ToB S1 - Microscopy and Epithelial Tissue

Question 1

Define tissue

Answer 1

Collection of cells specialised to perform a particular function

Question 2

How many times bigger is a millimetre than a nanometre?

Answer 2

1,000,000 times larger

Question 3

Define histology

Answer 3

Study of the structure of tissues by means of special staining techniques coupled with light and electron microscopy

Question 4

Name the six common types of biopsy and a tissue that would be sampled from each?

Answer 4

Curettage - scooping/scraping Eg endometrium of the uterus Smear

Mechanical exfoliation Eg cervix, buccal cavity

Direct incision - cutting and removal Eg skin

Needle - Eg breast, brain, kidney muscle

Endoscope - e.g lung, colon

Transvascular - Eg heart and liver

Question 5

Define biopsy

Answer 5

Removal of a small piece of tissue from an organ or part of the body for microscopic investigation

Question 6

Name two common fixatives

Answer 6

1) Glutaraldehyde
2) Formaldehyde

Question 7

Why is tissue fixed?

Answer 7

• Prevent autolysis and putrefaction
• Maintains cross-linked macromolecules

Question 8

Outline the process of fixation

Answer 8

• Tissue dehydrated with ethanol
• Cleared with xylene
• Embedded in wax
• Sectioned
• Rehydrated (xylene-ethanol-water)
• Stained
• Dehydrated again (water-ethanol-xylene)
• Mount specimen on slide

Question 9

What is Periodic acid–Schiff used to stain?

Answer 9

Carbohydrates and glycoproteins (magenta)

Question 10

What cell component would haemotoxylin stain?

Answer 10

Acidic cell components; Nucleolus - RNA, Chromatin - DNA

Question 11

What colour does eosin stain?

Answer 11

Pink

Question 12

What are the four types of light microscopy?

Answer 12

1) Confocal - scanning one or more focused beams, labelled with fluorescent probes, can eliminate ‘out of focus flare’, enable formation of 3D images
2) Phase contrast - uses interference effects produced when two sets of waves combine, enhances image of living, unstained cells
3) Darkfield - light from side is scattered, only refracted light seen
4) Fluorescence - Uses antibodies coupled to fluorescent stain

Question 13

What is the average diameter of a typical human cell?

Answer 13

10-20 micrometres

Question 14

How are shrinkage artefacts produced?

Answer 14

The rehydration and dehydration process leaving abnormalities on the final slide

Question 15

What does Eosin stain?

Answer 15

Basic components of a cell Eg most cytoplasmic proteins and extracellular fibres pink

Question 16

What colour does haemotoxylin stain?

Answer 16

Blue/purple

Question 17

Define epithelia

Answer 17

Sheets of contiguous cells, of varied embryonic origin that cover the external surface of the body and line the internal surfaces

Question 18

Define mucous membrane

Answer 18

An interior surface that opens to the exterior Eg GI tract, respiratory tract, genitourinary

Question 19

Define serous membrane

Answer 19

An interior surface that does not open out Eg pericardial sac, pleural sac, peritoneum, blood vessels, lymph vessels

Question 20

Name 3 locations of squamous epithelium

Answer 20

Any from: lining of blood and lymph vessels, lining of body cavities (pericardium, pleura peritoneum), pulmonary alveolar epithelium, loop of Henle, Bowman’s capsule, inner and middle ear

Question 21

Name 3 locations of cuboidal epithelium

Answer 21

Any from: thyroid follicles, small ducts of many exocrine glands, kidney tubules, surface of ovary

Question 22

Name 3 locations of columnar epithelium

Answer 22

Any from: Stomach lining, gastric glands, small intestine and colon, gallbladder, large ducts of some exocrine glands, oviducts, uterus

Question 23

Name 3 locations of pseudostratified epithelium

Answer 23

Any from: Lining of the nasal cavity, trachea and bronchi, epididymus, ductus deferens, auditory tube, lacrimal sac and large excretory ducts

Question 24

Name locations of transitional epithelium

Answer 24

• Ureters, bladder, urethra, renal calyces

Question 25

What is the function of the basement membrane?

Answer 25

Serves as a strong flexible layer to which epithelial cells adhere. It also serves as a molecular and cellular filter

Question 26

Explain the reason for the different rates of renewal of each type of epithelium

Answer 26

• turnover rates depend on cell function and location - Epidermis of skin - 28 days
• Small intestine epithelia are replaced every 4-6 days (from the base of the crypts)
• Some epithelia aren’t renewed but proliferation can be triggered to replace damaged/lost cells

Question 27

What are microvilli?

Answer 27

Apical extensions that greatly the surface area for selective absorption of intestinal contents

Question 28

What are sterocilia?

Answer 28

Very long microvilli, extends from the surface of the ducts deferens and the epididymis. They may also have an absorptive function

Question 29

What are cilia?

Answer 29

Extension from cells that beat in coordinated waves. Found in the lining of the trachea where they sweep mucus and dirt out of the lungs. Also found in the fallopian tubes, where they move the oven from the ovary to the uterus. Axoneme, 9+2 configuration