Connective Tissue and Cartilage (Edited) PDF

Connective Tissue DMSFI Histology Department  O L B 1. Compare and contrast connective tissues from E J epithelial tissues; A E 2. Identify the components of connective tissue R C and their functions; N T I I 3. Differentiate the types of connective tissues; N...

Connective Tissue DMSFI Histology Department  O L B 1. Compare and contrast connective tissues from E J epithelial tissues; A E 2. Identify the components of connective tissue R C and their functions; N T I I 3. Differentiate the types of connective tissues; N V G E 4. Name locations of the body having a specific connective tissue type. S I N T R O D U C T I O N I N T R O D U C T I O N I - Maintain the form of organs throughout the body N T R - Provide a matrix that supports and physically O connects other tissues and D cells together in organs U C - Interstitial fluid of connective tissue gives T metabolic support to cells as I the medium for diffusion of O nutrients and waste N products  - Originate from embryonic I mesenchyme N - Major constituent is the T Extracellular Matrix (ECM) R O Protein Fibers (collagens D and elastic fibers) U C Ground Substance: complex of anionic, hydrophilic T proteoglycans, I glycosaminoglycans (GAGS), O and multi-adhesive N glycoproteins (laminin, fibronectin, etc.) CONNECTIVE TISSUE CONNECTIVE TISSUE CONNECTIVE TISSUE CONNECTIVE TISSUE Cells of Connective Tissue CONNECTIVE TISSUE CELLS CONNECTIVE TISSUE CELLS FIBROBLASTS - Produce and maintain most of the tissue’s extracellular component - Synthesize and secrete collagen and elastin, GAGs, proteoglycans, and glycoproteins - Active fibroblast - Nucleus is large (Prominent) - Ovoid - Euchromatic FIBROBLASTS - Quiescent fibroblast “fibrocyte” - Smaller - Spindle-shaped - Contains a darker, more heterochromatic nucleus FIBROBLASTS ADIPOCYTES - Large, mesenchymal derived cells - Specialized for cytoplasmic storage of lipids as neutral fats, or less commonly for production of heat - Cushion and insulate the skin and other organs MACROPHAGES & MONONUCLEAR PHAGOCYTE SYSTEM - Macrophages – phagocytic ability and specialize in turnover of protein fibers and removal of dead cells, tissue debris, and other particulate material - Referred to as “Histiocytes” - Measures 10-30 um - Eccentric oval-shaped nucleus MACROPHAGES & MONONUCLEAR PHAGOCYTE SYSTEM - Irregular surface with pleats, protrusions, and indentations - Derived from bone marrow precursor cells that divide, producing monocytes - Monocytes and macrophages are the same cell at different stages of maturation - Macrophage-like cells have been given different names in different organs MACROPHAGES & MONONUCLEAR PHAGOCYTE SYSTEM MAST CELLS - Oval or irregularly shaped connective tissue cells - 7-20 um in diameter - Cytoplasm is filled with basophilic secretory granules - Nucleus is centrally situated - Abundant secretory granules - Have roles in local inflammatory response, innate immunity, and tissue repair PLASMA CELLS - B-lymphocyte-derived - Antibody producing cells - Large, ovoid cells with basophilic cytoplasm due to their richness of RER - Nucleus is generally spherical but eccentrically located - ”Clock-face” appearance PLASMA CELLS - Wandering cells in connective tissue - Leave blood via diapedesis - Increases greatly during inflammation Fibers COLLAGEN - Most abundant protein in the human body - Strong and resistant to normal and tearing forces Types - Fibrillar collagens (Type I, II, III) - Sheet forming collagens (Type IV) - Linking/anchoring collagens COLLAGEN TYPES COLLAGEN TYPES RETICULAR FIBERS - Consist mainly of collagen TYPE III - Characteristically stained black by impregnation with silver salts – termed as argyrophilic - Periodic acid-Schiff (PAS) positive - Occur in reticular lamina of basement membranes and surround adipocytes, smooth muscle, nerve fibers, and small blood vessels ELASTIC FIBERS - Form sparse networks interspersed with collagen bundles in many organs - Have physical properties to be stretched or distended and return to their original shape - Composite of fibrillin microfibrils embedded in a larger mass of cross-linked elastin ELASTIC FIBERS Ground Substance GROUND SUBSTANCE - Highly hydrated, transparent, complex mixture of macromolecules, principally of 3 classes: - Glycosaminoglycans (GAGs) - Proteoglycans - Multi-adhesive glycoproteins - Fills the space between cells and fibers in connective tissue - Viscous: acts both a lubricant and a barrier GROUND SUBSTANCE Ground Substance: GLYCOSAMINOGLYCANS Ground Substance: GLYCOSAMINOGLYCANS - 4 major GAGs found in proteoglycans - Dermatan sulfate - Chondroitin sulfate - Keratan sulfate - Heparan sulfate INTERSTITIAL FLUID - Ion composition similar to that of blood plasma - Contains plasma proteins of low molecular weight that pass through the thin walls of capillaries  Types of connective tissue LOOSE CONNECTIVE TISSUE - Also called “Areolar tissue” - Comprises a thick layer (Lamina propria) beneath the epithelial lining of the digestive system and fills the spaces between muscle and nerve fibers - Contains cells, fibers, and ground substance in roughly equal parts - Flexible and not very resistant to stress; delicate consistency LOOSE CONNECTIVE TISSUE LOOSE CONNECTIVE TISSUE DENSE CONNECTIVE TISSUE - Offers resistance and protection - Same components found in loose connective tissue, but with fewer cells and a clear predominance of collagen fibers over ground substance - Less flexible and far more resistant to stress than loose connective tissue Dense connective tissue: IRREGULAR - Bundles of collagen fibers appear randomly interwoven, with no definite orientation - Collagen fibers form a tough 3D network, providing resistance to stress from all directions - Closely associated with loose connective tissue - Examples: Deep dermis of the skin; capsules Dense connective tissue: REGULAR - Type I collagen fibers are arranged according to a definite pattern, with fibers and fibroblasts aligned in parallel - For resistance to prolonged or repeated stresses exerted in the same direction - Examples: Tendons and ligaments Dense connective tissue: REGULAR - Type I collagen fibers are arranged according to a definite pattern, with fibers and fibroblasts aligned in parallel - For resistance to prolonged or repeated stresses exerted in the same direction - Examples: Tendons and ligaments CONNECTIVE TISSUE PROPER  Special Types of connective tissue RETICULAR CONNECTIVE TISSUE - Fibers of type III collagen from a delicate 3D network that supports various types of cells - Fibrous network is produced by modified fibroblasts called reticular cells - Provides a framework with specialized microenvironments for cells in hemopoietic tissue and some lymphoid organs RETICULAR CONNECTIVE TISSUE RETICULAR CONNECTIVE TISSUE EMBRYONIC CONNECTIVE TISSUE: MUCOID TISSUE - Found mainly in the umbilical cord and fetal organs - With abundant ground substance composed chiefly of hyaluronic acid - Jelly-like with sparse collagen fibers and scattered fibroblasts - Principal component of the umbilical cord, where it is referred to as “Wharton’s Jelly” EMBRYONIC CONNECTIVE TISSUE: MUCOID TISSUE EMBRYONIC CONNECTIVE TISSUE: MUCOID TISSUE EMBRYONIC CONNECTIVE TISSUE: MUCOID TISSUE ADIPOSE TISSUE - Located throughout the body - Represents 15-20% of the body weight - Storage depot for neutral fats - Regulators of the body’s overall energy metabolism - Helps thermally insulate the body - Fills up spaces between other tissues and helps cushion and keeps some organs in place ADIPOSE TISSUE: Types - Brown Adipose Tissue - Contains cells with multiple lipid droplets interspersed among abundant mitochondria - Darker in appearance - White Adipose Tissue - More common type - Contains one very large droplet of whitish-yellow fat in the cytoplasm WHITE ADIPOSE TISSUE - Spherical when isolated but are polyhedral when closely packed - Very large cell that contains a single huge droplet of lipid that fills almost the entire cell - Signet ring in appearance WHITE ADIPOSE TISSUE - Unilocular cells - Function: - Long term energy storage BROWN ADIPOSE TISSUE - 2-5% in newborn body weight: Located mainly in the back, neck and shoulders - In adults – found in scattered areas like around the kidneys, adrenal glands, aorta, and mediastinum - Polygonal and generally smaller than cells of white adipose tissue BROWN ADIPOSE TISSUE - Brown fat: due to the very abundant mitochondria - Multilocular cells: due to many small lipid inclusions - Function: - Principal function of heat production SUMMARY ADIPOSE TISSUE ADIPOSE TISSUE Cartilage DMSFI Histology Department CARTILAGE - Special type of connective tissue - ECM rich in GAGS and proteoglycans - Firm, gelatinous consistency - Function: - Shock absorber - Cushioning and sliding for joints - Facilitates bone movement CARTILAGE - Components: - Chondrocytes - Amorphous ground substance (Absorbs water) - Fibers (Type II collagen, elastic) CARTILAGE - Cartilage cells (Chondrocytes) are housed inside a cavity (Lacunae) - No blood vessels, lymph vessels, or nerves - Get nutrients from the perichondrium TYPES HYALINE CARTILAGE - Most abundant type - Gross: Glistening and pearly white - Location: - Temporary skeleton - Costal cartilages - Epiphyseal plates of long bones - Articular surfaces of movable joints - Nose, Larynx, trachea, bronchi - Function: - Smooth, low-friction surfaces in joints - Structural support in the respiratory tract HYALINE CARTILAGE - Matrix: - Collagen Type II (40%) - Water (60-80%) - Cells: Chondrocytes and chondroblasts - Occupy little of hyaline cartilage mass - Appear in groups = ISOGENOUS AGGREGATES/GROUPS HYALINE CARTILAGE ELASTIC CARTILAGE - Grossly: Yellowish color and pliable - Location: - Auricle of the ear - External acoustic meatus - Eustachian or auditory tube - Epiglottis - Parts of larynx - Function: - Flexibility and stretchability ELASTIC CARTILAGE - Matrix: Less abundant than hyaline - Both collagen and elastic fibers present - Elastic fibers appear darkly stained with Van Gieson stain - Cells: Chondrocytes and chondroblasts ELASTIC CARTILAGE FIBROCARTILAGE - Cross between hyaline and dense connective tissue - Location: - Intervertebral discs - Attachment of certain ligaments - Symphysis pubis - Function: - Resistance to deformation under stress - Cushion between bone surfaces FIBROCARTILAGE - Matrix: - Abundant fibers of Collagen type I and II - No perichondrium - Cells: Few, single chondrocytes in aligned isogenous groups interspersed with fibroblasts FIBROCARTILAGE FIBROCARTILAGE FIBROCARTILAGE BONE TISSUE - Hardest connective tissue - Mineralized ECM - 90%: Collagen Type I and V - Matrix - Inorganic substance (Calcium hydroxyapatite) - Functions: - Protection and support - Movement - Mineral storage - Hematopoiesis BONE TISSUE - Compact (Cortical/Dense) - No spaces visible; solid mass - Comprises 80% of the bone tissue - Not occupied by bone marrow - Cancellous (Medullary/Spongy) - Contains numerous interconnecting areas called trabeculae - Comprises 20% of the bone tissue - Spaces are occupied by bone marrow BONE TISSUE BONE OSSIFICATION - Intramembranous ossification - Bone cells directly differentiate from mesenchyme and begin to secrete bone substance - Endochondral ossification - A preexisting matrix of hyaline cartilage is initially laid out that will progressively undergo ossification INTRAMEMBRANOUS vs. ENDOCHONDRAL BLOOD - Specialized connective tissue consisting of cells and ECM called plasma. - Formed elements in the plasma: - Erythrocytes (RBCs) - Leukocytes (WBCs) - Platelets BLOOD - Erythrocytes (Red blood cells) - Anucleated cells that function to carry and distribute oxygen into the tissues and CO2 to the lungs - Biconcave disc - 7-7.5 um in diameter - Histologic ruler BLOOD - Leukocytes (White blood cells) - Cells that leave the blood and migrate to tissues where they become functional and perform various activities related to immunity/protection BLOOD BLOOD - Thrombocytes (Platelets) - Anucleated cell fragments from a bone marrow cell, megakaryocytes - Promote blood clotting and help repair minor tears in the vessel walls – “Hemostasis” BLOOD Thank you! DMSFI Histology Department