How does the skin defend the body? (Select all that apply.) I. Skin serves as a sensory organ for pain. II. Skin serves as a sensory organ for touch. III. Skin serves as a sensory organ for temperature. IV. Skin has an acid pH.
The correct answer and explanation is:
The correct answer is I, II, III, IV.
Explanation:
The skin is the body’s largest organ and acts as a primary barrier against the external environment. Its defensive functions are multifaceted, extending beyond just a physical shield.
Firstly, the skin serves crucial sensory roles that contribute significantly to defense. As a sensory organ for pain (I), it contains nociceptors that alert the body to tissue damage from mechanical, thermal, or chemical insults. This warning system triggers protective reflexes, such as immediate withdrawal from a harmful stimulus, preventing further injury and potential infection. Similarly, the ability to sense temperature (III) allows us to detect extreme heat or cold, enabling prompt reactions to avoid burns, frostbite, or hypothermia, all of which can severely compromise bodily integrity. The sense of touch (II), while perhaps seeming less directly defensive than pain or temperature, is also vital. Mechanoreceptors allow us to perceive pressure, texture, and vibration. This enables us to safely interact with our environment, manipulate objects without causing self-harm, and maintain awareness of our physical boundaries, helping to prevent accidental injuries.
Beyond its sensory capabilities, the skin also employs chemical defenses. The surface of healthy skin maintains an acidic pH, typically ranging from 4.5 to 6. This acid pH (IV), often referred to as the “acid mantle,” creates an inhospitable environment for many harmful bacteria, fungi, and other pathogens that thrive in more neutral conditions. This continuous chemical barrier helps to inhibit the growth and colonization of potential invaders, supplementing the physical barrier formed by the skin layers themselves.
Therefore, all listed functions contribute to the skin’s comprehensive defense system, either by providing critical sensory warnings about potential harm or by creating a chemical environment that inhibits pathogens.