fluid
Explanation
This single-panel comic shows a woman wearing glasses (dressed in what appears to be lingerie or sleepwear) saying to her partner: "When we make love, each of our bodies contains over sixty fluid-filled compartments gyrating in unison."
The caption below reads: "Actual med students completely ruin the sexy doctor fantasy."
The joke plays on the popular "sexy doctor/nurse" fantasy or roleplay concept. In the fantasy version, a medical professional is seductive and alluring. But the comic shows what happens when someone actually dating a real medical student tries this scenario — the med student can't help but describe intimacy in cold, clinical, anatomical terms. The description of "sixty fluid-filled compartments gyrating in unison" is a technically accurate but deeply unsexy way to describe two human bodies during sex, referencing the many fluid-filled structures in the human body (joints with synovial fluid, the bladder, the stomach, cerebrospinal fluid compartments, bursae, the eyes, etc.).
The humor derives from the gap between the fantasy (a seductive medical professional) and the reality (someone whose medical training has made them incapable of seeing the human body in anything other than clinical, anatomical terms). It also plays on the common joke that too much scientific knowledge can drain the romance out of everyday experiences.