Introduction to Histology

Question 1

What are the 4 main tissue types?

Answer 1

Epithelial, connective, muscle and nervous tissue

Question 2

What is histology?

Answer 2

the microscopic study of normal cells and tissues

Question 3

What is pathology

Answer 3

the study of diseases cells and tissues

Question 4

What is disease associated with?

Answer 4

disruption of normal structure and function of tissues

Question 5

What induces alterations in tissue architecture?

Answer 5

infection,heat/cold, poison/drugs, genetic and congenital changes, ageing/wear and tear, cancers

Question 6

What do light microscopes reveal

Answer 6

basic cellular structure

Question 7

What do electron microscopes reveal?

Answer 7

ultra-structure

Question 8

What type of microscopy is commonly used in histology?

Answer 8

light microscopy

Question 9

What is the first step in obtaining tissues for microscopy and describe what is it

Answer 9

SPECIMEN COLLECTION. Biopsies need to be taken

Question 10

What is an incision/punch biopsy used for?

Answer 10

Collecting tissues from skin/oral surfaces

Question 11

What is a needle biopsy for?

Answer 11

Organs or lumps below the skin

Question 12

What is a endoscopic biopsy for?

Answer 12

For cavities inside body e.g. colonoscopy/endoscopy

Question 13

What is the second step in obtaining tissues for microscopy and describe what it is.

Answer 13

FIXATION. Preserves the structural arrangement, terminates all biochemical reactions and prevents tissue decomposition.

Question 14

Name 2 common fixatives

Answer 14

Formaldehyde and glutaraldehyde

Question 15

What is step 3 in obtaining tissues for microscopy and describe it

Answer 15

DEHYDRATION. water is removed from tissues as paraffin embedding is not compatible with water. water is removed gradually to avoid distortion

Question 16

What is the fourth step in obtaining tissues for microscopy and describe it

Answer 16

EMBEDDING. resins and paraffin wax used to support the tissue to allow thin sections to be cut from it. paraffin is not compatible with alcohol so alcohol is replaced by xylene.

Question 17

What is the fifth step for obtaining tissues for microscopy and describe it

Answer 17

SECTIONING. tissue sections must be thin and flat and ideally a single layer of cells. sections are mounted on glass slides

Question 18

What is the sixth step to obtaining tissues for microscopy and describe it

Answer 18

STAINING. makes cells and their components visible. allows identification of different cell and tissue features. Stains are not compatible with paraffin so reverse of dehydration occurs to remove paraffin wax and replace with water

Question 19

What is haematoxylin and eosin

Answer 19

the most commonly used staining technique. haematoxylin (basic dye) stains acidic structures (nucleic acids) purple/blue and eosin (acidic dye) stains basic structures (cytoplasmic proteins) red or pink

Question 20

What is the periodic acid-schiff reaction?

Answer 20

Stains complex carbohydrate magenta

Question 21

What is masson trichome?

Answer 21

stains connective tissues. nuclei stains blue, collagen stains green/blue, cytoplasm, muscle, red blood cells and keratin stain red

Question 22

What does immunohistochemistry do?

Answer 22

utilises antibody specificity for antigen.

Question 23

What is the seventh step in obtaining tissues for microscopy and describe it

Answer 23

VIEWING. Permanent mounts are made. stained sections are dehydrated again to replace water with xylene. a mounting medium and a cover-slip seal protect section