Session 1 - Epithelial Tissue and Microscopy

Question 1

What is Histology?

Answer 1

Histology is the study of the structure of tissues using specialised staining techniques combined with light and electron microscopy.

Question 2

What is Epithelial Tissue?

Answer 2

Epithelial tissue is sheets of contiguous cells, of varied embryonic origin, that cover the external surface of the body and line internal surfaces.

Question 3

What is simple epithelia?

Answer 3

This is epithelia that is one cell layer thick.

Question 4

What is stratified epithelia?

Answer 4

This is epithelia that is more than one cell layer thick.

Question 5

What is squamous epithelia? Name a location and function.

Answer 5

This is epithelia that is thin and squashed (flattened).
Function: lining of blood vessels.
Function: Lubrication.

Question 6

What is cuboidal epithelia? Name a location and function.

Answer 6

Cuboidal epithelia has a cube shape. One location is the Kidney and it absorbs and secretes.

Question 7

What is Columnar epithelia? Name a location and function.

Answer 7

Columnar epithelia has a column shape. One location is the stomach and a function is that it absorbs and secretes.

Question 8

What binds adjacent plasma membranes together?

Answer 8

Simple Columnar Epithelia with Microvilli and Occludin. Occludin is the key substance that binds the membranes together and it restricts certain proteins from entering certain areas of the cell.

Question 9

What is Pseudostratified epithelia?

Answer 9

This is where all of the cells rest on the basal lamina (the basement membrane) but only some reach the surface. Cells that reach the surface of columnar.
Pseudostratified epithelia can often appear to be stratified when they are actually simple.

Question 10

What is a function and location of pseudostratified epithelia?

Answer 10

Location: Nasal cavity.

Function: Mucus secretion. Generally secretion and absorption.

Question 11

What is transitional epithelia?

Answer 11

This is epithelia that can expand and shape. One location is the bladder, in order that the epithelia can extend when the bladder is full and distend when the bladder is empty.

Question 12

What is keratinised epithelia?

Answer 12

This is epithelia that has a layer of dead skin cells on top. Keratinised epithelia is often located on the skin (in the form of stratified squamous keratinised epithelia).
Function: protection against abrasion and prevention of water loss.

Question 13

Where is stratified squamous non-keratinised epithelia found?

Answer 13

Locations include the vagina and the surface of the cornea. Note that it is non-keratinised (so there is no layer of dead skin cells), this should point to you that it is not located on the skin (this would be keratinised squamous epithelia).
Function: protection against abrasion and water loss.

Question 14

What is Tissue?

Answer 14

Tissue is a collection of specialised cells which perform a specific/ particular function.

Aggregations of tissues constitute organs.

Question 15

What are some of the key functions of epithelial tissue?

Answer 15

• Protection
• Absorption
• Secretion
• Reproduction
• Sensation
• Lubrication
• Excretion

Question 16

What is another term for stratified epithelia?

Answer 16

Compound epithelia.

Question 17

What is metaplasia?

Answer 17

This is where some of the tissues in the body are able to change from one type of epithelium to another. For example in heavy smokers the pseudostratified columnar epithelia may become squamous stratified epithelia.

Question 18

What is neoplasia?

Answer 18

In disease changes may occur in the epithelia, giving rise to a tumour which is termed carcinoma.

Question 19

What is the relationship between mili-, micro- and nano- meters?

Answer 19

Milli = 10-3. 
Micro = 10-6. 
Nano = 10-9.

Question 20

What is the average size of most human cells?

Answer 20

10-20um in diameter.

Question 21

What are the size of red blood cells?

Answer 21

7.2um in diameter.

Question 22

What is the value of histology in diagnosis?

Answer 22

Histology provides a definitive diagnoses, especially in certain circumstances where symptoms between two conditions can be very similar. Such as Crohn’s disease and Ulcerative colitis. Histology is also key to providing a definitive diagnoses in cancer, for example it can tell a doctor whether a mole is benign or malignant.

Question 23

What is a biopsy?

Answer 23

A biopsy is the removal of a small piece of tissue from an organ or part of the body for microscopic examination.

Question 24

What is curettage as a biopsy technique?

Answer 24

It is the removal of tissue by scraping/spooning. It is used in the lining of the uterus.

Question 25

What biopsy technique is an endoscope used for?

Answer 25

Lung, intestine, bladder.

Question 26

What is a smear biopsy technique?

Answer 26

This is the use of mechanical exfoliation.

Question 27

How is a biopsy fixed? What does this mean?

Answer 27

A biopsy is fixed through the use of formaldehyde. In a fixed biopsy the micromolecules are cross-linked and the cellular structure is preserved.

Question 28

Once you have fixed a biopsy through formaldehyde what do you do?

Answer 28

• Dehydrate the tissue
• Add ethanol to clean the tissue
• Embed the tissue in wax
• Section the wax
• Rehydrate a section of wax
• Stain the tissue
• Dehydrate the tissue again
• The tissue is then ready to be mounted onto the microscope.

All of the dehydrating and hydrating can lead to the formation of shrinkage artefacts.

Question 29

What is used to stain acidic tissue?

Answer 29

Heamatoxylin. It colours the tissue purple/blue.

Question 30

What is used to stain a base tissue?

Answer 30

Eosin is used to stain basic components of cells pink.

Question 31

What is the Periodic Acids Schiff method of staining?

Answer 31

The PAS method stains carbohydrates and glycoproteins magenta.

Question 32

What is an advantage of phase contract light microscopy?

Answer 32

Phase contrast method uses interference effects of two combining light waves. It enhances the image of unstained cells.

Question 33

What is an advantage of Dark field microscopy?

Answer 33

Dark field microscopy excludes unscattered beam (light/electron) from the image and this is beneficial for live and unstained samples.

Question 34

What is an advantage of Confocal light microscopy?

Answer 34

This is where tissue is labelled with one or more fluorescent probes. It eliminates out of focus flare, it creates 3D from a series of 2D images and it is used for the imaging of living specimens.

Question 35

How are compound epithelial tissues classified?

Answer 35

Each is named on the basis of its superficial (top?) cell layer.

Question 36

Explain the position, structure and function of the basement membrane.

Answer 36

• The basement membrane refers to thin, flexible, acellular layer which lies between the epithelial cells and subtending connective tissue.
• It consists of a basal lamina which is laid down by the epithelial cells and therefore lies closest to them.
• Its thickness can be augmented by type 3 collagen.
• The basement membrane serves as a strong flexible layer to which epithelial cells adhere. It also serves as a cellular and molecular filter.

Question 37

Explain why there is a different renewal rate for different epithelial tissue.

Answer 37

The turnover for epithelial tissue depends on its location and function.
The time for skin to renew is approximately 28 days.
Cells lining the small intestine however regenerate every 4 to 6 days.
Physical damage or injury will however increase the rate of renewal.