Histology Guide virtual histology laboratory

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Histology Guide

Chapter 1 - Introduction

Electron microscopes are used to investigate the ultrastructure of biological specimens. This chapter demonstrates the potential of electron microscopy in understanding histology. Examples will be examined of electron micrographs acquired by transmission electron microscopy (TEM) and scanning electron microscopy (SEM).

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Fig 002 Microscopes

Transmission Electron Microscopy (TEM)

Transmission electron microscope (TEM) produces images of a specimen by scanning a thin section with a beam of electrons. Ultrathin tissue sections are stained with heavy metals (such as osmium tetroxide, uranium or lead salts). The images are colorless and have a resolution of 0.2 to 0.5 nm (or ~1000x greater than a light microscope).

Micrograph of an ultrathin section acquired by transmission electron microscopy (TEM).

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EM 006 Fibroblast

Ultrastructure of cellular organelles as seen by transmission electron microscopy (TEM).

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EM 001 Cell Structures

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EM 007 Nucleus

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EM 004 Cell Structures

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EM 008 Golgi Apparatus

Scanning Electron Microscopy (SEM)

Scanning electron microscopy (SEM) produces images of a specimen by scanning the surface with a beam of electrons. Biological specimens are coated with heavy metals (such as platinum or osmium tetroxide). The images are colorless and can have a resolution of 2 to 20 nm (or ~100x greater than a light microscope).

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EM 206 Red Blood Cells

The internal structure of biological specimens can be examined by scanning electron microscopy (SEM). Frozen specimens are physically broke apart (fracturing) and the topography of the fracture reveals details about its internal structure.

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EM 009 Freeze Fracture

Comparison of TEM and SEM

Micrographs of a mast cell as seen by transmission electron microscopy (TEM; ultrathin section) and scanning electron microscopy (SEM; freeze fracture).

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EM 014 Mast Cell (TEM)

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EM 015 Mast Cell (SEM)

Scanning Electron Microscopy

Ultrastructure of cellular organelles as seen by scanning electron microscopy (SEM).

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EM 011 Nuclear Envelope

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EM 010 Plasma Membrane

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EM 013 Endoplasmic Reticulum

Mitosis

Cells undergoing mitosis as seen by transmission electron microscopy (TEM).

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EM 207 Mitosis

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EM 115 Mitosis