Histology & Methods of Study

Question 1

List the steps of histologically preparing tissues

Answer 1

fixation, dehydration, clearing, infiltration, embedding, trimming

Question 2

Fixation

Answer 2

small pieces of tissue are placed in solutions of chemicals that cross-link proteins an inactivate degrative enzymes which preserve cell tissue and structures

Question 3

Dehydration

Answer 3

the tissue is transferred through a series of increasingly concentrated alcohol solutions ending in 100% which removes all the water

Question 4

clearing

Answer 4

alcohol is removed in organic solvents in which both alcohol and paraffin are miscible

Question 5

infiltration

Answer 5

the tissue is then placed in melted paraffin until it becomes completely infiltrated with this substance

Question 6

embedding

Answer 6

the paraffin inflitrated tissue is placed in a small mold with melted paraffin and allowed to harden

Question 7

trimming

Answer 7

the resulting paraffin block is trimmed to expose the tissue for sectioning (slicing) on a microtome

Question 8

microtome

Answer 8

used for sectioning paraffin embedded tissues for light microscopy.

Question 9

hematoxylin

Answer 9

behaves like a basic dye, staining basophillic tissue components. (DNA, RNA rich portions of cytoplasm, matrix of cartilge) dark blue or purple color

Question 10

eoisin

Answer 10

stains other cellular structures and collagen in a pink color

Question 11

light microscopy

Answer 11

microscope includes an optical system and mechaisms to move and focus the specimen. stained tissue with ordinary light passing through

Question 12

virtual microscopy

Answer 12

bright field microscopic preparations, conversions of stained tissue preparation into high resolution digital images and permits study of tissues using a computer or other device

Question 13

fluorescence microscopy

Answer 13

tissue sections are usually irrradiated with ultraviolet light and the emission is in the visible portion of the spectrum. adding fluroescin to molecules and having them bind to certain cellular compounds. immuhistologic staining

Question 14

Phase contrast microscopy

Answer 14

use a lens system that produces visible images from transparent objects and can be used with living cultured cells. light will pas differently through structures with different refractive indexes

Question 15

confocal microscopy

Answer 15

achieves higher power resolution by focusing a small point of high density light (like a laser) and uses a plate with a pinhole aperture in fronnt of the image detector. tis improves resoltuion because object in focus allows for greater localizaton of specimen compoents with more precision than the bright field microscope

Question 16

Polarizing microscopy

Answer 16

produces an image only of material having repetitive periodic macromolecular structure. allows recognition of stained and unstained structures made of highly organized subunits.

Question 17

electron microscopy

Answer 17

based on interaction of tissue comonents with beams of electrons

Question 18

transmission electron microscopy (TEM)

Answer 18

resolutoin around 3 nm can view as much as 400,000 times in detail. cryofracture and freeze etching are techniques that allow you to study without fixation

Question 19

scanning electron microscopy (SEM)

Answer 19

the beam does not pass through the specimen. specimen is first dried and coated with a heavy metal (gold) and then that reflects the electrons. uusually easy to interprent because they prent a 3 dimensional view

Question 20

autoradiography

Answer 20

localizes cell components synthesized using radioactive precurseors by detecting silver grains produced by weakly emitted radiation in a photographic emulsion coating the tissue section or cells. permits the study of unique cell processes such as tissue growth, cellular pathway of macromolecular synthesis.

Question 21

enzyme histochemistry

Answer 21

method of localizing cellular structures using a specific enzyme activty present in those structures. tissue sections are placed in a buffere containin the substrate of the enzyme. then the enzyme is allowed to act on substrate,

phosphatases, dehydrogenaes, peroxidase all can be found with this

Question 22

immunohistochemistry

Answer 22

highlly specific interaction between macormolecules like an antigen and its antibody. labeled antibodies are used in this method.

Question 23

direct immunohistochemistry

Answer 23

if a cell or tissue antigen of interest is detecteed by directly binding a labeled primary antibody specific fo that antigen

Question 24

indirect immunochemistry

Answer 24

uses an unlabeled primary antibody that is detected bound to its antigen with labeled secondary antibodies more commonly used

Question 25

In situ hybridization ISH

Answer 25

specfic gene sequences or mRNAs of cells can be detected microscopically using cDNA probes in this technique. nucleic acids

Question 26

artifacts

Answer 26

the many steps of tissue prep, staining, slide preparation can cause spaces and other things in the slide which are not normally there.

Question 27

PAS

Answer 27

to visualize carbohydrate structures