Microscopy and Cells

Question 1

Why does histology have value in diagnosis?

Answer 1

It has great value because it is definitive. It means we can be certain what something is and therefore about what is the best treatment.

Question 2

Define Biopsy.

Answer 2

The removal of a small piece of tissue from the body for examination under a microscope.

Question 3

What are the 6 types of Biopsy?

Answer 3

Smear - Cervix/ Buccal Cavity
Curettage (spoon with sharp edge) - Endometrium of Uterus
Needle - large bored and comes out with tissue inside (organs)
Direct Incision - skin/mouth/larynx
Endoscopic - pincers remove tissue (lung/intestine/bladder)
Trans-vascular - pincers through blood vessel (heart/liver)

Question 4

Define a tissue.

Answer 4

A collection of cells which are specialised to perform a particular function.

Question 5

What is a microtome?

Answer 5

It is an instrument used to cut tissue sections so that they can be examined under the microscope.

Question 6

What is the most common stain and what does it stain?

Answer 6

Haemotoxylin and Eosin.

H stains acidic components (such as the nucleus) purple and E stains basic components (cytoplasmic proteins) pink.

Question 7

Periodic Acid Schiff stains mucus and mucus secreting glands a prominent colour. What is this?

Answer 7

Magenta

Question 8

Why do biopsies need to be fixed?

Answer 8

A fresh biopsy is very wet and enzymes are present which will break down the structures. Glutaraldhyde/ Formaldehyde can be used to link macromolecules and so this preserves cellular structure and also kills any bacteria present.

Question 9

Outline the basics of tissue processing.

Answer 9

Tissues need to be embedded in wax to be sectioned.
To get to this point they undergo
Dehydration - cleaning with ethanol - xylene/ toluene (wax adhesive)
Then: the reverse happens so it can be stained because most stains are water soluble.
Then: process happens again so that section does not degrade.

Question 10

Why can tissue processing lead to shrinkage artefacts?

Answer 10

When tissue undergoes processing it goes through a number of chemical process and this can cause different parts of the sample to behave in different ways which can lead to changes of size - shrinkage artefacts

Question 11

What is phase contrast microscopy?

Answer 11

This uses the interference effects when two waves combine to produce clearer images. This can be used to detail living cells.

Question 12

What is dark field microscopy?

Answer 12

This is where an image is created from light scattering patterns.

Question 13

How does fluorescent microscopy work?

Answer 13

It uses 3 stains which are fluorescent and can be used to highlight different parts of the cell depending on which antibodies they are coupled to.

Question 14

What is the benefit of confocal microscopy?

Answer 14

It eliminates out of focus flare. It scans specimens with a laser beam and is able to produce 2D images which can then be built up into a 3D image. This process can be used on living specimens.

Question 15

What is the Limit of Resolution?

Answer 15

Minimum distance at which two objects can be distinguished.

Question 16

Why is the cell membrane impermeable to water soluble molecules?

Answer 16

The cell membrane is a phospholipid bilayer. The middle region is where the hydrophobic tails of the molecules are and so these will not allow water soluble molecules to pass through.

Question 17

What is the glycocalyx?

Answer 17

The glycocalyx is the name for the sugars on the outside of the cell membrane. These give specificity to protein action.

Question 18

What is synthesised in the smooth endoplasmic recticulum?

Answer 18

Lipids

Question 19

Where does protein synthesis occur in the cell?

Answer 19

It occurs in the RER where there are ribosomes to facilitate translation.

Question 20

What are the names of the three Cisternae in the Golgi network?

Answer 20

Cis, medial, trans

Question 21

What is the function of the Golgi complex?

Answer 21

To modify, sort, concentrate and package proteins/lipids synthesised in the ER.

Question 22

What are the three destinations for molecules passing through the Golgi?

Answer 22

Signal mediated diversion to lysosomes
Constitutive secretion into Intracellular space.
Signal mediated diversion to secretory vesicles for regulated secretion.

Question 23

What do lysosomes contain?

Answer 23

Lysosomes contain hydrolytic enzymes and they fuse with material that requires digestion. The glycocalyx of the plasma membrane prevents them breaking this down.

Question 24

Where are peroxisomes found?

Answer 24

Peroxisomes are found in the liver and kidneys and are responsible for detoxifying reactions by oxidation.

Question 25

In what type of cells will abundant mitochondria be found?

Answer 25

Cells which require large amounts of energy as this is where ATP is synthesised.

Question 26

What are micro filaments in the cell cytoskeleton?

Answer 26

They are cortical actin filaments of 5-9nm in diameter which lie under the plasma membrane and travel up micro villi and support their shape.

Question 27

What forms a tough mesh in the cytoplasm and provides structure and support?

Answer 27

Intermediate filaments.

Question 28

Where are micro tubules found?

Answer 28

These are long hollow tubular cylinders which are found in structures which move such a nerve fibres, mitotic spindle, cilia and flagella.

Question 29

What arrangement is seen in micro tubules in flagella/cilia?

Answer 29

9+2 arrangement.
The outer arms are able to make and break contact and this allows the cilia to beat. There are nine in a ring round the outside and two in the middle.