Mastoid process is part of which bone?

Correct Answer: A

Rationale: The correct answer is A: Temporal. The mastoid process is a bony projection located on the temporal bone, which is situated behind the ear. It serves as an attachment site for various neck muscles. The temporal bone also houses important structures like the middle and inner ear components. The other choices, B: Mandible, C: Maxilla, and D: Ethmoid, are incorrect because the mastoid process is not located on these bones. The mandible is the jawbone, the maxilla forms the upper jaw, and the ethmoid bone is located in the skull's orbit and nasal cavity. Therefore, based on its anatomical location and function, the correct answer is A: Temporal.

Correct Answer: D

Rationale: The correct answer is D: Eustachian tube. The Eustachian tube connects the middle ear to the back of the nose and throat, helping to equalize air pressure and drain fluid from the middle ear. Blockage of the Eustachian tube can lead to fluid accumulation in the middle ear, causing ear problems. The other choices, A: Saccule and B: Utricle, are structures in the inner ear related to balance and hearing, not fluid drainage. Choice C: External ear, refers to the outer ear structures and is not involved in middle ear fluid accumulation.

Correct Answer: D

Rationale: Metrorrhagia is defined as irregular bleeding between periods. Choice D is correct because it accurately describes the characteristic of metrorrhagia. Choice A is incorrect because fewer than 21 days between menses refers to polymenorrhea. Choice B is incorrect as excessive flow is known as menorrhagia. Choice C is incorrect because infrequent bleeding is termed oligomenorrhea.

Correct Answer: C

Rationale: Step-by-step rationale for the correct answer (C): 1. After delivery, the baby takes its first breath, increasing oxygen levels. 2. This leads to the closure of the foramen ovale to shift blood flow from the right to the left side. 3. Increased left atrial pressure occurs due to increased blood returning from the lungs. 4. This pressure change causes the foramen ovale to close. Summary of incorrect choices: A: Increased prostaglandin E2 does not directly affect flow through the foramen ovale. B: Increased flow through the pulmonary artery is expected after birth, but it does not directly impact the foramen ovale. D: Increased right atrial pressure would not cause a decrease in flow through the foramen ovale.

Correct Answer: B

Rationale: The correct answer is B: Human chorionic gonadotropin (hCG) stimulates the secretion of testosterone during embryonic development. hCG is produced by the developing embryo and acts on the Leydig cells in the testes to trigger the production of testosterone. This hormone plays a crucial role in male differentiation by promoting the development of male reproductive organs. A: Luteinizing hormone (LH) from the maternal pituitary gland is not involved in the early stages of male differentiation in the embryo. LH is typically involved in the regulation of testosterone production postnatally. C: Inhibin from the corpus luteum is not involved in the stimulation of testosterone secretion during embryonic development. Inhibin is mainly involved in the negative feedback regulation of FSH secretion. D: Gonadotropin-releasing hormone (GnRH) from the embryo's hypothalamus is not responsible for directly stimulating testosterone secretion during embryonic development. GnRH regulates the secretion