Histology and Cell Biology PDF for Physiotherapists

1 Histology and Cell Biology A Text and Atlas ‫اﻟﻔ‬ ‫ﺻ‬ For ‫ل اﻟ‬ PHYSIOTHERAPY ‫ا‬ ‫ﻟﻔر ﺳﻲ‬ ‫درا‬ BY ‫ﻗﺔ اﻻ‬ Staff Members of Histology Dep...

1 Histology and Cell Biology A Text and Atlas ‫اﻟﻔ‬ ‫ﺻ‬ For ‫ل اﻟ‬ PHYSIOTHERAPY ‫ا‬ ‫ﻟﻔر ﺳﻲ‬ ‫درا‬ BY ‫ﻗﺔ اﻻ‬ Staff Members of Histology Department Faculty of Medicine ‫اﻻ ول‬ Cairo University ‫و‬ ‫ﻟﻲ‬  2 Chapter 1 Cytology Intended Learning Outcomes (ILOs) By the end of this chapter, the student should be able to: 1- Describe the structure of the different components of the cell at both L.M. and E.M. levels, including: - Nucleus - Membranous organelles 2- Correlate between the structure and function of cellular components. 3- Predict the predominating organelles present in a cell to perform its function. ‫اﻟﻔ‬ The Cell is the structural and functional unit of all living tissues. The cell is ‫ﺻ‬ composed of: 1- Nucleus 2- Cytoplasm ‫ل اﻟ‬ ‫ا‬ ‫ﻟﻔر ﺳﻲ‬ ‫درا‬ ‫ﻗﺔ اﻻ‬ ‫اﻻ ول‬ ‫و‬ ‫ﻟﻲ‬ Nucleus Definition: The nucleus is the largest and the most distinct component of the cell. It is not found in RBCs & platelets (Not True Cells). Nuclei may have different numbers, shapes, sizes and locations.  3 L.M.: It appears as a large, basophilic structure that usually occupies the widest part of the cell. Appearance: May be Pale-stained (Vesicular or open face nucleus) as in nerve cells. Darkly-stained (Condensed or closed face nucleus) as in lymphocytes. Structure of the Nucleus 1. Nuclear membrane (envelope) 2. Nucleolus 3. Chromatin 4. Nuclear sap ‫اﻟﻔ‬ ‫ﺻ‬ ‫ل اﻟ‬ ‫ا‬ ‫ﻟﻔر ﺳﻲ‬ ‫درا‬ ‫ﻗﺔ اﻻ‬ ‫اﻻ ول‬ ‫و‬ 1. Nuclear Membrane (Envelope): ‫ﻟﻲ‬ L.M.: It appears as a single basophilic line. E.M.: It consists of two parallel membranes separated by a perinuclear space. The two membranes fuse at intervals forming openings called nuclear pores. The outer nuclear membrane: faces the cytoplasm and is continuous with the rough endoplasmic reticulum at certain sites, this membrane is studded with ribosomes. Inner nuclear membrane: has chromatin granules (peripheral chromatin). Nuclear pores: permit the passage of certain materials in both directions between the nucleus and cytoplasm.  4 2. Nucleolus: L.M.: it is a spherical, highly basophilic structure in the nuclei of cells. It is active in protein synthesis. It is basophilic due to the presence of RNA and DNA. E.M.: it consists of:- - Pars amorpha (Nucleolar organizer): are pale areas composed of DNA encoding for ribosomal RNA (rRNA). - Pars fibrosa: Small fibrils representing the early stage in the formation of rRNA by the DNA. - Pars granulosa: Large particles representing mature rRNA. 3. Chromatin: Consists of double-stranded DNA bound with histones and non-histone ‫اﻟﻔ‬ proteins. In non-dividing cells, chromatin is found in two forms: ‫ﺻ‬ Heterochromatin Euchromatin ‫ل اﻟ‬ Condensed inactive chromatin Extended active chromatin ‫ا‬ ‫ﻟﻔر ﺳﻲ‬ Present in closed face nuclei Present in open face nuclei Contains inactive genes. Contains active genes. Predominates in metabolically Predominates in metabolically ‫درا‬ ‫ﻗﺔ اﻻ‬ inactive cells. active cells involved in protein synthesis. ‫اﻻ ول‬ L.M.: visible by L.M. as coarse L.M.: invisible by L.M. & the nucleus granules & the nucleus appears dark appears pale basophilic basophilic ‫و‬ E.M.: It appears electron dense E.M.: lt appears electron-lucent ‫ﻟﻲ‬ Sites: 1- Adherent to the inner nuclear envelope (peripheral chromatin). 2- Around the nucleolus (nucleolus associated chromatin). 3- Scattered throughout the nucleoplasm (chromatin islands). 4. Nuclear sap: It is the semi fluid, colloidal solution found between the chromatin and the nucleolus and contains enzymes and lipoproteins.  5 Functions of the Nucleus: 1- It carries genetic information encoded in deoxyribonucleic acid (DNA) of the chromosomes. 2- It is important for cell division. 3- It forms RNA for protein synthesis. Cytoplasm It is formed of: 1- Matrix: It is a viscous colloidal solution formed of protein- carbohydrates- lipids- enzymes- minerals- ions- salts. 2- Organelles: They are living structures- differentiated –permanent- essential ‫اﻟﻔ‬ for vital processes of the cell. 3- Inclusions: They are not essential for vitality of cells. They may be present ‫ﺻ‬ or absent. ‫ل اﻟ‬ ‫ا‬ Organelles are classified according to the presence or absence of ‫ﻟﻔر ﺳﻲ‬ membranes into: A. Membranous Organelles B. Non-membranous Organelles ‫درا‬ ‫ﻗﺔ اﻻ‬ (contain enzymes) (Do not contain enzymes) ‫اﻻ ول‬ 1. Cell membrane (plasma 1- Ribosomes membrane). ‫و‬ 2- Centrioles 2. Mitochondria. ‫ﻟﻲ‬ 3. Endoplasmic reticulum (rough & smooth). 4. Golgi apparatus. 5. Lysosomes  6 A- Membranous Organelles 1- Cell Membrane Definition: A very thin membrane, approximately 7.5 nm thick that surrounds the cell. L.M.: Very difficult to be seen by the light microscope when stained with H&E. It can be stained with Ag or PAS. E.M.: appears as 2 dark lines, separated by a light one (trilamellar). ‫اﻟﻔ‬ ‫ﺻ‬ ‫ل اﻟ‬ ‫ا‬ ‫ﻟﻔر ﺳﻲ‬ E.M picture of two adjacent cells membranes ‫درا‬ ‫ﻗﺔ اﻻ‬ Molecular Structure of Cell Membrane:- 1- Lipid Component: (30%) ‫اﻻ ول‬ a) Phospholipid molecules: arranged into 2 layers (lipid bilayer). Each molecule has a polar head and a non-polar tail. ‫و‬ ‫ﻟﻲ‬ Hydrophilic polar End Hydrophobic Non-Polar End It forms the head of the phospholipid It forms the 2 tails of the phospholipid molecule. molecule. It is hydrophilic due to its great affinity It is hydrophobic as it has no affinity to aqueous solutions. to aqueous solutions. It is called polar as it is charged.It is called non-polar as it is non- charged. Heads are arranged at the outer and Tails are directed inwards, they face inner surfaces. each other in the center. b) Cholesterol: Present at the region of the hydrophobic tails.  7 2- Protein Component: (60%) a) Extrinsic protein (peripheral): Loosely attached at both sides of the lipid bilayer b) Intrinsic protein (integral): are present in the lipid bilayer in the form of: Small molecules Large molecules (Trans-membrane protein). Some integral proteins cross the membrane and act as pathways for ions and molecules (Trans- membrane transport). 3- Carbohydrate Component: (10%) Conjugated either with proteins or lipids (glycoproteins and glycolipids), forming the surface coat (Glycocalyx). ‫اﻟﻔ‬ ‫ﺻ‬ ‫ل اﻟ‬ ‫ا‬ ‫ﻟﻔر ﺳﻲ‬ ‫درا‬ ‫ﻗﺔ اﻻ‬ ‫اﻻ ول‬ ‫و‬ ‫ﻟﻲ‬ Functions of cell membrane: 1- Passive transport: a) Passive diffusion: movement of solute from a high concentration to a lower concentration. b) Facilitated diffusion (carrier-mediated diffusion): They need carrier and pass through integral protein (with concentration gradient) e.g. glucose. 2- Active transport: (against concentration gradient) needs energy, e.g. Sodium pump.  8 3- Bulk transport: a) Endocytosis: is the uptake of materials across the cell membrane into the cytoplasm of the cell. 1- Phagocytosis: is the process of engulfing solid particles by the cell membrane to form an internal phagosome (phagocytic vesicle) 2- Pinocytosis: is the process of engulfing fluid droplets by the cell membrane to form pinocytotic vesicles. 3- Receptor-mediated endocytosis (selective transport). Specific molecules bind to their receptors that accumulate at the plasma membrane. Gradual invagination of the plasma membrane forms the coated pits that become surrounded on the cytoplasmic side by protein molecules called ‫اﻟﻔ‬ clathrin. Clathrin molecules form a basket like cage that changes the shape of the ‫ﺻ‬ plasma membrane into vesicle like invagination called coated vesicle. b) Exocytosis: is a process for moving substances from the cytoplasm of the ‫ل اﻟ‬ cell to the outside. ‫ا‬ ‫ﻟﻔر ﺳﻲ‬ ‫درا‬ ‫ﻗﺔ اﻻ‬ ‫اﻻ ول‬ ‫و‬ ‫ﻟﻲ‬ Bulk transport Receptor- mediated endocytosis 4- Functions of the surface coat: they form receptors that participate in important interactions such as:- a) Cell adhesion: The glycocalyx helps in attachment of some cells to each other & to extracellular matrix components. b) Cell recognition. c) Cell immunity: It binds antigens to the cell surface.  9 5- Cell membrane modification: 1-Microvilli (increase the surface area for absorption) 2-Cilia (push particles at one direction) 3-Flagella (allow sperm movement) 4-Stereocilia (long microvilli) 6- Conduction of excitation waves : Transduction of extracellular signals into intracellular events. 2- Mitochondria Definition: Mitochondria are membranous organelles, responsible for cell ‫اﻟﻔ‬ respiration and energy production in the cell. Number: Mitochondria are more numerous in cells that have a high energy ‫ﺻ‬ requirement e.g. muscle cells, liver, heart and sperm cells. L.M.: They appear as rods, granules or filaments when stained with Iron ‫ل اﻟ‬ haematoxylin (appear dark blue) and with Janus green (appear green). ‫ا‬ ‫ﻟﻔر ﺳﻲ‬ E.M.: The mitochondria is surrounded by 2 membranes:- The outer membrane is smooth, ‫درا‬ The inner membrane forms incomplete shelves (cristae) which increase its ‫ﻗﺔ اﻻ‬ surface area, enhancing its ability to produce ATP. - The space in-between is called inter-membranous space. - The mitochondrial matrix contains the following:- ‫اﻻ ول‬ (1) Enzymes that synthesize ATP via the Krebs cycle. (2) Matrix granules which bind Mg+2 and Ca+2 (regulate the activity of some ‫و‬ mitochondrial enzymes. ‫ﻟﻲ‬ (3) Mitochondria have their own DNA and RNA. Diagram and E.M. picture of a mitochondrion  10 Functions of mitochondria: 1- Cell respiration and production of ATP through oxidation of fatty acids & glucose. ATP is the primary source of cell energy. That’s why they are called the power house of the cell 2- They can form proteins for themselves and can divide (self replication). 3- Endoplasmic Reticulum It is a system of interconnected membranous tubules and vesicles forming a reticulum in the cytoplasm. There are two types of ER, rough endoplasmic reticulum (rER) and smooth endoplasmic reticulum (sER). Rough Endoplasmic Reticulum Smooth Endoplasmic Reticulum ‫اﻟﻔ‬ (rER) (sER) It is a system of flattened membrane It is a network of membrane-bounded ‫ﺻ‬ bound tubules or sacs parallel to each interconnecting tubules. others. Its outer surface is studded with ribosomes, ‫ل اﻟ‬ It lacks ribosomes on its surface, which makes it appears smooth. ‫ا‬ which makes it appears rough. ‫ﻟﻔر ﺳﻲ‬ Site: Abundant in protein-forming cells as Site: Abundant in steroid-forming cells as in fibroblasts, chondroblasts and plasma cells. endocrine glands. ‫درا‬ ‫ﻗﺔ اﻻ‬ L.M.: In H&E stained sections, rER appears L.M.: Not visible as it lacks the surface basophilic. This basophilia is due to the ribosomes, but cytoplasmic acidophilia presence of ribosomes (rRNA). suggests presence of sER. ‫اﻻ ول‬ E.M.: appears as closely packed, membrane- E.M.: appears as branching, anastomosing bound, flattened cisternae that are studded with tubules or vesicles, with no ribosomes on ‫و‬ ribosomes on their outer surface. their outer surface. ‫ﻟﻲ‬ Functions of rER: Ff Functions of sER: 1- Accumulation of protein synthesized by 1- Synthesis of Lipids (as phospholipids & ribosomes. Cholesterol). 2- Segregation of the formed protein. 2- Synthesis of steroid hormones as 3- Initial glycosylation. testosterone and cortisol. 4- Packing of formed protein in membranous 3- Detoxification of drugs, hormones & vesicles that bud off from rER, called alcohol( in liver cells). "Transfer vesicles" and transfer protein to 4- Muscle contraction and relaxation Golgi. in skeletal muscle cells, where sER is 5- Protection of the cytoplasm from hydrolytic specialized for storage and release of Ca+2 enzymes inside its cisternae 5- Glycogen synthesis and storage in both 6- Intracellular transport. liver and skeletal muscle cells. 6- Intracellular transport  11 ‫اﻟﻔ‬ ‫ﺻ‬ 4- Golgi Apparatus Definition: Membranous organelle that is well developed in secretory cells. It is ‫ل اﻟ‬ ‫ا‬ considered the secretory apparatus of the cell. ‫ﻟﻔر ﺳﻲ‬ L.M.: In H&E-stained sections: it does not appear. It can be seen as an unstained ‫درا‬ ‫ﻗﺔ اﻻ‬ area (negative Golgi image) in protein secreting cells which have deeply basophilic cytoplasm. In silver (Ag)-stained sections: it appears as brown network of fibrils either: ‫اﻻ ول‬ Apical: between nucleus and secretory pole in secretory cells. Perinuclear: surrounds the nucleus in nerve cells. ‫و‬ E.M..: It consists of: ‫ﻟﻲ‬ Several membrane-bound flattened saccules. These saccules are slightly curved, with flat centers and dilated ends. They are interconnected with each other. Each saccule is formed of 2 faces: The immature (Convex, Cis face): receives transfer vesicles from rER. The mature (Concave, Trans face): from which secretory vesicles arise. Fate of Secretory vesicles: - Remain inside the cell in the form of lysosomes. - Release their content outside the cell by exocytosis  12 Functions: 1- Modification of proteins delivered from the rough endoplasmic reticulum by ‫اﻟﻔ‬ addition of carbohydrates and sulphates. 2- Concentration and packaging of these large molecules for cell secretion (by ‫ﺻ‬ exocytosis) or use within the cell. 3- Synthesis of lysosomes. ‫ل اﻟ‬ 4- Maintenance of cell membrane. ‫ا‬ ‫ﻟﻔر ﺳﻲ‬ ‫درا‬ ‫ﻗﺔ اﻻ‬ ‫اﻻ ول‬ The role of Golgi apparatus in maintenance of the cell membrane ‫و‬ ‫ﻟﻲ‬ 5- Lysosomes Digestive apparatus Definition: Lysosomes are membrane-bound organelles that function to digest nutrients, foreign and dead materials. Origin: Lysosomes contain hydrolytic enzymes which are synthesized in the rER and then transferred to the Golgi apparatus for further concentration and packing. Newly released Lysosomes from Golgi, are not involved in any of the digestive processes & are called primary lysosomes. Primary lysosomes when involved in digestive processes are called secondary lysosomes.  13 Site: Lysosomes predominate in phagocytic cells as in macrophages. L.M.: Lysosomes can be identified by histochemical staining e.g. acid phosphatase. E.M.: (I) Primary lysosomes: Spherical membranous vesicle surrounded by a single membrane Appear as homogenous vesicles. (II) Secondary lysosomes: Appear as heterogeneous vesicles: Types of secondary lysosomes: 1- Phagolysosome: formed by fusion of a phagocytic vacuole (solid-filled vacuoles) with a primary lysosome. ‫اﻟﻔ‬ 2- Multivesicular body: formed by fusion of a pinocytic vesicle (fluid-filled vacuoles) with a primary lysosome. ‫ﺻ‬ 3- Autophagolysosome: formed by fusion of an autophagic vacuole (vacuole containing old organelles) with a primary lysosome. 4- Residual bodies: contain indigestible materials. ‫ل اﻟ‬ Fate of residual bodies: they either: ‫ا‬ ‫ﻟﻔر ﺳﻲ‬ Accumulate within long lived cells (heart and brain) as lipofuscin pigment. Expelled outside the cell by exocytosis. ‫درا‬ ‫ﻗﺔ اﻻ‬ ‫اﻻ ول‬ ‫و‬ ‫ﻟﻲ‬ Diagram showing types of Lysosomes Functions of lysosomes: 1- Breakdown of materials ingested by endocytosis. 2- Turnover of torn out cellular components. 3- In cell metabolism, lysosomes are needed to release thyroid hormone from thyroglobulin stored in thyroid follicles. 4- Fertilization by helping the sperm to penetrate the ovum. 5- Post-mortem autolysis.  14 B- Non-membranous Organelles 1- Ribosomes Definition: Non-membranous electron-dense particles responsible for protein synthesis Number: Abundant in "protein synthesizing cells". L.M.: When abundant they cause cytoplasmic basophilia. E.M.: Small electron-dense granules, each is formed of 2 subunits: small & large. The large subunit contains a groove in its center which contains the polypeptide chain. ‫اﻟﻔ‬ They may be free in the cytoplasm or attached to rER by the large subunits. ‫ﺻ‬ ‫ل اﻟ‬ 2- Centrioles ‫ا‬ ‫ﻟﻔر ﺳﻲ‬ Definition: Cylindrical structures composed of highly organized microtubules (MTs). ‫درا‬ [MTs are fine tubules formed of tubulin protein ‫ﻗﺔ اﻻ‬ and they determine the shape of the cells]. L.M.: Centrioles can be demonstrated with iron ‫اﻻ ول‬ hematoxylin stain as two dark bodies near the nucleus. ‫و‬ E.M.: ‫ﻟﻲ‬ Centrioles appear as 2 cylindrical structures, perpendicular to each other. The wall of each cylinder is formed of 9 bundles of MTs, each bundle is formed of 3 MTs (triplets). Consequently, the wall of each centriole is formed of 9 x 3 = 27 MTs. Functions: 1- During cell division, the centrioles duplicate. Each pair moves to one pole of the cell and become organizing centers for MTs of the mitotic spindle. 2- Centrioles share in the formation of cilia and flagella.  15 Chapter 2 Epithelial Tissue Intended Learning Outcomes (ILOs) By the end of this chapter, the student should be able to: 1- Identify the general characters of epithelial tissue 2- List the classifications of epithelial tissue 3- Describe the structure of each epithelial type 4- Identify the functions and the sites of each epithelial type 5- Describe the structure and sites of neuroepithelium. ‫اﻟﻔ‬ The Basic Types of Tissues in the Body are: ‫ﺻ‬ 1- Epithelial Tissue 2- Connective Tissue 3- Muscular Tissue ‫ل اﻟ‬ 4- Nervous Tissue ‫ا‬ ‫ﻟﻔر ﺳﻲ‬ General Characters of Epithelial Tissue: It may be ectodermal, mesodermal or endodermal in origin. ‫درا‬ ‫ﻗﺔ اﻻ‬ It consists of closely packed cells with little intercellular material. It is avascular i.e. no blood vessels can penetrate between epithelial cells. Exchange of nutrients and waste products occurs through the underlying ‫اﻻ ول‬ connective tissue (C.T.) by diffusion. The upper surface of epithelium is free. The basal surface rests on ‫و‬ a basement membrane (B.M.) which separates the epithelium from the underlying C.T. ‫ﻟﻲ‬ It has high power of regeneration i.e. replaces damaged cells with new epithelial cells. Classification of Epithelium Epithelial tissue is classified into: 1- Surface epithelium. 2- Glandular epithelium. 3- Neuro-epithelium. 4- Myo-epithelium. (1) Surface Epithelium Is the epithelium that covers the outside surfaces of the body and lines all internal cavities.  16 Surface epithelium is classified according to the number of layers into: (A) Simple Epithelium formed of a single layer of cell, resting on a basement membrane. It is classified according to the shape of cells into four major classes: 1- Simple squamous 2- Simple cubical. 3- Simple columnar 4- Pseudostratified columnar (B) Stratified Epithelium formed of two or more cell layers. It is classified ‫اﻟﻔ‬ according to the shape of the superficial cells into four major classes: 1-Stratified squamous (keratinized & non-keratinized) ‫ﺻ‬ 2-Transitional 3- Stratified cubical 4- Stratified columnar ‫ل اﻟ‬ ‫ا‬ ‫ﻟﻔر ﺳﻲ‬ Types of Simple Epithelium ‫درا‬ ‫ﻗﺔ اﻻ‬ Simple Squamous Simple Cubical Simple Pseudostratified Epithelium Epithelium Columnar Columnar Epithelium Epithelium ‫اﻻ ول‬ - Single layer of flat -Single layer of cubical - Single layer of tall - Single layer of Structure cells with flattened cells, with central round columnar cells with cells of different nuclei. nuclei. basal oval nuclei. heights, all the cells ‫و‬ touch the basement -Height of the cells is ‫ﻟﻲ‬ membrane but not approximately equal to all cells reach the their width. free surface. - The nuclei are oval located at different levels giving false appearance of stratification. Provides thin Secretion: e.g. (i) Non-Ciliated (i) Non ciliated Functions membrane for: type: type: lining and sites - Thyroid follicles  17 (a) diffusion of gases - Acini &ducts of. Secretion: e.g. part of male urethra (e.g. alveoli of the salivary glands. and some ducts of stomach lungs) or salivary glands. (b) filtration of blood. Secretion & (ii) Ciliated type: Reabsorption: (e.g. Bowman’s absorption: e.g. in has motile cilia, e.g. convoluted kidney capsule of the renal intestine. with mucous- tubules corpuscle). secreting goblet N.B.: The free cells, to sweep out Provides surface has mucous- trapped smooth surface to: microvilli to particles e.g. Lining increase the (a) facilitate flow of of nasal cavity and surface area. blood (e.g. trachea. endothelium lining (ii) Ciliated type: ‫اﻟﻔ‬ the heart and blood - Lung bronchioles vessels). (b) to sweep out ‫ﺻ‬ easy movement of mucous. organs (e.g. mesothelium of - Female genital ‫ل اﻟ‬ peritoneum, pleura tract to move the ‫ا‬ ova. ‫ﻟﻔر ﺳﻲ‬ and pericardium). ‫درا‬ ‫ﻗﺔ اﻻ‬ ‫اﻻ ول‬ Stratified Epithelium ‫و‬ Stratified Squamous Transitional ‫ﻟﻲ‬ Structure Formed of 5-20 cell layers resting on a Formed of 5-8 cell layers resting on non-clear, clear wavy basement membrane. non-wavy basement membrane. -It gets its name for its ability to change its thickness as its cells can stretch and flatten to increase the internal volume of the organ e.g. full bladder. -The basal layer: columnar cells with Two states are identified: basal oval nuclei. They are mitotically Relaxed state: active - The basal cells: cuboidal cells with central  18 - The intermediate layers: polyhedral rounded nuclei. cells with central round nuclei. They - The Intermediate cells: polygonal cells with become smaller toward the surface. central rounded nuclei. The cells are separated - The superficial layers: flat cells with from each other by mucus-like substance flattened nuclei. which facilitates gliding of cells on each other. - The superficial cells: large, cuboidal, dome-shaped, some may be binucleated. ‫اﻟﻔ‬ Two types are present: Stretched state: Keratinized type: the surface is The epithelium flattens out (the cells become ‫ﺻ‬ covered by a tough protein called squamous) with apparent decrease in number keratin. of cell layers. Non keratinized type: not ‫ل اﻟ‬ ‫ا‬ covered by keratin. ‫ﻟﻔر ﺳﻲ‬ Function Protection Protection and distensibility. Sites skin, Lining the urinary tract e.g. urinary bladder and ‫درا‬ Keratinized type: in ‫ﻗﺔ اﻻ‬ external ear and nasal orifices ureter, so this epithelium is known as Non keratinized type: oral cavity, uroepithelium. esophagus and cornea ‫اﻻ ول‬ ‫و‬ (2) Neuro - Epithelium ‫ﻟﻲ‬ It is a modified type of epithelium which acts as a receptor. It is composed of sensory cells and supporting cells e.g. taste buds in the tongue. - Sensory cells have small hairs at their free surfaces, while their bases are surrounded with sensory nerve fibers. - Supporting cells surround and support the sensory cells.  19 Chapter 3 Connective Tissue Intended Learning Outcomes (ILOs) By the end of this chapter, the student should be able to: 1- Enumerate the different types of connective tissue cells and fibers & mention their functions. 2- Describe the histological structure of connective tissue cells. 3- Describe the histological structure of different types of connective tissue proper. 4- Enumerate the sites and functions of different types of connective tissue General Characteristics of C.T. ‫اﻟﻔ‬ proper. 5- Compare between the types of connective tissue proper according to the ‫ﺻ‬ amount and proportion of its components. ‫ل اﻟ‬ General Characteristics of Connective Tissue (C.T.): ‫ا‬ ‫ﻟﻔر ﺳﻲ‬ 1- Mesodermal in origin. 2- Formed of large amount of matrix & widely separated cells. 3- Penetrated by blood vessels, lymphatics and nerves. ‫درا‬ ‫ﻗﺔ اﻻ‬ 4- Supports and protects other tissues and organs. bxMbxMNBxmnbxmbhbaNB Components: It consists of three components: mnXmnXNja ‫اﻻ ول‬ 1. Cells: Fixed and free. ‫و‬ 2. Fibers: Collagen, elastic and reticular. 3. Matrix: C.T is classified into four types according to matrix consistency: ‫ﻟﻲ‬ Matrix Consistency Type of C.T. 1- Soft → C.T. Proper 2- Firm → Cartilage 3- Solid → Bone 4- Fluid → Blood  20 Connective Tissue Proper (I) C.T. Cells A- Fixed B- Free (stable, long- lived) (motile, short-lived) 1- UMCs 1- Plasma Cells 2- Pericytes 2- Mast Cells 3- Fibroblasts 3-Free Macrophages 4- Fat cells 4- Leucocytes 5- Fixed macrophages 6- Reticular cells ‫اﻟﻔ‬ (A) Fixed C.T. Cells ‫ﺻ‬ (1) Undifferentiated (2) Pericytes (3) Fibroblasts Mesenchymal Cells ‫ل اﻟ‬ (UMCs) ‫ا‬ * Origin: UMCs UMCs & Pericytes ‫ﻟﻔر ﺳﻲ‬ *Site: - Mainly in the embryo. Around blood The most common cells ‫درا‬ - In adult , in certain areas capillaries in C.T. proper ‫ﻗﺔ اﻻ‬ e.g. bone marrow ‫اﻻ ول‬ *Shape: ‫و‬ ‫ﻟﻲ‬ L.M. Small branched cell Branched cell with: Branched elongated with: Pale basophilic cell with: Pale basophilic cytoplasm. Deeply basophilic cytoplasm Central oval nucleus. cytoplasm. Central oval nucleus. Large oval pale nucleus with prominent nucleolus.  21 E.M. Many free ribosomes Many free "Features of protein Few other organelles ribosomes secreting cell" Few other organelles -Euchromatic (active) Actin & myosin. nucleus with large nucleolus. -Large amount of rER & many mitochondria. -Well developed Golgi apparatus. N.B.: Old inactive fibroblasts are called Fibrocytes. They can change to ‫اﻟﻔ‬ active fibroblast in wound healing. ‫ﺻ‬ ‫ل اﻟ‬ ‫ا‬ *Function 1) In embryo: Act as = UMCs of the adult 1) Formation of ‫ﻟﻔر ﺳﻲ‬ stem (Mother) Cells; can C.T. fibers & matrix. differentiate into all types - During injury of C.T. of C.T. cells. & blood vessels, 2) Healing of C.T. after injury. ‫درا‬ 2) In adult: they remain Pericytes can give rise ‫ﻗﺔ اﻻ‬ undifferentiated in certain to: areas to act as life-long Fibroblasts source for some cells Smooth muscle cells ‫اﻻ ول‬ e.g. Endothelial cells a) in bone marrow→ Blood cells - Pericytes can ‫و‬ b) around blood vessels contract & constrict ‫ﻟﻲ‬ → Pericytes blood vessels (4) Fat Cells (Adipocytes): Origin: UMCs 2 Types Unilocular Fat Cell Multilocular Fat Cell Site In white adipose C.T. In brown adipose C.T. L.M. Large oval (50-150 µm). Small rounded cells.  22 Nucleus: peripheral & flat. Nucleus: central , rounded Cytoplasm: a very thin film around a Cytoplasm: has many small single large fat droplet. fat droplets. In H&E-stained sections, fat dissolves and cells appear as large vacuoles Pigmented by the cytochrome (signet-ring appearance). pigments in the mitochondria In frozen sections, fat stains orange with Sudan III. EM Few mitochondria Many mitochondria Function - Storage of fat to release energy. Heat generator ‫اﻟﻔ‬ - Heat Insulator. ‫ﺻ‬ (5)Fixed Macrophages: Origin: Blood Monocytes. ‫ل اﻟ‬ Site: In loose C.T. along collagen fibers, known as Histiocytes. ‫ا‬ ‫ﻟﻔر ﺳﻲ‬ L.M.: Have a highly variable shape due to amoeboid movement. Nucleus: small, kidney-shaped & darkly-stained. Cytoplasm: Pale &granular. ‫درا‬ ‫ﻗﺔ اﻻ‬ Special stains: Vital stain e.g. Trypan blue. E.M.: Cytoplasm is rich in lysosomes and phagocytosed particles. Functions: ‫اﻻ ول‬ 1) Phagocytosis of foreign particles & microorganisms. 2) Fuse & form giant cell to engulf large foreign bodies. ‫و‬ 3) Act as antigen presenting cells to T-Lymphocytes. ‫ﻟﻲ‬ 4) Destruction of old RBCs in liver & spleen. (6) Reticular Cells: Origin: UMCs Site: In stroma of different organs e.g. spleen, lymph nodes. L.M.: Small branched cells with many long thin processes. Central rounded nucleus & pale basophilic cytoplasm. Functions: Form a reticular network with reticular fibers 1- Act as supporting cells. 2- Can act as phagocytic cells, on need.  23 (b) Free C.T. Cells (1) Plasma Cells (2) Mast Cells Origin Develop from activated B- UMCs in bone marrow lymphocytes. Site -In loose C.T. along blood Abundant in lymphoid tissues. vessels -In C.T. under epithelium of respiratory & digestive tracts. Shape - Large oval in shape. -oval cell L.M. -Nucleus is eccentric with a -Nucleus: central, rounded ‫اﻟﻔ‬ cart-wheel (clock-face) appearance. -Cytoplasm: is full of -Cytoplasm is basophilic with basophilic granules. ‫ﺻ‬ negative Golgi image -Special stain: granules can be stained metachromatically ‫ل اﻟ‬ with Toluidine blue (purple ‫ا‬ color instead of blue) ‫ﻟﻔر ﺳﻲ‬ ‫درا‬ ‫ﻗﺔ اﻻ‬ "Features of Protein secreting cell" well developed Golgi apparatus, large amount of rER & Cytoplasm is full of electron- many mitochondria. ‫اﻻ ول‬ dense granules that mask E.M. No secretory granules, as they other contents are secreted continuously. ‫و‬ 1-Secretion of Heparin: ‫ﻟﻲ‬ Functions Secretion of antibodies (anticoagulant) 2-Secretion of Histamine which initiates allergic reactions. 3-Secretion of Eosinophil Chemotactic Factor (ECF) which attracts eosinophils to the site of allergy. (3) Free Macrophages: - Have the same origin, structure and function of fixed macrophages. (4) Leucocytes: All blood leucocytes migrate from the blood stream to C.T. to perform their defensive functions.  24 (II) Connective Tissue Fibers White Collagen Yellow Elastic Reticular Fibers Fibers Fibers Origin Mainly Fibroblasts Fibroblasts Fibroblasts (+ chondroblasts & osteoblasts) LM Wavy branching Thin long Very thin fibers that branch & bundles, formed of branching fibers. anastomose forming a non-branching parallel Run singly not in network fibers bundles. Drawing ‫اﻟﻔ‬ ‫ﺻ‬ ‫ل اﻟ‬ ‫ا‬ ‫ﻟﻔر ﺳﻲ‬ Color & - Colorless when - Yellow in color Brown with Silver stain stain single, white when when fresh. (argyrophilic) ‫درا‬ ‫ﻗﺔ اﻻ‬ condensed. - Pink in H&E - Pink in color in H&E - Brown with (acidophilic) Orcein. ‫اﻻ ول‬ Character Strong , rigid & Stretchable Delicate & flexible not elastic Function Give strength to Give elasticity to Form the stroma ‫و‬ tissues & resist tissues (background) which supports stretching organs ‫ﻟﻲ‬ Types Many types, the most one type one type important are; I, II, III, IV,V, VII. Types of Connective Tissue Proper Classified according to the relative abundance of the basic components into: (I) Loose C.T. (II) Dense C.T. 1- Loose (Areolar) C.T. 1- White Fibrous C.T. 2- Reticular C.T. a-Regular b- Irregular 3- Mucoid C.T. 2- Yellow Elastic C.T. 4- Adipose C.T.  25 (I) Loose Types of C.T. Proper 1- Loose (Areolar) C.T.: (The most common type) Structure: - It contains: - All types of C.T. cells (mainly fibroblasts, fat cells & macrophages) and all types of C.T. fibers (mainly collagen), embedded in a loose matrix. - Contains potential cavities (areolae), which may be filled with fluids or gases. Sites: 1- Present allover the body except the brain. ‫اﻟﻔ‬ 2- Around organs and blood vessels. 3- Under epithelium; in submucosa & ‫ﺻ‬ dermis of skin. Functions: ‫ل اﻟ‬ 1- It binds tissues together & surrounds ‫ا‬ ‫ﻟﻔر ﺳﻲ‬ organs.. 2- It supports epithelium and blood vessels. ‫درا‬ ‫ﻗﺔ اﻻ‬ 2- Reticular C.T.: Structure: It is formed of: ‫اﻻ ول‬ a) Reticular Fibers: fine branching fibers. b) Reticular Cells: These are modified fibroblasts. ‫و‬ They are branched cells with long processes that ‫ﻟﻲ‬ are connected with each other. Reticular cells and fibers form a network (reticulum) which is stained brown by Silver stain (Ag). Sites& functions: Both reticular cells and fibers form the framework (Stroma) of organs (to support the functioning cells) e.g. lymph node, spleen & liver 3- Adipose C.T. It is a loose C.T., in which fat cells predominate. It consists of groups of fat cells, separated by fibrous septa.  26 There are 2 types: White Adipose C.T. Brown Adipose C.T. Structure: - Unilocular fat cells: large - Multilocular fat cells: small with flat peripheral nucleus with central rounded nucleus - Each cell contains a large - Each cell contains many fat single fat droplet. droplets. - Fat is not pigmented. - The fat is pigmented due to: - Poor blood supply a) High vascularity b) Cytochrome pigments in mitochondria ‫اﻟﻔ‬ ‫ﺻ‬ Sites: ‫ل اﻟ‬ - Under the skin *In fetus & newborn: ‫ا‬ ‫ﻟﻔر ﺳﻲ‬ - Mammary gland. - Interscapular region & axilla - Around the kidney *In adults only around thoracic aorta ‫درا‬ Functions: - Storage of fat. ‫ﻗﺔ اﻻ‬ - Heat insulator - Heat generation (in - Support of organs e.g. newly born infants) kidney. ‫اﻻ ول‬ - Forms the body contours, especially in females. ‫و‬ 4- Mucoid C.T.: ‫ﻟﻲ‬ Structure: Formed of: - Large amount of jelly-like ground substance rich in mucus and hyaluronic acid. - UMCs & fibroblasts that communicate by their processes. - Fine collagen fibers Sites: - Umbilical cord (Known as Wharton′s Jelly) - Pulp of.growing teeth - Vitreous humor of the eye Function: It protects near-by structures from pressure.  27 (II) Dense Types of C.T. Proper 1- White Fibrous C.T.: Structure: Formed of: Bundles of collagen fibers and fibroblasts with minimal ground substance. Types: 2 types according to the arrangement of collagen bundles: Regular White Fibrous C.T. Irregular White Fibrous C.T. Structure Parallel collagen bundles with Irregulary arranged collagen bundles fibroblasts in-between with fibroblasts in-between ‫اﻟﻔ‬ ‫ﺻ‬ ‫ل اﻟ‬ ‫ا‬ ‫ﻟﻔر ﺳﻲ‬ Sites - Tendons - Cornea - Periosteum - Perichondrium - Dermis of skin - Capsule of organs ‫درا‬ ‫ﻗﺔ اﻻ‬ Function Withstand stretch in one direction Withstand stretch in different directions ‫اﻻ ول‬ 2-Yellow Elastic C.T.: ‫و‬ Structure: Formed of: ‫ﻟﻲ‬ - Mainly elastic fibers (so appears yellow in fresh state) - Fibroblasts. Sites: - Aorta - Bronchi & bronchioles - Ligaments Function: Recoil after stretch.  28 Chapter 4 Cartilage Intended Learning Outcomes (ILOs) By the end of this chapter, the student should be able to: 1- Describe the histological structure of different types of cartilage (hyaline, yellow elastic & white fibrocartilage). 2- Differentiate between the three types of cartilage. ‫اﻟﻔ‬ 3- Elucidate the sites of each type of cartilage. ‫ﺻ‬ Definition: It is a specialized type of C.T. in which the matrix is rubbery (firm but flexible) to bear mechanical stress. ‫ل اﻟ‬ Characters of cartilage: ‫ا‬ ‫ﻟﻔر ﺳﻲ‬ Being a type of C.T., cartilage is formed of cells, fibers and ground substance (matrix). ‫درا‬ ‫ﻗﺔ اﻻ‬ The cells are widely separated by a considerable amount of intercellular substance (matrix). Cartilage is avascular (non-vascular), nourished by diffusion of O2 & nutrients ‫اﻻ ول‬ from surrounding C.T. or synovial fluid in the joint cavities. ‫و‬ It has no lymph vessels or nerves. ‫ﻟﻲ‬ Types of cartilage: There are three types of cartilage based on the amount of ground substance and the type of fibers embedded in it. These types are hyaline, yellow elastic and white fibrocartilage. Hyaline cartilage has the typical structure of cartilage. The other types are considered as variants of its basic structure. 1- Hyaline Cartilage The most common type. It appears translucent, with glassy appearance, (Hyalo = glass).  29 Sites: 1- Fetal skeleton 2- Epiphyseal plate 3- Costal cartilage 4- Articular surface of joints 5- Respiratory passages (nose, larynx, trachea & bronchi). Structure: A) Perichondrium: it is a capsule-like structure formed of dense fibrous C.T. that surrounds the hyaline cartilage except at the articular surface of joints. It is formed of two layers: 1- Outer fibrous layer: white fibrous C.T. formed of fibroblasts, collagen fibers (Type I), it is rich in blood vessels & nerves. ‫اﻟﻔ‬ 2- Inner chondrogenic (cellular) layer: rich in chondrogenic cells and chondroblasts. ‫ﺻ‬ Functions of Perichondrium: Nutrition of non-vascular cartilage (by diffusion). ‫ل اﻟ‬ Provides attachment for muscles. ‫ا‬ ‫ﻟﻔر ﺳﻲ‬ Formation of new cartilage cells during growth. ‫درا‬ ‫ﻗﺔ اﻻ‬ ‫اﻻ ول‬ ‫و‬ ‫ﻟﻲ‬ B) Cartilage Cells: 1- Chondroblasts (immature cartilage cells): Origin: arise from UMCs. Site: always on the surface of cartilage, at the inner aspect of perichondrium.  30 L.M.: Flat to oval or spindle in shape, with deeply basophilic cytoplasm. Flat, pale stained nucleus, with prominent nucleolus. They can divide. EM: Features of protein forming cells (euchromatic nucleus, abundant ribosomes, rER, large Golgi apparatus & many mitochondria). Functions: 1- Formation of cartilage matrix and change into chondrocytes. 2- Formation of cartilage collagen (type II). 3- Cartilage growth from outside (appositional growth). ‫اﻟﻔ‬ 2- Chondrocytes (mature cartilage cells): Origin: They develop from chondroblasts. When chondroblasts mature, ‫ﺻ‬ they secrete enough matrix to be completely surrounded by it and imprisoned in lacunae, they are now called chondrocytes. ‫ل اﻟ‬ L.M.: ‫ا‬ Rounded with pale basophilic cytoplasm. ‫ﻟﻔر ﺳﻲ‬ Rounded, darkly-stained, central nucleus. ‫درا‬ ‫ﻗﺔ اﻻ‬ Embedded in the matrix inside spaces called lacunae, either singly or in groups and surrounded by capsule of condensed matrix. The superficial cells are small, oval and single in their lacunae & ‫اﻻ ول‬ parallel to the surface. ‫و‬ The older cells become deeper in the matrix. They are rounded or triangular. They divide once or twice giving clusters of cells formed of 2 ‫ﻟﻲ‬ or 4, up to 8 cells (isogenous groups) surrounded with darkly stained capsule of condensed matrix. This group of cells is called cell nest. They account for interstitial growth of cartilage. E.M.: Features of protein forming cells. Functions: Maintain the cartilage matrix, by continuous secretion of new matrix around them. C) Fibers: Collagen fibers (type II). They can’t be seen by LM, so the matrix appears homogenous, and transparent. This is because: – Fibers are very thin. – Fibers have the same refractive index as the surrounding matrix.  31 D) Ground substance (Matrix): It is produced by chondroblasts and chondrocytes. It is rubbery, homogenous, transparent and deeply basophilic. The matrix consists of: proteoglycans, glycoproteins and water. 2- Yellow Elastic Cartilage It is yellow in fresh state, more opaque & flexible. Structure: Covered by perichondrium. ‫اﻟﻔ‬ Has the same structure of hyaline cartilage, but with large number of branching ‫ﺻ‬ elastic fibers embedded in the matrix forming a network that gives this type the yellow color, with few collagen fibers (type II). ‫ل اﻟ‬ Chondrocytes form small cell nests (mostly 2 cell isogenous groups). ‫ا‬ ‫ﻟﻔر ﺳﻲ‬ Sites: it is found where support with flexibility is required: ‫درا‬ Ear pinna. ‫ﻗﺔ اﻻ‬ Eustachian tube. ‫اﻻ ول‬ Epiglottis and some laryngeal cartilages External auditory canal. ‫و‬ ‫ﻟﻲ‬ White fibrocartilage Elastic cartilage  32 3- White Fibro Cartilage It is not surrounded with perichondrium. It is a tough type of cartilage which is important in bone to bone attachment. Structure: It is formed of dense collagen fibers (type I), present in parallel thick bundles. Cartilage cells (chondrocytes) inside lacunae are present in rows between collagen bundles, embedded in very scanty matrix around them. Sites: Intervertebral disc. Mandibular joint. ‫اﻟﻔ‬ Symphysis pubis. Sternoclavicular joint. ‫ﺻ‬ Growth of Cartilage 1- Appositional Growth: It is the growth resulting from the addition of new layers of cartilage to the surface by the activity of the inner cellular layers of ‫ل اﻟ‬ ‫ا‬ perichondrium (chondroblasts). ‫ﻟﻔر ﺳﻲ‬ 2- Interstitial Growth: It is the growth of cartilage from inside by division of chondrocytes which proliferate and produce matrix around them. ‫درا‬ ‫ﻗﺔ اﻻ‬ ‫اﻻ ول‬ ‫و‬ ‫ﻟﻲ‬  33 Chapter 5 BONE Intended Learning Outcomes (ILOs) By the end of this chapter, the student should be able to: 1- Describe the general structure of bone. 2- Correlate between structure of bone cells and their function. 3- Identify structure and function of bone coverings. 4- Describe the histological structure of compact and spongy bone. 5- Describe types of bone ossification. It is a hard, strong and highly vascular type of C.T. ‫اﻟﻔ‬ It is formed of bone cells & fibers (collagen type 1) embedded in solid matrix. The matrix is solid due to deposition of mineral salts (mainly calcium and ‫ﺻ‬ phosphorus) Functions of bone: ‫ل اﻟ‬ ‫ا‬ 1- Body support by forming the bony skeleton. ‫ﻟﻔر ﺳﻲ‬ 2- Protects the vital organs (brain, heart and lungs). 3- Serves as storage for calcium & phosphorus. ‫درا‬ ‫ﻗﺔ اﻻ‬ Structure of bone: A- Bone Matrix & fibers. B- Bone cells (osteogenic cells, osteoblasts, osteocytes & osteoclasts). ‫اﻻ ول‬ C- Bone coverings: Periosteum (outer covering) & Endosteum (inner covering). ‫و‬ A- Bone Matrix ‫ﻟﻲ‬ 1- Organic component (Osteoid): 35%, consists of: Fibers: collagen fibers mainly Type I, arranged in bundles. Ground substance: of proteoglycans and glycoproteins. 2- Inorganic component: 65%, formed mainly of Ca phosphate & carbonate salts. They are present: on the surface of collagen fibers and within the ground substance. It is responsible for the hardness of bone. 3- Water. Bone matrix is therefore arranged in the form of closely packed layers (lamellae) of calcified collagen bundles, embedded in calcified ground substance.  34 B- Bone Cells There are 4 types of bone cells: 1- Osteogenic Cells (Osteoprogenitor cells) Origin: UMCs & pericytes. Site: Inner layer of periosteum and endosteum. LM: Flat cells with flat nuclei & pale basophilic cytoplasm. EM: Few organelles (ribosomes & centrioles), i.e. features of mitotically active cells. Functions: 1- They can divide and give rise to osteoblasts. 2- They are active: a) During bone growth and ‫اﻟﻔ‬ b) In adults during bone fractures and repair. 3- They give rise to chondroblasts in areas of poor vascularity. ‫ﺻ‬ 2- Osteoblasts (Bone Forming Cells) Origin: Osteogenic cells. ‫ل اﻟ‬ ‫ا‬ Site: Under the periosteum and in the endosteum as ‫ﻟﻔر ﺳﻲ‬ a single continuous layer. L.M.: ‫درا‬ Oval branched cells with few processes. ‫ﻗﺔ اﻻ‬ Rounded eccentric pale nuclei & prominent nucleoli. Cytoplasm is deeply basophilic with an unstained area called negative ‫اﻻ ول‬ Golgi image. Its cytoplasm is very rich in alkaline phosphatase enzyme. ‫و‬ E.M.: All features of "active protein forming cells": rich in rER, well developed ‫ﻟﻲ‬ Golgi and many mitochondria. Functions: They are the "bone forming cells" as they are responsible for: 1- Synthesis of organic matrix of bone (osteoid). 2- Secretion of alkaline phosphatase enzyme which deposits Ca salts in the matrix. 3- When osteoblasts are surrounded by calcified matrix, they change into osteocytes imprisoned inside lacunae.  35 3- Osteocytes (Mature Bone Cells) Origin: Osteoblasts. Site: Present singly inside bony lacunae, between bone lamellae. L.M.: Osteocyt Osteo - Smaller than osteoblasts. e cytes processes Oval, flat, branched cells with dark nuclei, inlacunae pale basophilic canalicul i cytoplasm. They contain alkaline phosphatase enzyme. Osteocytes in lacunae E.M.: Present inside lacunae and contain less rER and smaller ‫اﻟﻔ‬ Golgi than osteoblasts. The cells have thin processes that extend inside the ‫ﺻ‬ cylindrical bony canaliculi. Adjacent cell processes of the neighboring osteocytes are connected by gap junctions. The cells are ‫ل اﻟ‬ ‫ا‬ intercommunicated to exchange nutrients and waste ‫ﻟﻔر ﺳﻲ‬ E.M. Of osteocyte in lacuna products, since the matrix is calcified. Functions: ‫درا‬ ‫ﻗﺔ اﻻ‬ They are the "bone maintaining cells" (bone preserver): 1- Maintain bone matrix by formation of collagen fibers & glycoproteins. 2- Maintain calcification of the matrix by continuous deposition of Ca salts ‫اﻻ ول‬ (continuous exchange between bone & blood). ‫و‬ 4- Osteoclasts (Bone Resorbing Cells) ‫ﻟﻲ‬ Origin: Formed by fusion of many blood monocytes. Sites: At the bony surfaces undergoing resorption. They are located in Howship's lacuna (a shallow depression near the bone marrow cavity produced by their erosive action). L.M.: It is a multinucleated giant cell with foamy acidophilic cytoplasm and multiple nuclei. The cell has a brush border, facing the bone surface.  36 Microvilli Nuclei Vacuoles Actin filaments Multiple nuclei Vacuoles Bone rER Mitochondria Osteocytes Brush border Lysosomes L.M. PICTURE OF E.M. picture of osteoclast OSTEOCLAST E.M.: ‫اﻟﻔ‬ The ruffled surface facing the bone consists of microvilli. The cytoplasm contains many mitochondria, Golgi apparatus, many ‫ﺻ‬ lysosomes & multiple vesicles. Functions: They are the "bone eating (resorbing) cells". They are responsible ‫ل اﻟ‬ ‫ا‬ for bone remodeling during growth or after fractures. ‫ﻟﻔر ﺳﻲ‬ This function is produced by: 1- Release of CO2 by the action of its carbonic anhydrase enzyme → produce an acidic medium → dissolves Ca salts → decalcification ‫درا‬ ‫ﻗﺔ اﻻ‬ [CO2 + H2O → HCO3- + H+]. 2- Their lysosomal enzymes (osteolytic enzymes) cause lysis of the organic matrix. ‫اﻻ ول‬ N.B.: Osteoclasts are not phagocytic cells. ‫و‬ C- Bone Coverings ‫ﻟﻲ‬ A) Periosteum: It is the vascular C.T. layer covering the outer bone surfaces. It consists of: 1- Outer fibrous layer: a layer of dense collagen fibers & fibroblasts. It is very rich in blood capillaries. 2- Inner osteogenic (cellular) layer: formed of osteogenic cells, which can divide and differentiate into osteoblasts, in case of growth and fracture. Functions of Periosteum: 1- Nutrition (supplies bone with blood). 2- Muscle attachment. 3- Repair of fractures. 4- Appositional growth (osteogenic cells differentiate into osteoblasts which form bone matrix).  37 B) Endosteum: It lines the bone marrow cavities. It is formed of a single layer of osteogenic cells in a delicate layer of loose C.T. Function of Endosteum: It supplies osteogenic cells for growth and repair of bone. Types of bone: Anatomical types: (classified according to shape) 1- Long bones 2- Short bones 3- Flat bones 4- Irregular bones ‫اﻟﻔ‬ Histological types: (classified according to structure) ‫ﺻ‬ 1- Compact (Ivory) bone. 2- Spongy (Cancellous) bone. ‫ل اﻟ‬ ‫ا‬ ‫ﻟﻔر ﺳﻲ‬ Methods of Preparation of Bone Sections ‫درا‬ ‫ﻗﺔ اﻻ‬ The presence of Ca salts in bone matrix makes it a hard tissue difficult to be cut. 1- Decalcification Method: ‫اﻻ ول‬ - The bone is treated with mineral acid as 10% nitric acid to dissolve Ca salts. Bone becomes soft, thus sections can be easily cut and stained. ‫و‬ - This method is used to demonstrate bone cells and soft tissues. ‫ﻟﻲ‬ 2- Grinding Method: (Not for Spongy Bone) - Bone is left to dry in air, cut into small pieces by saw, then grinned using a carborandum wheel. - Ground sections are examined without staining to demonstrate: Bone lamellae Lacunae Canaliculi (No cells) Volkmann's canals.  38 COMPACT BONE Sites: It is present in the shafts of long bones & also covering the surface of spongy bone. ‫اﻟﻔ‬ ‫ﺻ‬ ‫ل اﻟ‬ ‫ا‬ ‫ﻟﻔر ﺳﻲ‬ Structure: It is formed of: 1- Periosteum: covers the bone from outside. ‫درا‬ ‫ﻗﺔ اﻻ‬ 2-External Circumferential Lamellae: Bone lamellae that are present under the periosteum, and arranged in layers parallel to the circumference of the bone. They are formed of osteocytes in their lacunae between the calcified collagen ‫اﻻ ول‬ bundles. 3- Haversian Systems (Osteons): The "Structural Units" of compact bone. ‫و‬ They are cylindrical structures running parallel to the long axis of bone. Haversian system is formed of: ‫ﻟﻲ‬ 1- Central vascular canal (Haversian Canal) which contains blood vessels, nerves & loose C.T. 2- Concentrically arranged bone lamellae (5-20) layers around the Haversian canal. 3- Osteocytes inside their lacunae are embedded between bone lamellae, lacunae are connected together by canaliculi, through which cells get their nutrition. Volkmann's Canals: are transverse or oblique canals, linking the Haversian canals in the Haversian systems with one another and with the periosteum and bone marrow cavity to get better nutrition. 4- Interstitial Lamellae: present in between Haversian systems. They consist of irregularly arranged lamellae.  39 5- Internal Circumferential Lamellae: Bone lamellae that surround the bone marrow cavity. 6- Endosteum: lines the central marrow cavity. SPONGY (CANCELLOUS) BONE Sites: present in the center of the epiphysis, also in flat, short & irregular bones. Structure: Periostium It is formed of branching Outer and anastomosing fibrous layer inner irregular bone trabeculae. osterogenic Osteocytes in their lacunae layer ‫اﻟﻔ‬ are embedded in these trabeculae. Osteocyte No Haversian systems. ‫ﺻ‬ inside lacuna The trabeculae enclose multiple irregular Osteoblasts ‫ل اﻟ‬ ‫ا‬ marrow cavities. ‫ﻟﻔر ﺳﻲ‬ The surface is covered by Bone marrow cavities periosteum and the bone marrow cavities are lined by endosteum. ‫درا‬ LM picture of spongy bone. ‫ﻗﺔ اﻻ‬ Clinical Note: Osteoporosis is a bone disease characterized by decreased bone density with ‫اﻻ ول‬ increased risk of fracture due to increased bone resorption versus bone formation. ‫و‬ ‫ﻟﻲ‬  40 Chapter 6 Blood Intended Learning Outcomes (ILOs) By the end of this chapter, the student should be able to: 1- Describe the structure (L.M. & E.M.) and number of RBCs and correlate variations in these parameters with medical disorders. 2- Describe the histological structure (L.M. & E.M.) of blood elements (RBCs, granular & non-granular leucocytes) and correlate structure with function. 3- Compare between RBCs and Leucocytes. 4- Define the total and differential leucocytic count and correlate them with ‫اﻟﻔ‬ medical disorders. ‫ﺻ‬ - Definition: Blood is a specialized type of connective tissue that is composed of formed elements (cells) suspended in a fluid matrix called plasma. ‫ل اﻟ‬ ‫ا‬ - The volume of blood in a normal adult human is approximately 5 Liters. ‫ﻟﻔر ﺳﻲ‬ Blood Components ‫درا‬ (I) Plasma (55%) ‫ﻗﺔ اﻻ‬ (II) Cells (45%): 1-Red Blood Corpuscles (RBCs) (Erythrocytes). ‫اﻻ ول‬ 2-White Blood Cells (WBCs) (Leucocytes). 3-Platelets (Thrombocytes). Functions of Blood: ‫و‬ 1- Transport of oxygen (O2), nutrients and hormones to tissues. ‫ﻟﻲ‬ 2- Removal of carbon dioxide (CO2) and waste products of cell metabolism. 3- Regulation of body temperature. 4- Defense against infection. Examination of Blood Cells: Blood cells can be examined by preparing a blood film: - A small drop of blood is spread on a glass slide into a thin film and left to dry in air. - The film is then stained with a Neutral stain called Leishman′s stain.  41 Red Blood Corpuscles (RBCs) (Erythrocytes) RBCs are the most numerous blood elements. RBCs are responsible for the transport of oxygen and carbon dioxide to and from the tissues of the body. Shape: L.M.: Top View: rounded, non-nucleated with dark periphery & pale center. Side View: biconcave, thick at the periphery, thin at the center. This shape provides the RBCs with large surface area which helps gas exchange. ‫اﻟﻔ‬ ‫ﺻ‬ Rouleaux Appearance: Sometimes in blood smears, RBCs ‫ل اﻟ‬ ‫ا‬ may appear adhering in columns like piles of coins, due to their ‫ﻟﻔر ﺳﻲ‬ high surface tension, forming rouleaux appearance. Rouleaux Appearance ‫درا‬ ‫ﻗﺔ اﻻ‬ E.M.: RBCs are NOT TRUE CELLS i.e. they have NO nuclei & NO organelles. They are membranous bags full of hemoglobin (Hb), surrounded by cell ‫اﻻ ول‬ membrane. ‫و‬ Size: 6 - 9 μm in diameter (average 7.5 μm). ‫ﻟﻲ‬ Thickness: 2.0 μm at periphery, and less than 1 μm at its center. E.M. Picture of RBCs Color: In unstained blood film: RBCs appear greenish yellow due to their content of the pigment Hb. In a blood film stained with Leishman′s stain, RBCs are acidophilic (as Hb is a basic protein) with pale central area (about ⅓ diameter of RBC). These are described as Normochromic RBCs.  42 Number of RBCs: The average number of RBCs is 5 millions / mm3 The normal RBCs number is: In adult males In adult females 4.5 – 5.5 millions / mm3 4 – 5 millions / mm3 The number is less in females due to: 1- Monthly blood loss with menstruation. 2- Inhibitory effect of female hormones on the bone marrow. ‫اﻟﻔ‬ Abnormal Number of RBCs: ‫ﺻ‬ (I) Polycythemia: increase in the number of RBCs above 6 millions /mm3. 1- Physiological: Excessive production of RBCs by the bone marrow due to ‫ل اﻟ‬ Hypoxia (low O2 tension) e.g. high altitude, muscular exercise. ‫ا‬ 2- Pathological: Chronic lung or heart disease. ‫ﻟﻔر ﺳﻲ‬ (II) Anemia: decrease in the number of RBCs below 4 millions/mm3 and/or ‫درا‬ ‫ﻗﺔ اﻻ‬ decreased Hb concentration inside RBCs. Types and causes of Anemia: ‫اﻻ ول‬ 1- Deficiency anemia: due to deficiency of protein, iron or vitamin B12 in diet. Pernicious anemia is caused by a severe deficiency of vitamin B12, due to failed production of intrinsic factor by the stomach. ‫و‬ 2- Aplastic anemia: Damage to the bone marrow by x-ray irradiation, ‫ﻟﻲ‬ chemotherapy or prolonged use of antibiotics. 3- Hemorrhagic anemia: due to excessive loss of blood e.g. excess menstrual bleeding, bleeding nose or piles. 4- Hemolytic anemia: excessive destruction of RBCs due to abnormal shape or abnormal Hb content. Life Span: Is about 120 days. Old RBCs are phagocytosed by macrophages in liver and spleen. Iron is reused in formation of new RBCs, while pigments are excreted as bile pigments.  43 Osmotic Pressure (O.P): RBCs are osmotically fragile. They maintain their shape only in isotonic solution, (0.9% NaCl [saline] = O.P of plasma). Adaptation of RBCs to Perform their Functions Factor Mode of adaptation (I) Structure of - Plasmalemma is elastic & flexible to squeeze inside Plasmalemma narrow capillaries. (II) Shape - Biconcave increasing surface area for gas exchange. (III) Content 1- No nuclei, No organelles, so: [RBCs contain 66% - RBCs do not divide & ‫اﻟﻔ‬ water, 33% Hb & - More space for Hb. 1% enzymes]. 2- Contain enzymes as Hb reductase (combine with O2) & carbonic anhydrase (carry CO2). ‫ﺻ‬ ‫ل اﻟ‬ White Blood Cells (WBCs) (Leucocytes) ‫ا‬ ‫ﻟﻔر ﺳﻲ‬ According to the Type of Granules, Leucocytes are Classified into: ‫درا‬ ‫ﻗﺔ اﻻ‬ Granular Leucocytes Non-Granular Leucocytes (Contain Specific granules + (Contain only Non-Specific granules) ‫اﻻ ول‬ Non-Specific granules) 1- Neutrophils 1- Lymphocytes ‫و‬ 2- Eosinophils ‫ﻟﻲ‬ 3- Basophils 2- Monocytes Total Leucocytic Count: It is the total number of leucocytes per cubic mm of blood which is 4000-11000 / mm3. Differential Leucocytic Count: It is the percentage of each type of leucocyte relative to the total number of leucocytes.  44 Abnormalities in the Total Leucocytic Count Leucocytosis Defintion: It is the increase in the total number of leucocytes above 11,000/mm3 Causes; 1- Physiological Leucocytosis: occurs in pregnancy & newly born infants. 2- Pathological Leucocytosis: occurs in acute and chronic infections. Leucopenia Definition: It is the decrease in the number of leucocytes below 4000 /mm3. Causes: Typhoid fever, influenza virus, X-ray irradiation or after taking certain antibiotics. ‫اﻟﻔ‬ (I) Granular Leucocytes ‫ﺻ‬ Neutrophils Eosinophils Basophils ‫ل اﻟ‬ ‫ا‬ ‫ﻟﻔر ﺳﻲ‬ Percentage 60-75% (the most 2-4% 0-1% (the least) common) Diameter 10-12 µm 12-14 µm 10-12 µm ‫درا‬ ‫ﻗﺔ اﻻ‬ L.M. : (a) Nucleus: Single, segmented (2-4 Bilobed (Horse-Shoe) S-shaped or irregular lobes), connected by connected by thick ‫اﻻ ول‬ thin chromatin threads), chromatin threads so it is called Polymophonuclear ‫و‬ Leucocytes (PMNLs) ‫ﻟﻲ‬ (b) Granules 1) Non- Specific = (1ry / = Primary Lysosomes that stain purple with azure Azurophilic) (containing hydrolytic enzymes  45 2)Specific Pale Pink, Large, coarse, Coarse Basophilic (2ry) acidophilic (appear granules, may mask the Granules: Contain: shiny red), nucleus, 1- Phagocytin Contain: (Bactericidal) Contain: 1- 1-Histamine 2- Lactoferrin 1- Histaminase 2- 2-Heparin (Bacteriostatic) 2- Sulphatase 3- 3-Eosinophil Chemotactic 3- Collagenase Factor (ECF) E.M.: 1- All cells have few organelles: few mitochondria, small Golgi, few rER + 2 types of granules. 2- Neutrophils have pseudopodia. ‫اﻟﻔ‬ ‫ﺻ‬ ‫ل اﻟ‬ ‫ا‬ ‫ﻟﻔر ﺳﻲ‬ Diagram of Neutrophil Blood Film showing Neutrophil ‫درا‬ ‫ﻗﺔ اﻻ‬ ‫اﻻ ول‬ ‫و‬ ‫ﻟﻲ‬ Diagram of Eosinophil Blood Film showing Eosinophil Diagram of Basophil Blood Film showing Basophil  46 Neutrophils Eosinophils Basophils Functions. 1- (I) Role in Allergy 1-Secrete Heparin 2- 1- Attracted to the site which is an Neutrophils are the 1st line of of allergy by "ECF" anticoagulant. defense against foreign Eosinophil 2-Secrete invaders. chemotactic factor, Histamine which 1- Neutrophils leave the blood released by initiates allergic vessels and enter the C.T. for Basophils or mast reaction by Phagocytosis of bacteria. cells. increasing capillary 4- 2- Destruction of bacteria by3- 2- Terminate the permeability. the 2 types of granules. allergic reaction by; 3-Secrete 5- 3- Dead neutrophil containing A-Destroying Eosinophil the dead bacteria + damaged histamine by chemotactic C.T. form Pus. histaminase. factor (ECF) which 4- Pus produces Pyrogens ‫اﻟﻔ‬ B-Engulfing the Ag/Ab attracts which elevate body temperature complex at the site of Eosinophils to (fever) to inhibit bacterial allergy. terminate allergic ‫ﺻ‬ growth. reaction. 5- Stimulation of the bone marrow to form more ‫ل اﻟ‬ neutrophils. (II) Role in Parasitic ‫ا‬ Clinical note: In 6- Attraction of monocytes to ‫ﻟﻔر ﺳﻲ‬ infections severe allergy, the site of infection to remove Inactivate and kill generalized pus and debris. parasitic larvae. vasodilation & 7- Secretion of trephone ‫درا‬ severe drop in ‫ﻗﺔ اﻻ‬ substance which helps in blood pressure healing. occurs → Anaphylactic ‫اﻻ ول‬ shock. ↑% Neutrophila ( ↑ 75%) Eosinophilia Basophilia ↑ ‫و‬ ( 5%) 1- Allergic ‫ﻟﻲ‬ Acute pyogenic infections 1- Allergic diseases diseases. e.g. urticaria, eczema (e.g. acute tonsillitis, acute 2- Parasitic & bronchial asthma. appendicitis, abscess) diseases. 2-Parasitic diseases 3- Chicken pox. e.g. ascariasis & 4- Liver cirrhosis. bilharziasis. ↓% ↓ Neutropenia ( 60%) Eosinopenia 1-Exposure to irradiation , X-ray. ( ↓ 1%) 2-Prolonged use of certain Treatment with antibiotics (e.g cortisone (inhibits chloramphenicol). formation in bone 3-Influenza and typhoid fever. marrow).  47 (II) Non-Granular Leucocytes - They do not contain specific granules in their cytoplasm. - They contain only non-specific (azurophilic) granules. - They have rounded or indented nuclei (non-segmented). - They are of 2 types: (1) Lymphocytes (2) Monocytes ‫اﻟﻔ‬ (1) Lymphocytes ‫ﺻ‬ Percentage: 20-30% (the 2nd most common type). Function: They are the cells responsible for the specific immune ‫ل اﻟ‬ response (The 2nd line of defense against foreign invaders). ‫ا‬ ‫ﻟﻔر ﺳﻲ‬ Lymphocytes Are Classified According To Diameter & Activity Into: ‫درا‬ ‫ﻗﺔ اﻻ‬ 1- Small (Inactive) Lymphocytes. ‫اﻻ ول‬ 2- Large (Active) Lymphocytes. ‫و‬ ‫ﻟﻲ‬ Small Lymphocyte Large Lymphocyte  48 Small (Inactive) Large (Active) Lymphocytes Lymphocytes Diameter 6-8 µm 12-15 µm Percentage 15-20% 5-10 % L.M.: Rounded, dark (condensed) & Rounded with an indentation, Nucleus filling most of the cytoplasm pale with clear nucleolus Scanty, appears as a thin rim Cytoplasm around the nucleus, pale Abundant, deeply basophilic basophilic ‫اﻟﻔ‬ ‫ﺻ‬ Few organelles; few More organelles; mitochondria, E.M.: mitochondria, small Golgi, many rER, well-developed Golgi ‫ل اﻟ‬ribosomes & a pair of centrioles. & ribosomes. ‫ا‬ ‫ﻟﻔر ﺳﻲ‬ ‫درا‬ ‫ﻗﺔ اﻻ‬ ‫اﻻ ول‬ ‫و‬ ‫ﻟﻲ‬ Functional Classification of Lymphocytes 1) B Lymphocytes 2) T Lymphocytes 3) Natural Killer Cells (1) B Lymphocytes: Percentage: 25-30% of circulating small lymphocytes Life span: Short (few days to 3 months). Development: ▪ In mammals: in Red bone marrow. ▪ In Birds: in Bursa of Fabricius. Maturation: In the bone marrow, B Lymphocytes acquire surface receptor which are programmed for a particular antigen.  49.Functions of B Lymphocytes: a) Humoral Immunity (1ry immune response): - T-Helper cells help B Lymphocytes to recognize the antigen. - Some activated B cells proliferate & differentiate into → Plasmablast → Plasma cells which secrete the specific antibody against the antigen. - Other B cells remain as Memory cells. b) Memory Cells (2ry immune response): - If the body is exposed to the same Ag, memory B cells will differentiate to plasma cells rapidly, even years after the 1st exposure. ‫اﻟﻔ‬ ‫ﺻ‬ (2) T Lymphocytes: Percentage: 60-80% of circulating small lymphocytes. Life span: Long (1-2 years) ‫ل اﻟ‬ ‫ا‬ Development & Maturation: Stem cells leave bone ‫ﻟﻔر ﺳﻲ‬ marrow to thymus gland where they are educated to recognize antigen by addition of T Cell Receptors (TCR) ‫درا‬ ‫ﻗﺔ اﻻ‬ on their surfaces. Functions: Cell-Mediated Immunity ‫اﻻ ول‬ Attack foreign cells directly i.e. Cell-to-Cell Contact. - When T cells contact an antigen or foreign cells as (viruses, fungi and tumor cells), they become activated into large T lymphocytes. ‫و‬ ‫ﻟﻲ‬ - Activated T lymphocytes, undergo cell division and form both: Effector T Cells Memory T Cells (Cytotoxic T & Helper T) - Cytotoxic T Cells: secrete Perforins that produce Pores in the membrane of the foreign cell leading to its lysis. - Helper T Cells: help activation of B Lymphocytes during the humoral immune response. - Memory T C