TEJIDO SANGUÍNEO | ¡Fácil explicación! (Histología)

Hello, how are you? I'm

Dr. Romy, and this is Sala QSP, your

medical channel. In today's video, I'm going to talk about

blood tissue, so without further

ado, let's begin. To

talk about blood tissue, it's important to

remember that in connective tissue, we had

three types:

embryonic,

mature, and

specialized. Blood tissue is precisely

a type of specialized connective tissue.

With that introduction,

we can begin our topic: What is

blood? Blood is

composed of cells and

extracellular material. These cells are fluids

and some solutes that form a

viscous element called

blood tissue.

In an adult, it represents approximately 6 liters. This

means that an older adult

will have approximately 6 liters of blood,

which represents 7 to 8% of their

total body weight. For example, if I

weigh 50 kg, those 50 kg represent 100%

of my total body weight, and I want to know

how many kilograms of my 50 kg are equivalent to

my blood, using a rule of three

will give me a result. 3.5 kg, so

out of the 50 kg I weigh, 3.5 kg

corresponds to my blood. You can also

do this calculation with a

slightly simpler formula using your

body weight multiplied by

0.07, which will give us the same

result. What are the functions

of blood tissue? It will help us

transport oxygen and

nutrients, it will transport waste products and

carbon dioxide from the cells, it will

help in the distribution of hormones and

regulatory substances, it will maintain

homeostasis, and it will transport cells and

humoral agents of our

immune system. How is blood composed? It will

be composed of 45%

cells and 55% plasma. The

cells that make up

blood will be a red series, which

we know as red blood cells, which will

be formed by erythrocytes, a

white series, which will be our

white blood cells, and finally, we will

have platelets. As for the

plasma, it will be made up of

91-92% water, 7-8%

proteins, and 1% electrolytes. 1 to 2%

per solute. So the component that

makes up the largest amount of plasma will

be water. We will also have certain

proteins, for example,

albumin, globulins, and

fibrinogen. Let's talk about hematocrit.

Hematocrit is a test that

will help us measure the number of

erythrocytes in our

blood. We will put a

blood sample in a microhematocrit tube and

take it to a centrifuge. This

centrifuge will spin

this tube thousands of times per minute,

which will help separate the

liquid and solid parts. The

liquid part, which we will see at the

top, will be the

plasma, and the solid part, which will be

at the bottom, will correspond

to the number of erythrocytes.

So, hematocrit allows us

to measure the number of erythrocytes

a person has. Normal values

worldwide are 35

to 45% for women and 39 to

50% for men. However, these values ​​will vary.

Modifications In those patients

who live in high-altitude regions

This is because at high altitudes there is

a lack of oxygen and the body, to

compensate for this lack of oxygen, begins to

increase its population of erythrocytes, which is why

at high altitudes women

normally have a hematocrit of

42 to 50% and men of 47 to 60%.

Here we have a table from the

histology book by Paula Ros showing the

cells that make up blood,

the formed elements of blood.

The normal number of erythrocytes

in men is 4.7 to 5.7 million

cells, and for women, 3.9 to 5

million cells. As for the

white blood cell series, which are leukocytes, the

normal number for both men and women is

3,500 to 10,500 cells per

liter. Regarding platelets, the

normal amount is 150,000

to

450,000 cells per liter. Remember that

the number of erythrocytes will change

in patients who live at

high altitudes because the

lack of oxygen causes their

erythrocyte population to increase. Therefore, at high

altitudes, the normal

erythrocyte count for men

is 5.4 to 5.6 million cells per

liter, and for women, 4.7 to 4.9

million cells per liter. Let's talk

a little bit about the proteins that

make up plasma. Remember that

these represent approximately 7%,

and the main ones are albumin,

globulins, and fibrinogen.

Albumin is the main

protein component of plasma; it is

synthesized in the liver. These proteins

exert oncotic pressure and

also act as

transport proteins, helping to

transport certain drugs.

Albumins are proteins that, wherever they are found, whether

in tissues

or blood vessels, will

draw water along with them. That's why it's

important for these albumins to be

present in the blood

vessels because they

prevent the fluid

flowing within our

blood vessels from leaking into our

tissues. In a pathological case, when there is

a loss of albumin from our

blood vessels and we have a greater

amount in our tissues,

this albumin will also leak into our

tissues. This results in

edema, which is the accumulation of

fluid in the interstitial space. The

level of

our tissues is affected

because when the amount of albumin

in the tissues increases, it draws water away

from our blood vessels, causing

the affected tissue to become waterlogged.

Normal albumin levels range

from 3.4 to 5.4 g/L. Another

important protein in

blood tissue is globulins. We

have two types: immunoglobulins, which are

antibodies, and non-immune globulins,

which are transport proteins.

We also have fibrinogen, which is

synthesized in the liver and

participates in coagulation.

Thanks to thrombin, fibrinogen is

transformed into fibrin, and fibrin acts

like glue, binding

cells—

erythrocytes and platelets—to form

a clot and subsequently a scab.

Let's talk about the difference between serum and

plasma. It's important to emphasize that when

we take a blood sample

without the use of an anticoagulant,

for example, through

venipuncture, serum is serum, while plasma is plasma. This will

be the blood sample that we

will take using an

anticoagulant; an example of this is

citrate and heparin. The plasma

will also contain fibrinogen. Now let's talk about

the main cells that make up

our blood tissue, which are

the erythrocytes.

Erythrocytes are anucleate cells; they do

not have a nucleus, nor do they

have organelles. Their main function is to

transport oxygen and eliminate

carbon dioxide. They

live for approximately 120 days and have a

surface area of ​​140 microns squared, a

diameter of 7.8 microns, a thickness

of 2.6 microns at the periphery, and 0.8 microns at the

center.

This cell has

the shape of a biconcave disc

with a depression in the

center. Now, speaking of the

plasma membrane of this cell, it is

important to remember certain

proteins. The plasma membrane of this

cell, like any other

plasma membrane, is a bilayer. The phospholipid layer

contains

transmembrane proteins that span

the entire plasma membrane. We also

have peripheral proteins. The

important transmembrane proteins to

remember are glycophorin

C and Band 3 proteins. Other

peripheral proteins to consider

include

alpha and beta spectrin, the

Band 4.1 protein complex, and the ankyrin protein complex.

While erythrocytes

lack organelles and a nucleus, they do

have an important element inside:

hemoglobin. This

protein helps

transport oxygen and

carbon dioxide. Without hemoglobin,

the erythrocyte cannot perform this

function. Remember that a protein is a

chain of 10 to 12 amino acids.

When approximately 5 to

10 amino acids are joined, it forms a polypeptide. The

union of five amino acids simply

forms a peptide. So, why

is it important to remember these

concepts? Because this protein,

called hemoglobin, is made up of

four polypeptide chains.

These polypeptides that will

form this protein will be the

globins, and we will have four types of

globins: alpha globin, beta globin,

delta globin, and gamma globin.

So, hemoglobin will be

formed by four globin chains.

What will these four globin chains be

that will form the

hemoglobin protein? It will be formed by

two alpha chains and two beta chains.

In addition to these

four polypeptide chains,

four other proteins will be added to them,

which will be known as the heme group.

The heme group will be the

porphyrin protein plus an iron molecule in

its center, and it is to this

iron molecule that the

oxygen or carbon dioxide molecules will bind. So,

we can see here that the

heme group will be formed by a protein

known as porphyrin, and in its

center, we will have an

iron molecule. That is the heme group that will

bind to the four globin chains of

each erythrocyte. It can transport

four molecules of oxygen or four

molecules of carbon dioxide. Why is this?

Because we only have four

iron ion molecules to which

oxygen and carbon dioxide can bind, and this is

how the hemoglobin in erythrocytes is formed,

allowing it to fulfill this vital function

for our tissues. During

gestation, different

types of hemoglobin are synthesized:

hemoglobin A, hemoglobin A

sub2, and hemoglobin F or

fetal hemoglobin. Hemoglobin A is the one

found in the greatest quantity in an

adult, constituting approximately 96%

of the hemoglobin present in our

body. Hemoglobin A sub2 is

found

in approximately 3%. On the other hand,

hemoglobin F or fetal hemoglobin

constitutes only 1% of the

hemoglobin present in our body.

However, during fetal life, there will be a

greater quantity of this type of

hemoglobin because it is the

main hemoglobin of the fetus. How will it be?

Hemoglobin A is composed of two

alpha chains and two beta chains. Hemoglobin A2

is composed of two

alpha chains and two delta chains, and

fetal hemoglobin is composed

of two alpha chains and two gamma chains.

Now let's talk about the [ __ ] blood

group system. We have four

blood groups: group A,

group B, and group AB.

Whether a person has

type A, type

B, or type AB blood depends on the

presence of certain proteins

found on the

plasma membrane of the erythrocyte. These

proteins are the antigens. As I

mentioned, there are certain

proteins on the plasma membrane of the

erythrocyte. It is to these peripheral proteins that

other proteins, known

as antigens, bind. This is what gives

an erythrocyte its characteristic of being

group A, group B, or group AB. Where do

these antigens bind? They

bind to glycophorins. All

human beings have enzymes that

synthesize the antigen, meaning

that all They will derive from blood

type O. Here we are seeing the structure

of the antigen O, which is the base antigen.

However, for a person to be

group A or group B, these people will

have certain enzymes that will change

the antigen or add a molecule,

giving it the characteristic of

becoming group A or group B. For

a person to have group A blood, their

base antigen O will undergo a

modification thanks to the enzyme alpha-

glucosyltransferase. People with

type A blood have this enzyme, alpha-

glucosyltransferase, which will

add a molecule of n-ethylgalactosamine to this base antigen. The

addition of n-

ethylgalactosamine to the antigen O

converts the antigen O into antigen A, and that is

how we get type A blood.

People with type B blood will

have the enzyme galactose transferase,

which will add a

molecule of galactose to the base antigen O. So, the

addition of galactose to the antigen O

converts the blood to type B. And

people with type AB blood will have

both enzymes: alpha-

glucosyltransferase and galactose.

Therefore, transferase will have

both types of proteins on the surface

of the erythrocyte's plasma membrane; they will

have type A antigens and

type B antigens. The relevance

of knowing the blood groups is

that they will produce certain

antibodies. People with

type A blood will create

anti-B antibodies. Why? Because they will only

recognize other erythrocytes that

also have the type A antigen. When

an erythrocyte with type

B antigens comes into contact with a

type A erythrocyte, the latter will secrete

anti-B antibodies because it does not recognize the proteins

on the plasma membrane of

this erythrocyte. On the other hand, those with

type B blood will create

anti-A antibodies for precisely the same reason:

since the antigens or proteins

on the plasma membrane of

type B erythrocytes have galactose, they will not

recognize other erythrocytes that do not

have this protein. People

with type AB blood will not have

antibodies because they have both

proteins on their surface. Having

both proteins allows them to recognize

type B or type A cells because they have the

same proteins. Not having antibodies

and being able to receive blood types A, B, and O

because they don't generate

antibodies against type O either, they are

known as universal recipients.

People with type A blood

can receive blood of any type. Type

O will generate anti-

A and anti-B antibodies because type A and

type B erythrocytes have proteins foreign to

type O, they will generate antibodies that

destroy these cells because they won't

recognize them. However, a

characteristic of type O is that they will

be universal donors. Why? Because

types A, B, and

AB do not generate antibodies against

type O, therefore type O can

donate to any group. Okay, why don't

any generate antibodies against type O?

Because they all have the

base of this protein. Let's talk about the

Rh blood group system. Besides

having a blood type, whether type O, A, B,

or AB, we also have an

Rh system. What does the Rh system mean?

Like antigens, these are simply

proteins on the

plasma membrane of the erythrocyte. These

proteins, known as

Rh antigens, will bind to

transmembrane proteins that... The

Rh30 polypeptide and the

Rh50 glycoprotein are Rh antigens. Rh derives from *Resus*, a monkey

in which

these antigens were first found. There are more than 47-49

types of Rh antigens; however, the

most important are the D antigen, the

C antigen, and the E antigen.

The

D antigen is the most abundant. These proteins,

found on the plasma membrane of

erythrocytes, determine whether a

person is Rh positive or Rh negative. A

person with the Rh antigen or protein

on their erythrocytes is Rh

positive, and a person without this

protein on their plasma membrane is

Rh negative. When an

Rh positive person comes into contact with an

Rh negative person, they generate antibodies that

destroy the Rh negative erythrocyte

because it is different and

foreign to the Rh negative erythrocyte.

This is what

happens when an Rh negative mother

has an Rh positive baby in her womb; the

mother's blood comes into contact with the baby's blood. The

mother's blood recognizes the

baby's red blood cells as

foreign simply because they have the

Rh protein. Since these red

blood cells are unfamiliar to the mother, she begins to produce

antibodies against her

own child's blood.

The baby's red blood cells begin to be destroyed. In a

desperate and compensatory response, the baby

begins to produce more red blood cells, causing

its organs to swell. This

results in kernicterus, a

pathology that affects the

central nervous system and is quite dangerous.

This clinical condition, where the mother

begins to destroy her

own child's blood, is known as

erythroblastosis fetalis. Now let's

talk about the cells that

make up

the white blood cells,

or leukocytes. There are two types

of leukocytes:

granulocytes and

agranulocytes. Granulocytes are

cells that possess

granules, while agranulocytes are cells

that do not possess granules, or may

contain very small granules in

small quantities. Among the granulocytes,

we have neutrophils,

basophils, and

echinoderms. Among the agranulocytes, we

have lymphocytes and monocytes.

Let's talk first about neutrophils.

Neutrophils are the

most abundant leukocytes

in the blood. They measure approximately

10 to 12 microns. Their nucleus has

multiple lobes

connected by thin cords, which are

also nuclear material. So,

neutrophils have many lobes connected

by thin cords, which are also

nuclear material. They constitute

approximately 60 to 70% of

total white blood cells and have a

lifespan of approximately one week.

How many lobes can a

neutrophil have? Two to four lobes.

Precisely because of the number of lobes

this cell has, it is also

called a polymorphonuclear leukocyte.

Neutrophils in women have

a tail on one of their

lobes, known as a...

The Barr body is

only found in cells that have the

X chromosome, specifically in

female cells. Here we can see in the

histological slide the neutrophil or polymorphonuclear leukocyte,

which will have a nucleus

with multiple lobes joined by

thin cords. And women will have

this little tail on one of their

lobes, known as the

Barr body. Neutrophils will

have three types of granules:

primary or azurophilic granules.

Azurophils are simply

lysosomes. Okay, the primary or

azurophilic granules are simply

lysosomes. We will have

secondary or specific granules, and

tertiary granules. These are mobile cells that

leave the circulation and

migrate to the connective tissue. They are one of

the main defense cells of

our body. Let's talk now about

eosinophils. Eosinophils are

the leukocytes that mainly

act against parasites. They measure

approximately the same as the...

Neutrophils will have two lobes in their

nucleus; they will be bilobed. They will

constitute 4% of total white blood cells

and will have a lifespan of

approximately 3 to 4 days. Like

neutrophils, they will have

azurophilic granules, which are lysosomes, and

specific granules. What will

these specific granules be?

We will have the major basic protein, the

cyanophil cationic protein,

the eosinophil peroxidase, and

finally, the

eosinophil-derived neurotoxin. These

first three granules will be responsible

for exerting a cytotoxic effect on

protists and certain parasites, and the

eosinophil-derived neurotoxin is what

will cause dysfunction of

the parasites' nervous system.

We can see this here in a slide

where we can see an eosinophil. Here

we have the cell, and

we can observe that its nucleus will

have two lobes. Ova, right? It looks like a U, a

horseshoe, it can also look like a little

kidney. So, in that way you

'll recognize the ecii, speaking of

basophils, which will also be

cells that will have granules. They will

measure approximately 10 microns, they will

have abundant and large granules, they will

represent 0.5 percent of the

total white blood cells, and they will live

approximately two to three days. They will also

have specific granules and

azurophilic granules. How are we going to

recognize a basophil on the histological slide?

We're going to observe a cell

like you're seeing here in this photograph

or in this one, where we're going to see the

cell with a central nucleus, but

before seeing the nucleus,

the number of granules will be more visible. As

you can see, it looks like multiple dots,

multiple specks that we're going to find

on this cell. Those are the granules of

the basophils. So, whenever

we see this cell with many granules,

as we're also seeing on this

histological slide, we're talking about a

Basophils. Now we're going to talk about

those cells that don't have

granules, the

agranulocytes. Let's talk first about

lymphocytes. Lymphocytes measure

approximately 6 to 15 microns, have

a spherical nucleus with a slight

indentation, constitute

approximately 30% of

total white blood cells, and have a lifespan

of approximately a few months to

several years. We have three types of

lymphocytes: T lymphocytes, B lymphocytes, and

natural killer cells. T lymphocytes

differentiate in the thymus and

participate in the destruction of

antigens that enter our

body. Let's talk first about

CD8 cytotoxic lymphocytes. These

lymphocytes are responsible for

cell-mediated immunity. They are

cells that destroy other

cells that have been modified by

viruses or cancer cells.

CD4 helper lymphocytes are those

responsible for

antibody-mediated immunity. These lymphocytes

will act with the major

histocompatibility complex. Regulatory T lymphocytes

will prevent

excessive activity of the immune system,

meaning they will control other

cell types. Gamma and

Delta lymphocytes will act against

infectious agents and also against

tumor cells. B lymphocytes are those

that will differentiate in the blood vessels and

bone marrow and will participate in

antibody production; they will express

immunoglobulin M and also

immunoglobulin D. Natural

killer lymphocytes are... These are going to be the

natural killers of our body. How are we going to

recognize a lymphocyte in a

histological slide? We'll see that we'll

have a cell where the

plasma membrane and cytoplasm will be

scarce, almost imperceptible. Why? Because

the nucleus will be so large that it will

cover almost the entire cell, as we

're seeing here in this image. It will

have a very large nucleus that may

have a small indentation. So, a

very large nucleus where we can barely

see the periphery of the cell is a

lymphocyte. Finally, we're going to talk about

monocytes, which are also a

type of granulocyte. They will

measure approximately 18 microns. They will

have a spherical nucleus with a

pronounced indentation. They will constitute

approximately 3 to 8% of the

total white blood cells. They will circulate

in the blood for approximately 3 days.

Monocytes transform into macrophages

when they leave the

bloodstream. When they are in the

bloodstream, they are known as monocytes.

When they leave the blood vessels and

migrate to the tissues, they are known as macrophages.

Macrophages, depending on the tissue they are in,

will

receive different names. Macrophages

found in bone tissue

are known as osteoclasts. When they are

in the tissue of the

respiratory system, they are known

as alveolar macrophages or

dust cells. Kuffer cells are

macrophages

found in the liver. How will we

recognize a monocyte on the histological slide? It

will be a cell where

we can barely see the

cytoplasm and the plasma membrane.

Obviously, here the nucleus is

displaced to one side, but like

the previous cells, it will have

a fairly large nucleus, but

its indentation will be noticeable. As

you can see here, it looks like a heart; it will have

a pronounced indentation, a

large nucleus, but with a

very pronounced indentation. When this monocyte migrates

to the tissues and transforms into a

macrophage, we will see the macrophage

in the same way, a

cell that will have a The central nucleus is

rounded, but it won't be

very large

or pronounced; it will be a medium-sized central nucleus

surrounded by

multiple vacuoles in the cell's cytoplasm. This is what

a macrophage looks like. Remember, a

monocyte when it's in the

bloodstream, a macrophage when it molts into

certain tissues. Finally, we'll

talk about platelets or thrombocytes,

which are cells that measure two to

three microns. They are anucleate and

derive from megakaryocytes. In

fact, thrombocytes are fragments

of a megakaryocyte. They have a lifespan of

approximately 10 days. What are

the functions of platelets?

Platelets

monitor blood vessels, looking for

leaks or ruptures; form

blood clots to plug

any

damaged blood vessels; and repair

damaged tissues beyond the

blood vessels. Thrombocytes have

four zones. These cells have

a peripheral zone located on the

periphery of... These cells have a

structural zone, an organelle zone, and a

membranous zone. Finally, we can

observe here the

normal values ​​for both the red blood cell series and the

white blood cell series, each of the leukocytes, and the

number of platelets. This is a chart

from Rose Paulina's book. Lastly,

we have here a histological slide

where we can see different types of

leukocytes to review. Here

we can see a monocyte because we are

seeing a cell with a fairly

large nucleus displaced towards the periphery

with a prominent indentation, making

its nucleus resemble a heart. Here

we have a neutrophil because we

have a cell that will have

multiple lobes that will be joined

by thin cords, which

will also be nuclear material. We

also have a eosinophil where we

can observe here that it will have two

lobes; it will be bilobed, and

a

horseshoe shape will appear. Here we have a lymphocyte,

since we will also have a

fairly large central nucleus, but there will not

be a pronounced indentation in the

deepest part. In this slide, we can

observe the erythrocytes, which are

clearly visible and distinguishable.

This is how you will

recognize the different cells of the

blood tissue. We have reached the end

of the video. If you liked it, please leave

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your friends. I tried to summarize this topic as much as

possible, so today I'm not going to

talk about Homo esthesia because I think it

deserves a separate video. Don't forget to

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