Flashcards in Lecture 1 & 2: Background And History Deck (27):
1. Histology is the study of the microscopic anatomy of cells and tissues of plants and animals.
2. Histopathology is “The science or study dealing with the cytologic and histologic structure of abnormal or diseased tissue.”
Be able to recognize the distinct slides of tissues from lecture 1.
Do it. Check those pages.
What contributions did Bichat make to the field of histology?
French guy who was proclaimed the father of modern histology; believed that each organ contained specific tissues or membranes. He identified over 21 of these. He hypothesized that diseases attacked specific tissues, not the whole body.
- Less acurately, he divided the body into the organic life (heart, intestines), and Animal LIfe (Ears, brain, eyes)
Describe the contributions of Virchow to histology?
German guy who suspected from early on that the Cell Theory (All life is made of cells, and all cells came from existing cells) was correct.
What contribution did Kolliker make to histology
Applied Schwann's theory to embryonic animal development and wrote what's widely considered the first official textbook on histology. (And another one on embryology)
Describe the contributions of Schleiden
Botanist who correctly came up with the idea that all life is composed of cells, but incorrectly thought that cells arise from budding from the nucleus. (Called the Free Cell Theory)
What contributions did Schwann make to histology
Animal zoologist who noticed similarities between plant tissues and animal tissues - Identified cartilage, eggs, and 5 types of tissues
What'd Janssen do?
Produced the first operational compound microscope with a magnification of 30x
What'd Hooke do?
Described cork and other cells and introduced the term “cell.”
What'd Leeuwenhoek do?
Made over 247 simple microscopes capable of magnifications of around 100x. Sent 26 of them to the Royal Society. Among his observations: RBCs, protozoa, striations of skeletal muscle, sperm cells, bacteria.
1. Define Refraction of light
2. What is the Refractive Index Formula?
3. What is the refractive index of air?
1. When light waves travel through a vaccum, they travel at a fixed velocity. However it is slower when traveling through air or water or stuff and the Refractive Index defines it's fixed velocity through that medium.
2. Refractive Index = (Velocity of Light in a Vaccum)/(Velocity of light in This Medium)
What happens when light passes from one medium to another at an angle?
How are diopters measured?
The light bends based on the refractive index and angle of the beam. Perpendicular light should pass right through without bending.
A diopter is 1/(focal length of the lens in meters)
Define Focal Point
Define Focal Length
1. The point through which all parallel rays of light will pass after passing through each part of the lens.
2. The distance from the center of the lens to the focal point.
More diopters means an increased focal length
Describe a real image and how it forms
- Requires a convex lens converging onto a focal point, and the object needs to OUTSIDE that focal point.
- Real image is inverted, can be projected onto a screen, and can be magnified
- Greatest magnification occurs when focal length is very small, and the object is as close to focal point as possible.
Describe a virtual image and how it is formed
- Object must be placed INSIDE the focal point
- Upright (not inverted), CANNOT be projected onto a screen, but CAN be magnified
- No point exists when the rays radiating off of the object are brought into focus
How would one increase resolution?
- The ability for a microscope to distinguish two small points as separate points
- This requires the diameter of diffraction lines around the points to be reduced
- Increased resolution = Higher Refractive Index, shorter wavelength
What is the formula for finding resolution? Know what each symbol represents
Resolution d = (0.61 * Lambda)/(n * sin(alpha))
0.61 = Constant measuring human capability of the eye i think
Lambda = Wavelength of Light (3800)
n = Refractive index of medium surrounding the object (Air is 1.0)
sin(alpha) - Angle of the cone of light entering the Objective Lens (max angle = 180°)
nsin(alpha) = Numerical Aperture. N has a maximum of 1.4 (oil), which means highest possible NA is 1.4
What is the N.A. of 4x magnification?
What are methods to decrease the wavelength (lambda)?
At 4x magnification, NA = about 0.10
At 100x, magnification = about 1.2
Instead of solar light, U.V. Light only has about 2500 A
Electrons even smaller at 0.05A
What is the highest possible resolution in a light microscope?
How about in comparison to a transmission electron microscope?
For light microscopy, the strongest resolution possible is "about" 5 um.
For transmission electron microscopes, the theoretical resolution is about 0.01 angstroms, but we've only ever gotten it down to about 5-10 angstroms (1 angstrom = 0.1 nm)
What are the components of a Compound Light Microscope (Also called a Bright Field Microscope)
- Light Source
- Stage - Holds stuff. Usually 6-10 um
- Objective Lens - Also called magnification lens - close to object
- Ocular Lens
- (Short version): From the light source, object passes through objective lens and produces an real image in front of the ocular lens. That image is viewed by the eye as an inverted virtual image.
What are the pros and cons to a compound light microscope?
+ Ability to magnify
+ Ability to resolve structural detail
- Specimen must be thin
- Relatively little contrast in the unstained specimen
How does a phase contrast microscope work. List it's advantages.
- This weird one converts invisible phase shifts in light passing through a transparent specimen into changes in brightness.
-These can be used to examine unstained tissues, including live cells.
- Different structures of the cell have different n's, which defracts the light into out-of-phase.
- Non-slowed light waves are compared to retarded light-waves.
Briefly say what flourescence microscopes do (oddly not in the objectives)
- Can detect specific wavelengths that molecules radiate (autoflourescent), which can be seen under a U.V. Light source.
- Usually used to detect antibodies and antigens in immunochemical staining.
- Flourescent "tracer" molecules can be injected into animals to be detected later
Define how a confocal scanning microscope works
- Invented in the 50s by Minsky, this weird one adds a pinhole to the confocal plane of the lens to eliminate out-of-focus light, which helps construct 3D images
- Combines the technology (components) of a light microscope, fluorescence equipment, and laser scanning.
- If I'm understanding this right, the laser moves across the specimen using a rotating mirror, and a photomultiplier tube absorbs the light it produces to be analyzed
- Eventually, a 3D shape of the specimen is produced across a monitor
List the advantages of a Confocal Microscope
- Very thin optical images of the specimen are created (typically 1 μm thick).
- Out-of-focus images are subtracted from the image by the computer program.
- Computer can make 3-D reconstructions of the specimen by stacking individual images.
Describe how a Transmission Electron Microscope Works
- TEMs utilize electrons rather than light. A specific voltage is set between an anode and a cathode; potential difference usually ranges between 20k and 200k Volts
- The electrons are derived from a heated tungsten filament
- Electromagnets act as the condenser, objective, and projection lens
- The specimen needs a holder to hold in place, and a viewing screen and photographic film for viewing