Which of the following blood elements is involved in protecting the body from pathogens?

a: Basal ganglia - The basal ganglia are involved in motor control and coordination but not in respiratory regulation.

b: Parietal lobe - The parietal lobe is involved in sensory processing and spatial awareness but not in respiratory regulation.

c. Medulla: The medulla oblongata, specifically the respiratory center within it, is responsible for the involuntary control of respiration, including setting the basic rhythm of breathing and responding to changes in blood pH and oxygen levels.

d: Hypothalamus - The hypothalamus regulates various physiological processes, including temperature regulation and hormone secretion, but not respiration.

a. Pathogen: A pathogen is a disease-causing organism like bacteria, virus, or parasite. It can trigger an immune response, but not necessarily a hypersensitivity reaction.

b. Allergen: An allergen is a foreign substance (like pollen, dust mites, or food) that can trigger an immune response in an already sensitized individual. This response can lead to allergy symptoms like hay fever or anaphylaxis

c. Immunogen: An immunogen is any substance that can trigger an immune response, but not necessarily a hypersensitivity reaction. It can be a pathogen, allergen, or other foreign substance.

d. Fibrinogen: Fibrinogen is a blood protein involved in blood clotting, not allergic reactions.