Chapter 1 - Introduction

Ultrastructure is the architecture of cells that is visible at higher magnifications than found on a standard optical light microscope. Electron microscopes is widely used to investigate the ultrastructure of biological specimens.

This chapter demonstrates the potential of electron microscopy in understanding histology.

Fig 002 Microscopes

Transmission Electron Microscopy (TEM)

TEM produces two-dimensional images of a specimen by imaging 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 ~0.1 nm (~1000 times greater than a light microscope).

Example micrograph of a cell imaged by TEM that explains how these images should be viewed.

EM 006 Fibroblast

Schematic comparison of a cell imaged by TEM and light microscopy.

Fig 007 Cell Structures

Figures

Schematic representations of a simple columnar cell from images acquired by TEM, SEM, and freeze fracture.

	Fig 009 Cell Structures
	Fig 010 Nucleus
	Fig 014 Mitochondria

Ultrastructure of Cells (TEM)

	EM 001 Cell Structures (Nucleus / Golgi Apparatus / Mitochondria / Endoplasmic Reticulum)
	EM 007 Nucleus
	EM 004 Cell Structures (Nucleus / Centrosome / Microtubules)
	EM 008 Golgi Apparatus
	EM 304 Endoplasmic Reticulum
	RD 006 Smooth Endoplasmic Reticulum
	EM 026 Rough Endoplasmic Reticulum

Scanning Electron Microscopy (SEM)

Scanning electron microscope (SEM) produces three-dimensional images of a speciment by measuring the relative differences in the reflection of a focused beam of electrons scanned across a specimen. Biological specimens are usually coated with a thin layer of metal (such as platinum) to form a replica that is then imaged. This allows the surface structures of organelles, cells, and tissues to be visualized. The images are colorless and have a resolution of ~10 nm (~100 times greater than a light microscope).

	EM 206 Red Blood Cells
	EM 195 Podocytes

Freeze Fracture

Freeze fracture technique reveals the internal structure of biological specimens. Frozen specimens are physically broke apart (fracturing) and the exposed surface is coated with evaporated platinum. This replica is then imaged by TEM.

Fig 011 Freeze Fracture

Freeze fracture forms enface views of membrane-bound compartments that give striking three-dimensional representations.

EM 009 Freeze Fracture

Ultrathin Section versus Freeze Fracture

Mast cell as seen in an ultrathin sections and by freeze fracture.

	EM 014 Mast Cell (TEM)
	EM 015 Mast Cell (Freeze Fracture)

Ultrastructure of Cells (Freeze Fracture)

Freeze fracture reveals interior surfaces of cells.

	EM 046 Small Intestine
	EM 011 Nuclear Envelope
	EM 295 Plasma Membranes
	EM 010 Plasma Membrane
	EM 013 Endoplasmic Reticulum

Mitosis

Cells undergoing mitosis as seen by TEM.

	EM 207 Mitosis
	EM 115 Mitosis