Cell Appearance
What cells look like depends mostly on two things:

• How they are stained
• What tissue they belong to

During development of the fetus, identical cells eventually become specialized for certain functions and take on special shapes (skin cells are flat, blood cells are round, nerve cells are irregular). Cells divide to form  tissues (nervous tissue, epithelial [skin] tissue, and so on).  

Two or more tissue types collect together to form different organs, such as brains, kidneys, liver, lung, and others. Organs contain more than one type of tissue. For example, intestines have smooth muscle tissue, epithelial tissue, vascular tissue, and connective tissue. Blood is considered a tissue of cells,  and each type of tissue is made up of cells with different features and functions.

Relationships of Cell Parts

Each part of a cell has a job to do. The main jobs are cell division, making repairs and producing energy, secretions, proteins, and fats. Please see the chart below.

• Reproduction - skeleton-like structures in the cell help genes control division
• Energy - oxidation of foods in the mitochondria create energy for the cell
• Secretions - Golgi body collects and bundles chemical secretions
• Protein - endoplasmic reticulum contains  RNA that makes protein; Golgi helps to refine certain proteins by adding on sugar groups

Relationships of Cell Functions

Cells have to do four major things to stay alive and thrive. Rather than just naming parts of a cell and what they do, we thought you would enjoy it more if we helped you to think of a cell as a living, reproducing unit that must do certain things in order to survive. Each of these is the theme for a stop along our tour of "Cells Are Us." 

A Summary of What We Know About Cells. They are:

• Very small (typically seen only under a microscope).
• Specialized for particular functions (for example, skin cells, bone cells, blood cells).
• Work together in organs that may contain several cell types
  of tissues.
• Self regulate (although they need help from other cells and organs).
• Reproduce by division.

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