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Nerve & Muscle Tissue
What are the core concepts of histology?
Histology Topics for Lincoln Scholars Program

Every beginning biology student learns three fundamental principles of cell biology: 

Together these three assertions comprise Cell Theory, one of the cornerstones of biology.

Tissue biology also has fundamental organizing principles, by which cells are organized into tissues. 

Put most simply, our bodies are composed of four different kinds of stuff, traditionally regarded as the four basic tissue types

To elaborate a bit further, each of the four basic tissue types has its own distinctive character, a set of properties which unites all examples of that tissue type while distinguishing that type from examples of the other three tissue types. 

The four tissue types are defined not by fundamental differences among the cells which comprise them (most of which share all the characteristic structures and functions of all eukaryotic cells) but by relationships among the cells within each tissue type.

Practically every cell in the body belongs to one of the four basic tissue types (note caveat below).  Most organs include tissues of all four types.

The four basic tissue types are muscle tissue, nervous tissue, epithelial tissue, and connective tissue.

These, then, are the core concepts of histology:  Four basic tissue types, together with the characteristic properties of each type, muscle, nervous, epithelial, and connective.  To "unpack" these concepts in much greater detail, see basic tissue types or follow any of the links in the text above. 

Understanding how certain organs work -- notably the kidney and the lung and the liver -- requires some detailed knowledge of microanatomy that is unique to each organ; for example, podocytes and juxtaglomerular apparatus in the kidney, or interalveolar septa in the lung and bile canaliculi in the liver.  But only a tissue-level perspective can organize that knowledge and make it far easier to comprehend, by revealing how all three of these organs share with pancreas the same basic glandular tissue architecture, of epithelial parenchyma supported by connective tissue stroma

For a brief essay on how the four basic tissues are arranged in relation to one another to form organs, see "What are the most common patterns of tissue organization?"

For a much longer and more formal introduction to the basic concepts of histology, see "Basic tissue types."

Histology Topics for Lincoln Scholars Program

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CAVEAT:  Several of the generalizations above have peculiar exceptions.  A few of these exceptions are important; others are mainly curiosities.  Some of the more important exceptions are listed below.

Below are a few significant exceptions to the core-concept generalizations outlined above.

Comments and questions:

SIUC / School of Medicine / Anatomy / David King
Last updated:  10 January 2023 / dgk