HISTO PRELIM 24-25 PDF - Epithelial Cells & Histology

Topic 1 Prelim: Epithelial Cells MT 207: Derlith Reann Mitchao - Lumen, RMT Histology...

Topic 1 Prelim: Epithelial Cells MT 207: Derlith Reann Mitchao - Lumen, RMT Histology SY 2024-2025 Prepared by: Herda, Princes Alitha 1ST SEMESTER MUSCLE Elongated Moderate Strong EPITHELIAL CELLS contractile amount contraction; cells body EPITHELIUM movements ​ An avascular (having few or no blood vessels) NERVOUS Elongated None Transmission tissue, which lacks direct blood supply cells with of nerve ​ Derived from a greek word “epi” means “upon” extremely fine impulses and “thele” means “nipple” processes ​ Most epithelial tissues are renewed continuously ​ Have distinctive type shape varying from spherical to elongated or epileptic Classification of Epithelial Tissue ​ Nutrients delivered by diffusion for example (polyhedral) blood vessels in connective tissue Based on the number of layers of cell Basic Functions ➔​ Simple = 1 layer ➔​ Stratified = 2 or more layers 1.​ Protection of the body from abrasion and injury Based on shapes of cells in superficial layers (ex. Skin and esophagus) 2.​ Absorption of material from lumen (ex. Tubules ➔​ Squamous Epithelium = Flat (lapad) in kidney, small and large intestine) ➔​ Cubodial Epithelium = Cube-like 3.​ Transportation of material along the surface (ex. ➔​ Column Epithelium = Column-like Cilia mediated transport in the trachea) ➔​ Transition Epithelium = Urothelium 4.​ Secretion of mucus, hormones, and proteins (ex. (seen in urine) Glands) 5.​ Gas exchange (ex. Alveoli in the lungs) COMMON TYPES OF COVERING EPITHELIA 6.​ Lubrication between two surfaces (ex. Mesothelium of pleural cavity) Major Cell Form Examples of Main Feature Distribution Function MAIN CHARACTERISTICS OF FOUR BASIC TYPES OF SIMPLE Squamous Lining of Facilitates TISSUE (ONE vessels the LAYER OF (endothelium); movement of Tissue Cells Extracell Main CELLS) Serous lining the viscera ular Functions of cavities: (mesothelium Matrix pericardium, ), active pleura, transport by EPITHELIAL Aggregated Small Lining of peritoneum pinocytosis polyhedral amount surface or (mesothelium) (mesothelium cells body cavities; and glandular endothelium), secretion secretion of biologically CONNECTIVE Several types Abundant Support and active of fixed and amount protection of molecules wandering tissues/organs (mesothelium cells )  Cuboidal Covering the Covering,sec (a) By light ovary, thyroid retion microscopy cilia Columnar Lining of Protection, intestine, lubrication, gallbladder absorption, secretion STRATIFIED Squamous Epidermis Protection; (TWO OR keratinized prevents MORE (dry) water loss (b) SEM of the LAYERS OF apical surfaces of this epithelium CELLS) Squamous Mouth, Protection, shows the density nonkeratini esophagus, secretion; of the cilia zed (moist) larynx, vagina, prevents anal canal water loss Cuboidal Sweat glands, Protection, developing secretion ovarian (c) TEM of follicles cilia Transitional Bladder, Protection, ureters, renal distensibility calyces Columnar Conjunctiva Protection PSEUDOSTRATIFIED Lining of Protection, (LAYERS OF CELLS WITH trachea, secretion; 2. MICROVILLI NUCLEI AT DIFFERENT bronchi, nasal ciliamediated LEVELS; NOT ALL CELLS cavity transport of -​ Smaller than cilia; composed of action REACH SURFACE BUT particles microfilaments ALL ADHERE TO BASAL trapped in -​ Are anchored to a network structure - LAMINA) no cell form mucus out of terminal-web which contains actin filaments to the air stabilize microvillus passages -​ Function: aid in absorption SPECIALIZATION OF EPITHELIAL CELLS (a) A high-magnification light microscope shows many parallel microvilli and their connections to the terminal (APICAL DOMAIN) web in the underlying cytoplasm. (X6500) 1. CILLIA ​ Elongated, motile structures that have a greater diameter length than microvilli. ​ Arise from basal bodies ​ Function: aid in the transport of material along the surface of epithelial cells.  DESMOSOMES ​ Located beneath the adhering junctions, also assist in cell to cell attachment GAP JUNCTION ​ Are communicating junctions, provide a low resistance channel to permit passage of ions and small molecules between adjacent cells. (b) SEM of a sectioned epithelial cell shows both the internal and surface structure of individual microvilli and the association with actin filaments and intermediate filaments of the terminal web. 3. STEREOCILLIA ​ Long microvilli; consist of actin microfilaments ​ Functions: help in absorption Junctional complexes of epithelial cells SPECIALIZATION OF LATERAL SURFACE (LATERAL DOMAIN) ZONULA OCCLUDENS (TIGHT JUNCTION) ​ Completely surrounds the apical cell borders to seal the underlying intercellular cleft from the outside environments ZONULA ADHERENS (ADHERING JUNCTIONS) ​ Found beneath the tight junction, also forming a bond-like junction surrounding the entire cell and serving to attach adjacent cells.  NOTE: ZONULA OCCLUDENS (tight junction), ​ LOCATION : lining the posterior surface of the ZONULA ADHERENS (adhering junction), AND cornea; lining blood vessels and lymphatic DESMOSOMES ARE UNDER JUNCTIONAL vessel (endothelium); lining the surface of the COMPLEX body cavities (pericardial, pleural, peritoneal, mesothelium), and the lining of the alveoli of the SPECIALIZATION OF LATERAL SURFACE lungs. (LATERAL DOMAIN) SIMPLE SQUAMOUS EPITHELIAL CELL BASAL LAMINA CLINICAL SIGNIFICANCE ​ Sheet of extracellular material o all epithelial MESOTHELIOMA (cancer of the mesothelium) cells in contact w/ subjacent connective tissue at the basal surfaces. ​ A neoplasm that arises from the surface of ​ Macromolecular components of basal laminae: pleural and peritoneal cavities. It is occasionally found in the pericardial mesothelium.. ​ Commonly seen in individuals who are either Laminin - these are large glycoprotein exposed to asbestos or who smoke. molecules that self assemble to form a lace-like sheet Type IV Collagen - monomers of type IV ENDOTHELIAL CELLS collagen and self assemble further to form a self like sheet associated with the laminin ​ Flattened, elongated, oriented parallel to the layer direction of blood flow and rest on a basement ENTACTIN (nidogen - a glycoprotein) & membrane (proteoglycan w/ heparan sulfate side ​ The wavy structure is called the internal elastic chains) - these glycosylated proteins and lamina. The endothelium, subendothelium others serve to link together the laminin connective tissue and the internal elastic lamina and type IV collagen sheets. compromise the tunica intima. ​ The cells and basement membrane are linked by junctionals called “hemidesmosomes”. RETICULAR LAMINA Beneath the basement membrane is a subendothelial cell under connective tissue. ​ Layer below of type IV collagen ​ These are reticular fibers made of type III collagen in the underlying connective tissue by ATHEROSCLEROSIS anchoring fibrils. ​ The formation of deposits of yellowish plaques that contain cholesterol, lipid material, and Type III Collagen - More diffuse network lipophages (macrophages with engulfed lipids) bound to the basal lamina by anchoring ​ These deposits when hardened may occlud fibrils of type IV collagen blood than to distant tissue and blood clots may form on exposed collagen in subendothelial SIMPLE SQUAMOUS EPITHELIAL CELL connective tissue. ​ Clot formation / dislodged pieces of plaque may ​ Composed of one layer uniform flat cells which result in vascular occlusion and stroke rest on the basement membrane. The simplest ​ Endothelial dysfunction, dyslipidemia, of epithelial. inflammatory and immunologic. ​ Apical surfaces are smooth and the width of the cell is greater than height ​ FUNCTION : allows passage of materials by diffusion and filtration in sites where protection is not important; secretes lubricating substances in serosae  SIMPLE CUBOIDAL EPITHELIAL CELL ​ LOCATION: found in the digestive tract, oviducts (fallopian tubes) in the female reproductive ​ Composed of one layer of uniformed cuboidal system and ductuli efferences testis of the cells which rest on the basement membrane reproductive system ​ The cells height, width, and depth are roughly equal. Nuclei are centrally & spherical & shape. SIMPLE COLUMNAR EPITHELIAL CELL ​ FUNCTIONS: secretion and absorption ​ LOCATION : distal and collecting tubules of the CLINICAL SIGNIFICANCE kidney; found lining most of the tubules in the Celiac (coeliac) Disease: gluten allergy kidney and in some excretory glands. ​ Disorder of the small intestine where it lacks SIMPLE CUBOIDAL EPITHELIAL CELL microvilli; if left untreated, coeliac disease can CLINICAL SIGNIFICANCE lead to malabsorption anemia bone disease and rarely some forms of cancer HYPERTHYROIDISM (goiter) ​ HISTOLOGIC FEATURES: blunting of villi, presence of lymphocytes among epithelial cells ​ Characterized by the overproduction of thyroid (intraepithelial lymphocytes) & increased hormone lymphocytes within the lamina propria ​ SYMPTOMS : nervousness, irritability, (connective tissue) tachycardia, increased perspiration, difficulty ​ cannot absorb; most of the components of blood sleeping, muscle weakness, warm moist skin, depends with the absorption of food trembling hands, hair loss. ​ Seen most often in woman (aged 20-40 yrs old) PSEUDOSTRATIFIED COLUMNAR EPITHELIUM GRAVE’S DISEASE (diffuse toxic goiter) ​ one layer of non uniformed that vary in shape ​ The most common form of hyperthyroidism and height (tall & short basal cells); stem cells​ ​ Autoimmune disease (antibodies to TSH ​ most widespread type of pseudostratified receptor) columnar epithelium is found in the respiratory ​ SIGNS : exophthalmos tract and has long fingerlike, motile structure ​ Diagnostic test is antibodies test called cilia cell the apical surface of the cell ​ FUNCTION: secretion, particularly of mucus; HASHIMOTO'S THYROIDITIS population of mucus by ciliary action ​ LOCATION: nonciliated type is found in male ​ The most common cause of hypothyroidism sperm carrying duct; ciliated variety line in the ​ Associated with enlargement of the thyroid gland trachea, most of the upper respiratory tract (goiter) ​ Characterized by TSH and TPO antibody PSEUDOSTRATIFIED COLUMNAR EPITHELIAL CELL CLINICAL Simple Columnar Epithelium SIGNIFICANCE ​ one layer of columnar cells resting on the BRONCHITIS basement membrane ​ Cell’s height is greater than its width. the ​ Disease marked by acute or chronic elongated nucleus is most often located in the inflammation in the bronchial tubes (bronchi). basal region of the cell The inflammation may be caused by infection ​ FUNCTION: absorption; secretion of mucus, (virus, bacteria) or by exposure to irritants. enzyme and other substances, ciliated type propels mucus (or reproductive cells) by ciliary action  ​ In chronic bronchitis, the surface epithelium may STRATIFIED CUBOIDAL EPITHELIUM undergo hyperplasia and loss of cilia; the pseudostratified epithelium is often replaced ​ Top layer: columnar ​ Basal layer: cuboidal ​ Composed of 2 or 3 layers of cells STRATIFIED SQUAMOUS EPITHELIUM ​ LOCATION; conjunctive, some large ducts in the ​ contains several layers of cells in the superficial exocrine glands layer being flattened ​ protects the body against injury abrasion STRATIFIED CUBOIDAL EPITHELIUM dehydration and infection CLINICAL SIGNIFICANCE ​ Blockage from ducts, causing the saliva to back up inside the duct as it cannot exit into the mouth ​ Most common: salivary stone (calculus/calculi) ​ Forms from salts in the saliva ​ This causes the saliva to back up inside the duct resulting in gland swelling ​ Removal of a stone may require surgery or lithotripsy (treatment by focused high-intensity ​ Basal cells: cuboidal or columnar that are acoustic pulses) metabolically active Surface cells: squamous ​ calculus/calculi - a blocked duct and gland keratinized filled with stagnant saliva may become infected with bacteria STRATIFIED SQUAMOUS EPITHELIUM CLINICAL SIGNIFICANCE TRANSITIONAL EPITHELIUM PSORIASIS ​ a stratified epithelium of then referred to a urothelium ​ Chronic inflammatory skin disease characterized ​ lines in the excretory channels leading from a by pink to salmon-colored plaques with silver kidney (renal calyces, ureters, bladder and scales and sharp margins proximal segment of the urethra) ​ Clinical feature: T-lymphocyte-mediated ​ may contain four to six layers in the relaxed immunologic reaction state ​ Symptoms: itching, joint pain, nail pitting, and ​ histological appearance can changed when nail discoloration stretched ​ Pathologic examination: thickened epidermis, ​ surface cells are other described as "dome extensive overlying parakeratotic scales, shaped" and are called dome called (which may microabscess in the stratum corneum layer, and contain two nucleoli) or umbrella cells (they micropostules within the stratum granulosum contain extra membrane) and spinosum layers GLAND BARRETT SYNDROME -​ are composed of epithelial cells and can be ​ Complication of gastroesophageal reflux disease classified as endocrine and exocrine according marked metaplasia of the SSE of the distal to how the secretory products leaves the gland esophagus into simple columnar as a response to prolonged reflux-induced injury ​ Patients have high risk of developing adenocarcinoma  A.​ Endocrine Glands: release products into SIMPLE GLANDS AND COMPOUND interstitial fluid or directly into the bloodstream GLANDS CLASSIFIED ACCORDING TO (no ducts) B.​ Exocrine Glands: secrete products through THEIR MORPHOLOGY ducts into the lumen or directly onto the body Simple Tubular Glands surfaces (has ducts) ​ have no ducts, straight tubules and can be Classification: product found in large and small intestine A.​ Serous gland: watery proteinaceous fluid (EX. Simple Branched Tubular Glands parotid, von Ebner of the tongue, pancreas, and sweat gland) ​ don't have ducts, secretory glands are split into B.​ Mucous gland: secretes mucus, a mixture of 2 or more tubules & can be found in the stomach glycoprotein and water ( EX. goblet cells in the small and large intestine, respiratory epithelium, Simple Coiled Tubular Glands hard and soft palates, stomach epithelium) C.​ Seromucous (mixed) gland: have both serous ​ have long ducts, secretory are formed by coiled and mucous secretion (EX. submandibular, tubules sublingual, tracheal glands) D.​ Sebaceous gland: produce lipids (skin Simple Acinar Glands Classification: mechanism ​ have short unbranched ducts A.​ Merocrine (eccrine): most common, only Compound Tubular Glands secretory product is being released from the cell by exocytosis without loss of cell material ( EX. ​ have branched ducts, secretory cells are formed release of zymogen granules by pancreatic into branched tubules acinar cells) B.​ Apocrine: the secretory product is released Compound Acinar Glands together with part of apical cytoplasm of the secretory cell (EX. lipid secretion of the ​ branched ducts, secretory units are branched mammary gland) acini C.​ Holocrine: product is released by disintegration of the cell when a secretory cell dies and a new Compound Tubuloacinar Gland one is formed from a nearby basal cell; the entire cell is released (EX. sebum released by ​ branched ducts, secretory units are formed by the cells of sebaceous glands) both an acinar component and tubular component (ex. submandibular and sublingual Classification: morphology glands A.​ Unicellular: products are released directly onto PATHOLOGIC TERMS the surface of an epithelium ( ex. Goblet cells) B.​ Multicellular: many secretory cells arranged in ★​ Metastasis: spread of malignant neoplasm from different organizations its site of origin to a remote site through blood -​ Consist of numbers of secretory glands and lymphatic vessels arranged in different organizations classified generally simple glands and compound glands which can be classified according to their morphology ★​ Dyslipidemia: disorder of lipoprotein metabolism causing amounts of lipids and lipoproteins in the blood ★​ Osteomalacia: abnormal bone mineralization, resulting to soft, weak bones ★​ Metaplasia: reversible process of one mature cell type changes into another mature cell type ★​ Microabscess: collection of neutrophils and its neutrophils debris within the parakeratotic scale in the psoriasis ★​ Micropostule: collection of neutrophils within the epidermis ; abutting the parakeratotic scale in the skin disease psoriasis ★​ Parakeratosis: persistence of the nuclei of keratinocytes into the stratum corneum of the skin or mucous membrane; parakeratotic scales containing neutrophils are seen in the skin  Topic 2 Prelim: Connective Tissue MT 207: Derlith Reann Mitchao - Lumen, RMT Histology SY 2024-2025 Prepared by: Herda, Princes Alitha 1ST SEMESTER 5. Hematopoietic Connective Tissue CONNECTIVE TISSUE ​ Blood (carry nutrients) ​ Are of mesodermal origin and consist of a ​ Bone Marrow (produce blood) mixture of cells, fibers, and ground substance. ​ Classification and function of connective tissue are based on the differences in the composition and amounts of cells. ​ Vascular; has many mixture unlike epithelial tissue (cells, fibers, and ground substance) FUNCTIONS ​ Provides structure for the body. ​ Provide metabolic support ​ Where the epithelial cells lay down CELLULAR DIFFERENTIATION OF CONNECTIVE TISSUES TYPES OF CONNECTIVE TISSUES Mesenchymal cells 1. Connective Tissue Proper ​ fixed cells (adipocytes and fibroblasts -formed ​ Dense regular tissue and reside in the connective tissue) ​ Dense regular connective tissue ​ Dense Irregular connective tissue Hematopoietic stem cells ​ Loose Connective tissue ​ wandering cells (mast cells, macrophages, 2. Specialized Connective Tissue plasma cells, and leukocytes - differentiate in the BM and migrate from the blood circulation ​ Adipose tissue into connective tissue) ​ Reticular tissue ​ Elastic tissue Note: cells found in the CT proper include fibroblasts, macrophages, mast cells, plasma 3. Embryonic connective Tissue cells, and leukocytes. ​ Mesenchymal connective tissue Fibroblasts are responsible for synthesis and ​ Mucous connective tissue maintenance of the extracellular material. Macrophages, plasma cells, and leukocytes, have 4. Supporting Connective Tissue defense and immune functions. ​ Cartilage ​ Bone (framework of the body)  Function: CELL TYPE REPRESENTATIVE REPRESENT ​ Responsible for the synthesis of all components PRODUCT OR ACTIVITY ATIVE of the extracellular matrix (fibers and ground FUNCTION substance) of connective tissue. ​ Synthesize and secretes collagen and elastin. Fibroblast, production of fibers and Structural ​ Involves in wound healing chondroblast ground substance , osteoblast, odontoblast Plasma cell Production of antibodies Immunologic (defense) Lymphocyte Production of Immunologic immunocompetent cells (defense) Eosinophilic Participation in allergic and Immunologic leukocyte vasoactive reactions, (defense) modulations of mast cell activities and the inflammatory process, parasite Neutrophilic Phagocytosis of foreign Defense Macrophages leukocyte substances, bacteria ​ Also called tissue histiocytes Macrophage Secretion of cytokines and Defense ​ Are highly phagocytic cells (debris eater) that Defense other molecules, are derived from blood monocytes; have highly phagocytosis of foreign developed phagocytic ability and specialize in substances and bacteria, turnover of protein fibers and removal of antigen processing and apoptotic cells (dead cells), tissue debris, or presentation to other cells other particulate materials Mast cell and Liberation of Defense ​ May be named differently in certain organs. basophilic pharmacologically active (participate in ​ Derived from precursor cells called monocytes molecules (e.g. histamine) allergic circulating in the blood. reaction Adipocyte Storage of neutral fats Energy reservoir, heat CELL LOCATION MAIN FUNCTION TYPE CELLULAR DIFFERENTIATION OF CONNECTIVE TISSUES Monocyte Blood Precursor of macrophages Fibroblasts ​ Their nuclei are ovoid or spindle-shaped and Macrophages Connective Production of cytokines, can be large or small in size depending on their tissue, chemotactic factors, and stage of cellular activity lymphoid several other molecules ​ They have pale-staining cytoplasm (not obvious) organs, lungs, that participate in and contain well-developed RER and rich Golgi bone marrow inflammation (defense), complexes antigen processing and ​ Mag depende sya if very active ang iyang presentation fibroblast and different size also Kupffer cell Liver Same as macrophages  Important molecules released from these granules Microglia cell Nerve tissue Same as macrophages includes: of the CNS ​ Heparin – a sulfated glycosaminoglycan that acts locally as an anticoagulant Langerhans Skin Antigen processing and ​ Histamine – promotes increased vascular cells presentation permeability smooth muscle contraction ​ Serine proteases – activates various mediators of inflammation Dendritic cell Lymph nodes Antigen processing and ​ Eosinophil and neutrophil chemotactic presentation factors (ECF & NCF) –attracts leukocytes ​ Leukotrienes C4, D4, & E4 (or the slow reacting substance of anaphylaxis, SRSA – Osteoclast Bone (fusion Digestion of bone also trigger smooth muscle contraction of several macrophages) PLASMA CELLS ​ Derived from B lymphocytes Multinuclear Connective Segregation of digestion of ​ Large, ovoid cells that have a basophilic giant cell tissue (fusion foreign bodies cytoplasm due to their richness in rough ER of several ​ Have the ability to secrete antibodies (primary macrophages) function) that are antigen specific ​ Histological features include an eccentrically placed nucleus, a cartwheel pattern of chromatin in the nucleus. MAST CELLS ​ Clock-face appearance ​ Are of bone marrow origin and are distributed ​ Life span: 10-20 days chiefly around small blood vessels. ​ Don't have granules ​ Oval and round in shape, with a centrally placed nucleus whose cytoplasm is filled with basophilic secretory granules and may be obscured (dli ma klaro) by the cytoplasmic granules. ​ Functions during immediate hypersensitivity reactions (occur within a few minutes after penetration by an antigen of an individual previously sensitized to the same or a very LEUKOCYTES similar antigen). [desensitization] ​ Considered the transient cells of connective ​ Mast cell granules display metachromasia – tissue they can change the color of some basic dyes ​ They migrate from blood vessels into connective from blue to purple or red. tissues thru diapedesis (ability of leukocytes to ​ Perivascular mast cells – near small blood go pass from the blood vessel to the outer part vessels in skin and mesenteries of it) ​ Mucosal mast cells – mucosa lining digestive ​ Increase greatly during inflammation and respiratory tracts. ​ Recall: cardinal signs of inflammation – redness (rubor), swelling (tumor), color  FIBERS ​ Produced by fibroblast occurs in the reticular lamina of basement membranes and typically Three main types of connective tissue surrounds adipocytes, smooth muscle and nerve fibers: fibers and small blood vessels. ​ Abundant reticular fibers also characterize in the Collagen fibers stroma of HEMATOPOIETIC TISSUE (bone marrow), the spleen, and lymph nodes. ​ formed by collagen ​ Support rapidly changing populations of ​ The most common and widespread fibers in proliferating cells and phagocytic cells connective tissue ​ Key element of all connective tissues as well Elastic fibers as epithelial basement membranes and the external laminae of muscle and nerve cell ​ formed by elastin and fibrillin ​ MOST ABUNDANT PROTEIN IN HUMAN ​ The most numerous component of the elastic BODY. fiber system. ​ MAJOR PRODUCT OF FIBROBLAST. ​ Elastin is resistant to digestion by most proteases but is easily hydrolyzed by pancreatic elastase. Collagen fibers: TYPES OF COLLAGEN ​ Thinner than the type I collagen fibers and form sparse networks interspersed with collagen ★​ FIBRILLAR COLLAGEN - notably collagen type I, II, and III have polypeptide subunits bundles in many organs, particularly those that aggregate to large fibrils clearly visible in subject to regular stretching or bending. light electron microscope. ​ In the wall of large blood vessels, especially ★​ TYPE IV COLLAGEN network sheet-forming, arteries, elastin also occurs as fenestrated have subunits produced by epithelial cells and sheets called elastic lamellae. are major structural proteins of external ​ Elastic fibers and lamellae are not strongly laminae and all epithelial basal laminae. acidophilic and stain poorly with H&E; they are ★​ LINKING/ANCHORING COLLAGENS are short stained more darkly than collagen with other collages that link fibrillar collagens to one stains such as orcein and aldehyde fuchsin. another (forming larger fibers) and other components of ECM Reticular fibers ​ Found in delicate connective tissue of many organs, notably in the immune system, reticular fibers consist mainly of collagen type III, which forms an extensive network (reticulum) of thin (diameter 0.5-2 µm) fibers for the support of many different cells. ​ Are seldom visible in hematoxylin and eosin (H&E) preparations but are characteristically stained black after impregnation with silver salts and are thus termed argyrophilic. (derived from the silver’s symbol in the periodic table - AG / latin word of silver argentum meaning bright or white) ​ Reticular fibers are also periodic acid-Schiff (PAS) positive, which, like argyrophilia, is due to the high content of sugar chains bound to type III collagen α chains.  GROUND SUBSTANCE DENSE CONNECTIVE TISSUE ​ Ground substance of ECM is highly hydrated DENSE REGULAR CONNECTIVE TISSUE (watery-like) , and transparent. ​ Complex mixtures of 3 major kinds of ​ Composed of coarse collagen bundles that are macromolecules: GLYCOSAMINOGLYCANS densely packed and oriented into parallel (GAGS), PROTEOGLYCANS and cylinders. Long, thin fibroblasts are found among MULTIADHESIVE GLYCOPROTEINS. the fiber bundles and are oriented in the same ​ Hyaluronan forms a viscous, pericellular network direction as the fibers. which binds a considerable amount of water, ​ FUNCTION: provides resistance to traction giving it an important role in allowing molecular forces in tendons and ligaments diffusion through connective tissue and in ​ Walay gap (clear) lubricating various organs and joints. DENSE IRREGULAR CONNECTIVE TISSUE Four major GAGs found in proteoglycans are dermatan sulfate, chondroitin sulfates, ​ Can be found in the mammary gland and also in other places such as capsules of organs. This keratan sulfate, and heparan sulfate type of tissue is generally not a richly Dermatan Sulfate vascularized tissue. ​ Medjo blurry ang collagen bundles -​ For wound repair, regulations of blood coagulation and response to infection CLINICAL CORRELATION Chondroitin Sulfates HYPERTROPHIC SCARS AND KELOIDS -​ Help to form cartilage that cushions the joints ​ Are disorders caused by accumulation of excessive amounts of collagen deposited in Keratan Sulfate the skin by hyperproliferation of fibroblasts -​ For corneal development and maintenance of TENDINOSIS transparency of the tissue ​ A degenerative disease that occurs within the substance of a tendon. Histologic exam Heparan Sulfate reveals abnormal fibrotic structure including collagen disorganization, decreased fiber -​ Regulate interaction between cell to cell and diameter, and increased mucoid ground extracellular matrix substance. LOOSE (AREOLAR) CONNECTIVE TISSUE ★​ GLYCOPROTEINS - synthesized on RER, mature in the Golgi apparatus, where the ​ A very common type of connective tissue that GAG side-chains are added, and secreted supports many structures which are normally from cells by exocytosis under some pressure and low friction. It ★​ AGGRECAN one of the best studied usually supports epithelial tissue, forms a layer around small blood and lymphatic proteoglycans. Abundant in cartilage vessels, and fills the spaces between muscle ★​ INTERSTITIAL FLUID - ground substance of and nerve fibers. connective tissue, has an ion composition ​ It is sometimes called AREOLAR TISSUE. similar to blood plasma. ​ FUNCTION: provides suspension and support for tissues that are not subjected to strong forces anc forms conduits in which vessels and nerves course. ​ LOCATION: mesentery, large and small intestine  CLINICAL CORRELATION WHIPPLE DISEASE ​ A multisystemic disease caused by an infection of Tropheryma whippleii. (bacteria that affects small intestine) ​ Primarily affects the small intestine. ​ Clinical symptoms include abdominal pain, flatulence, malabsorption, and diarrhea ​ The lamina propria (LCT) of the small intestine reveals an increased number of BROWN ADIPOSE TISSUE macrophages. ​ Brown adipocytes contain many small lipid inclusions and are therefore called SPECIALIZED CONNECTIVE TISSUE MULTILOCULAR ​ Also called the hibernating gland ADIPOSE TIISUE ​ Mitochondria of this type of adipose tissue have THERMOGENIN or UNCOUPLING ​ A special form of connective tissue and has rich PROTEIN (UCP-1) neurovascular supply. Represents 12- 20% of ​ PRINCIPAL FUNCTION: HEAT PRODUCTION the body weight in normal men and 20-25% of the body weight in normal women. (men naturally has more muscle percentage than women) ​ The largest repository of energy in the body. ​ TWO TYPES OF ADIPOSE TISSUES: 1.​ White Adipose Tissue -​ More common type 2.​ Brown Adipose Tissue -​ Has abundant mitochondria thus the dark appearance (brown color) CLINICAL CORRELATION OBESITY ​ Hypertrophic obesity is a disorder characterized by an increase in total body fat, particularly by expansion of preexisting fat cells. Obesity increases the risk for a number of conditions, including diabetes, hypertension, high cholesterol, stroke, and coronary artery disease. RETICULAR TISSUE ​ A specialized loose connective tissue that provides a delicate supporting framework for WHITE ADIPOSE TISSUE many highly cellular organs such as endocrine glands, lymphoid organs, the spleen, and the ​ Specialized for long-term energy storage. liver. ​ White adipocytes are called UNILOCULAR (one lobe)  CLINICAL CORRELATION MUCOUS CONNECTIVE TISSUE CIRRHOSIS ​ Best example of mucous connective tissue is the jellylike matrix found in the umbilical cord, ​ A liver disorder caused by chronic injury to the WHARTON'S JELLY. This does not hepatic parenchyma. differentiate beyond this stage ​ Major causes include alcoholism and chronic infection with hepatitis B or C virus. PATHOLOGICAL TERMS FOR ​ Characterized by the collapse of the delicate CONNECTIVE TISSUE supporting reticular connective tissue with increased numbers of collagen and elastic ​ URTICARIA fibers. -​ an itchy skin eruption, also known as ​ Symptoms include jaundice, edema, and hives, characterized by wheals with coagulopathy pale interiors and well-defined red margins, often result of an allergic response to insect bites, foods, drugs. ​ PRURITUS -​ itching of the skin due to a variety of causes including hyperbilirubinemia, and allergic and irritant contact conditions. ​ CIRRHOSIS -​ an abnormal liver condition characterized by diffuse nodularity, due to fibrosis and regenerative nodules of hepatocytes; frequent ELASTIC CONNECTIVE TISSUE causes are alcohol abuse and viral hepatitis ​ Consists predominantly of elastic material, ​ JAUNDICE and this allows distension and recoil of the -​ yellow staining of the skin, mucous structure. This tissue can be found in some membranes, or conjunctiva of the vertebral ligaments, arterial walls, and in the eyes caused by elevated blood levels bronchial tree of the bile pigment bilirubin. ​ COAGULOPATHY CLINICAL CORRELATION -​ a disorder that prevents the normal clotting process of blood; causes may MARFAN SYNDROME be acquired, such as hepatic dysfunction, or congenital, such as ​ An autosomal dominant disorder caused by decreased clotting factors, as seen in FBNI gene mutation, which affects the inherited conditions like hemophilia. formation of elastic fibers, particularly those ​ NECROSIS found in the aorta, heart, eye, and skin. -​ irreversible cell changes that occur as ​ Signs and symptoms include tall stature with a result of cell death. long limbs and long, thin fingers and enlargement of the base of the aorta accompanied by aortic regurgitation EMBRYONIC CONNECTIVE TISSUE MESENCHYMAL CONNECTIVE TISSUE ​ Found in the developing structures in the embryo. It contains scattered reticular fibers and mesenchymal cells, which have irregular, star or spindle shapes and pale-stained cytoplasm. ​ Embryonic red blood cells (stem cells) can be seen in this specimen  Topic 3 Prelim: Muscle Tissue MT 207: Derlith Reann Mitchao - Lumen, RMT Histology SY 2024-2025 Prepared by: Herda, Princes Alitha 1ST SEMESTER HISTOLOGICAL CLASSIFICATION MUSCLE TISSUE SKELETAL MUSCLE ​ composed of cells that optimize the universal cell property of contractility -​ Single multinucleated cell ​ actin microfilaments and associated proteins to -​ generate the forces necessary for the muscle CARDIAC MUSCLE contraction -​ drives movement within organ systems, of -​ Branching striations blood, and of the body as a whole -​ Intercalated disc -separates on cell from another cell ​ Origin: Mesodermal -​ Glycogen (to produce ATP) ​ Essentially all muscle cells are of mesodermal origin -​ nucleus and differentiate by a gradual process of cell lengthening w/ abundant synthesis. SMOOTH MUSCLE ​ The forces necessary for sliding are generated by other protein affecting the weak interactions in the -​ no striations; nucleic bridges between myosin and actin ​ Stains RED with H & E (hematoxylin and eosin) staining of myoglobin (transport oxygen) SKELETAL MUSCLE ​ Have striated appearance because of the way their MUSCLE CELL ORGANELLE fibers are organized. They are voluntary, meaning we can consciously control them. These muscles SARCOPLASM attach to the bones throughout the body enabling us to move. ​ Cytoplasm of muscle ​ Won't work without nerve synapses ​ Greek word sarkos=flash + plasm ​ Skeletal (or Striated) Muscle consists of muscle fibers which are long cylindrical multinucleated cells with diameters of 10-100 SARCOPLASMIC RETICULUM ​ A small population of reserve progenitor cells called muscle satellites remains adjacent to the ​ Smooth ER most fibers of differentiated skeletal muscle. Sarcolemma DEVELOPMENT OF SKELETAL MUSCLE CELLS ​ Sarkos + lemma (Greek) = husk ​ Muscle cell membrane ​ Skeletal muscle begins to differentiate are when ​ External lamina mesenchymal cells call MYOBLASTS fuse together to make longer multinucleated tubes ​ Myotubes synthesize the proteins to make up Functional Classification myofilaments and gradually begin to show cross striations by light microscopy VOLUNTARY ​ Part of the myoblast population doesn’t fuse and differentiate but remains as a group of ​ Under the conscious control mesenchymal cells called muscle satellite cells ​ Skeletal muscle located on the external surface of the muscle fibers inside the developing external lamina. Satellite cells proliferate and produce new muscle fibers INVOLUNTARY following muscle injury ​ Contract in response to the control of autonomic nervous system ​ Cardiac and Smooth muscle (e.g. Heart)  ORGANIZATION OF SKELETAL MUSCLE Epimysium ​ External sheath of dense irregular connective tissue ​ Surrounds the entire muscle ​ Septa of this tissue extends inward carries large nerves, blood vessels and lymphatics Perimysium ​ Thin connective tissue layer that immediately surrounds each bundles of the muscle fibers called fascicle ​ Each fascicle of muscle fibers makes up a functional unit that works together ​ Nerve, blood vessels, lymphatics penetrate the perimysium to supply each fascicle Endomysium ​ Very thin delicate layer of reticular fibers and scattered fibroblast ​ Surrounds the external lamina of individual muscle fibers ​ In addition to nerve fiber, capillaries form a rich network in the endomysium bringing O2 to the Myofibrils ​ highly organized, containing muscle fibers primarily long cylindrical filament bundles ​ consist of an end-to-end repetitive arrangement of sarcomeres A band (dArk) ​ Dark band ​ contain both the thick filaments and the overlapping portions of thin filaments ​ anisotropic or birefringent in polarized light microscopy I band (lIght) ​ Light band ​ consist of the portions of the thin filaments which do not overlap the thick filaments ​ isotropic, do not alter polarized light ​ In the TEM band is seen to be bisected by a dark transverse line the Z disc. The repetitive functional subunit of the contractive apparatus, the sarcomere extends from Z Disc to Z disc and is about 2.5μm long in resting muscle. ​ Mitochondria and sarcoplasmic reticulum are found between the myofibrils, which typically have 1-2 μm diameters. ​ The A and I banding pattern in the sarcomere is due ORGANIZATION OF MUSCLE FIBERS mainly to the regular arrangements of thick and thin ​ All 3 layers plus the dense irregular connective myofilaments composed of myosin and F actin tissue of a tendon at myotendinous junctions which respectively organized within each myofibril in join the muscle to bone skin or another muscle symmetric pattern containing thousands of each ​ The sarcoplasm is highly organized containing filament types. primarily long cylindrical filament bundles called myofibrils that run parallel to the long axis of the fiber Thick myosin ​ 1.6-μm long and 15-nm wide Troponin (Thin ​ complex of three subunits: filament ​ occupy the A band at the filament TnT, TnC, and TnI. middle region of the regulatory ​ TnT= attaches to tropomyosin sarcomere protein) ​ TnC= binds with Ca2+ Myosin ​ a large complex with two ​ TnI= regulates the identical heavy chains and two actin-myosin interaction pairs of light chains Myosin heavy ​ thin, rodlike motor proteins SARCOPLASMIC RETICULUM & chains/Myosin twisted together as myosin Tails tails TRANSVERSE TUBULE SYSTEM ​ 150-nm long and 2-3 nm thick SARCOPLASMIC RETICULUM Myosin head ​ bind both actin, forming ​ In between the sarcoplasm between parallel transient cross bridges myofibrils are mitochondria and cisternae of the between the thick and thin smooth ER called SARCOPLASMIC RETICULUM filaments ​ Membranous smooth ER; Surrounds the myofibrils ​ Contains pumps and other protein for Ca2+ sequestration Actin filaments ​ thin, helical actin filaments ​ 1.0-μm long and 8-nm wide ​ run between the thick TRANSVERSE OR T-TUBULES filaments ​ At each sarcomere, two terminal cisternae of SR contact a deep imagination of the sarcolemma called TRANSVERSE OR T-TUBULES ​ Triggers Ca2+ release from sarcoplasmic reticulum ​ Long fingerlike invaginations of the cell membrane Terminal cisternae ​ Adjacent to each T-tubule Triad ​ Complex of a T-tubule with two terminal cisternae ​ Allows depolarization of the sarcolemma in a T-tubule to affect the sarcoplasmic reticulum and trigger release of Ca2+ ions into cytoplasm THIN FILAMENTS HAVE TWO TIGHTLY ASSOCIATED REGULATORY PROTEINS: Tropomyosin ​ 40-nm-long coil of two (Thin filament polypeptide chains regulatory ​ Location: in the groove protein) between the two twisted actin strands  MECHANISM OF CONTRACTION Fast glycolytic ​ Ca2+ binding to troponin causes tropomyosin to ​ Fibers specialized for rapid, short term contraction, change shape and allow the myosin heads to bind few mitochondria and capillary and depend largely on the actin subunits, forming cross bridges between anaerobic metabolism of glucose derived from short thick and thin filaments glycogen, features which make such fibers appear ​ The myosin heads then pivot with ATP hydrolysis, white. Rapid contractions lead to rapid fatigue as which pulls the thin filaments along the thick lactic acid produced by glycolysis accumulates. filaments. ​ With Ca2+ and ATP present, a contraction cycle Fast oxidative-glycolytic ensues in which myosin heads repeatedly attach, pivot, detach, and return, causing the filaments to ​ Fibers have physiological and histological features slide past one another, shortening the sarcomere. intermediate between slow oxidative and fast ​ When the membrane depolarization ends, Ca2+ is glycolytic again sequestered, ending contraction and allowing the sarcomeres to lengthen again as the muscle SMOOTH MUSCLE relaxes. ​ Synapses of motor axons with skeletal muscle are ​ Specialized for slow, steady contraction called MEPs, NMJs, or myoneural junctions; the ​ Influenced by autonomic nerves and various neurotransmitter is acetylcholine. hormones ​ A motor axon may form many terminal branches, each ending on an MEP of a muscle fiber; all fibers MAJOR COMPONENT innervated by branches of that axon comprise a motor unit. ​ blood vessels ​ digestive tracts SKELETAL MUSCLE FIBER TYPE ​ respiratory tract ​ urinary tract IDENTIFICATION: ​ reproductive tracts ​ and associated organs 1.​ maximal rate of contraction (fast or slow fibers) 2.​ their major pathway for ATP synthesis (oxidative LENGTH phosphorylation or glycolysis) ​ Small blood vessel: 20μm FAST VS. SLOW RATES OF FIBER CONTRACTION ​ Pregnant uterus: 500μm ​ Due largely to myosin isoforms with different maximal CELL rates of ATP hydrolysis ​ Central ​ Broadest Part EACH OF THESE FEATURES EXISTS AS A CONTINUUM IN SKELETAL MUSCLE FIBERS, BUT ​ Size: 5-10μm FIBER DIVERSITY IS DIVIDED INTO 3 MAJOR ​ Mononucleated TYPES: SLOW OXIDATIVE ​ Fibers of smooth muscle (also called visceral muscle) ​ Muscle fibers are adopted for slow contraction over are elongated, tapering & unstriated cells, each of long periods without fatigue, having many which is enclosed by an external lamina & a network mitochondria, surrounding capillaries and much of type 1 and type 2 collagen fibers comprising the endomysium. myoglobin, all features that make fresh tissue rich in ​ Tropomyosin and troponin is lacking in smooth these fibers dark or red color. muscle ​ proteins controlling the sliding filaments here include ​ Myosin light-chain kinase (MLCK) and Calmodulin -​ Controls the sliding filaments -​ Calmodulin – Ca2+ binding protein SMOOTH MUSCLE FIBER TYPES ​ Smooth muscle is not under voluntary control & its fiber typically lacks well-defined neuromuscular  junction. Contraction is most commonly stimulated by CLINICAL MANIFESTATION autonomic nerves. ​ Thin and thick filaments in smooth muscle fibers do HYPERTROPHY & HYPERPLASIA not form sarcomeres ​ Thin actin filaments attach to α-actinin located in ​ Variation in diameter of muscle fibers depends on dense bodies that are located throughout the sarcoplasm and near the sarcolemma facto: muscle, age, gender, nutritional status & ​ Contraction causes cells to shorten individually. physical training of individual ​ Sarcoplasmic reticulum is less well-organized in ​ Exercise enlarges the skeletal musculature by smooth muscle fibers, and there is no transverse stimulating the formation of new myofibrils & growth tubule system. in the diameter of the individual muscle fiber. ​ Process is characterized by increased cell volume= CARDIAC MUSCLE HYPERTROPHY ​ Tissue growth by an increase in the number of cells = ​ Striation HYPERPLASIA ​ similar to skeletal muscle ​ hyper (Greek) = above + trophe = nourishment ​ unique because they are branched and ​ hyper + plasis (Greek) = molding interconnected ​ work involuntarily ​ continuously contracting to pump blood throughout MYASTHENIA GRAVIS the heart ​ Autoimmune disorder ​ a unique characteristic of cardiac muscle ​ Circulating antibodies against proteins of ​ presence of transverse line that cross at irregular acetylcholine receptors intervals with myocardial cells join ​ Extraocular muscles of the eyes are commonly the ​ intercalated disc: interfaces between adjacent cells & first affected consist of many junctional complexes ​ Antibody binding to the antigenic sites interfere with ​ composed of man desmosomes and fascia adherens acetylcholine alteration of their receptors. junction, both provide strong intercellular adhesion during cell's constant contractile activity. DYSTROPHIN CARDIAC MUSCLE FIBERS ​ Large actin-binding protein ​ Involved in the functional organization of myofibrils ​ also striated, only consisting of individual cylindrical cells, each containing 1 or 2 central nucleic & linked by adherent & gap junctions at prominent intercalated DUCHENNE MUSCULAR DYSTROPHY disc. ​ Mutations of the dystrophin gene can lead to ​ sarcomeres of cardiac muscle; organized & function defective linkages between the cytoskeleton and the similarly to those of skeletal muscle extracellular matrix ​ Contraction of cardiac muscle is intrinsic at nodes ​ of impulse-generating pacemaker muscle fibers ​ Autonomic nerves regulate the rate of contraction ISCHEMIA ​ Most common injury sustained by cardiac muscle ​ Tissue damage due to lack of oxygen when coronary arteries are occluded by heart disease ​ Heart cant regenerate new cells and can be due to atherosclerosis LEIOMYOMAS (myoma) ​ Benign tumors ​ commonly called fibroids ​ Develop from smooth muscle fibers; occur in the wall of uterus IMPORTANT COMPARISONS OF THE THREE TYPES OF MUSCLE  Topic 4 Prelim: Bone MT 207: Derlith Reann Mitchao - Lumen, RMT Histology SY 2024-2025 Prepared by: Herda, Princes Alitha 1ST SEMESTER Osteocytes BONE ​ Enclosed in lacunae, spaced throughout ​ Main constituent of the adult skeleton mineralized matrix ○​ Provides solid support for the body ​ Features: ○​ Protects vital organs (cranial, thoracic ○​ Have processes in canaliculi (250-300 cavities) nm diameter) ○​ Encloses medullary cavities containing ○​ Communicate via gap junctions with bone marrow (blood cell formation) osteoblasts and bone-lining cells ​ Acts as a reservoir of calcium, phosphate, and ○​ Function as mechanosensors detecting other ions mechanical load and microdamage ​ Specialized connective tissue composed of: ○​ Maintain calcified matrix (death leads to ○​ Osteocytes – Found in lacunae matrix resorption) between bone matrix layers, with cytoplasmic processes in canaliculi OSTEOCLASTS ○​ Osteoblasts – Growing cells that synthesize and secrete organic matrix ​ Large, motile, multinucleated cells responsible components for bone resorption. ○​ Osteoclasts – Giant, multinucleated ​ Derived from fused bone marrow-derived cells involved in removing calcified bone monocytes. matrix and remodeling bone tissue ​ Require M-CSF and RANKL from osteoblasts for ​ Lined by connective tissue layers containing development. osteogenic cells: ​ Reside in resorption lacunae (Howship lacunae) ○​ Endosteum – Internal surface on bone surfaces surrounding marrow cavity ​ Form a sealing zone and ruffled border for ○​ Periosteum – External surface efficient bone resorption. BONE CELLS Bone Matrix Osteoblasts ​ 50% inorganic (mainly calcium hydroxyapatite, also bicarbonate, citrate, Mg²⁺, K⁺, Na⁺). ​ Origin: Mesenchymal stem cells ​ 50% organic (90% Type I collagen, small ​ Functions: proteoglycans, glycoproteins like osteonectin). ○​ Produce organic components of bone ​ Osteocalcin and matrix vesicle phosphatases matrix (Type I collagen, proteoglycans, promote calcification. osteonectin) ​ Collagen-mineral association provides bone ○​ Secrete osteoid (collagen-rich material) hardness and resistance. for bone appositional growth ○​ Release osteocalcin (binds Ca²⁺ and concentrates minerals) ○​ Release matrix vesicles rich in alkaline phosphatase (raises local PO₄³⁻ concentration)  Periosteum & Endosteum EPIPHYSEAL GROWTH PLATE ZONES ​ Periosteum (external covering): 1.​ Resting Cartilage – Typical hyaline cartilage ○​ Outer fibrous layer (Type I collagen, 2.​ Proliferative Zone – Chondrocytes divide, fibroblasts, blood vessels). secrete Type II collagen, form vertical columns ○​ Inner cellular layer (osteoblasts, bone 3.​ Hypertrophic Zone – Swollen chondrocytes lining cells, osteoprogenitor cells). secrete Type X collagen, stiffening matrix ○​ Sharpey’s fibers anchor periosteum to 4.​ Calcified Cartilage Zone – Chondrocytes bone. release matrix vesicles, hydroxyapatite ​ Endosteum (internal lining): formation ○​ Covers trabeculae in marrow cavities. 5.​ Ossification Zone – Bone tissue appears, ○​ Contains osteoprogenitor cells, osteoblasts secrete osteoid, forming woven osteoblasts, and bone lining cells in a bone sparse collagen matrix. METABOLIC ROLE OF BONES LAMELLAR BONE CALCIUM MOBILIZATION ​ Most adult bone (compact or cancellous) ​ Characterized by multiple layers (lamellae) of Parathyroid Hormone (PTH) calcified matrix (3-7 μm thick) ​ Lamellar Organization: ​ Raises blood calcium levels ○​ Parallel sheets or concentric rings ​ Stimulates osteoclasts and osteocytes for bone around a central canal resorption ○​ Osteon (Haversian system) – Complex ​ Indirectly stimulates osteoclasts via osteoblasts of concentric lamellae surrounding a secrete RANKL RECEPTOR ACTIVATOR OF central canal (100-250 μm diameter) NUCLEAR FACTOR KAPPA BETA (NFkB ○​ Lacunae – Between successive ligand) lamellae, each containing an osteocyte ○​ Canaliculi – Contain osteocyte dendritic Calcitonin: processes ○​ Perforating (Volkmann) canals – ​ Lowers blood calcium levels Connect osteons, have fewer concentric ​ Directly inhibits osteoclasts, reducing bone lamellae resorption ​ Compact Bone: ○​ Outer layer: Circumferential lamellae JOINTS beneath periosteum ○​ Inner layer: Fewer circumferential Synarthroses (Limited/No Movement): lamellae around marrow cavity ​ Synostoses – Bones linked, no movement OSTEOGENESIS (Bone Development) (e.g., skull in adults) ​ Syndesmoses – Dense connective tissue joins ​ Intramembranous Ossification: bones (e.g., tibiofibular ligament) ○​ Osteoblasts differentiate directly from ​ Symphyses – Fibrocartilage between bones mesenchyme and secrete osteoid (e.g., intervertebral discs, pubic symphysis) ○​ Forms most flat bones (skull, jaws, scapula, clavicle Diarthrotic (Movable) Joints: ​ Endochondral Ossification: ​ Preexisting hyaline cartilage matrix is ​ Synovial Membrane – Contains: eroded and replaced by ○​ Macrophage-like (Type A) cells – osteoblast-secreted osteoid Remove debris, regulate inflammation ​ Occurs in long bones via epiphyseal growth plates ​  ​ Fibroblastic (Type B) cells – Produce OSTEOPOROSIS hyaluronan, proteoglycans, and synovial fluid for lubrication ​ Common in immobilized patients and postmenopausal women. MEDICAL APPLICATION ​ Imbalance in bone turnover – bone resorption exceeds formation. OSTEOSARCOMA ​ Leads to calcium loss and reduced bone mineral density (BMD). ​ Primary bone tumors are uncommon, ​ Increases risk of fractures due to weakened accounting for only 0.5% of all cancer deaths. bones. ​ Osteosarcoma can develop from ​ BMD is measured using dual-energy X-ray osteoprogenitor cells. absorptiometry (DEXA scans). ​ Secondary (metastatic) bone tumors are more common. OSTEOGENESIS IMPERFECTA ("Brittle Bone ​ Cancer cells can spread to bones through blood Disease") or lymphatic vessels. ​ Common sources of metastatic bone tumors ​ Congenital disorder caused by genetic include: mutations. ➔​ Breast ​ Osteoblasts produce deficient or defective Type ➔​ Lung I collagen. ➔​ Prostate gland ​ Leads to fragile bones prone to fractures. ​ Collagen deficiency reduces bone strength and BONE DENSITY AND MECHANICAL STIMULATION resiliency. DISORDER ​ Spectrum of disorders, varying in severity. ​ Osteocyte network functions as a OSTEOMALACIA & OSTEITIS FIBROSA CYSTICA "mechanostat", monitoring mechanical loads. ​ Signals cells to adjust ion levels and maintain ​ Tetracycline binds to newly deposited osteoid bone matrix.Resistance exercise increases bone matrix during mineralization. density and thickness in affected areas. ​ Fluorescent under UV light, allowing ​ Lack of exercise or weightlessness (e.g., visualization of new bone. astronauts) leads to decreased bone density. ​ Used to measure bone growth rate for ​ Bone loss occurs due to the lack of mechanical diagnosing bone disorders. stimulation of bone cells. ​ Procedure: ○​ Tetracycline administered twice (11-14 OSTEOPETROSIS("Marble Bone Disease") days apart). ○​ Bone biopsy performed, sectioned ​ Genetic disease causing dense, heavy bones. without decalcification, and examined. ​ Osteoclasts lack ruffled borders, leading to ○​ Fluorescent lamellae indicate bone defective bone resorption.Results in bone growth; distance between layers reflects overgrowth and thickening. growth rate. ​ Marrow cavities become obliterated, reducing ​ Osteomalacia blood cell formation; Leads to anemia and loss -​ Calcium deficiency in adults. of white blood cells; Caused by mutations in -​ Leads to deficient calcification of newly genes for proton-ATPase pumps or chloride formed bone. channels in osteoclasts. -​ Causes partial decalcification of already mineralized bone matrix. -​ Results in soft, weakened bones prone to fractures. ​ Osteitis Fibrosa Cystica – Increased osteoclast activity leading to bone matrix removal and fibrous degeneration. RICKETS RHEUMATOID ARTHRITIS ​ Caused by calcium deficiency in children. ​ Chronic inflammation of the synovial membrane. ​ Bone matrix fails to calcify properly. ​ Leads to thickening of connective tissue in the ​ Epiphyseal plates become distorted due to body joint. weight and muscle activity. ​ Macrophages release collagenases and ​ Ossification is impeded, leading to slow bone hydrolytic enzymes. growth and deformities. ​ Destruction of articular cartilage occurs over ​ Causes: time. -​ Insufficient dietary calcium. ​ Bones come into direct contact, causing pain -​ Vitamin D deficiency, impairing Ca²⁺ and joint damage. absorption in the small intestine. DISEASES RELATED TO GROWTH HORMONE (GH) SLIPPED/HERNIATED DISC AND IGF-1 ​ Caused by degeneration of collagen loss in the 1.​ Pituitary Dwarfism annulus fibrosus. ○​ Caused by GH deficiency during ​ Disc shifts or dislocates from its normal position; childhood. Leads to displacement of the nucleus ○​ Leads to reduced growth and short pulposus.Most commonly occurs in the posterior stature due to lack of IGF-1 stimulation region of the intervertebral disc. of epiphyseal cartilage. ​ If it compresses nerve plexuses, it causes: 2.​ Gigantism Severe pain & Neurologic disturbances ○​ Caused by excess GH during childhood. ​ Pain is often felt in areas innervated by the ○​ Results in excessive long bone growth, affected nerve fibers, typically in the lower leading to abnormally tall stature. lumbar region. 3.​ Acromegaly ○​ Caused by excess GH in adulthood. ○​ Since epiphyseal cartilage is absent, bones cannot grow in length. ○​ Instead, bones thicken, especially long bones, hands, feet, and facial bone  Topic 4 Prelim: Bone MT 207: Derlith Reann Mitchao - Lumen, RMT Histology SY 2024-2025 Prepared by: Herda, Princes Alitha 1ST SEMESTER Location Joints, ribs, External ear, Intervertebral CARTILAGE nose, auditory discs, pubic respiratory tube, symphysis, Overview of Cartilage tract epiglottis tendons ​ Definition: Cartilage is a tough, flexible connective tissue with an extracellular matrix Function Smooth Flexible Tensile (ECM) rich in glycosaminoglycans (GAGs), surfaces for support strength, proteoglycans, collagen, and elastic fibers. joints, support resistance to ​ Functions: Provides structural support, resists compression mechanical stress, and serves as a precursor for bone formation. ​ Types: ○​ Hyaline Cartilage Hyaline Cartilage ○​ Elastic Cartilage ○​ Fibrocartilage ​ Most common type, glassy appearance. ​ Location: Joints (articular cartilage), nose, FEATURE HYALINE ELASTIC FIBROCART larynx, trachea, bronchi, fetal skeleton. CARTILAGE ILAGE ​ Functions: ○​ Provides smooth surfaces for joint movement. ECM Type II Type II Type I ○​ Forms the template for bone Composition collagen, collagen, collagen, development in embryos. aggrecan aggrecan, Type II ○​ Supports respiratory structures. elastic fibers collagen Matrix Cells Chondrocyte, Chondrocyte Chondrocyte, ​ Composition: Type II collagen fibers, chondroblasts , fibroblasts proteoglycans (aggrecan), GAGs (hyaluronan, chondroblast chondroitin sulfate, keratan sulfate), water. s ​ Features: ○​ Highly hydrated for shock absorption. ○​ Territorial matrix (near chondrocytes) Chondrocyte Small Small Isolated or stains darker due to GAGs. Arrangement isogenous isogenous aligned in groups groups rows Chondrocytes ​ Found in lacunae, often in isogenous groups Perichondriu Present Present Absent (small clusters from a single cell division). m