What is the small repeating unit in the contractile apparatus of skeletal muscle?

Correct Answer: C

Rationale: The correct answer is 'Sarcomere.' The sarcomere is the smallest repeating unit within myofibrils and is responsible for muscle contraction in skeletal muscle. It consists of overlapping actin and myosin filaments arranged in a highly organized structure that allows for the sliding of filaments during muscle contraction. 'Myofibril' (choice A) is incorrect because it is a larger structure composed of sarcomeres. 'Actin' (choice B) and 'Myosin' (choice D) are incorrect as they are individual proteins that are components of the sarcomere, not the smallest repeating unit itself.

Correct Answer: C

Rationale: The correct answer is C. The ovaries are responsible for producing eggs (ova) and hormones (estrogen and progesterone). They are essential for reproduction, including the release of eggs for fertilization and for regulating the menstrual cycle. The fallopian tubes, as mentioned in choice A, transport eggs from the ovaries to the uterus for potential fertilization. The vagina, described in choice B, serves as the birth canal and also connects the uterus to the external environment. The cervix, as stated in choice D, is the lower part of the uterus that connects it to the vagina and also plays a role in protecting the uterus from infections and serving as a passage for menstrual flow.

Correct Answer: B

Rationale: The corrected answer is B: 'Vulva: external structures of the female genitalia.' The vulva includes external structures such as the labia, clitoris, and vaginal opening. These structures play roles in sexual arousal and protection of the internal genital organs. Choices A, C, and D are incorrect because they are internal reproductive organs. The ovaries produce eggs, the uterus houses the developing fetus, and the vagina serves as the birth canal. Hence, they are not components of the female external genitalia.

Correct Answer: B

Rationale: The correct answer is the Integumentary system (Option B). The integumentary system, which includes the skin, hair, nails, and glands, serves various functions such as providing protection against external factors, sensory reception, regulating body temperature (thermoregulation), maintaining water balance (osmoregulation), insulating the body, and absorbing vitamin D from sunlight. The nervous system (Option A) is responsible for transmitting signals throughout the body. The endocrine system (Option C) produces and secretes hormones to regulate bodily functions. The digestive system (Option D) is involved in breaking down food for nutrient absorption. Therefore, the primary functions described in the question align with those of the integumentary system, making it the correct choice.

Correct Answer: B

Rationale: Apoptosis is the process of programmed cell death, not uncontrolled cell growth (Choice A). It plays a vital role in embryonic development by eliminating unnecessary or damaged cells, sculpting organs, and ensuring proper tissue organization. Through apoptosis, the embryo undergoes controlled cell death to shape structures accurately. This mechanism is essential for the precise development of organs and tissues, emphasizing the significance of apoptosis in embryogenesis. DNA replication (Choice C) and cell division (Choice D) are essential cellular processes but are not directly related to apoptosis or its role in embryonic development.