CONTENTS HISTOLOGY FOR MEDICAL STUDENTS
ATLAS OF HISTOLOGY IMAGES

CONNECTIVE TISSUE
BLOOD


CONNECTIVE TISSUE IS SPECIAL IN THAT IT IS BUILT FROM CELLS AND INTERCELLULAR MATTER

Blood belongs to connective tissue and like other types of connective tissues is composed of cells (formed elements) and intercellular matter (plasma).

PLASMA (55-60%) water - 90-93%, organic substances 6-9%, inorganic substances - 1%; the last two include: proteins 60-75 g/l, carbohydrates, lipids, electrolytes

FORMED ELEMENTS (40-45%)

these are subdivided into white blood cells or leucocytes, red blood cells or erythrocytes and platelets or thrombocytes

erythrocytes and platelets perform their functions within the vessel lumen, while leucocytes function primarily in the tissues

ERYTHROCYTES

shapes:

normal shape: biconcave disc - discocyte

pathological shapes - poikilocytes:

structure:
no nucleus; cytoplasmic membrane bears a negative charge due to special carbohydrate molecules of sialic acid in the glycocalix, harbors transport proteins, easily permeable for anions and hardly for cations (K+, Na+); no membrane organelles, from non- membrane organelles only microfilaments are represented; cytoplasm is mostly filled with hemoglobin; hemoglobin is a glycoprotein composed of 4 globin chains, each of which is linked to one molecule of heme; heme is a vitamin B12 derivative  and contains one iron ion in the ferrous state; hemoglobin is equally efficient at binding and releasing oxygen, on the contrary its binding capacity is superior to liberation for CO2 and CO; erythrocytes contain an enzyme carbonic anhydrase, which catalyzes the following reaction:
in tissues > CO2+H2O <=> H+ + HCO3- < in lungs;
fetal hemoglobin is referred to as Hemoglobin F, it possesses a higher oxygen affinity; in fetuses and newborns hemoglobin and erythrocyte levels are higher than in adults; adult hemoglobin is called Hemoglobin A; hemoglobin with bound oxygen is oxyhemoglobin, that without - deoxyhemoglobin, hemoglobin with bound CO is called carboxyhemoglobin, hemoglobin with attached CO2 molecule(s) is carbohemoglobin, hemoglobin with ferric ion is known as methemoglobin

functions:
transport of oxygen and carbon dioxide, maintenance of blood buffers

PLATELETS

varieties: juvenile, mature, senescent, degenerative and giant

structure:
no nucleus; are pieces of cytoplasm with elements of Golgi complex and smooth endoplasmic reticulum, with mitochondria, ribosomes, glycogen inclusion bodies, microtubules, microfilaments, glycolytic enzymes are present as well as a number of granule types; all elements having a structure of a granule are called granulomere, while all non-granular cytoplasmic components are referred to as hyalomere; there are receptors for blood clotting factors on cytoplasmic membrane

alpha granules contain:

delta granules contain: ADP, ATP, calcium ions, serotonin, histamine

lambda granules or azurophilic granules, or lysosomes: (see neutrophils)

microperoxisomes: (see peroxisomes)

properties:
platelets are able to be activated, this process is accompanied by release of granule contents into the intercellular space, and, additionally, inner aspect of granular membrane with receptors for adhesion molecules and coagulation factors on it becomes accessible for inactive clotting factors, which through interaction with these receptors fix to them and then turn activated; platelets are capable of attaching themselves to injured vessel wall (adhesion) and stick to each other (aggregation)

functions:
participation in blood coagulation and thrombus formation



LEUCOCYTES

on the basis of presence or absence of  SPECIFIC granules leucocytes are divided into 2 major group: granular leucocytes (or granulocytes) and nongranular leucocytes (or agranulocytes)

both granulocytes and agranulocytes possess NONSPECIFIC GRANULES, which are essentially lysosomes, and their composition is similar in all leukocytes

granular leucocytes are a heterogeneous group that includes

agranular leucocytes are

BASOPHILS

structure:
cells are spherical in shape, in the peripheral blood there are mainly the most mature forms (with segmented nuclei), having, as a rule, a bi-lobed nucleus, their cytoplasm contains specific and nonspecific granules; specific granules stain well with basic (alkaline) dyes; azur-2, a basic dye, has a dark blue color; therefore, staining a blood smear with azur-2-eosin by Giemsa method should turn specific granules of a basophil dark blue; however, due to sulfated proteoglycans within these granules they take a violet-purple tinge, i.e. they show the phenomenon of  metachromasia which is defined as change from the initial color of a dye

specific granule content:

nonspecific (or azurophilic) granule content: see neutrophils

properties:

functions:
are determined by versatile actions of granule contents as well as by elaboration and secretion of a host of biologically active substances which are not stored within granules such as tumor necrosis factor a, prostaglandin D2, thromboxane А2, interleukin 4, leukotrien C4 and others



EOSINOPHILS

structure:
cells are spherical in shape, in the peripheral blood there are mainly the most mature forms (with segmented nuclei), having, as a rule, a bi-lobed nucleus, their cytoplasm contains specific and nonspecific granules; specific granules stain well with acidic dyes; eosin, an acidic dye, has red or pink color; therefore, staining a blood smear with azur-2-eosin by Giemsa method should turn specific granules of an eosinophil red or pink; one eosinophil is home to approximately 200 specific granules, on the outer surface of eosinophils there are receptors for IgG, IgE, complement components C3b,C4,C1s, C3a, C5a and others

composition of specific granules:

composition of nonspecific (or azurophilic) granules: see neutrophils

properties:

functions:
are determined by actions of granule contents as well as by secretion of a host of biologically active substances which are not stored within granules such as platelet activating factor, thromboxane B2, leukotrien C4 and B4



NEUTROPHILS

structure:
in the blood of a healthy human neutrophils of various degrees of maturity are present: juvenile neutrophils (metamyelocytes) - the youngest, rods - more mature, and segmented neutrophils - the most mature; neutrophils are spherical in shape, in the cytoplasm, in addition to all basic organelles, there are specific (primary and secondary) and nonspecific granules; specific granule content is alkaline or neutral in pH, pH for nonspecific granules is acidic; specific granules stain with both acidic and basic dyes; eosin, an acidic dye, has red or pink color, azur-2, a basic dye, has a dark blue or violet color; therefore, staining with azur-2-eosin by Giemsa method should turn specific granules of a neutrophil brown violet; nuclei of juvenile neutrophils have an indentation on one of their sides, nuclei of rods are horseshoe-shaped, segmented neutrophils have three- or four-lobed, sometimes bilobed; on the outer surface of neutrophils there are receptors for C3b complement component, Fc-receptors for IgG, as well as for many immunologic mediators and other biologically active substances

composition of secondary specific granules:

composition of primary specific granules:

nonspecific (azurophilic) granules:
(nonspecific granules are lysosomes)

properties:

functions:
are determined by substances in granules, properties of the cells and by synthesis of multiple biologically active substances



LYMPHOCYTES

structure:
spherical cells with round or slightly indented (in large lymphocytes) nuclei and small cytoplasmic compartment, which contains poorly developed organelles, nonspecific granules (lysosomes) could be seen; morphologically lymphocytes are divided into small, medium, and large lymphocytes; functionally - divided into T- and B-lymphocytes, natural killers, T-lymphocytes are divided in turn into T-killers, T-helpers, T-suppressors, T-memory cells; lymphocytes possess receptors for antigens, immunologic mediators, hormones, and for a host of biologically active substances

properties:

functions:



MONOCYTES

structure:
large round or oval cells with horseshoe-shaped nuclei and quite voluminous cytoplasm, which contains multiple lysosomes (nonspecific granules), phagosomes; cytoplasm stains bluish gray (color of cigar smoke); there are receptors on cytoplasmic membrane for various immunologic mediators, complement components, Fc-receptors for IgG, hormones, biogenic amines, eicosanoids, growth factors, etc.; monocytes are immature cells, than upon leaving the circulation into the tissues, where they differentiate into macrophages

properties:

functions:

NORMAL VALUES normal quantities 
in 1 liter of blood
normal dimensions
(diameter, µm)
spanlife
erythrocytes females - 3.7- 4.5*1012/l
males - 4.5- 5.5*1012/l

decrease in erytrocyte number - erythropenia,
increase - erythrocytosis

7.1 (6-8)- normocyte

pathological:
< 6 µm - microcyte;
> 8 µm - macrocyte

100-120 days
platelets 200-400*109/l 2 - 4 5-8 days
leucocytes 3.7-8*109/l

decrease in leucocyte number - leucopenia, increase - leucocytosis

basophils
10-12 to 2 days
eosinophils
12-14 to 2 days
neutrophils
10-12 6-8 days
lymphocytes
small - 6-7, medium - 7-9, large - 9-16 from several hours to decades
monocytes
16-20 from several hours to decades

HEMOGRAM is leucocyte differential count plus concentration of blood cells per liter

 

LEUCOCYTE DIFFERENTIAL COUNT
is percentage of leucocytes

all leucocytes are 100%, of those:
basophils eosinophils neutrophils lymphocytes monocytes
juvenile rods segmented
0-0.5% 1-5% 0-1% 1-6% 60-65% 20-35% 2-8%

One of the most important diagnostic sign is
deviation of the leucocyte differential count to the left.
This is an incerase in the number of juvenile and rods neutrophils.

AGE-RELATED CHANGES IN BLOOD CELL COUNTS

erytrocytes:6-7*1012/l in newborns, get lower post partum and by 10-14 days of life are at adult levels, a decrease continues for 3 to 6 months, then gradual return to adult counts at puberty

leucocytes: 10-30*109/l in neonates, in the first two weeks of life decline to  9-15*109/l, reach adult levels at puberty

neutrophil/lymphocyte ratio: at birth - comparable to adults, 4 days - concentrations equalize, and then lymphocyte counts rise through the age of 1-2 years, after that decline and turn even at 4 years, before puberty neutrophils rise and lymphocytes drop

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