Blood Physiology

Professor A.M.A Abdel GaderMD, PhD, FRCP (Lond., Edin), FRSH (London)

Professor of Physiology, College of Medicine &

King Khalid University Hospital Riyadh

Lecture # 4 & 5

LeucocytesWhite Blood Cells (WBCs)

Granulocytes, The Monocyte-Macrophage

System

Leucocytes (WBCs)

• General Characteristics & types of WBCs• Genesis (Production) of WBCs• Life Span of WBCs• Defense properties of neutrophils &

macrophages– Chemotaxis– Diapedesis– Amaeboid Motion– Phagocytosis

Blood Film

Hematopoiesis

Leucocytes (WBCs) – cont.

General Characteristics & types of WBCs

• Types of WBC1. Granular (polymorphnuclear):

• Neutrophil 62%.– 10-16um, nucleus 2-5 lobes, purple

cytoplasmic granules

• Eosinophil 2.3%.– 12-18um, 2 lobes nucleus, coarse red

granules

• Basophil .4%.– 10-14um, rarely segmented nucleus,

nucleus hidden by large round bluish granules

Leucocytes (WBCs) – cont.

General Characteristics & types of WBCs

• Types of WBC2. Agranular WBC

– Monocytes 5.3%• 15-20um, kidney shape nucleus

– Lymphocyte 30%• round nucleus

– small (5-8um) – large (9-15um)

Formed Elements of Blood• Red blood cells ( erythrocytes )• White blood cells ( leukocytes )

– granular leukocytes• neutrophils• eosinophils• basophils

– agranular leukocytes• lymphocytes = T cells, B cells, and natural killer

cells• monocytes

• Platelets

Leucocytes (WBCs) – cont.

Genesis (Production) of WBCs

Pluripotential stem cell

Committed Stem cell

RBCs WBCs Platelets

Mylocytic Lymphocytic Linage Linage

Hematopoiesis

Leucocytes (WBCs) – cont.

Genesis (Production) of WBCs- leucopoiesis)

Sites of WBC formation• Granulocytes (neutrophil, basophil,

eosinophil):

– bone marrow

• Agranulocytes – lymphocytes- bone marrow,

thymus, lymphoid tissues– monocytes- bone marrow

Life Span of WBCs

Granulocytes:• 4 to 8 hrs (transit time ) in blood circulation• 4 to 5 hrs in tissues

– In infections life span a few hours

Monocytes :– 10 to 20 hrs in blood circulation– Leave capillaries to tissues, increase in size

to become tissue macrphages which live for months

Life Span of WBCs-cont.

Lymphocytes:

• A few hrs in blood circulation >> tissues >> lymph >>> Blood (Recirculation)

?Life span: weeks to months

Leucocytes (WBCs)

• General Characteristics & types of WBCs• Genesis (Production) of WBCs• Life Span of WBCs• Defense properties of neutrophils &

macrophages– Chemotaxis– Diapedesis– Amaeboid Motion– Phagocytosis

Defense properties of neutrophils & macrophages

• Attack and destroy bacteria, viruses

• Sequence of events:– Chemotaxis– Diapedesis– Amaeboid Motion– Phagocytosis

Netrophils function-cont.

Defense properties of neutrophils & macrophages-cont

Phyagocytosis: Engulfing and killing of bacteria or any

invading organism

Steps: Chemotaxis:

– Bacterial & viral toxins• Products of damaged tissues:

attract neutrophil to accumulate at infected site.

– Opsonization: plasma substances (IgG) attached to the bacteria to make them easy to phagocyte

Diapedesis

Diapedesis

http://www.whfreeman.com/immunology/CH01/diapedesis.htm

Defense properties of neutrophils & macrophages

• Attack and destroy bacteria, viruses

• Sequence of events:– Chemotaxis– Diapedesis– Amaeboid Motion– Phagocytosis

Defense properties of neutrophils & macrophages

• Attack and destroy bacteria, viruses

• Sequence of events:– Chemotaxis– Diapedesis– Amaeboid Motion– Phagocytosis

Phagocytosis- cont.

Phagocytosis is selective:Distinguish self from non-self…... How?

– Normal tissues have smooth surface– Normal tissues have protective

protein surface– Antibodies coating bacteria

(Opsonization)

Phagocytosis

Phagocytosis by neutrophils- cont.

Neutrophils attach to bacteria & encircled it with pseudopodia and take it into a vacuole (phagosome).

• One Neutrophil can engulf 3 to 20 bacteria• One Macrophage can engulf up to 100 bacteria

Microbial killing: fusion of neutrophil granules with vacuole,

– Discharge of lysozyme, myeloperoxidase enzymes into the vacuole, killing and digesting the engulfed bacteria.

– Release of Free radicals by oxidizing agents: superoxide, hydrogen peroxide to kill the bacteria

Leucocytes (WBCs) – cont.

• Types of WBC1. Granular (polymorphnuclear):

• Neutrophil 62%.– 10-16um, nucleus 2-5 lobes, purple

cytoplasmic granules

• Eosinophil 2.3%.– 12-18um, 2 lobes nucleus, coarse red

granules

• Basophil .4%.– 10-14um, rarely segmented nucleus,

nucleus hidden by large round bluish granules

Blood Film

Eosinophils

Function: • Phagocytosis: Phagocytosis is same as neutrophil,

but less efficient

• Chemotaxis: eosinophil attracted towards chronic inflammation/allergic tissue (allergic disease of skin & lungs)

By eosinophil chemotactic factor

Phagocytose (& detoxify) antigen/antibody complexes

Eosinophils cont,

•High eosinophil count:– Parasitic (hook worm, ascaris,

bilharzia)– Allergic (asthma, rhinitis, drug

reaction)– Allergic skin diseases

Leucocytes (WBCs) – cont.

• Types of WBC1. Granular (polymorphnuclear):

• Neutrophil 62%.– 10-16um, nucleus 2-5 lobes, purple

cytoplasmic granules

• Eosinophil 2.3%.– 12-18um, 2 lobes nucleus, coarse red

granules

• Basophil .4%.– 10-14um, rarely segmented nucleus,

nucleus hidden by large round bluish granules

Leucocytes (WBCs) – cont.

• Types of WBC1. Granular (polymorphnuclear):

• Neutrophil 62%.– 10-16um, nucleus 2-5 lobes, purple

cytoplasmic granules

• Eosinophil 2.3%.– 12-18um, 2 lobes nucleus, coarse red

granules

• Basophil .4%.– 10-14um, rarely segmented nucleus,

nucleus hidden by large round bluish granules

Blood Film

Basophils

• Similar to tissue mast cells• Non-phagocytic cells• Granules: dark blue color.• Granules contain:

– Heparin– Histamine – Serotonin (5HT).

Released during allergic reactions

Hematopoiesis

Blood Film

Defensive Functions of the Monocytes

• Directly: – phygocytosis of bacteria, dead cells

etc

• Indirectly:– Cooperates with lymphocytes by:

•Recognizing the foreign body •Ingesting the foreign body •Processing the foreign body•Presenting it to lymphocytes

Monocyte-macrophage system

Reticulo-endothelial System

Reticuloendothelial System-RES

Blood Monocyte Tissue macrophage

Attached (fixed) Mobile

Function is phagocytosis of:• Bacteria• Viruses• Dead tissues• Foriegn particles

Immune function

Reticuloendothelial System-RES

• RES is widespread in the body

Cells of the RES:– Monocytes (blood macrophages)– Mobile and fixed tissue Macrophages – Specialiazed endothelial cells in bone

marrow, lymph nodes and spleen– Reticular cells of lymph nodes spleen &

bone marrow.

Reticuloendothelial System-RES

Cells of the RES - Distribution:

• Tissue Macrophages in skin SC tissues

• Tisssue Macrophages of lymph nodes• Tissue macrophages in lungs• Macrphages (kupffer cells) in the

liver• Macrphages in the spleen and

bone marrow

Reticuloendothelial System-RES

Blood Monocyte Tissue macrophage

Attached (fixed) Mobile

Function is phagocytosis of:• Bacteria• Viruses• Dead tissues• Foriegn particles

Immune function