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Learning objectives
The student should be capable to:
1. Know about composition of blood.
2. Describe the functions of blood.
3. Be familiar with plasma and its composition.
4. Know about RBCs: their structure, function and count.
5. Know about WBCs: their types, structure, function and count.
6. Know about Platelets: their structure, function and count.
Lecture outline
Composition of blood And Cellular elements
Blood is slightly denser and approximately 3-4 times more viscous
than water, blood consists of cells which are suspended in a liquid.
Blood consist of cellular material.
 99% red blood cells, with

white blood cells and

platelets making up the remainder.

Water, amino acids, proteins, carbohydrates, lipids, hormones,
vitamins, electrolytes, dissolved gases, and cellular wastes.
By volume.
Plasma is about 92% water, with plasma proteins as the most
abundant solutes.
The main plasma protein groups are
 albumins,
 globulins, and

fibrinogens.
The primary blood gases are
 oxygen,
 carbon dioxide, and

nitrogen.
Blood functions include:
 Transport of cells and compounds.
 Regulate pH and electrolytes of interstitial fluids.
 Limit blood loss through damaged vessels.
 Defend against pathogens and toxins.
 Absorb and distribute heat as a part of temperature
regulation.
The Composition of Whole Blood.
 Separated blood:
 Centrifuged blood:
 Plasma 55%
 Buffy coat
 WBCs <1%
 Erythrocytes
 Hematocrit, 45%.
 Plasma.
 90% water
 10% solutes
o Ions, e.g., Na+, Cl-, Ca++
o Nutrients, e.g., simple sugars, amino acids, lipids
o Wastes, e.g., urea, ammonia, CO2
o Miscellaneous: O2, hormones, vitamins, plasma proteins.
 Plasma proteins.
 Albumin
o Helps control osmotic pressure
o Helps control diffusion of water (recall edema)
 Globulin
o Includes antibodies (Abs)
o Transport proteins (lipids, iron, copper, etc.)
 Fibrinogen
o Involved in clotting
 Serum: Blood plasma from which the protein fibrinogen, which
causes clotting of the blood, has been removed.
The Composition of Whole Blood:
 Formed elements.
 RBCs (erythrocytes)
 WBCs (leukocytes)
o Granulocytes
o Agranulocytes
 Blood smear
o Light microscope
o Stained
RBCs:
 In embryos they are produced in their GALL BLADDER, then in
their LIVER, and starting from the second half of their lives – in
their BONE MARROW.
 They are oval single-nucleus cells.
 Red blood cells (RBCs) are the most numerous cells in the body.
They circulate for about four months before being recycled;
millions are produced each second. The hemoglobin inside
transports oxygen from the lungs to peripheral tissues and
carbon dioxide from the tissues to the lungs.
Properties of RBCs

Transport oxygen and carbon dioxide in blood stream

Have large surface to volume ratio
o Speeds up gas loading/unloading

Lack most organelles
o Makes more room for hemoglobin

Degenerate after about 120 days.
Leukocytes (WBCs).
produced in RED BONE MARROW, some of them (lymphocytes) in
thymus, spleen and lymph nodes. They are the most diverse cells,
morphologically and functionally.
In the human body: 4-10 thousands in 1 ml of blood.

Part of defense system
o Protect against bacteria, viruses, parasites

Attracted to sites of infection

Diapedesis: leave capillary by squeezing between endothelial
cells.

Amoeboid movement
o Travel toward infection

Exhibit chemotaxis — Move toward specific chemicals
released by bacteria or injured cells.
 Granulocytes
WBCs with granules in cytoplasm
o Visible with LM

Neutrophils

Eosinophils

Basophils

Phagocytic

Larger than RBCs

Lobed nuclei.
 Neutrophils.
60% of WBCs

Lobed nucleus

Light staining granules

Digestive enzymes
Function

Phagocytize & destroy bacteria

First cells to respond to infection

Secrete antibacterial chemicals

Phagocytize & digest bacteria.
 Eosinophils.

1-4% of WBCs

Lobed nucleus

Eosin-staining granules

Phagocytize allergen-Ab complexes

Secrete antihistamine

Attack parasites.
 Basophils.

0.5% of WBCs

Lobed nucleus

Large granules stained dark purple
Granules
o Histamine – creates inflammation in allergic reaction.
 Lymphocytes.

Agranulocyte

20-45% of WBCs

Spherical, dark-staining nucleus

Thin rim of blue staining cytoplasm

Each lymphocyte recognizes and acts against a specific
antigen.
 T lymphocytes can attack foreign cells directly.
 B lymphocytes transform into plasma cells and secrete
antibodies.
 Monocytes.

Agranulocyte

4-8% of WBCs

Horseshoe shaped nucleus

Grey-blue stained cytoplasm

Become wandering macrophages after diapedesis.
 Platelets.
Fragments of megakaryocytes in bone marrow
Attracted to hemorrhage
o Plugs leaks
o Promotes constriction of blood vessel
o Triggers inflammation
o Initiates clotting reaction.
 Hematopoiesis.

Occurs in red marrow

Red marrow replaced by yellow in limbs between 8-18 yrs

Blood stem cells
o Pleuripotential

Myeloid stem cell

Lymphoid stem cells.
Sickle cell disease :

Genetic condition

1 nucleotide substitution

1 amino acid substitution

Hbs

With low O2 Hbs polymerizes

Creates “sickle” shape

Genetic condition

1 nucleotide substitution

1 amino acid substitution

Hbs

With low O2 Hbs polymerizes

Creates “sickle” shape
Disorders of the Blood


Disorders of leukocytes

Leukemia – a form of cancer

Classified as lymphoblastic or myeloblastic
Disorders of platelets

Thrombocytopenia

Abnormally low concentration of platelets.
The Blood Throughout Life :

First blood cells develop with the earliest blood vessels

Mesenchyme cells cluster into blood islands

Late in the second month


Liver and spleen take over blood formation
Bone marrow becomes major hematopoietic organ at month 7