Glossary: T-Z

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Tissue

Definition: Any of the distinct types of material of which animals or plants are made, consisting of specialized cells and their products. Tissues are organized into organs, which are then organized into organ systems.

Examples:

• Epithelial tissue: Covers the body surface and lines internal organs.
• Connective tissue: Supports and connects other tissues.
• Muscle tissue: Contracts to produce movement.
• Nervous tissue: Transmits nerve impulses.

Context/Function: Tissues are the building blocks of organs and organ systems. They work together to carry out the functions of the body.

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Virus

Definition: An infective agent that typically consists of a nucleic acid molecule in a protein coat, is too small to be seen by light microscopy, and is able to multiply only within the living cells of a host. Viruses are not considered to be living organisms because they are not able to reproduce on their own.

Examples:

• Influenza virus: Causes the flu.
• HIV (human immunodeficiency virus): Causes AIDS (acquired immunodeficiency syndrome).
• Ebola virus: Causes Ebola virus disease.

Context/Function: Viruses are a major cause of disease in humans, animals, and plants. They can also be used in biotechnology to deliver genes to cells.

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