L2- How to examine cells and tissues

Question 1

Define the word ‘tissue’?

Answer 1

Tissue: latin word that means ‘woven’

- Groups of cells that are similar in structure and perform a common or related function

Question 2

What are the 4 broad tissue classifications?

Answer 2

1. Epithelial
2. Connective
3. Muscle
4. Nerve

Question 3

Epithelial tissue general cxtics?

Answer 3

• line surfaces of every part of body
• found on edge of other tissues and surround other tissues
• sometimes found in clusters –> glands
• polarised when at surfaces: have basement membrane and secrete from apical surfaces
• held together by strong anchoring proteins
• communicate through junctions at lateral and basal surfaces

Question 4

Connective tissue

a) Main cells
b) Main products

Answer 4

• consists of cells and ec proteins/glycoproteins and gels

a) - fibroblasts
- chondrocytes
- osteocytes/osteoblasts/osteoclasts
- stem cells/progenitor cells/bone marrow/blood/adipocytes

b) - fibres
- ground substance
- wax and gel like materials

Question 5

Nerve tissue cxtics

Answer 5

• nerves can be short (um) or long (cm)
• main fast communication system in body
• cells congregate into nerve fibres
• fibres congregate into nerves that can be dissected

Question 6

Name of nerve cells?

Answer 6

Neurons

Question 7

Muscle tissue

a) Types of muscle
b) major functions
b) What hormones do they secrete

Answer 7

a) Skeletal, cardiac and smooth
b) Movement, stability and movement of tissue contents
c) Natriuretic factors: control water balance and myostatins: stops heart growing too large

Question 8

Why is connective tissue different from the other types of tissue?

Answer 8

Only tissue that has a liquid tissue in form of blood

Question 9

Define the limit of resolution

Answer 9

The smallest distance by which two objects can be seperated and still be distinguishable as two seperate objects

Question 10

Compare light microscopy and electron microscopy

Answer 10

Light microscope

• can view images in natural colours
• large field of view
• cheap and easy prep
• can view living and moving objects
• magnification: x 600
• resolution: 0.25 um

Electron microscope

• only monochrome images seen
• limited field of view
• difficult and expensive
• can only view dead and inert objects
• magnification: x500,000
• resolution: 0.25 nm

Question 11

Requirements to image tissues by light microscopy

Answer 11

• need to preserve tissue to prevent it from putrefaction (rotting): formalin
• Need to embed the tissue in a substance that allows it to be sliced thinly: paraffin wax
• need to stain the tissue so you can see all cell components

Question 12

Outline the process of fixation

Answer 12

Formalin solution:

• formaldehyde has to be buffered usually by NaCl
• always 10 percent

Question 13

Outline process of paraffin wax embedding

Answer 13

• dehydrated in different concentrations of alcohols
• immersed in dissolved hot paraffin wax overnight
• tissue orientated in mould and more wax added
• alowed to cool to room temp
• gently eased out of mould

Question 14

What are the two most commonly used stains and what do they stain?

Answer 14

Haematoxylin and Eosin

Haematoxylin only: stains nucleus blue

Eosin only: stains cytoplasm and EC matrix pink

Both: nuclei clearer and more detail in cytoplasm

Question 15

Compare paraffin wax formalin fixed vs Frozen section

Answer 15

Paraffin wax embedded tissue section:

• uses fixed tissues
• takes 24-48 hours
• pathological diagnosis

Frozen section:

• uses fresh tissues
• 10-20 mins
• intraoperative consultation
• has poor retention of stain