Lab Two

Total Magnification

The perceived increase in the size of an object when viewed using a microscope. TM is equal to the magnifying power of the ocular lens multiple by the magnifying power of the objective lens being used; thus for a 10x ocular lens and a high dry objective, the total magnification is 10x X 40x or 400x

Scanning Lens

Either 4x or 5x; use this for initial location of a specimen.

Mechanical Stage

Flat, horizontal platform below the object lenses that the slide rests on. The stage has an opening so the light can pass through the specimen from below. This stage is equipped with a mechanical device that can be used to move the slide backwards and forward and side to side.

Body Tube

Holds the ocular lenses in place

Totipotent Stem Cell

A cell that has the capacity to divide and produce cells that may differentiate into any of the cells of the mature organism.

Pluripotent Stem Cell

A cell that has the limited capacity to divide into a restricted number of adult cell types. Can give rise to a more limited variety of cell types.

Revolving Nosepiece

A circular mechanism located at the bottom of the body tube and attached to three or four objective lenses. It can be rated to position the desired lens in the light path.

Whole Mount

An entire structure, uncut, is embedded in mounting resin directly on the slide and covered with a glass coverslip.

Objective Lens

One of either three or four magnifying lenses attached to the revolving nosepiece. Each objective lens is marked with its magnification factor and is marked with unique colored rings for quick identification. Microscopes may have any or all of the following objective lenses (scanning lens, 10x or low power lens, 40x or high power lens, and 100x or oil immersion lens.

Substage Light

A high-intensity light source. Light rays from this source pass through the specimen, through the objective lens and the ocular lenses to the eye.

40x (high power) Lens

Also called a high, dry objective; used for specimens that require a greater degree of magnification.

Ocular Lens

Also called an eyepiece. The microscopes in our lab have two eyepieces at the superior end of the body tube (binocular). The macular lenses on the microscope have a magnification power of 10X. one of the ocular lenses has a pointer in it that may be positioned by rating that ocular lens.

Condenser

A small lens located beneath the stage that concentrates the light onto the specimen. The condenser can be raised and lowered. For most work, the condenser should be positioned as close to the stage as possible (raised position)

Section

A thin piece of specimen is shaved from the whole specimen to permit light to reveal greater structural detail. Sections are usually between 10 and 100 microns thick, which is usually thicker than one cell diameter. Therefore, several layers of cells may be present in the section. Some sections, called thin sections, are on the oder of 1 micron thick, which is usually less than one cell diameter. Therefore, subcellular structures are more easily discerned than in thicker sections. Sections can be either longitudinal sections which are made lengthwise, parallel to the long axis of the structure, or transverse (cross sections) which are made perpendicular to the long axis.

Ectoderm

Brain, spinal cord, all other neurons, sensory receptors, adrenal medulla, skin (epidermis), pituitary gland, connective tissue of head.

Fine Adjustment Knob

Like for coarse adjustment knob, but is used for finer focusing after coarse focusing knob has been used.

Endoderm

Lining of the gut, lining of the lungs, lining of the bladder, liver, pancreas, larynx, trachea, lung, thymus gland, thyroid, parathyroid gland, urinary bladder, vagina, urethra.

10x (low power) Lens

May also be used to locate a specimen; this objective lens may be suitable for viewing some specimens that do not need greater magnification.

Mesoderm

Muscles, blood, bone, sex organs, adrenal cortex, lymphatic tissue, urogenital system, heart and blood vessels, most connective tissues.

Iris Diaphragm

Regulates the amount of light that passes through the specimen. The diaphragm is adjusted by rotating a lever attached to the side of the device.

Resolution

The ability to distinguish between closely positioned objects. The human eye can resolve objects that are about 100 micro meters apart. Under ideal conditions, the compound light microscope has a resolving power of 0.2 micro meters. Without good resolution, magnified objects may appear blurry and indistinct. Resolution is specified as "r", the minimum distance at which the objects can be perceived as distinct from each other. Thus, the smaller the "r" the better the resolution.

Squash

The cell specimen is broken using pressure- usually used to release chromosomes from nuclei, then processed as a smear is.

Contrast

The difference in intensity between the specimen and the surrounding background. It is most conveniently altered by using the iris diaphragm located below the substage condenser.

Working Distance

The distance between the bottom of the objective lens and the top of the cover glass on the slide. The higher the magnification the smaller the working distance. The working distance between the highest powered objective and the slide can be less than a mm, so care must be taken to keep an objective lens from hitting the slide.

Smear or Drop

The specimen(s) are in suspension then dried directly onto the glass slide where they are fixed, stained, and mounted in resin under a coverslip. This preparation is usually used for blood cells or semen.

Field of Vision

The surface area which can be seen when looking through the light microscope. The area decreases with increasing power of magnification.

100x (oil immersion) Lens

Used for viewing extremely small objects, such as blood cells or bacterial cells; this lens must be immersed in oil when used.

Coarse Adjustment Knob

Used to bring the specimen into focus by increasing or decreasing the distance between the objective lens and the specimen.