In which structure are lymphocytes produced?

A. Epiglottis: The epiglottis is a leaf-shaped flap of cartilage located at the root of the tongue. It covers the opening of the trachea during swallowing to prevent food and liquids from entering the airway. This function is crucial for protecting the respiratory tract from aspiration.

B. Arytenoids: The arytenoid cartilages are small, paired cartilages that are involved in the movement and tension of the vocal cords but do not cover the opening of the trachea.

C. Thyroid: The thyroid cartilage is the largest cartilage of the larynx and forms the Adam's apple but does not cover the trachea.

D. Cricoid: The cricoid cartilage is located below the thyroid cartilage and is the only complete ring of cartilage around the trachea. While it provides support, it does not cover the opening of the trachea.

A. Lysozyme within tears destroy bacteria.: Lysozyme is an enzyme found in tears that helps to break down the cell walls of bacteria, acting as a chemical barrier and part of the innate immune system's first line of defense.

B. Chemotaxis attracts phagocytes to the site where the pathogen invaded.: This is part of the inflammatory response, which occurs after the first line of defense has been breached; therefore, it is not considered a first line of defense action.

C. Natural killer cells are the first lymphocytes to react to infection.: While natural killer cells play an essential role in the immune response, they are part of the second line of defense and respond after pathogens have entered the body.

D. Phagocytes ingest microbes when they enter the body.: This is part of the second line of defense, as phagocytes respond to pathogens that have breached the first line of defense, which includes physical and chemical barriers.