Description

This video is about histology, its history, and how histological slides are prepared.

In this video, I cover:

• Short history of histology: First light microscope and early discoveries.
• Basic cell properties: Differences between prokaryotic and eukaryotic cells.
• Microscopy techniques:
  • Light Microscope:
    • Brightfield
    • Phase-Contrast
    • Darkfield
    • Fluorescence Microscope
  • Transmission Electron Microscope (TEM)
  • Scanning Electron Microscope (SEM)
• Histological slide preparation and staining:
  • Biopsy
  • Fixation
  • Dehydration
  • Paraffin Infiltration
  • Staining (Hematoxylin & Eosin – H&E)
• Quick look into how to differentiate cells under a microscope (Muscle Tissue).

Enjoy!

Transcript

Introduction
0:00
hello welcome to a video in this video
0:01
I’m going to talk about the basics of
0:03
cell biology where I’m going to talk
0:04
about the properties of the you credit
0:06
cell I’m also going to talk about the
0:07
differences between the eukaryotic cell
0:09
and appropriate Excel and I also got
0:12
attacked by the basics of histology
0:13
where I’m gonna take it through the
0:15
journey of how tissue in the human body
0:17
ends up looking like this so over many
0:20
years we have been looking at cells
0:22
through simple light microscopes just
0:25
like the one you see right here so if we
History of Histology
0:28
take a quick look into the history of
0:30
histology there has been a lot of people
0:31
that have contributed to the development
0:33
of microscope but it’s all we really
0:36
started with Robert Hooke and Marshall
0:38
OMA Pinckney who in year 1700 were the
0:42
first people who used the term cell they
0:45
use this simple light microscope you see
0:48
right here and how do they work well
0:51
they used candle just like this one this
0:54
is they used this as a source of light
0:56
because they didn’t have any electricity
0:57
at that time and they use this glass
1:00
bulb filled with water to focus the
1:03
light into a specimen something they
1:05
wanted to observe and then that light
1:07
would then reflect it into this
1:09
microscope where they had different
1:12
lenses to magnify this image and with
1:16
those lenses they could actually see the
1:19
the cells of the specimen they’re
1:22
looking at so here’s what they looked at
1:24
this is a bark tissue from a tree called
1:26
cork oak so this is a plant you Kratt
1:29
Excel and each black spot we’re gonna
1:32
present one eukaryotic cell so in the
Different Cellular Characteristics
1:35
astrology in order to understand the
1:37
differences between tissues in order to
1:39
understand the differences between
1:40
nervous and muscle tissues for example
1:42
you need to understand the different
1:44
cellular characteristics so I’m not
1:46
gonna go too much in details under this
1:48
because that’s gonna be for other videos
1:49
but mainly the first thing you want to
1:52
look at when you look at tissues like
1:53
that is what cells are you looking at
1:55
what are their functions here I’ve used
1:58
three muscle tissues as an example here
2:01
you see the skeletal muscles and the
2:03
cardiac muscles and small muscles so
2:06
what cells are looking at what are their
2:08
functions will they know that muscle
2:09
tissues I need to apply force so they’re
2:12
movable
2:13
so how do you differentiate between them
2:14
even though they have the same function
2:16
well you know that skeletal muscles are
2:18
going to be long cylindrical just like
2:19
you see here
2:20
cardiac muscles are going to be short
2:22
and branched some of these muscles for
2:25
examples for me like that
2:26
well this muscle is cells from a dead
2:30
while swarm us also I’m going to be very
2:33
narrow and elongated so that we’re gonna
2:38
be very close to each other so you need
2:41
to look at the shape of the cells but
2:44
you also need to look at the cell
2:45
nucleus so you know that the skeletal
2:47
muscles are gonna be multi nuclide and
2:49
they’re gonna have many nuclei it’s like
2:51
you see here while cardiac muscles are
2:54
gonna have one nucleus not be the same
2:56
goes to smooth muscles only one nucleus
2:58
and you also need to look at the shape
3:00
of the nucleus as well because only by
3:02
looking at these three pictures you can
3:04
already tell that the nucleus are shaped
3:07
differently and you’ll also see that
3:09
when I start talking about the
3:10
epithelial tissue in other videos so you
3:13
need to understand what cells you’re
3:15
looking at and their shape another thing
3:17
you want to look at is you know those
3:19
alternating black and white stripes you
3:22
see in the skeletal muscles and and
3:24
cardiac muscles smooth muscle doesn’t
3:26
have that that’s why it’s called smooth
3:28
so that’s just one example of of how to
3:32
differentiate between cells and
3:34
histology so just to go through with
Basic Properties of Cell
3:36
some basic properties of a cell you know
3:38
that cells have genetic material just
3:40
like you see here that’s gonna be the
3:41
purple in one cell and they also
3:43
reproduce like mitosis and meiosis this
3:46
is a picture of cell division or
3:49
production and the cells obtain and
3:52
produce energy and also capable of
3:54
metabolism so when you eat food there
3:56
that just did and then there used to
3:59
produce energy and the cells are also
4:02
capable of transporting and materials
4:04
here of use exocytosis and endocytosis
4:06
is an example here the cell uses
4:09
vesicles to transfer a lot of materials
4:10
outside and inside the cells as two
4:13
examples of cell transporting materials
4:16
another function cells can do is a
4:19
respond to stimuli so if you ever hold
4:21
your hand about
4:22
Kendall was gonna happen is that pain
4:25
receptors on cells are gonna be
4:27
stimulated that’s gonna send a signal to
4:30
the central nervous system that’s gonna
4:32
where you’re gonna feel the pain that’s
4:34
why it takes a little time before you
4:35
feel the pain of heat you know what’s
4:38
gonna happen is that they’re going to
4:39
send a signal to your muscle to remove
4:42
the arm that’s gonna be one example of
4:44
cells responding to stimuli another
4:47
thing cells are capable of is self
4:49
regulations and an example of that is
4:51
apoptosis so if a cell noticed that
4:54
something is wrong with it it can it
4:56
actually has the ability to kill itself
5:00
so that it doesn’t reproduce that
5:02
mistake all the time there are going to
5:04
be some differences between prokaryotic
Difference between Procaryote and Eucaryote Cell
5:06
cells and you correct cells as well so
5:08
your attic cells has new cell nucleus
5:11
broken itself doesn’t have that they
5:12
have something called nuclear weed which
5:14
is just a thin membrane that doesn’t
5:17
really separate it from the cytoplasm
5:18
you kradic cells are really complex
5:20
cells they have what is called membrane
5:22
bound organelles where most of the
5:25
organelles in the you chronic seller can
5:27
have membranes prokaryotic cells doesn’t
5:30
have that and their ribosomes New Relic
5:32
cells are also going to be bigger and
5:33
they’re gonna have more RNA materials so
5:36
there aren’t going to be a lot of
5:37
differences between the eukaryotic and
5:39
prokaryotic cells but the main
5:40
difference I want to highlight is a size
5:43
different between them in this picture
5:45
you can kind of see the differences in
5:47
size of the eukaryotic cells so
5:50
pro-catholic cells are usually gonna be
5:51
between 1 to 5 micrometers big while the
5:56
you correct cells are gonna be
5:57
everything between 10 and 100
5:59
micrometers and a lot of it’s a really
6:02
big difference between them so if you go
Main components for a Microscope to work
6:04
over to microscopes there are going to
6:06
be three main components for a
6:08
microscope to work is need a source of
6:10
light just like you see here
6:12
I need a specimen to observe it’s going
6:15
to be this one and tissue slides and
6:17
also need the system of lenses to focus
6:20
the light on a specimen and enlarge in
6:22
it so we mainly have two types of
Types of microscopes
6:24
microscopes we have light microscopes
6:26
and we have electron microscopes
6:28
light microscopes are going to use lamp
6:30
and lenses to focused light on a
6:32
specimen and enlargement while in
6:35
electro
6:35
hopes you can use magnets to focus the
6:38
electrons through on a specimen so in
6:41
transmission electron microscopes the
6:43
electrons are going to go through the
6:45
specimen and then detected while in
6:47
scanning electron microscopes you hear
6:50
the electrons are going to go down and
6:51
then they have electron detector which
6:54
is going to detect the electrons like
6:56
that bounces off the specimen so
6:59
electrons can go down this way and then
7:00
bounce off the specimen and then
7:02
detected so in light microscopes we
Light Microscope (Brightfield, Phase contrast, Darkfield, Fluorescence)
7:04
mainly going to have four methods of
7:06
looking at cells I’m gonna have
7:08
brightfield microscope which is the most
7:10
frequently used microscope in histology
7:12
you get pictures just like that with
7:14
white background they also have phase
7:16
contrast microscope where you see the
7:18
contrast between the different
7:21
organelles in the cell here you can see
7:23
a cell under division I believe this is
7:25
telophase because you can see the
7:27
chromosomes on either side of the cell
7:28
and you also have dark field microscope
7:31
which is going to be opposite of
7:32
biofeedback scope this one’s gonna have
7:34
black background and light and whites
7:37
cells and you also have fluorescence
7:40
microscope this is my favorite because
7:41
this one uses fluorescents use the
7:44
antibodies to sit on the cell and then I
7:47
use fluorescence and then detects it and
7:49
you can see beautiful pictures like this
7:52
one so that’s light microscope if you go
Electron Microscope (Transmission, Scanning Electron microscope)
7:55
over to electron microscopes electron
7:57
microscopes are gonna be more specific
7:58
they’re gonna look at cells in more
8:01
detailed view and they’re gonna zoom in
8:03
even more you can in transmission
8:05
electron microscopes you’re able to
8:07
actually see the organelles as you see
8:09
here so I’ve gone with a scanning
8:11
electron microscope Siri the electrons
8:13
comes down and bounces off the specimen
8:16
and then detected on a on the electron
8:18
detector and that forms an image of the
8:20
specimen here you can see a cross
8:22
section of a leaf you can see the cells
8:24
inside of it as well so how do we get
The process of obtaining a histological slide
8:27
those slides where do you get them from
8:28
well first the patient goes to the
1. Biopsy from a patient
8:31
doctor where the tissue is removed and
8:33
thus remove tissue is called a biopsy
8:35
the biopsy is then sent to a
2. Fixation (Formalin)
8:37
pathological laboratory for fixation and
8:40
fixation is an extremely important step
8:42
because a fixation kills the tissue so
8:45
that destruction of the cells is
8:47
prevented
8:47
and fixations also keeps tissue as close
8:51
to its natural state as possible by
8:53
forming those cross links in protein
8:56
just like you see here there are a lot
8:58
of different ways to fixate the tissue
9:00
but the most frequently used is formalin
9:03
as you see here after fixation you need
3. Dehydration
9:07
to remove the water from the inside to
9:09
replace it with wax solvent like
9:11
paraffin and here you need to take it
9:14
through a gradually increasing alcohol
9:17
so that all the water can be infused out
9:20
so after removing water you need to dip
4. Paraffin Infiltration
9:22
it in paraffin actually which is the
9:24
same material as you will find in candle
9:26
this is how we do it in a laboratory I
9:29
work in we just take the tissue and dip
9:31
it in paraffin and then we will get what
9:34
is called tissue blocks which I should
9:36
we’ll stay like that forever
9:37
you then need to cut the tissue block
5. Cutting with microtome
9:40
using a microtome and place it on a
9:42
glass slide just like that after that
6. Coloring with Hematoxylin and Eosin (H&E)
9:46
you need to color it and hematoxylin a
9:49
scene or H and E we call them is the
9:52
most frequently used coloring method
9:54
here the habit of saline binds
9:57
substances which with negative charge
9:59
just like the phosphate groups in DNA
10:01
and RNA while you seen buying substances
10:05
with positive charge just like the amino
10:08
acids in the cytoplasm in the cells and
10:10
in this picture you can I kind of see
10:13
the differences here the hematoxylin
10:15
stains acidic structures blue just like
10:19
the the DNA and the using stains bit but
10:23
a basic structures pink just like the
10:25
amino acids so in histology we’ll mainly
10:28
divide the tissues into four groups you
10:30
have the nervous tissue epithelial
10:32
tissue muscle tissue and connective
10:35
tissue and in my next histology videos
10:37
I’m going to try to show how we can
10:39
differentiate and recognize the cells
10:42
through microscopes