The BloodThe Blood

Discuss the composition of blood including the functions of the various components

Explain the anatomy and functions of the red blood cells, including a description of blood typing

Discuss the types of white blood cells found in the blood and give the functions of each

Give a brief accounting of the platelets

Review hemopoiesis, including RBC and leukocyte formation

what’s in

red blood cells white blood cells

platelets

plasma

carbon dioxide

digested food

waste (urea)

hormones

oxygen

The Blood

plasma

red blood cell white blood cell

platelets

Functions of Blood

Distribution - nutrients, wastes, hormones, gases, etc.

Self-sealing – hemostasis

Disease/ infection fighting

Blood = connective tissue

extracellularmatrix:Plasma

specialized cells:

(= Formed elements)

RBCs

WBCs

Plateletscolor ?volume ?

Plasma CompositionPlasma Composition

Water 92%

Plasma proteins 7% Other solutes

1%

Transports organic and inorganic molecules, formed elements, and heat

Plasma ProteinsPlasma Proteins

There are some proteins that are essential which swims in the blood:

example

Fibrinogen (4%) Essential component of clotting system (conversion to insoluble fibrin)

Plasma

A straw-coloured liquid that carries the cells and the platelets which help blood clot.

• carbon dioxide

• glucose

• amino acids

• proteins

• minerals

• vitamins

• hormones

• waste materials like urea.

It also contains useful things like;

BLOOD CELLS BLOOD CELLS

Red and White Blood Cells

Platelets

Platelets WBCs

RBCs

.1%

99.9%

..Why whitewhite blood cells

RBCs = Erythrocytes

Measured by hematocrit or PCV

Most abundant blood cell: 1000 RBCs/1 WBC

Contain hemoglobin, carry O2

Very regular shape - biconcave discs

NO Nucleus: Lifespan ~ 120 days replacement rate ~ 3 mio RBCs / sec

Red Blood Cells

contain haemoglobin, a molecule specially designed to hold oxygen and carry it to cells that need it.

can change shape to an amazing extent, without breaking, as it squeezes single file through the capillaries.

a biconcave disc that is round and flat without a nucleus

Structure of Hemoglobin (Hb)Structure of Hemoglobin (Hb)

Fe ion in heme group reversibly binds O2

How many oxygen

molecules can 1

Hb molecule

carry?

Acclimatization• People living at high altitudes usually have

large number of RBCs.• Compensate for low oxygen concentration at

high altitudes

Clinical Brief

Anemia:Reduced oxygen carrying ability of blood.

Causes

One cause of anemia is iron deficiency anemia as iron is essential to make hemoglobin which is needed to transport oxygen

WBCs = LeukocytesWBCs = Leukocytes

Quantity and type determined by differential WBC count

Circulating WBCs are only a small fraction of total WBCs. Most are located in BETWEEN CELLS

There are many types of WBC

White Blood Cells

there are many different types and all contain a big nucleus.

the two main ones are the lymphocytes and the PHAGOCYTES .

some lymphocytes fight disease by making antibodies to destroy invaders by dissolving them.

other lymphocytes make antitoxins to break down poisons.

PHOGOCYTES engulf and digest micro-organisms .

Phagocytic cell

Other phagocytes Other phagocytes

LymphocytesLymphocytes

~ 20% - 30% of circulating WBCs Relatively small (slightly larger than RBCs) Large round nucleus

Antibodies Pathogens contain antigens (chemicals) on

their sufaces These antigens stimulate lymphocytes to

produce specific antibodies Antibodies can:

» kill bacteria » neutralize toxins» Cause bacteria to clump together (agglutination)

Specificity

• Antibodies specific for bacteria A (eg. measles) will not attack bacteria B (eg. chicken pox)

Immunity

After an illness (e.g. chicken pox), antibodies against chicken pox persist and remain in the blood

Thus, the person is said to be immune to chickenpox

Memory cells

Special type of lymphocytes (WBCs) Formed after an infection / illness Remain in the blood stream for life Able to be activated very quickly if person

encounters the same antigen again Person is said to be immune to that

infection/ illness

Vaccines

Dead or harmless form of the pathogen (BCG vaccine against tuberculosis)

Toxoid – the inactivated toxin from the pathogen (tetanus vaccines)

Organ transplant and tissue rejection

Replacement of diseased organ with healthy one

BUT new organ must not be rejected by body

(Body detects new organ as foreign particle Defence system kicks in)

Prevention of tissue rejection

Donor and recipient must be close relatives Suppress immune system

» Use of drugs called immuno-supressive drugs» X-ray of bone marrow to reduce blood production

Platelets = ThrombocytesPlatelets = Thrombocytes

Cell fragments of Megakaryocytes

(~ 4,000 thrombocytes per Megakaryocyte)

~ 160 m

Lifespan ~ 12 days

involved in blood clotting

Platelets

Platelets are bits of cell broken off larger cells.

Platelets produce tiny fibrinogen fibres to form a net. This net traps other blood cells to form a blood clot.

Blood clotting Clotting of blood seals the wound Prevents excessive blood loss Prevents foreign particles from entering blood

Blood ClottingInjury/ Ruptured blood vessel

Thrombokinase(enzyme)

Prothrombin(inactive)

Thrombin(active)

Fibrinogen(soluble)

Fibrin(insoluble)

Blood Clot

Activates platelets to release

catalyses

(Ca2+, Vit K)

catalyses

Forms meshwork

Why doesn’t blood clot in undamaged blood vessels?

Anticlotting substance called heparin Produced in liver Thrombokinase able to neutralize the action

of heparin

Abnormal Blood Cell Counts

Leukopenia < 2,500/ L (normal 6000 – 9000)

Leukocytosis > 30,000/ L

Thrombocytopenia: < 80,000/ L (normal ~ 350,000)

Thrombocytosis: > 1,000,000/ L

Also

Lymphopenia vs. _____________

_________vs. Neutrophilia

Hemopoiesis = Blood Cell FormationHemopoiesis = Blood Cell Formation

Hemocytoblasts: One type of stem cell for all blood cells

In red bone marrowIn red bone marrow

. . . then differentiation into 4 types of progenitor stem cells:

Erythroblast

Myeloblast

Monoblast

Lymphoblast

Fig 20.8