Zoology ICytology, Embryology &

HistologyBy

Dr/ Alyaa RagaeZoology Lecture

Faculty of Oral and Dental MedicineFuture University

Microscope Definitions

A microscope 

is an instrument used to see objects that are too small for the naked eye.

The science of investigating small objects using such an instrument is called microscopy . 

Microscopic means invisible to the eye unless aided by a microscope.

There are many types of microscopes, the most common and first to be invented is the optical microscope  which uses light  to image the sample. Other major types of microscopes are the electron microscope  (both the transmission electron microscope  and the scanning electron microscope ) and the various types of  scanning probe microscope .Microscopes can be separated into several different classes. One grouping is based on what interacts with the sample to generate the image, i.e., light or photons (optical microscopes), electrons (electron microscopes) or a probe (scanning probe microscopes). 

Types of Microscopes:

Types of Microscopes:

Microscopes are essential for biological studies Light microscopes: cellular resolution Can magnify up to 2000xo Light microscope o dark-fieldo phase contrasto fluorescence o Confocal laser scanning microscope

Electron microscopes: subcellular resolutiono SEM Can magnify up to 100,000xo TEM Can magnify up to 250,000x

Scanning probe Microscope o (Atomic force microscope)

Types of microscopes

The Optical Microscope, often referred to as the "light microscope".It is a type of microscope which uses visible light and a system of lenses to magnify images of small samples.

Power of Magnification =power of eye lens X power of objective lens (5, 10, 15) (10, 40, 100)Magnification only up to 1000-2000 times

1- The Light Microscope (1635)

Fluorescence MicroscopeFluorescence Microscope can be used in biological molecules when linked with fluorescent molecules (fluorochromes) in order to create specific fluorescent probes.

Types of microscopes

Fluorochrome, such as fluorescein or green fluorescent protein (GFP) illuminate a green light.

2- The Electron Microscope (E.M.)The biggest advantage is that they have a higher resolution and are therefore also able of a higher magnification (up to 2 million times) that can give the human eye the fine structures.

They are extremely expensive.Sample preparation is often much more elaborate.It is not possible to observe moving specimens (they are dead).It is not possible to observe color.

Types of microscopes

There are two different types of electron microscopes, scanning electron microscopes (SEM) and transmission electron microscopes (TEM).

In the TEM method, an electron beam is passed through an extremely thin section of the specimen. You will get a two-dimensional cross-section of the specimen.

SEMs, in contrast, visualize the surface structure of the specimen, providing a 3-D impression. The image above was produced by a SEM.

2- The Electron Microscope (E.M.)

Types of microscopes

SEM picture of pollen grains

TEM picture of Mitochonderion

Types of microscopes

Atomic Force Microscope 1980s at IBM Research - ZurichAFM provides a 3D surface profile.

Samples viewed by AFM do not require any special treatments.

Do not damage the sample.

AFM modes can work perfectly well in ambient air or even a liquid environment.

AFM can provide higher resolution than SEM.

Dark Field Microscope

• Greater resolution• Light reaches

specimens only from the side

• Only the specimen itself is illuminated

Candida sp.

Treponema pallidum

Types of microscopes

Types of microscopes

Microscopy: Phase Contrast

May be used to visualize live samples and avoid distortion from cell stain

Image contrast is derived from the differential refractive index of cell structures.

Confocal laser scanning microscope

Confocal laser scanning microscopy (CLSM or LSCM) is a technique for obtaining high-resolution optical images with depth selectivity

Pawley JB (editor) (2006). Handbook of Biological Confocal Microscopy (3rd ed.). Berlin: Springer. ISBN 038725921X

Method of work

laser scanning process, which scans the three dimensional surface of an object point-by-point by means of a focused laser beam, and creates the over-all picture by electronic means similar to those used in scanning electron microscopes. This CSLM design combined the laser scanning method with the 3D detection of biological objects labeled with fluorescent markers for the first time.

Two and three dimensions and time

series images

Cells

The cell is the functional basic unit of life. It is the smallest unit of life that is classified as a living thing.

Humans have about 100 trillion or 1014 cells; a typical cell size is 10 µm and a typical cell mass is 1 nanogram .

The largest cells are about 135 µm in the anterior horn in the spinal cord, while granule cells  in the cerebellum, the smallest, can be some 4 µm

and the longest cell can reach from the toe to the lower brain stem  (Pseudounipolar cells ). The largest known cells are un fertilised ostrich egg cells , which weigh 3.3 pounds

Cells

There are two types of cells: eukaryotic and prokaryotic. Prokaryotic cells are usually independent, while eukaryotic cells are often found in multicellular organisms.

Cells (Prokaryote)• The prokaryote cell is

simpler, smaller, lacking a nucleus than a eukaryote cell.  

• There are two kinds of prokaryotes:  bacteria  and

 archaea.• Nuclear material of

prokaryotic cell consist of a single chromosome that is in direct contact with cytoplasm. Here, the undefined nuclear region in the cytoplasm is called nucleoid.

Cells (Eukaryote)

Eukaryotic cells are about 15 times wider than a typical prokaryote and can be as much as 1000 times greater in volume. The major difference between prokaryotes and eukaryotes is that eukaryotic cells contain membrane-bound compartments in which specific metabolic activities take place

Cells (Eukaryotes)

Comparison between Eu & prokaryotes

Differences between prokaryotes and eukaryotes

Differences between Plant cell and Animal cell

Comparison between animal and plant cells