1. Nerve Cell (Neuron): These cells are the basic unit of the nervous system. They are responsible for transmitting signals throughout the body, allowing us to think, feel, and move.

* Function: Receive and transmit electrical and chemical signals.

* Key Feature: Long, branching extensions (axons and dendrites) that facilitate signal transmission.

2. Muscle Cell (Myocyte): These cells are responsible for contraction and movement. There are different types of muscle cells (smooth, skeletal, and cardiac), each with a specialized function.

* Function: Generate force and movement.

* Key Feature: Contain specialized proteins (actin and myosin) that slide past each other to generate contraction.

3. Red Blood Cell (Erythrocyte): These cells are found in the blood and their primary function is to transport oxygen throughout the body.

* Function: Carry oxygen from the lungs to the body's tissues and remove carbon dioxide.

* Key Feature: Lack a nucleus and contain hemoglobin, a protein that binds oxygen.

4. Skin Cell (Keratinocyte): These cells make up the outermost layer of skin, providing a protective barrier against the environment.

* Function: Protect the body from physical damage, infection, and dehydration.

* Key Feature: Produce keratin, a tough protein that gives skin its strength and structure.