His To Blood

Histology of blood

Ma. Minda Luz M. Manuguid M.D.

blood  def.: specialized, liquid connective tissue ubiquitous in the human body, circulating in a closed system of vessels Blood cells: Erythrocytes, Leukocytes, Thrombocytes Ground substance: Plasma Extracellular fibers: potential (Fibrinogen) become actual fibers (Fibrin) when blood clots

Blood cells Erythrocytes – red blood cells Leukocytes – white blood cells Granulocytes • Neutrophils • Eosinophils • Basophils

Agranulocytes • Lymphocytes • Monocytes

Thrombocytes – platelets

Erythrocytes  most prevalent of blood cells: 25 trillion in p.b.; comprise 45% of total blood volume  anucleate biconcave discs 7-8µm in diameter, 2µm thick at the edges, 1µm at the center; bound by plasma membrane  Hemoglobin is 1/3 of rbc mass  cytoskeletal proteins:

Erythrocytes (RBC, Red corpuscles) Red blood cells  no nucleus  cytoplasm is entirely acidophilic (red)  biconcave shape,  6.5 to 8.4μ in diameter  indention or notches and minor surface irregularities are considered normal variations. 

erythropoiesis CFU-S → BFU-E → CFU-E EPO →→→ Erythroblast colony burst colony ↓ forming forming basophilic unit-Spleen unit-Erythroid

Erythroblast

forming

unit-Erythroid

↓

polychromatophilic

EPO: Erythropoietin Erythroblast orthochromatic

Erythroblast

↓

 erythroblast – proNormoblast  basophilic erythroblast – early Normoblast  polychromatophilic erythroblast – intermediate Normoblast  orthochromatic erythroblast – late Normoblast

Rbc maturation  Immature cells have delicate, fine nuclear chromatin which gradually becomes coarsely clumped or condensed. The size of the nucleus decreases; nucleoli are reduced in number or lost completely as in red cells. The nuclear shape which is initially round or oval may become uniquely configured as in myeloid cells. Mitotic competence is lost as cells differentiate.

Rbc maturation  although most erythroid and myeloid cells decrease in size as they mature, the cytoplasm becomes relatively increased in volume, compared to the nucleus. The cytoplasm becomes less basophilic and increasingly eosinophilic.

Pronormoblast / erythroblast  The pronormoblast (E1) is the earilest recognizable red cell precursor. They are 15- 20µ in diameter with fine granular chromatin and 0-2 nucleoli. The cytoplasm is deeply basophilic without granules.

Basophilic erythroblasts Basophilic normoblasts:  E2:The chromatin is slightly coarser and the cell slightly smaller than the pronormoblast. Nucleoli may be indistinct. The cytoplasm remains deeply basophilic.  E3 : The chromatin becomes increasingly coarse compared to the E2 stage. The cytoplasm remains

Polychromatophilic erythroblasts  E4: polychromatophilic normoblasts: Hemoglobin production becomes evident from the muddy mix of the bluestaining RNA and the red-staining hemoglobin resulting in the

Orthochromatic erythroblast  The E5 orthochromatic normoblast is smaller than the E4 stage.  hemoglobin is abundant while ribosomes decrease in number.  The nuclear chromatin is

reticulocytes  Polychromatophilic red cells are larger than mature erythrocytes and still contain ribosomes and mitochondria, giving the cell a blue tint. When polychromatic RBCs are stained with a supravital dye (new methylene blue or cresyl violet) ribosomes clump to form a blue stained

Reticulocytes & erythrocytes Reticulocyte – immature rbc with aggregated reticular clusters of ribosomes  used as marker for bone marrow hematopoiesis e.g. in treating anemia

erythrocytes  Normal mature erythrocytes are biconcave discs (approximately 8 um in diameter; 2.5 um thick at the periphery; 1.0 um thick at the center). This results in an area of central pallor (about 1/3 the dia.)

Erythroid hyperplasia & normal marrow

Granulocytes

Leukocytes: Myeloid series

 the mature forms of the myeloid series (neutrophils, eosinophils, basophils), all have lobed (segmented) nuclei. The degree of lobation increases as the cells mature.

myeloblast  earliest recognizable myeloid cell is the myeloblast (10-20m dia) with a large round to oval nucleus. There is fine diffuse immature chromatin (without clumping) and a prominant nucleolus.  The cytoplasm is basophilic without granules. Although one may see a small golgi area adjacent to the nucleus, granules are

promyelocyte  promyelocyte (1020m) is slightly larger than a blast. Its nucleus, although similar to a myeloblast shows slight chromatin condensation and less prominent nucleoli.  The cytoplasm contains striking azurophilic granules or primary granules. These granules contain myeloperoxidase, acid phosphatase, and

myelocyte  when secondary granules can be recognized, the cell becomes a myelocyte.  slightly smaller than promyelocytes, have eccentric round-oval nuclei, often flattened along one side. The chromatin is fine, but shows evidence of condensation. Nucleoli may be seen in early stages but not in the late myelocyte.  Primary azurophilic granules are still present, but secondary granules predominate. Secondary granules (neut, eos, or baso) first appear adjacent to the

metamyelocyte  Metamyelocytes (1018m) are slightly smaller than myelocytes.  They have kidney shaped indented nuclei and relatively dense chromatin, especially along the nuclear membrane.  The cytoplasm is faintly pink with almost no blue background. Numerous secondary granules (neutro, eos, or baso) clearly

bands  Bands, slightly smaller than juveniles, are marked by a U-shaped or deeply indented nucleus. Opposite sides or lobes are of roughly equal size or diameter. There is no nuclear constriction > than 1/2 the lobe diameter. The chromatin is heavily clumped and secondary or specific granules either neutrophilic or basophilic predominate.

neutrophils  Segmented (segs) or polymorphonuclear (PMN) leukocytes (average 14 m dia) are distinguished by definite lobation with thin thread-like filaments of chromatin joining the 2-5 lobes. The chromatin of the segmented neutrophil is coarsely clumped and the cytoplasm is pink due to large numbers of secondary granules.  In practice when examining peripheral blood, neutrophils are the only leukocytes to be divided into myelocyte, juvenile, band, and PMN stages. Eosinophils and

neutrophils  the mature neutrophil (12-15u dia) is characterized by segmentation into 2-5 lobes. The chromatin is dense and clumped with distinct lighter areas of parachromatin.  The cytoplasm is lightly eosinophilic with variable numbers of light staining "neutral" granules and a few and a few

eosinophils  The large orange granules of the eosinophil make it the most readily recognizable cell in the blood. The eosinophil (12-15u diameter) has chromatin similar to that of a neutrophil, but usually fewer (2-3) lobes.  Normally 0-6% eosinophils are found in the peripheral blood.  The eosinophil specific granules contain rhomboid crystals by EM. This core contains Major

basophil  The purple-black, often large coarse irregularly sized granules of the basophil are chacteristic and may obscure the nucleus of this relatively uncommon cell.  the mature nucleus is segmented into 2-3 lobes.  Basophils (12-15u dia) contain heparin and large amounts of

Agranulocytes

monocytes  the largest (12-20u dia) cells normally found in the peripheral blood.  have abundant blue-gray, sometimes very pale pink cytoplasm with small, generally indistinct, granules. One may see fine reddish granules of variable prominence. Occasionally, large azurophilic granules will be seen. Cytoplasmic vacuoles are often seen.  The nucleus is irregular,

lymphocytes  vary greatly in size (720m dia) and in nuclear and cytoplasmic character.  The small lymphocyte (7-12m dia) has a round-oval nucleus with dense clumped "smudgy" chromatin; no visible nucleolus.  Scanty light blue cytoplasm, while usually agranular, may contain a few

lymphocytes

 Lymphocytes with peripherially clumped chromatin and often deep blue cytplasm similar to plasma cells are termed plasmacytoid lymphocytes.  Normal peripheral blood lymphocyte percentages vary from 15-60%.

Plasma cell  Terminally differentiated lymphocytes or plasma cells (left panel) are rarely found in the peripheral blood.

platelets  Immediately above the leukocytes in the buffy coat lies a thin layer of platelets. On Wright's stained peripheral smear platelets are small (25m) round-oval anuclear bits of pale blue cytoplasm containing azurophilic granules.  Smaller platelets tend to be older; while

Thrombocytes

megakaryocytes

 Megakaryocytes undergo endomitosis - a process whereby DNA is duplicated without cell division. Thus MKs become polyploid during amplification.  Most platelet forming MKs have a ploidy of 16N, (range 4N - 64N).  MKs are the largest normally occuring cells in the

megakaryocytes  Closer inspection of MKs shows a network of platelet demarcation zones forming fissures throughout the MK cytoplasm. The membranes of this demarcation system eventually form cytoplasmic platelet

megakaryocyte

platelets

 Platelet granules are of two types: alpha granules and dense bodies.  Alpha granules contain Platelet Derived Growth Factor, platelet factor 4, Factors V & XIII and fibrinogen.  Dense bodies contain serotonin,nucleotides (ADP) and calcium. Lysosomes containing hydrolytic

Thrombocytes / platelets  The peripheral blood platelet count ranges from 150 - 450 x 10 /L.  About 2/3 of platelets circulate, while 1/3 are in the splenic pool or other extravascular locations.  During its lifespan the average megakaryocyte (MK) gives rise to approximately 4,000 platelets which live an average of 9-12 days.  In the steady state, where platelet production = platelet destruction, daily

That’s all !