Blood & Hematopoiesis在线视频

Hello, everyone,

I am Xin Zhang

from the First Affiliated Hospital

of Shantou University Medical College.

Welcome to the online

clinical histology courses.

In this session,

we will discuss blood and hematopoiesis.

Blood is the only tissue

that flows throughout our body.

This red liquid carries oxygen

and nutrients to all parts of the body

and brings waste products

back to our lungs,

kidneys and liver for disposal.

It is also an essential part

of our immune system,

crucial to fluid and temperature balance,

a hydraulic fluid for certain functions

and a special highway

for hormonal messages.

As such an important tissue,

we call blood is a river of life!

In this session,

we will first go through

the general characteristics of blood

include physical properties,

components, and functions of blood.

Then we will discuss Hematopoiesis

and hematopoietic system

and finally review two cases

to understand the relationship

between hematopoiesis defects

and blood disorders.

Blood is a specialized connective tissue

and is the only liquid tissue in our body.

Color range is between

Oxygen-rich scarlet red

and Oxygen-poor dark red.

Total blood volume

is equal to 7~8% body weight,

around 4～6 liters.

The pH value is between 7.35 and 7.45.

The temperature is around 38℃

and other parameters are listed here.

From our fundamental studies,

we knew that Human blood

is composed of around 55% plasma

and 45% cellular components.

Plasma is Straw-colored,

sticky fluid.

More than 90% is water

and solutes include proteins,

nutrients, Hormones, Electrolytes,

Metabolites and so on.

The cellular component

consists of three major cell types:

red blood cells (RBCs),

white blood cells (WBCs),

and platelets.

Among them,

only WBCs are complete cells.

RBCs have no nuclei and organelles,

Platelets are cell fragments

Most formed elements survive

in the bloodstream

for only a few days.

Most blood cells

are terminally mature cells,

originate from bone marrow

and do not divide

Now we can give a description to Blood

according to it's composition.

Blood is a suspension of

non-dividing end-stage cells

of three types namely,

red cells (erythrocytes),

White cells (leucocytes)

and platelets (thrombocytes).

The suspending fluid is the Plasma.

Then let's see the functions of blood.

As we mentioned before,

blood is so important

because has a number of functions

that are central to survival.

We classified it into

three major functions:

first,

transportation,

blood carries oxygen

and essential nutrients

to cells and tissues,

removes waste materials,

such as carbon dioxide,

urea, and lactic acid.

Blood also transports hormones

from one part of the body to another,

transmitting messages,

and completing important processes.

Another important function of the blood

is its protective action

against disease.

As part of immune system,

white blood cells

defend the body against infections,

foreign materials, and abnormal cells.

The platelets in blood

enable the clotting,

or coagulation, of blood

to minimize blood loss

when a blood vessel is damaged.

The third important function

is regulation,

blood can regulate pH level,

body temperature

and electrolyte composition

of the interstitial fluids

to maintain homeostasis.

Blood is one of the most regenerative

and plastic tissues,

Blood cells have a limited life span,

Thus,

these blood cells

need to be renewed continuously.

That is why hematopoiesis

is so important.

Hematopoiesis

is the process of formation

of mature blood cellular components

from immature precursor cells,

which occurs

during embryonic development

and throughout adulthood to produce

and replenish the blood system.

Human hematopoiesis

is a very complex process.

Blood cells are one of the first

differentiated cell lineages

generated in the embryo.

It initiated in the yolk sac

during the third

week of development,

which is very beginning of embryogenesis.

Because the embryo requires red cells

for the transport of maternal oxygen

to support its growth and development.

Which means

the hematopoiesis develops

together with embryo,

span before and after birth stages,

and functions throughout the whole life.

Thus,

it undergoes sequential,

spatial and temporal changes

during development.

To discuss the ontogeny of hematopoiesis,

we can divide the process into two parts,

Prenatal and postnatal stages

which means before and after birth.

Hematopoietic regulation

in the human fetus

differs greatly from that in an adult.

In an adult,

homeostatic maintenance

is a prime function

of hematopoietic regulation,

whereas in the embryo and fetus,

constant changes

characterize all phases

of hematopoiesis.

Knowledge

of developmental hematopoietic regulation

helps clinicians

to interpret postnatal hematologic data.

This picture shows us the overview of

hematopoietic site transition

during development,

we can see it changes from yolk sac

to placenta

which are the extra-embryonic site,

then transit to intra-embryonic sites AGM,

fetal liver and finally to the bone marrow.

This slide shows us

the hematopoietic sites

change and contributions

to hematopoiesis during development

beforeand after birth.

Here we listed the hematopoietic sites

and time

during the whole development process.

Then next,

let's look at

the development of hematopoietic cells.

Hematopoietic stem cells

are the seeds for all the lineages

of blood cells,

originate from yolk sac

and finally reside in red bone marrow,

constitutes about

0.5% of total bone marrow cells

similar to small LC in shape,

they have two properties:

multipotency and self-renewal.

Means they can generate

all linages of blood cells

and can copy themselves

to maintain the pool of HSCs.

This picture shows us the whole process

of hematopoietic stem cells

to generate

the all type of mature blood cells,

from long-term HSCs

to mobilized to short-term HSCs

then differentiate to

common lymphoid progenitors

and common myeloid progenitors,

then to Erythrocytic progenitor,

Megakaryocytic progenitor,

Granulocytic progenitor

and Lymphocytic progenitor,

and finally all type of mature blood cells

Other than haematopoietic stem cells,

the hematopoietic microenvironment,

termed stem cell niche,

ensures haematopoietic homeostasis

by controlling the proliferation,

self-renewal, differentiation

and migration of HSCs

and progenitor cells at steady state

and in response to emergencies and injury.

We will take bone marrow,

the major hematopoietic site of adult

as an example

to discuss the organization

of hematopoietic microenvironment.

The bone marrow is organized

as hematopoietic islets,

composed of hematopoietic cells,

stromal cells,

and the extracellular matrix.

Stromal cells include Reticular cells,

Fibroblasts, Macrophages,

Endothelial cells and Adipocytes.

They support hematopoietic stem cells

to control the hematopoiesis.

Stromal cells express

and secrete

extracellular matrix glycoproteins,

and adhesion molecules

to allow the fixation

of hematopoietic cells

within the bone marrow microenvironment,

control the migration

of hematopoietic cells

within and out of the bone marrow.

They also produce haemopoeitic

growth factors and cytokines,

which are glycoprotein hormones

that regulate the proliferation

and differentiation

of haemopoietic progenitor cells

and the function of mature blood cells.

Here in this slide,

we listed

all the hematopoietic growth factors

and cytokines

required in the hematopoiesis.

Now we have gone through

the process of hematopoiesis,

many molecules and cells

are involved in this complicated process.

Any defects or abnormalities

may cause quality

and quantity change of blood cells

and lead to disorders.

And so far,

the etiology of most of these disorders

are still not known.

Now,

we review two cases

to understand the relationship

between hematopoiesis

and blood disorders.

Case#1

A 37 year male,

a primary school teacher,

came to visit the office

and complained of weakness and fatigue.

He is pale and gave

a history of petechiae

and hematuria.

CBC test showed that

all types of blood cells

are lower than normal

but blood smear showed normocytic RBCs.

Then Reticulocyte Count

showed less than 1%

and Bone Marrow biopsy

showed more than 70%

are yellow marrow.

And the diagnosis is aplastic anemia.

The second case is a 39 year old female,

who has the history of

fibrocystic breast disease.

Seen for routine work-up

prior to breast biopsy.

Physical Examination found

Moderate splenomegaly.

CBC test showed high number of WBC

Bone marrow biopsy

showed Markedly hypercellular

with increased megakaryocytes

and Cytogenetics test

found translocation

between #9 and #22 chromosomes

which is known as

Philadelphia chromosome

and 90%

of Chronic Myeloid leukemic patients

carry this mutation.

This mutation will cause uncontrolled

myeloid cell proliferation.

And patients was diagnosed with CML.

Now let's summarize this session,

we discussed

the general characteristics of blood

include blood components and Functions.

Then we discussed Hematopoiesis

During development,

which occurs in spatially

and temporally distinct sites.

We also discussed

interaction of Hematopoietic stem cells

with microenvironment

and generate all lineages

of mature blood cells.

Finally,

we review two cases to understand

the relationship between hematopoiesis

and blood disorders.

That's all for this session,

see you next time.