Body Logistics Lecture 2

Question 1

Sate the meaning of the term ‘tissue’ and provide an example of each of the 4 types.

Answer 1

Tissue is a Latin word that means ‘woven’.

Epithelial tissue
Nervous tissue
Muscle tissue
Connective tissue

Question 2

What is epithelial tissue?

Answer 2

Often on the edge of other tissues and surrounded by other tissues.
Sometimes in clusters within other tissues for example, GLANDS.
Polarised when at surfaces, made of fibres, held together by strong anchoring proteins.
Communicate through ‘junctions’ at their lateral and basal surfaces.
Collagen IV is found in epithelial basement membranes and separates a variety of epithelial and endothelial cells.

Question 3

What is connective tissue?

Answer 3

Consists of cells and extracellular proteins/glycoproteins and ‘gels’ (earwax is a gel).

They include fibroblasts which make fibres, chondrocytes which make cartilage.
Also includes stem cells.

Question 4

What is muscle tissue?

Answer 4

Consists of muscle cells.
3 types:
Skeletal (moving)
Cardiac (moves blood)
Smooth (moving tubes)

Question 5

What is nerve tissue?

Answer 5

Nerve cells (neurons) and several support cells.
Can be very short (micromitres) or very long (cm to m).

The main fast communication system in the body.
Cells congregate into nerve. fibres.
Fibres congregate into nerves that can be dissected and visualised by the eye.

Question 6

State the relationship between milli, micro and nano metres.

Answer 6

1000 micro metres = 1 mm.
1000 nano = 1 micro.

Question 7

What is histology?

Answer 7

Microscopic study of tissues and organs through sectioning, staining and examining those sections under a microscope

Question 8

What is the process of fixation to prepare for tissue staining in histology?

Answer 8

The biopsy is preserved in chemicals to prevent it from damage. This is called ‘fixation’.
Formalin is the most common fixative chemical. It is 37% aqueous solution of formaldehyde usually supplemented with 0.9% sodium chloride solution.

1. Sample is left in fixative for 24-48 hours.
2. Sample is washed and hydrated in a series of alcohol solutions of increasing % up to 100% and then in solvents which are miscible with alcohol and hot paraffin wax (xylene or toluene). They are immersed in hot parrain wax overnight.
3. Placed in a mold, hot wax completely covers specimen and set aside to harden.
4. Mounted on a microtome. Thin sections of tissue (2-10micrometres) are cut with a diamond knife.
5. These sections are picked up with a fine paintbrush and floated on surface of a warm water bath.
6. Putting glass microscope slide under floating section and specimen floats onto surface of slide. Microscope slide is coated with albumin first (which is sticky) to help the specimen adhere to the slide when dry.
7. Left to dry.

Question 9

Describe the process of tissue staining in histology.

Answer 9

1. The paraffin is dissolved with toluene or xylene and rehydrated through different % of alcohols from 100% to 0.
2. The most common stain is haematoxylin and eosin.
3. Immerse sections in a solution of aqueous haematoxylin. Wash in water and transfer into alcohol.
4. Slides are emerged in eosin. This is acidic so binds to basic structures e.g. intracellulaire and extra cellular proteins.
5. Wash with alcohol and mount in a non-aqueous mounting medium.
6. Coverslip applied and examined under a microscope.

Question 10

What is the limit of resolution?

Answer 10

The minimum distance at which two objects can be distinguished.

Limit of resolution is proportional to the wavelength used by the viewing system.

Question 11

Why is histology important is diagnosis?

Answer 11

By analysing the tissue specimen, you can diagnose and find out the severity of a disease and issue a prognosis.