Blood Cells PDF

Blood Cells Dr. Heba Kalbouneh DDS, MSc, DMD/PhD Professor of Anatomy, Histology and Embryology  Blood - Specialized form of connective tissue - Components: - Blood cells (several types) - Plasma (extracellular matrix) Dr. He...

Blood Cells Dr. Heba Kalbouneh DDS, MSc, DMD/PhD Professor of Anatomy, Histology and Embryology  Blood - Specialized form of connective tissue - Components: - Blood cells (several types) - Plasma (extracellular matrix) Dr. Heba Kalbouneh  Functions of Blood Transports nutrients and respiratory gases Transports waste products to organs and tissues where they can be recycled or released Transports hormones Transports immune cells throughout the body Helps regulate body temperature Maintains of acid-base and osmotic balance Blood is propelled mainly by Dr. Heba Kalbouneh rhythmic contractions of the heart About 5-6 Liters of blood in an average adult moves unidirectionally within the closed circulatory system Dr. Heba Kalbouneh  Collected blood in which clotting is prevented by the addition of anticoagulants (eg, heparin , citrate or EDTA) can be separated by centrifugation into layers that reflect its heterogeneity Dr. Heba Kalbouneh  HEMATOCRIT: Ratio of the volume Physical Characteristics of RBCs to the volume of whole blood Example: a hematocrit value of 40% means that there are 40 ml of RBCs in 100 ml of whole blood Normal hematocrit: Fluid Males=40-53% – Living 45% Females= 36-48% Cells (formed elements) – RBC Erythrocytes (carry oxygen) BUFFY – WBC Leukocytes (immune) Top layer= plasma COAT – Platelets Thrombocytes (clotting) – Non living (Matrix) 55% Plasma (pale yellow fluid) Middle layer= buffy coat – 90% water – 10 % (electrolytes, nutrients, Dr. Heba Kalbouneh proteins (albumin), waste Bottom layer=RBCs (CO2, ammonia, urea), gases, (Packed Cell Volume) hormones)  Values are those used by the US National Board of Medical Examiners Serum = everything in plasma, minus the clotting factors Copyright © McGraw-Hill Companies  Albumin: Fibrinogen:  The most abundant plasma protein  The largest plasma protein Is made in the liver  Is made in the liver Helps maintain the osmotic pressure in Important for clot formation capillaries Transports steroid hormones and fatty acids Fresh plasma The importance of proteins inside the plasma is to prevent fluid loss and to create osmotic pressure (to keep the blood inside the blood vessels) Plasma cell Globulins (α, β and or γ globulins): α and β globulins γ-globulins (Immunoglobulins Are made mainly by liver (antibodies): Transport fat soluble vitamins, lipids secreted by plasma cells and iron Dr. Heba Kalbouneh  Preparing a blood smear Polychromatic stains: Blood cells can be studied histologically in smears prepared Giemsa Wright by spreading a drop of blood in a thin layer on a microscope Leishman slide Copyright © McGraw-Hill Companies Dr.Figure Heba12-3 Kalbouneh  The Staining of Blood Cells Blood film/ smear: a drop of blood is spread on a glass slide and left dry in air Staining: with neutral stain e.g Leishman’s stain Leishman’s stain: formed of a mixture of: – Eosin, an acidic dye that stains pink to red – Methylene blue, a basic dye that stains blue to purple Dissolved in methyl alcohol (fixative) Azure dye!! Blood film/smear Dr. Heba Kalbouneh Erythrocytes (RBCs) Small, biconcave discs Transport oxygen and CO2, cytoplasm is full of hemoglobin molecules Have no nuclei or organelles Male: 4.5-5.5 million/mm3 Female:4-5 million/mm3 Pick up O2 at lung capillaries and release it at body tissue capillaries During their maturation process, the erythrocytes extrude their nuclei, and the mature RBCs enter the bloodstream, without their nuclei Fate: Survive for ~100-120 days in the circulation. Worn out RBCs are removed by macrophages of the spleen, bone marrow and liver. Dr. Heba Kalbouneh  Biconcave shape provides 20-30% greater surface area than a sphere relative to cell volume, facilitating gas exchange The biconcave shape along with the fluidity of the plasma membrane (50% proteins) permits erythrocytes to bend and adapt to the small diameters and irregular turns of capillaries Erythrocyte consists of an outer Dr. Heba Kalbouneh plasma membrane enclosing hemoglobin and a limited number of enzymes necessary for maintenance of plasma membrane integrity and gas transport functions Eosinophilia/ acidophilia due to their High content of Hemoglobin (basic protein) The pale staining of the central region is a result of its biconcave disc shape Normochromic RBCs Immediately beneath the plasma membrane is a Top view meshwork of proteins (Spectrin and Ankyrin) forming a cytoskeleton This submembranous meshwork stabilizes the The cell membrane is membrane, maintains the cell shape, and highly selective and provides the cell elasticity required for passage flexible through capillaries Sectional view Normocytic RBCs Dr. Heba Kalbouneh Size 6-9 um in diameter (7.5 um) Thickness 2.6-µm thick at the rim, but only 0.75-µm thick in the center !!!!! Erythrocytes can be used as a size reference for other cell types  Dr. Heba Kalbouneh Caused by mutations in genes relating to membrane proteins (mostly Spectrin and Ankyrin) that allow for the erythrocytes to maintain their biconcave shape Cell Membrane Sugar chain of glycoprotein The glycocalyx is a glycoprotein and glycolipid covering that surrounds the cell membranes  LM LM: Blood film stained with Leishman: Rounded Non nucleated Dr. Heba Kalbouneh Acidophilic (with pale central area) A zone of central pallor is about 1/3 the size of the RBC TEM SEM EM: Have no nucleus or organelles Filled with hemoglobin Electron dense and homogenous  Rouleaux appearance occurs to some extent in all films Dr. Heba Kalbouneh. Rouleaux formation: RBCs may adhere to one another loosely in stacks called Rouleaux (pile of coins) In slow (not in normal) circulation Due to surface tension caused by their biconcave surface (reversible) Abnormalities of Erythrocytes Abnormal staining: Change from the normal size, shape or staining Hypochromia: Denotes a decrease in the properties of erythrocytes are important intensity of staining indicator of disease. However, some of these Indicates a decreased amount of abnormalities may be found in healthy individuals hemoglobin Frequently accompanies microcytosis Abnormal sizes: Microcytes (9um) Hypochromic microcytic anemia Anisocytosis (different sizes) Abnormal shapes: Dr. Heba Kalbouneh Due to changes either in the cell membrane or Hb content Poikilocytes (Poikilocytosis) Spherocytes Ovalocytes Sickle cells Dacrocytes Elliptocytes Sickle cell anaemia results One of the most sever changes in shape occurs Teardrop shaped cells from abnormal hemoglobin during SICKLING of RBCs in sickle cell anemia where erythrocytes take on the form of crescents  Production of erythrocytes in the bone marrow, is stimulated by erythropoietin Erythropoiesis Erythropoietin is produced by the kidneys When RBC count drops, such as during blood loss, the resulting oxygen-deficiency state, hypoxemia, is detected by the kidneys. Anemia: a decrease in the total number of RBCs (and/or hemoglobin) Dr. Heba Kalbouneh The kidneys respond by increasing their Polycythemia: an increase in the erythropoietin secretion, which leads to total number of RBCs (and/or increased red blood cell production hemoglobin)  People living at high altitudes Athletes whose demand for oxygen is more usually have higher RBC count as a elevated, also have higher RBC counts. response to lower oxygen levels. Dr. Heba Kalbouneh RBC plasma membranes have glycoprotein antigens on their external surfaces Dr. Heba Kalbouneh A B A B O Rh+ Glycophorin A is an integral membrane protein. The glycosylated extracellular domains of the glycophorins include antigenic sites that form the basis for the ABO blood typing system  RBCs WBCs (Erythrocytes ) (Leukocytes ) Types 1 type 5 types Not true cells True cells Number Male: 4.5-5.5 million/mm3 4500-11000/mm3 female:4-5 million/mm3 Diameter 6-9um (7.5um) 6-20um Life span 120 days Few days-years Origin and Bone marrow Bone marrow and lymphoid tissue maturation Shape Biconcave discs Spherical Function Gas exchange Defense Motility Non motile Motile Function exclusively within Function mainly OUTSIDE blood vessels in vascular system the tissues  Leukocytes Originate in the bone marrow and released continuously into the blood Travel in bloodstream but function mainly outside blood vessels (in loose CT) Leukocytes form a mobile army that helps protect the body from damage by bacteria, viruses, parasites, toxins and tumor cells 5 types organized into 2 groups – Granulocytes Neutrophils Eosinophils Basophils – Agranulocytes Lymphocytes Monocytes Dr. Heba Kalbouneh  Leukocytes (White Blood Cells) Granulocytes Agranulocytes Neutrophil Eosinophil Basophil Monocyte Lymphocyte  Non-specific granules Cytoplasmic granules Azurophilic granules Specific granules Lysosomes Secondary granules Primary granules Granulocytes Dr. Heba Kalbouneh Cytoplasmic granules (containing enzymes or chemicals)  makes cytoplasm look grainy Single multi-lobed nucleus (segmented) All are phagocytic; they engulf and consume foreign cells and material 3 main types: Small granules, pale pink/ Large granules, blue Large granules, Red salmon pink Basophil EOSINOPHIL Neutrophil  Neutrophils The most common leukocyte 2-5 lobes in nucleus connected by “threads” of nuclear material (polymorphs) Light pink cytoplasm Called neutrophils because cytoplasm takes up red (acidic) and blue (basic) stains equally Specialized for responding to Bacterial invasions- Acute infections- Acute pyrogenic infections Neutrophils are short-lived cells with a half- Dr. Heba Kalbouneh life of 6-8 hours in blood and a life span of 1- 4 days in connective tissues before dying by apoptosis.  In females, the inactive X chromosome (Barr body) may appear as a drumstick-like appendage on one of the lobes of the nucleus (about 3% of neutrophils in peripheral blood) Neutrophils are the first WBCs that leave the blood in large numbers to reach the site of inflammation Why??? Cells of acute infection 1- The most abundant Dr. Heba Kalbouneh 2-The most motile 3- Neutrophil chemotactic factors are the first released  Specific granules Azurophilic granules (secondary) (primary) Form H2O2, - Lysozyme - Myeloperoxidase HOCL: powerful cytotoxin - Phagocytin - Acid hydrolase (bactericidal) - Defensins - Lactoferrin (bacteriostatic) - Collagenase Different names for neutrophils: Polymorphs Pus cells Myelocytes Microphages Dr. Heba Kalbouneh Cells of acute inflammation Pus is pyrogenic  Dead neutrophils, bacteria, lysed ECM, and tissue-fluid form a viscous, usually yellow collection of fluid called pus. Few organelles Dr. Heba Kalbouneh Neutrophilia Neutropenia  Dr. Heba Kalbouneh Pyogenic is referring to bacterial infections that make pus while pyrogenic is producing heat  Basophils Rarest leukocyte – might not see these under the microscopes Usually have bi-lobed, S-shaped nuclei obscured by the large basophilic granules Has large granules that stain dark purple/ blue in basic dyes (basophil = basic loving) Granules contain histamine, heparin and eosinophilic chemotactic factor that mediate inflammation in allergic reactions and parasitic infections Dr. Heba Kalbouneh Mast cell  Both basophils and mast cells have surface receptors for immunoglobulin E (IgE), and secrete their granular components in response to certain antigens and allergens. Allergen IgE antibody Plasma cell Dr. Heba Kalbouneh  Exposure may be by ingestion, inhalation, injection, or direct contact In some individuals substances such as certain pollen proteins or specific proteins in food are allergenic, that is, elicit production of specific IgE antibodies, which then bind to receptors on mast cells and immigrating basophils. Upon subsequent exposure, the allergen combines with the receptor-bound IgE molecules, triggering rapid exocytosis of the cytoplasmic granules. Release of the inflammatory mediators in this manner can result in bronchial asthma, cutaneous hives, rhinitis, conjunctivitis, or allergic gastroenteritis. Immediate or type 1 hypersensitivity In some individuals a second exposure to a strong allergen, such as that Dr. Heba Kalbouneh delivered in a bee sting, may produce an intense, adverse systemic response. Basophils and mast cells may rapidly degranulate, producing vasodilation in many organs, a sudden drop in blood pressure, and other effects comprising a potentially lethal condition called Anaphylaxis or anaphylactic shock.  Basophils account for up to 15% of infiltrating cells in allergic dermatitis and skin allograft rejection Dr. Heba Kalbouneh  Eosinophils Usually have bi-lobed nuclei connected by a short “thread” of nuclear material Large cytoplasmic granules, which stain red with the acidic eosin dye (eosinophil = eosin loving) Help in ending allergic reactions Dr. Heba Kalbouneh and in fighting parasitic infections  Crystalloid granule Specific granules (Crystalloid granules): - Oval in shape, with flattened crystalloid cores -Two parts: Externum (pale): contains histaminase and sulfatase Internum (dark): contains basic protein to kill parasites Eosinophils have a particular phagocytic affinity for antigen- antibody complex Dr. Heba Kalbouneh Dr. Heba Kalbouneh Neutrophil Eosinophil Basophil Percentage Most Least (WBCs) Size 12-15um 12-15um 12-15um Life span Few days Few days Few days Nucleus 2-5 lobes 2 lobes Irregular (S-shaped) Phagocytic Most Least activity Motility Most Least Diapedesis General features of granulocytes (Gr. dia, through + pedesis, to leap) -Spherical in blood stream, irregular in connective tissue -Highly motile with different shapes due to their amoeboid movement -Leave blood stream by migrating between the endothelial cells by a process called diapedesis  Agranulocytes Single non-lobulated nucleus Granules in cytoplasm are too small to see (nonspecific granules, azurophilic granules, primary granules, lysosomes) 2 types based on structure (not cell lineage): – Lymphocytes – Monocytes Monocytes Largest leukocytes Bluish cytoplasm (frosted glass appearance) & a large C-shaped nucleus Highly motile and phagocytic Travel through bloodstream to reach connective tissues, where they transform into macrophages (large phagocytic cells) Dr. Heba Kalbouneh Are precursor cells of macrophages, osteoclasts, microglia, and other cells of the mononuclear phagocyte system in connective All monocyte-derived cells are tissue antigen-presenting cells  Monocytes and macrophages are the same cells at different stages of maturation Dr. Heba Kalbouneh Microglia Kupffer Cells CNS Liver MONONUCLEAR PHAGOCYTIC SYSTEM Macrophages Monocyte Dendritic cells Bone marrow Lymph node Connective tissue Dust cells Spleen Lung Osteoclasts Bone ( all characterized by phagocytic activity) Langerhans cells resorption Epidermis  Lymphocytes Smallest leukocytes Round nucleus occupies most of cell volume Cytoplasm is light clear blue Increased numbers are commonly seen in viral infections Lymphocytes vary in life span according to their specific function, some live for a few days and some live for many years Cell mediated immunity T cells – Has different types, some directly kill foreign or infected cells; others activate phagocytes to destroy microbes Humoral immunity B cells Dr. Heba Kalbouneh – Differentiate into plasma cells – Secrete antibodies that bind to specific antigens and mark them for destruction by phagocytic cells Long term immunity Lymphopoiesis: the process by which lymphocytes are formed Precursor cells in bone marrow Dr. Heba Kalbouneh Thymus Directly into blood BM T Lymphocytes Natural killer lymphocytes B Lymphocytes  Morphologically lymphocytes can be classified into: The amount of cytoplasm depends upon state of activity of the lymphocyte In circulation blood there is predominance of Large small inactive lymphocytes Small (9-18 m) (6-9 m) Active lymphocyte Inactive lymphocyte Different types express specific cell surface proteins Dr. Heba Kalbouneh CD4 or 8 B lymphocyte T lymphocyte Natural killer lymphocyte  Small Large (6-9 m) (9-18 m) Inactive lymphocyte Active lymphocyte Darkly stained cell Lightly stained cell Dr. Heba Kalbouneh  Immunohistochemistry Direct method Anti-CD4 labeled with fluorescent tag CD4 Immunohistochemistry Using CD 4 Antibody ??????? CD 4 + Dr. Heba Kalbouneh T Helper lymphocyte  Neutrophils and monocytes are highly The small lymphocyte has phagocytic and engulf scanty cytoplasm (contain few microorganisms and cell debris in a Dr. Heba Kalbouneh organelles but large number of NON-SPECIFIC manner (Innate ribosomes ) immunity) While Account for basophilic The activity of lymphocytes is always cytoplasm directed against SPECIFIC foreign agents (Adaptive immunity)  Lymphocytes B Lymphocyte T Lymphocyte Natural killer cells (NULL Lymphocyte) Kill virus-infected, Memory cell Plasma cell transplanted and neoplastic cells Produces antibodies (innate immunity) Large granular lymphocytes Activated lymphocytes Cytotoxic Suppressor Kill virus-infected, Suppresses immune response to self Ag transplanted and Suppresses immune response of T and B lymphocytes neoplastic cells (adaptive immunity) Helper Dr. Heba Kalbouneh Help cytotoxic T cells and B cells in their immune functions Innate immunity: We are born with innate immunity. It is non-specific, which means that the innate cells are not able to distinguish one type of pathogen from another. Cells of innate immunity: Neutrophils, Basophils, Eosinophils, Mast cells, Monocytes (macrophages and Suppressor T cells switch off the dentritic cells), natural killer cells immune response when the stimulus is removed Adaptive (acquired) immunity is the body's ability to recognize and respond to specific foreign substances (antigens: microbes, parts of microbes, or non-microbial substances, such as pollen) Damage to suppressor cells can Cells of adaptive immunity: B and T result in autoimmune disease lymphocytes Memory cells allow a more rapid response if the antigen appears again later Natural killer cells and T which allows a very rapid response upon cells play a major role in subsequent exposure to the same antigen. graft rejection Basis of immunity/vaccination The retrovirus that produces acquired immunodeficiency Dr. Heba Kalbouneh syndrome (AIDS) infects and rapidly kills helper T cells. Reduction of this key lymphocyte group cripples the patient’s immune system rendering them susceptible to opportunistic bacterial, fungal, protozoan, and other infections that usually dealt with easily in immunocompetent individuals.  Different types express specific cell surface proteins TCR CD8 CD4 TCR B cell Cytotoxic T cell Helper T cell Note: Receptors of B cells are immunoglobulins that bind antigens directly; those on T cells react only with antigen on MHC molecules and this requires the additional cell surface proteins CD4 or CD8. Dr. Heba Kalbouneh T lymphocytes are said to be MHC restricted "CD" stands for "cluster of differentiation”: are surface molecules that help differentiate one cell type from another  Major histocompatibility complex MHC Glycoprotein on cell membrane Two classes: MHC-I On surface of all nucleated cells Coupled to peptide formed within the cell MHC –II On surface of APCs If the MHCs on cells Coupled to peptide product of proteins of a tissue graft are not similar to those that T the cells had ingested (peptide product of lymphocytes encountered during their Ag digestion) development, the grafted cells will induce a strong immune reaction by T cells of the recipient. To these lymphocytes, the unfamiliar MHC Dr. Heba Kalbouneh epitopes on the graft’s cells are recognized as markers of “non-self ” cells that they must eliminate.  Self- peptide bound to MHC-1 MHC-1 MHC-1 mRNA Self-peptide is derived from the proteins that are synthesized by the cell (Self Antigen) Endogenous protein mRNA Dr. Heba Kalbouneh Peptide fragment Normal cell  Viral- peptide bound to MHC-1 MHC-1 MHC-1 mRNA Viral peptide is derived from the viral proteins that are synthesized by the viral infected cell (non-self Viral mRNA Antigen) Dr. Heba Kalbouneh viral peptide fragment Viral infected cell  Mutant peptide bound to MHC-1 MHC-1 MHC-1 mRNA Mutant peptide is derived from the mutant proteins that are synthesized by the Mutant protein cancerous cell mRNA (non-self Antigen) Dr. Heba Kalbouneh Peptide fragment Cancerous cell  Cytotoxic CD8 T cells: Antigen in virus infected, transplanted or neoplastic cells bind to MHC-I molecules Ag-MHCI complex Ag/ MHC-I complex Viral peptide MHC-I Dr. Heba Kalbouneh virus CD8 TCR Viral infected cell Cytotoxic T cell  Cytotoxic T cell When the Ag- MHCI complex binds to receptors on cytotoxic CD8 T cells They TCR CD8 Proliferate Ag/ MHC-I complex Activate Release Perforins and granzymes (proteases) Dr. Heba Kalbouneh virus Perforins form pores in the cell membrane through which granzymes can enter, inducing apoptosis Viral infected cell  Ag/ MHC-II complex Antigen presenting cell (macrophage, dentritic cell, B lymphocyte) Phagolysosome Lysosome Phagosome MHC-II Dr. Heba Kalbouneh Ag Ag Macrophage Ag (APC) Dr. Heba Kalbouneh Helper CD4 T cells: When Ag is phagocytosed by antigen presenting cells (APCs) e.g macrophages, dentritic cell and B lymphocytes It binds to MHC-II molecules Ag-MHCII complex Ag/ MHC-II complex MHC-II Phagosome phagolysosome Ag CD4 TCR Macrophage (APC) T Helper cell Dr. Heba Kalbouneh T Helper cell When the Ag- MHCII complex binds to receptors on Helper CD4 T cells IL-1 They Proliferate Activate Secrete Lymphokines (cytokines) to Stimulate T and B cells Macrophage (APC)  When a B lymphocyte is stimulated by T helper cells B cell Proliferate Activate Dr. Heba Kalbouneh Activated B lymphocytes: plasma cells memory cells 1- differentiate into plasma cells (secrete antibodies) 2- differentiate into memory cells (Rapid response on the 2nd exposure to the same Ag) Life long immunity (vaccination)  B cells: When the specific Ag binds to receptors on B cells Dr. Heba Kalbouneh receptor-mediated endocytosis and fragments of the Ag bind to MHC-II molecules Ag-MHCII complex Ag/ MHC-II complex Ag MHC-II Free Ag B cell (APC)  T Helper cell T Helper cells bind to Ag-MHCII complex on the B cells Stimulates proliferation and differentiation (activation) of B cells TCR CD4 Ag/ MHC-II complex B cells Dr. Heba Kalbouneh Proliferate Activate Activated B lymphocytes: 1- differentiate into plasma cells (secrete antibodies) 2- differentiate into memory cells (Rapid response on the 2nd exposure to the same Ag) B cell (APC) Life long immunity (vaccination) Never Let Monkeys Eat Bananas Most common to least Dr. Heba Kalbouneh Thrombocytes (Platelets) Small non-nucleated cytoplasmic fragments Formed by fragmentation of the cytoplasm of megakaryocytes in the bone marrow Number: 200,000-400,000/mm3 Shape: biconvex discs Cytoplasm: purple, granular In stained blood smears, platelets often Diameter: 2-4 um appear in clumps Lifespan about 10 days Control the bleeding by plugging the defects in blood vessels and activating blood clotting cascades Platelete has 2 zones  Outer pale basophilic (clear) peripheral zone: hyalomere  Central dark granular zone: granulomere Dr. Heba Kalbouneh Hyalomere: contains cytoskeleton and membranous channels Have thick glycocalyx Cytoskeletal elements  Microtubule Microtubule and microfilament  Actin filaments Maintain shape and help Dense tubular contractions of platelets and system Open canalicular squeezing, clot retraction system Membrane channels Open canalicular system Dense tubular system Granulomere: contains granules and organelles Alpha granules: clotting factors, growth factors Dense (delta) granules: serotonin (absorbed from plasma), ATP, ADP Delta granule Alpha granule Lambda granules: lysosomes (aid in clot resorption) Lambda granule Dr. Heba Kalbouneh  Their main function is to continually monitor the vascular system and detect any damage to the endothelial lining of the vessels. If the endothelial lining breaks, the platelets adhere to the damaged site and initiate a highly complex chemical process that produces a blood clot Thus preventing blood loss Dr. Heba Kalbouneh Useful links (optional) http://highered.mheducation.com/sites/dl/free/0072507470/291136/t_cell_dependent_an tigens.swf http://highered.mheducation.com/sites/dl/free/0072507470/291136/Cytoxic_T_cell_activ ity_against_target_cells.swf http://highered.mheducation.com/sites/dl/free/0072507470/291136/immResponse.swf Some basic concepts in general histology Chromatin Heterochromatin Euchromatin Formed of DNA. 2 Forms: – Euchromatin: extended active chromatin (pale). – Heterochromatin: condensed inactive chromatin (dark) Nucleolus It is a spherical dark mass not surrounded by a membrane. Usually one. Function: formation and assembly of ribosomal RNA (rRNA), which is responsible for protein synthesis in the cytoplasm Nucleoli Dr. Heba Kalbouneh  H&E Active nucleus Inactive nucleus  Note: The nucleus stains blue (basophilic) using H&E Lightly basophilic: active Deeply basophilic and small: inactive Active nucleus (Euchromatin) Dr. Heba Kalbouneh Nucleolus Inactive nuclei (Heterochromatin)  Note: The cytoplasm stains pink/red (acidophilic) using H&E The organelle (when prominent) that produces basophilia in the cytoplasm is the ribosome Dr. Heba Kalbouneh Copyright © McGraw-Hill Companies Dense irregular connective tissue  Bundles of collagen fibers are randomly interwoven with no definite orientation  Provides resistance to stress from all directions  Dermis of skin (deeper layer), organ capsules, submucosa Dense regular connective tissue Parallel Bundles of collagen fibers with few fibrocytes aligned with collagen and separated by very little ground substance Dr. Heba Kalbouneh  Parenchyma / Stroma: The parenchyma of an organ consists of that tissue which conducts the specific function of the organ and which usually comprises the bulk of the organ. Stroma is everything else -- connective tissue, blood vessels, nerves, ducts. It is made up of all the parts without specific functions of the organ For Example: The parenchyma of the heart is muscle tissue (cardiac muscle cells). The nerves, intrinsic blood vessels, and connective tissue of the heart comprise the stroma. Dr. Heba Kalbouneh  Reticular connective tissue Consists of reticular cells (modified fibroblasts) and the network of reticular fibers formed by them Forms the structural framework (stroma) in which the cells of the organ are suspended In the liver, bone marrow, lymph nodes and the spleen (Reticulo-Endothelial organs) Reticular cell Reticular fibers are thin and branching forming a network Dr. Heba Kalbouneh  Types of capillaries Sinusoidal capillaries Continuous capillaries  Exhibit wide diameters with wide  Are most common gaps between endothelial cells  Endothelium forms solid lining  Basement membrane incomplete or absent Adjacent cells are held together with Allow large molecules (proteins and blood tight junctions cells) to pass between the blood and  Found in most organs surrounding tissues  Found in liver, spleen, and bone marrow Fenestrated capillaries  Endothelium contains pores (fenestrations) Found wherever active capillary absorption or filtrate formation occurs  Found in endocrine glands, small intestine, and kidney Dr. Heba Kalbouneh