Histology for Physiotherapy PDF

1 Histology for Physiotherapy Histology & Cell Biology Histology and Cell Biology For Physical Therapy By Staff Members 2024-2025 2...

1 Histology for Physiotherapy Histology & Cell Biology Histology and Cell Biology For Physical Therapy By Staff Members 2024-2025 2 Histology for Physiotherapy CONTENTS Cytology 1. Cell membrane 2. Membranous organelles 3. Non membranous organelles 4. Inclusions 5. Nucleus Tissues of the body 1. Epithelial tissues 2. Connective tissues 3. Cartilage 4. Bone 5. Blood 6. Muscles tissus 7. Nervous tissue System of the body 1. Cardiovascular system 2. Lymphatic system 3. Respiratory system 4. Skin 5. Digestive system 6. Endocrine system 7. Urinary system 8. Reproductive system _______________________________________________________________________ 3 Histology for Physiotherapy Histology: Science studies the normal microscopic structure of tissues and cells. Cytology: Science studies the cell. Cell: The structural and functional unit of all living tissues. Microscope: Instrument used to visualize tissues and cells Cell Cytoplasm Nucleus Staining: Hematoxylin and Eosin routinely used to color tissues and cells  Hematoxylin (basic): Stains acidic structures of the cell → Basophilic (Blue)  Eosin (acidic): Stains basic structures of the cell → Acidophilic (Pink) Organization of the cell: 1) Cytoplasm: Makes up most of the cell, between the cell membrane and nucleus. It is jelly-like composed mainly of water constantly streaming. 2) Nucleus: The genetic control center of eukaryotic cell A. Organelles: 1) Membranous cytoplasmic organelles 2) Non membranous organelles B. Inclusions: (non-essential for vitality of the cells may be present or absent). _______________________________________________________________________ 4 Histology for Physiotherapy _______________________________________________________________________ 5 Histology for Physiotherapy A. Membranous Organelles 1. Cell Membrane Definition: The outer cover of the cell LM: H & E: Cannot be seen because very thin (8-10 nm). Can be visualised by special stain: Silver or PAS EM: Formed of three layers (Trilamellar): two densely stained layers separated by a light one. This 3 layered- structure is called unit membrane. Molecular structure of cell membrane: 1. Lipids (30%): A. Phospholipid molecules: Arranged in two lipid layers (bilayers). Phospholipid molecule is formed of a head (hydrophilic) and a tail (hydrophobic). Heads appear deeply stained while the tails in the middle of the cell membrane appear unstained. This explains the trilaminar appearance by EM. B. Cholesterol: Constitutes 2% of lipid contents is present on the cytoplasmic surface of the cell membrane. It maintains the integrity of membrane. _______________________________________________________________________ 6 Histology for Physiotherapy 2. Proteins (60%): A. Peripheral (Extrinsic) proteins: Small molecules. Outside the lipid bilayer. B. Integral (Intrinsic) proteins: Large globules: Extend through the full thickness (Transmembrane) 3. Carbohydrate (10%) On the outer surface of the cell membrane attached to outer protein and outer lipid in the form of (glycoprotein & glycolipid). Form cell coat (glycocalyx) Function of cell coat is cell recognition. Functions of the cell membrane: Transport of materials in and out-wards the cell by several ways: 1. Passive transport: substances transported across cell membrane from high concentration to low concentration with no energy requirements: A) Simple diffusion: dissolved gases (O2, CO2 ) and small molecules. B) Facilitated diffusion: Lipid insoluble molecules, cross the cell membrane through binding to specific membrane component called carrier. C) Osmosis: Diffusion of water against concentration gradient, from low concentration solution to high concentration solution. 2. Active transport: Requires energy (ATP) to actively transport substances across the cell membrane against concentration gradient (e.g. sodium-potassium pump). _______________________________________________________________________ 7 Histology for Physiotherapy Bulk transport: Transport particles A. Endocytosis which may be; ❖ Phagocytosis: Solid particle taken into cell forming phagosomes. ❖ Pinocytosis: Fluid droplets taken into cell forming pinocytotic vesicles. B. Exocytosis: Cells discharge their secretory vesicles and residual bodies to outside the cell. 3. Mitochondria Definition: membranous organelle, concerned with the energy production. Their number varies from one to thousands in liver cells (active). LM: Visualized by using special stains. Stained black with iron hematoxylin. EM: Each mitochondrion has two membranes: 1- Outer smooth membrane. 2- Inner membrane which is folded into cristae that increase the surface area. Function: 1. Providing the cell by energy by generation of ATP. 2. Maintain calcium levels of the cell. 3. Endoplasmic Reticulum Formed of interconnected tubules. There are two types: A. Rough Endoplasmic Reticulum (RER) B. Smooth Endoplasmic Reticulum (SER) _______________________________________________________________________ 8 Histology for Physiotherapy A. Rough Endoplasmic Reticulum (RER): Site: Located mainly near the nucleus and the Golgi apparatus. LM: basophilic due to the presence of ribosomes on the surface. EM: A series of connected parallel flattened tubules (cisternae) with ribosomes attached to its surface. Function: Plays a central role in the synthesis of proteins. Proteins travel as transfer vesicles to Golgi apparatus. B. Smooth Endoplasmic Reticulum (SER): LM: When increase the cell shows acidophilic cytoplasm EM: A series of branched tubules anastomose in an irregular pattern. Smooth because it lacks the attached ribosomes. Functions: 1. Lipid synthesis: e.g. in steroid-secreting cells such as cells of adrenal cortex. 2. Regulation of mineral metabolism e.g. HCL production in the stomach. 3. Calcium storage: in skeletal and cardiac muscle to control muscle contraction. 4. Glycogen metabolism: e.g. in liver cells, enzymes involved in regulating glycogen metabolism are associated with the SER membrane. 5. Drug detoxification: e.g. in liver cells due to the presence cytochrome P450 enzyme in the SER membrane. _______________________________________________________________________ 9 Histology for Physiotherapy 4. Golgi complex (Apparatus) Definition Membranous organelle that processes packages and sorts of macromolecules such as proteins and lipids after their synthesis. LM: In the deeply basophilic cytoplasm of the protein secreting cells as plasma cell, its position appears as non-stained area called Negative Golgi Image. EM: A. Flat vesicles: It is composed of flattened sacs in the form of stacks called cisternae. Each stack has a convex immature surface facing the nucleus called (Cis Face) and a concave mature surface towards the cell membrane called (Trans Face). B. Microvesicles: Derived from rough endoplasmic reticulum and fuse with the convex surface. C. Macrovesicles: Formed from the mature surface of Golgi. It remains within the cytoplasm as lysosomes or exocytosed.. Function: 1- Protein modification by the addition of carbohydrates and phosphate. 2- Share in the formation of lysosomes. 3- Keeping the cell membrane intact through the process of exocytosis. 5. Lysosomes Definition: Vesicles containing hydrolytic enzymes, are disposal unit of the cell. Abundant in phagocytic cells e.g. macrophage. LM: Visualized by immunohistochemical techniques. _______________________________________________________________________ 10 Histology for Physiotherapy EM: Types of lysosomes: 1. Primary lysosomes: spherical homogenous electron-dense vesicles as it has not entered into a digestive process. 2. Secondary Lysosomes: appear heterogeneous electron-dense vesicles as they contain digested elements, it include three subtypes: a) Heterophagosome: when fuses with solid particles (phagosome) b) Multivesicular body: when fuses with fluid droplets (pinocytotic vesicle). c) Autophagosome, when fuses with the own old organelle. Fate of the digested material 1- Digested nutrients diffuse through the lysosomal membrane and enter the cytoplasm for reuse. 2- Indigestible compounds are retained within vacuoles (residual bodies) extruded outside Functions of lysosomes 1. Digestion of old organelles = Maintenance of cell health 2. Digestion of engulfed foreign invaders as bacteria = Defense of the body 3. Digestion of the whole cell after death = autolysis 4. Help the sperm to penetrate the ovum (fertilization) 5. In thyroid gland: breaks inactive hormone into the active form. 6. In bones: osteoclast release enzymes for destroying material around the cell. _______________________________________________________________________ 11 Histology for Physiotherapy B. Non-Membranous Cell Organelles The organelles that have no membranes They include: 1. Ribosomes. 2. Microtubules 3. Filaments protein Large subunit 1. Ribosomes Definition: Non-membranous, site of protein synthesis mRNA Origin: Formed in the nucleolus and pass to the cytoplasm Number: More in protein synthesizing cells Small subunit LM: Not seen by H&E but when abundant shows cytoplasmic basophilia. Free Polysomes EM: 2 subunits a small and a large unites. Attached Types of ribosomes: 1. Free: scattered diffusely & singly 2. Polysomes: linked together by a strand of mRNA 3. Attached: bind to the outer surface of rER Function of ribosomes: Protein synthesis: Free ribosomes: Form proteins for local use in the cell Attached ribosomes: Form proteins for export by secretion. 2. Microtubules Hollow, cylindrical tubules, about 25nm in diameter with variable length. Function: 1. Form the cytoskeleton of the cell. 2. Form centrioles 3. Form cilia and flagellum. 4. Form mitotic spindle during mitosis to guide movement of chromosomes. _______________________________________________________________________ 12 Histology for Physiotherapy Centriole: A pair of cylindrical rods oriented at a right angel to each other near the nucleus. Seen in the cells that can divide. Each centriole consists of 9 bundles of microtubules. Each bundle is called triplets as it is composed of 3 microtubules. Functions of centrioles: during cell division, centrioles duplicate and each pair move to the opposite poles of the cell forming the microtubule organizing center (MTOC) and the mitotic spindle. 3. Filaments A. Thin (Microfilaments-actin): in muscle fibre B. Intermediate C. Thick (myosin): in muscle fibre Functions of filaments: They are supportive elements in cells. Responsible for muscle contraction. Movement of some cells (amoeboid movement). NB: Cytoskeleton of the cell includes microtubules, intermediate and thin filaments Cytoplasmic inclusions Non-living temporary components of the cytoplasm produced as a result of cell activities. Organelles Inclusions Metabolically active Inert Permanent Temporary Essential non-essential for vitality Like body organs Storage food e.g. mitochondria e.g. glycogen Types of inclusions are: 1-Stored food e.g. carbohydrates and lipids. _______________________________________________________________________ 13 Histology for Physiotherapy 2-Colored pigments. 3- Crystals A. Stored food: 1. Carbohydrates: are stored in cells in the form of glycogen for energy reserve, especially in liver and muscle cells 2.Lipids: are stored in fat cells. H & E stain Adipocytes (fat cells) appears like a signet ring appearance. A. Pigments: Pigmentation means the coloration of certain tissues which may induced by endogenous or exogenous pigment. ❖ Endogenous pigments: Formed by cells and include: 1. Hemoglobin in RBCs: the most important pigment in the body. 1. Melanin pigment in melanocytes: responsible for coloration of skin, hair, and iris. 2. Lipofuscin pigment: Accumulated as residual bodies in cells of nerve, heart, and liver. ❖ Exogenous pigments: Reaches the cell from outside. There are many types: 1- Carotene: In some vegetables as orange pigment of carrots. is lipid soluble so color fat. 2- Carbon particles: In tobacco. Reaches lungs in heavy smokers, phagocytosed by dust cells. 3- Tattoo marks: Vital stains as trypan blue introduced into skin causing permanent coloration. C-Crystals: Protein metabolism product e.g. uric acid crystals, accumulate in cells of the joints causing gout disease. This leads to attacks of painful arthritis, kidney stones, kidney failure. _______________________________________________________________________ 14 Histology for Physiotherapy Nucleus Definition: Membrane bounded structure which is the cell control center. Contains the genome encoded in DNA. In eukaryotic cells. Number: Most cells have a single nucleus, though some have none e.g. RBCs and some have multiple e.g. skeletal muscle. Structure of the nucleus: 1. Nuclear membrane 2. Nucleolus 3. Chromatin 4. Nucleoplasm 1-Nuclear envelop (membrane) Definition: Double membrane encloses the nucleus. Consists of 2 parallel membranes, separated by a narrow space and perforated with pores. The outer membrane faces cytoplasm and is rough, continuous with RER. The inner membrane is fibrillar due to its attached peripheral chromatin. Function: Contains pores which control the movement of substances in and out of the nucleus. 2-Nucleolus Definition: Non membranous spherical basophilic bodies in the nucleus. The sites of ribosome production. Prominent in protein synthesizing cells. Function: Contains DNA in the center control rRNA production that passes through nuclear pore to the cytoplasm. 3-Chromatin Definition: Combination of DNA, histone and other proteins that make up chromosomes. LM: appear as basophilic granules and threads. EM: There are two types: 1. Euchromatin: less compact, lightly stained, contain genes that are frequently expressed by the cell. 2. Heterochromatin: more compact form, darkly stained contains DNA that is infrequently expressed. _______________________________________________________________________ 15 Histology for Physiotherapy Functions of nucleus: 1. Coordinates cell´s activities including growth, metabolism, protein synthesis, and cell division. 2. Stores genetic information. 3. Direct formation of protein inside the cell by formation of the 3 types of RNA 4. Stores the hereditary material DNA. Nucleic acids DNA: Formed of a large number of chemical compounds called nucleotides, linked together in a very long chain. Arranged like a ladder, twisted into the shape of a winding staircase, called a double helix. Each nucleotide is formed of 3 units: a sugar molecule called deoxyribose, a phosphate group (P), and one of four nitrogenous bases. The 4 bases are: adenine (A), guanine (G), thymine (T) and cytosine (C). Structure of RNA: The same as DNA but differs in: DNA RNA Function Carry all genetic information. Translates these genetic in formations into assembled protein Location Inside nucleus and mitochondria Nucleus & cytoplasm and ribosome Types Only one type 3 types Appearance Double helix Single strand Sugar Deoxyribose Ribose Bases A&G&C&T A&G&C&U &pairing (A-T) and ( G-C) (A-U) and (C- G) Types of RNA: 1. m RNA: formed from DNA in nucleus, carry the genetic 3 letter codons called the secret language to ribosome. 2. tRNA: has 2 arms, brings the wanted amino acid to ribosome. 3. rRNA: act as a factory for protein synthesis. _______________________________________________________________________ 16 Histology for Physiotherapy Tissues of the body 4 basic tissues form the body 1. Epithelial tissues 2. Connective tissues 3. Muscular tissues 4. Nervous tissues _______________________________________________________________________ 17 Histology for Physiotherapy Epithelial tissue Epithelium tissue is a layer of cells covering body surfaces, lining hollow organs and form glands and sensory organs. General characters of epithelium: Have morphological polarity i.e. apical portion differs from basal portion. Cells rest on basement membrane which connect them to underlying CT. Cells are attached to each other by cell junctions. Cells are tightly packed with little extracellular space. Avascular but innervated. Cells can divide and renew such as in skin. Functions: Covering and lining "barrier". Protection as in stratified epithelium. May be absorptive as in intestine or secretory as in stomach. Sensation as in neuroepithelium. Contractility as in (myoepithelial cells). Types of epithelium 1. Surface epithelium: Covering and lining epithelium 2. Glandular epithelium: Forming glands. 3. Neuroepithelium: Forming special sense organs for smell, taste, hearing and vision. 4. Myoepithelium: For contractility I. Surface (covering and lining) epithelium Classified according to: Number of cell layers: 1. Simple : Formed of a single layer of cells 2. Stratified: Formed of more than one layer Shape of surface cells 1. Squamous 2. Cuboidal 3. Columnar _______________________________________________________________________ 18 Histology for Physiotherapy A) Simple epithelium types 1. Simple squamous: single layer of spindle-shaped with central flattened nuclei. Sites: Endothelial lining of blood and lymphatic vessels, Bowmans capsule in the kidney and alveoli of lung. 2. Simple cuboidal: single layer of cubical cells with central rounded nuclei. Sites: thyroid follicles and kidney tubules. 3. Simple columnar: single layer of tall rectangular cells with basal oval nuclei. Sites: digestive tract (stomach and intestine). 4. Simple columnar ciliated: as columnar type plus cilia at apical surface. Sites: uterus & fallopian tubes and central canal of spinal cord. 5. Pseudo-stratified columnar: appears as two layers of cells but it is actually a single layer. All cells rest on basement membrane. Tall cells reach the surface and short cells do not, so nuclei appear at different levels. Sites: male genital ducts. 6. Pseudo-stratified columnar ciliated: with cilia on the surface Sites: upper respiratory passages. B) Stratified epithelium types More than one layer has protective function. According to shape of superficial layer, there different types: A. Stratified squamous 1. Stratified squamous non keratinized: superficial cell layer is flattened Sites: oral cavity, esophagus, cornea, vagina and anal canal. 2. Stratified squamous keratinized: superficial layer covered with keratin. Sites: in skin. B. Stratified cuboidal: superficial cell layer is cuboidal C. Stratified columnar: superficial cell layer is columnar _______________________________________________________________________ 19 Histology for Physiotherapy D. Transitional: change shape according to the state of organ. Formed of many layers of cuboidal cells. Superficial cells are large, dome-shaped to allow stretching of organ without rupture of cells Sites: urinary bladder and ureter. _______________________________________________________________________ 20 Histology for Physiotherapy II. Glandular epithelium Form glands. Glands classified according to: A. Presence or absence of ducts: Endocrine glands: with no ducts (Ductless), secrete hormones directly into blood. Exocrine Glands: with ducts, secrete products on the surface through ducts. Mixed glands: Exocrine and endocrine B. Number of secretory cells: Unicellular: single cell, e.g. goblet cells. Multi-cellular: more than one cell. C. Type of secretion: Serous: Liquid secretions rich in protein e.g. serous acini of pancreas and parotid glands. Mucous: viscous e.g. goblet cells and mucous acini of sublingual salivary glands. Mixed: have both mucous and serous secreting cells e.g. submandibular glands. Watery: sweat glands. Waxy: wax-like e.g. external ear glands. Mineral: secrete HCl e.g. parietal cells of stomach. Fatty: secrete fatty secretion e.g. sebaceous glands. Hormones: ovary secret estrogen and progesterone. Testis secrete testosterone. III. Neuro-epithelium Structure 1. Sensory (hair) cells: columnar with hairlets on apical Supporting Sensory surfaces. basal surfaces surrounded by sensory nerve fibers. 2. Supporting (sustentacular) cells: in-between sensory cells, tall elongated and darkly stained (supportive function). 3. Basal (stem) cells: near basement membrane between other two cell types. Stem Sites: 1. Taste buds in tongue 2. Olfactory epithelium of nose 3. Cochlea of inner ear. Function: sensory receptors for special stimuli. _______________________________________________________________________ 21 Histology for Physiotherapy Connective tissue Origin: Mesodermal origin Characteristics of connective tissue: Formed of cells widely separated by extracellular matrix with embedded fibre. Rich in blood vessels, nerves and lymphatics. Functions: Mechanical support: Connect and hold tissues and organs in place. Nutritional support: Provides a passage for blood vessels and nerves to organs and tissues. Immunological protection: Cells involved in immunological defense e.g. macrophages, lymphocytes, plasma cells, etc. are located within connective tissue. Fat: storage site. Mast cell Macrophage Connective tissue is composed of: A. Connective tissue cells. 1. Undifferentiated Mesenchymal cells (UMCs) 2. Fibroblasts 3. Macrophages 4. Fat cells 5. Plasma cells B. Extracellular matrix: 1. Ground substance 2. Fibers Fat cell Fibroblast Collagen fibers A. Connective tissue cells Reticular fibers 1. Undifferentiated Mesenchymal cells (UMCs) Elastic fibers Undifferentiated cells that can differentiate into other types of CT cells Sites: Mesenchymal tissue in embryo Functions: Differentiate to CT cells, blood cells, smooth muscles and endothelium _______________________________________________________________________ 22 Histology for Physiotherapy 2. Fibroblasts The most abundant CT cell. Connective tissue forming cells. LM: Flattened or fusiform in shape with processes. Have abundant basophilic cytoplasm. Nucleus is central, pale with prominent nucleolus. EM: Show criteria of protein forming cells increase in rough endoplasmic reticulum, prominent Golgi apparatus and mitochondria. Functions: 1. Produce connective tissue fibers. 2. Produce connective tissue ground substance. 3. Wound healing 3. Macrophages LM: Large cells with irregular cell outline and variable shapes due to pseudopodia. Acidophilic cytoplasm, dark hyperchromatic kidney-shaped nucleus. EM: Pseudopodia, numerous lysosomes, residual bodies, and mitochondria. Functions: Phagocytosis of foreign bodies, invading micro-organisms. 4. Mast Cells LM: Rounded, cytoplasm is full of basophilic granules, EM: Ribosomes, RER, Golgi, mitochondria, and larger membrane bound granules. Functions: 1. Secrete heparin, anticoagulant prevents blood clotting. 2. Secrete histamine which promotes capillary leakage, edema, _______________________________________________________________________ 23 Histology for Physiotherapy 5. Plasma Cells LM: Rounded cells with intense basophilic cytoplasm showing -ve Golgi EM: Cytoplasm is rich in RER, ribosomes, mitochondria and prominent supranuclear Golgi complex. The nucleus is eccentric with chromatins arranged in a radiating manner, resembling ‘cart-wheel’ or clock face. Functions: Antibodies secretion and immune defense the body. 6. Reticular Cells LM: branched flattened cells with poorly staining nuclei and cy- toplasm Functions: 1. Phagocytic activity. 2. Act as stem cells. 3. Reticular fibers formation forming stroma of most organs providing support. B. Extracellular matrix 1. Ground substance: Form the major component of connective tissue Background material within which all other connective tissue elements are embedded. Secreted mainly by fibroblasts. Composed of glycoproteins, proteoglycans, and glycosaminoglycan Functions: Acts as a medium for nutrients and waste transfer between CT cells and blood. Acts as physical barrier prevents the spread of microorganisms. Ground substance is modified in the special forms of connective tissue: In blood (plasma): Ground substance is watery lacks stabilizing macromolecules. In connective tissue proper: Ground substance is soft jelly like. In bone: Ground substance is rigid due to deposition of Ca salts in bone In cartilage: Ground substance is rubbery _______________________________________________________________________ 24 Histology for Physiotherapy 2. Connective tissue fibers Formed of protein. Have variable diameters and organization. In tendons, fibers run parallel to resist forces in the direction in which muscle produces force. In bone fibres arranged in alternating parallel layers. Types of fibres: 1. White collagen fibres 2. Yellow elastic fibers 3. Reticular fibres 1. White collagen fibers: The most common fibrous protein in the body. White in fresh state Stained acidophilic with H & E. Strong, gives strength to the tissue (greater tensile strength than steal). The fibers are wavy do not branch Present as bundles Show characteristic transverse striations by electron microscopy. 2. Yellow elastic fibers: Yellow in fresh state Fibers branch and anastomose. Stained with orcein stain (appear reddish brown). Stretch easily and recoil in original position. 3. Reticular fibers: Fibers branch and anastomose forming a fine network. Fibers are too thin to be seen by routine H&E Stained with silver brown. Transverse striations similar to collagen fibers. _______________________________________________________________________ 25 Histology for Physiotherapy Types of CT proper A. Loose Connective Tissue: 1. Loose Areolar Connective Tissue 2. Adipose Connective Tissue 3. Reticular connective Tissue 4. Mucoid connective Tissue B. Dense Connective Tissue: 1. White Fibrous Tissue 2. Yellow Elastic Tissue 1. Loose areolar Tissue Commonest type, so called ordinary. Contains air spaces, so called areolar. Consists of all types of CT cells and all types of fibers, especially collagen. Sites: Fill the spaces between different tissues and acts as packing material for organs. Function: Act as packing material for organs. 2. Adipose Tissue Aggregation of unilocular fat cells (with a large fat vacuole) Sites: subcutaneous tissue and yellow bone marrow. Function: Provides a store house of fat Helps to conserve the body heat. Acts as cushion in many sites and provides contour in others. 3. Reticular Tissue Formed of anastomosing networks of reticular fibers and reticular cells. Stained with silver. Sites: forms the stroma of organs as liver and spleen. 4. Mucoid Tissue Embryonic CT with abundant jelly like matrix, few collagen fibres and few fibroblasts. Sites: in the umbilical cord. _______________________________________________________________________ 26 Histology for Physiotherapy 5. White Fibrous Tissue Formed of collagen fibers mainly Fibres present in bundles Contain modified fibroblast called tendon cells. It appears in response to tensile strain. Types: 1. Regular: regular bundles, resist stretch in one direction: as cornea, tendons. 2. Irregular: irregular bundles, resist stretch in many directions: as sclera, capsules of organs. 6. Yellow Elastic Tissue: Formed mainly of elastic fibers Few fibroblasts. Sites: Elastic membranes as in aorta Elastic ligaments as ligamentum flavum between vertebrae to facilitate movement Ligamentum nuchae to facilitate neck movement. _______________________________________________________________________ 27 Histology for Physiotherapy Yellow elastic CT Loose areolar Reticular Adipose White Fibrous CT Mucoid _______________________________________________________________________