye focuses light onto the retina?

Correct Answer: B

Rationale: The lens of the eye is responsible for focusing light onto the retina. It plays a crucial role in adjusting the focus to allow for clear vision. After the light passes through the lens, it reaches the retina where it is converted into neural signals for the brain to interpret. The cornea is the transparent outer layer of the eye that helps in focusing light, but its main function is to protect the eye. The pupil is the opening in the center of the iris that regulates the amount of light entering the eye. The iris is the colored part of the eye that controls the size of the pupil.

Correct Answer: A

Rationale: The correct answer is 'Epithelial.' Epithelial tissue is characterized by cells that cover internal and external surfaces, such as the lining of the stomach. It lacks an extracellular matrix, has tall and thin cells, and does not contain blood vessels. The other choices are incorrect because connective tissue typically has an extracellular matrix, muscle tissue is composed of contractile cells, and cartilage is a type of connective tissue with a specific extracellular matrix and cell arrangement.

Correct Answer: A

Rationale: The parathyroid gland is not involved in the release of hormones during stress. It is responsible for regulating calcium levels in the blood by secreting parathyroid hormone. During stress, the adrenal cortex, posterior pituitary, and hypothalamus play crucial roles in releasing stress hormones like cortisol, adrenaline, and oxytocin. Therefore, the correct answer is the parathyroid gland, as it is not directly associated with the release of stress-related hormones.

Correct Answer: D

Rationale: The correct answer is D, the Hypothalamus. The hypothalamus is responsible for releasing key hormones like thyrotrophic-releasing hormone, growth hormone-releasing hormone, and gonadotropin-releasing hormone. These hormones play essential roles in regulating various body functions by influencing the activities of other endocrine glands. Choices A, B, and C are incorrect because the thymus is involved in immune function, the pituitary gland releases different hormones, and the pineal gland primarily produces melatonin, not the hormones mentioned in the question.

Correct Answer: B

Rationale: The urethra is the correct answer as it is a structure shared by both the male reproductive and urinary systems. It functions as a conduit for both urine from the bladder and semen from the reproductive system, making it a crucial component of both systems. The bladder (Choice A) is solely part of the urinary system, storing urine. The prostate (Choice C) and seminal vesicle (Choice D) are structures specific to the male reproductive system, involved in producing and secreting components of semen.