Major components of bloodI. Fluid component - plasma.

B. Plasma proteins - 7%a. albumin

b. fibrinogen

c. alpha, beta, and gamma globulins - gamma globulins are IgG antibodies (immunoglobulins)

A. Water - 90%

C. Inorganic salts - 0.9%

D. Other organic molecules - 2.1% (vitamins, amino acids, lipids, hormones, etc.)

3.6 - 6.1 billion erythrocytes per ml of normal human blood.

Major components of bloodII. Cellular components - blood cells - two basic types

1. no nucleus in mature erythrocyte

2. biconcave disk shape

3. mature cell is essentially a sac of hemoglobulin4. 7-8 μm in diameter

5. most common type of blood cell

6. reticulocytes - Young erythrocytes recently released into blood that still contain ribosomal RNA that precipitates and stains as a sort of reticulum.

A. Erythrocytes - red blood cells

http://medic.med.uth.tmc.edu/edprog/histolog/blood/b12.jpg

Erythrocyte

http://www.mc.vanderbilt.edu/histo/blood/platelets.jpg

http://www.unomaha.edu/~swick/blood.html

Sickle cell anemia

B. Leucocytes

1. White blood cells that can be sub-divided into a number of major sub-types.

2. At the light level, these sub-types are distinguished by their 1) nuclear and 2) cytoplasmic structure as characterized by specific staining patterns.

3. Stains for this purpose were first developed by Dimitri Romanovsky in 1891.

a. These initial stain mixtures were later modified by other investigators,

b. Romanovsky type stains called Leishman's or Wright's stains for example.

4 - 11 million leukocytes per ml of normal human blood.

C. Romanovsky stain 1. Main components are methylene blue and eosin

2.Blood cells are classified by the type of stain that binds to them or their components.

a. basophilia - affinity for methylene blue which is a basic stain.

b. azurophilia - affinity for azure dyes (purples) which result from the oxidation of methylene blue in the mixture.

c. acidophilia or eosinophilia - affinity for eosin which is an acid stain (yellowish-pink)

d. neutrophilia - affinity for complex dyes that are formed in the mixture that have a salmon-pink to lilac color. The term neutrophilia comes from the early misconception that these dyes were neither acid nor base and thus neutral.

Note that the names of a number of leukocytes are based on their type of staining.

D. Leucocyte classification systems

1. Two major types of classification are used for leukocytes.

•granulocytes - cells with specific granules that are quite evident by virtue of the fact that they have affinity for specific stains.

•agranulocytes - blood cells that don't have obvious specifically stained cytoplasmic granules.

a. One classification system is based on appearance of the stained cell cytoplasm - whether or not visible “granules” are present

granule - a stained, membrane bound vesicle in the cytoplasm

b. The second classification system is based on the morphology of the stained nucleus.

Leukocyte classification systems

•mononuclear - nucleus is not composed of identifiable lobes. Nucleus may be irregular.

•polymorphonuclear - nucleus is composed of two or more distinct lobes.

Nuclear lobes are distinct structures that are connected by a thin bridge of nucleoplasm surrounded by nuclear membrane.

E. BASIC LEUKOCYTE CELL TYPES1. Granulocytes

a. the neutrophil (most common leukocyte)

•Compose 60-70% of the leukocytes

•Nucleus is polymorphonuclear - has 2-5 lobes linked together by fine threads of chromatin - sometimes referred to as “PMNs” (PolyMorphonuclear Neutrophils)

•Cytoplasm contains azurophilic and other specifically staining, small membrane bound granules - these are often not particularly evident.

•Granules are lysosomes that contain enzymes for digestion of phagocytosed particles, e.g. bacteria.

•First line of defense against microorganisms - phagocytose bacteria - sometimes called “microphages”

•Capable of amoeboid movement

NEUTROPHILS

Band neutrophil Mature neutrophil

http://www.som.tulane.edu/classware/pathology/Krause/Blood/BL10d.html http://missinglink.ucsf.edu/lm/IDS_101_histo_resource/blood_cells.htm

b. the eosinophil

BASIC LEUKOCYTE CELL TYPES

•Compose 1-4% of the leukocytes

•Nucleus is polymorphonuclear - usually bilobed. Sometimes called “PMEs” (PolyMorphonuclear Eosinophils).

•Cytoplasm contains ovoid, eosinophilic (acidophilic) membrane-bound granules

•Granules are larger than those of neutrophils

•Granules are lysosomes that contain enzymes that can degrade phagocytosed particles

•Recognize and phagocytose antigen-antibody complexes and particles that are associated with these complexes that are formed during an immune response.

•Capable of amoeboid movement

•May be involved in preventing blood clotting at times when it is best that it not occur.

Granulocytes

EOSINOPHIL

http://www.users.globalnet.co.uk/~aair/eosinophils.htm

http://www.echt.chm.msu.edu/courseware/blockII/Pathology/InfectiousDisease_6.html

http://www-medlib.med.utah.edu/

WebPath/HEMEHTML/HEME004.html

http://www.unomaha.edu/~swick/blood.html

Don’t confuse with a band neutrophyll.

http://pathhsw5m54.ucsf.edu/case17/image175.htmlhttp://missinglink.ucsf.edu/lm/IDS_101_histo_resource/blood_cells.htm

BASIC LEUKOCYTE CELL TYPESGranulocytes

c. the basophil•Compose 0-1% of leukocytes.

•Have a large irregular lobed nucleus that is often S-shaped - polymorphonuclear. Sometimes called “PMBs” (PolyMorphonuclear Basophils)

•Cytoplasm is filled with specifically staining granules larger than those in other granulocytes.

•Granules are membrane bound and contain histamine and heparin that are secreted by exocytosis.

•Histamine - causes dialation of blood vessels and in effect makes them leaky. This allows serum proteins such as antibodies to infiltrate into tissues. Heparine - anticoagulant.

•Have limited capacity for amoeboid movement and phagocytosis. Function in allergic reactions and inflammatory response.

BASOPHIL

http://www-medlib.med.utah.edu/WebPath/

HEMEHTML/HEME005baso.html

Probably an aberrant neutrophil

BasophilProbably a

Plasma cell/ http://www.unomaha.edu/~swick/blood.html

http://pathhsw5m54.ucsf.edu/case17/image176.html

http://diaglab.vet.cornell.edu/clinpath/modules/heme1/baso.htm

http://missinglink.ucsf.edu/lm/IDS_101_histo_resource/blood_cells.htm

BASIC LEUKOCYTE CELL TYPES

2. Agranulocytes

a. Lymphocytes

•Numbers in blood vary, usually 20-30% of circulating leukocytes. Second most common leukocyte in normal blood.

•Have a spherical nucleus - mononuclear.

•Small lymphocytes have very little cytoplasm. Nucleus is surrounded by a thin halo of blue cytoplasm in stained material (6-8 μm in diameter).

These cells are unactivated lymphocytes.

Two populations, one that can become T-lymphocytes and the other B- lymphocytes.

When activated by encounter with foreign antigen presented by a macrophage - become large lymphocytes that are capable of mitosis.

BASIC LEUKOCYTE CELL TYPES

Agranulocytes

•Large lymphocytes (10-14 μm in diameter) have more cytoplasm relative to nuclear size - mononuclear.

Small lymphocytes (either B- or T-lymphocytes) develop into large lymphocytes after encounter with foreign antigen and activation in an immune response.

These cells undergo repeated mitotic division to form clonal populations of either B- or T- lymphocytes

If large B-lymphocytes, the clonal cells become either B-memory cells or plasma cells (even larger in size) that actively produce antibodies that function in humoral mediated immunity

If large T-lymphoctes, the clonal cells differentiate into a number of different types of cells that function in cell mediated immune response.

B- and T- lymphocytes cannot be differentiated with the light microscope using standard stains.

BASIC LEUKOCYTE CELL TYPES

Agranulocytes

Lymphocytes

http://www.meddean.luc.edu/lumen/

MedEd/Histo/HistoImages/hl2B-55.jpg

Similar in size to a erythrocyte

Small lymphocyte

Larger than a erythrocyte

Large lymphocyte

http://missinglink.ucsf.edu/lm/IDS_101_histo_resource/blood_cells.htm

Lymphocytes - Clockface nuclei

BASIC LEUKOCYTE CELL TYPES

Agranulocytes (lack obvious stained granules)

b. Monocytes

2-6% of circulating leukocytes

Nucleus is usually kidney- or horseshoe-shaped (may be oval) and may be positioned off center - mononuclear

Chromatin often fibrillar in appearance

Nucleus usually has 2-3 nucleoli

More cytoplasm than a lymphocyte

As is the case with other leukocytes, monocytes are circulating blood cells that can cross the capillary endothelium and move into surrounding tissues. When monocytes do this they differentiate into macrophages.

DIAPEDESIS = EXTRAVASATION = TRANSENDOTHELIAL MIGRATION

http://multimedia.mcb.harvard.edu/

BASIC LEUKOCYTE CELL TYPESAgranulocytes

MONOCYTE

http://www.unomaha.edu/~swick/blood.htmlhttp://missinglink.ucsf.edu/lm/IDS_101_histo_resource/blood_cells.htm

c. Megakaryocyte

Very large cells (40-100 μm in diameter) found in red bone marrow.

Irregular lobed nucleus -mononuclear.

Form platelets by fragmentation of pseudopodia.

Platelets are enucleate disk-like cell fragments that are 2-5 μm diameter often appear in clumps in blood smears. Function in clotting.

BASIC LEUKOCYTE CELL TYPES

Agranulocytes (lack obvious stained granules)

BASIC LEUKOCYTE CELL TYPESAgranulocytes

MEGAKARYOCYTE

http://www.deltagen.com/target/histologyatlas/atlas_files/hematopoietic/bone_marrow_40X.jpghttp://pro.corbis.com/images/42-18705415.jpg?size=67&uid=%7B42A68054-F702-4052-A48A-85113043EB0D%7D

III. Hematopoiesis

A. Blood cells have short life in circulatory system and so they must be continually renewed.

1. erythrocytes and leukocytes are derived from stem cells in the red bone marrow of mammals.

2. lymphocytes are derived from stem cells in the bone marrow and also in the lymphatic organs.

B. Hematopoiesis involves a series of stem cell stages:

http://www.som.tulane.edu/classware/pathology/Krause/Blood/EP.html

1. Hemocytoblast - multi-potent stem cell that divides to form stem cells for erythrocytes or the various types of leukocytes

B. Hematopoiesis of erythrocytes

1. Proerythroblast - formed from division of hemocytoblast - essentially the stem cell for the erythrocyte cell line. Divides by mitosis to form many

2. Basophilic erythroblasts - starts synthesis of hemoglobin. Repeated mitotic divisions to form many

3. Polychromatic erythroblasts - more hemoglobin synthesis. Repeated mitotic divisions to form many

http://www.som.tulane.edu/classware/pathology/Krause/Blood/EP.html

4. Normoblasts - synthesizes abundance of hemoglobin. Divides 3 times. After last division the cells extrude their nuclei and become

5. Reticulocytes - no further division. Hemoglobin synthesis completed. Organelles either autophagocytosed or exocytosed. Cells become

6. Mature erythrocytes

B. Hematopoiesis of erythrocytes

http://www.som.tulane.edu/classware/pathology/Krause/Blood/EP.html

http://www.mc.vanderbilt.edu/histo/blood/platelets.jpg

http://medic.med.uth.tmc.edu/edprog/histolog/blood/b12.jpg

B. Hematopoiesis of other blood cell types

1. Staged sequences of developmental cell types as described in text.

Acute myelogenous (myeloblastic) leukemia (AML)

1. Characterized by the presence of (lots of) myeloblasts (undifferentiated granulocyte precursors) in the bone marrow and blood.

2. These malignant cells do not differentiate normally.

3. The diagnosis of AML is made when over 30% of the marrow cells are myeloblasts.

AML Presents clinically with:

1. Features of bone marrow failure, e.g., anemia, infections, bruising or bleeding.

2. Leukemic infiltration of organs (e.g. central nervous system, lymph nodes, skin) may produce specific signs or symptoms.

Without treatment AML is rapidly fatal.

Cure rate in children, chemotherapy 40 - 50%, stem cell transplant from brother/sister 55-60%.