Where does fertilization of the egg by sperm typically occur?

Correct Answer: B

Rationale: Fertilization of the egg by sperm typically occurs in the fallopian tube. After ovulation, the egg is released from the ovary and travels through the fallopian tube, where it may encounter sperm for fertilization. The fallopian tube provides the ideal environment, including necessary nutrients and conditions, for fertilization to take place before the fertilized egg moves towards the uterus for implantation. Choices A, C, and D are incorrect because fertilization does not occur in the ovary, uterus, or vagina. The ovary releases the egg, the uterus is the site for implantation, and the vagina is part of the birth canal but not the typical site for fertilization.

Correct Answer: C

Rationale: The bone marrow is the correct answer. It is the primary site for immune cell production and maturation. The bone marrow is responsible for generating various types of blood cells, including white blood cells crucial for the immune system's function. The liver, kidneys, and spleen have essential functions in the body, such as filtering blood, detoxification, and storage of blood, respectively. However, they are not primarily involved in immune cell production and maturation, making them incorrect choices for this question.

Correct Answer: D

Rationale: The QRS complex on an ECG represents ventricular depolarization. This electrical activity is generated by the ventricular muscle cells. While the SA node generates the P wave, the AV node delays the impulse, and the Bundle of His and Purkinje fibers assist in rapidly conducting the impulse through the ventricles, it is the ventricular muscle cells that specifically create the QRS complex. Therefore, choice D, Ventricular muscle cells, is the correct answer. Choices A, B, and C are incorrect as they are primarily involved in initiating and coordinating the electrical impulses in the heart but do not directly generate the QRS complex on an ECG.

Correct Answer: A

Rationale: The stratum corneum, the outermost layer of the epidermis, is primarily composed of keratinized dead cells. These cells are flattened, fully keratinized, and lack nuclei, serving a protective function for the skin. Melanocytes are responsible for producing melanin, providing skin pigmentation. Langerhans cells are involved in the immune response within the skin. Merkel cells are associated with sensory functions in the skin, particularly in touch sensations. Therefore, the correct answer is A as it accurately reflects the main constituent of the stratum corneum, which acts as a barrier against external factors.

Correct Answer: A

Rationale: The correct answer is A: Head, neck, and trunk. The axial skeleton comprises bones located in the head, neck, and trunk region, such as the skull, vertebral column, and rib cage. These bones provide structural support and protect vital organs like the brain, spinal cord, and heart. Choices B and C are incorrect because arms, legs, hands, and feet are part of the appendicular skeleton, not the axial skeleton. The appendicular skeleton is responsible for movement, manipulation, and mobility, while the axial skeleton primarily provides central support and protection for essential organs.