**Core Concept:** The multiple-choice question is asking about the cell type with the greatest transmembrane voltage difference. In the context of human physiology, voltage differences across cell membranes are crucial for generating and propagating electrical signals, such as in neurons and muscle cells. Transmembrane voltage differences are measured in millivolts (mV).

**Why the Correct Answer is Right:** The correct answer, option D (Cardiac Muscle Cells), is right because these cells have the highest transmembrane voltage difference (-90mV resting membrane potential) among the given choices. This voltage difference is maintained by the action of ion channels, specifically voltage-gated sodium and potassium channels in cardiac cells. These channels regulate the flow of ions (mainly sodium and potassium ions) across the cell membrane, which is essential for generating and maintaining the electrical activity of the heart.

**Why Each Wrong Option is Incorrect:**

A. Neurons (option A) have a resting membrane potential of -70mV, which is lower than cardiac muscle cells. Neurons rely on voltage-gated ion channels for their electrical activity, primarily sodium and potassium channels.

B. Enteric neurons (option B) also have a resting membrane potential of around -70mV, similar to neurons. These neurons play a crucial role in the autonomic nervous system and gastrointestinal motility.

C. Epithelial cells (option C) have a resting membrane potential ranging from -40mV to -60mV. Although these cells have a voltage difference, it is lower than that of cardiac muscle cells. Epithelial cells are involved in ion transport and maintaining tissue homeostasis.

D. Myocytes (option D) in cardiac muscle cells have the highest transmembrane voltage difference of -90mV, contributing to the generation of the cardiac action potential.

**Clinical Pearls:**

1. Voltage-gated ion channels are essential for maintaining and modulating cell membrane potentials.
2. The resting membrane potential is crucial for the proper function of different cell types, including neurons, muscle, and epithelial cells.
3. Understanding transmembrane voltage differences is essential for understanding cellular function and the pathogenesis of various diseases, including those affecting cardiac and neuronal function.