Connective Tissues PDF

Connective Tissues Extracellular Matrix and Cells Lecture Outline 1. Overview 2. Characteristics of Fibrous CT 3. Ground Substance 4. Heterogeneous Cell Populations Overview Remember: CT have lots of extracellular components, quite vascular, and innervated. CTs are divided into 2 major groups...

Connective Tissues Extracellular Matrix and Cells Lecture Outline 1. Overview 2. Characteristics of Fibrous CT 3. Ground Substance 4. Heterogeneous Cell Populations Overview Remember: CT have lots of extracellular components, quite vascular, and innervated. CTs are divided into 2 major groups: 1. Fibrous (Proper) CT: loose, dense, and reticular 2. Special CT: elastic, adipose, cartilage, bone, and blood. FUNCTION: Connect, suspend, support, movement, nutrition, insulation, defense, thermoregulation, water metabolism, repair, regeneration, and storage. Fibrous CTs Properties: - Most ubiquitous tissues in the body - Connect other tissues to form organs - Made up of cells( fibroblasts) and extracellular fibers (collagen and elastin) - Highly vascularized and innervated Common origin Mesenchymal cells (mesenchyme) are immature cells and they are the common cells of origin for most CTs as they act as the stem cells. Important for growth and repair for most CTs Characteristics of Fibrous Connective Tissues 1. Abundant amounts of extracellular matrix.Stroma(fibers). Amorphous ground substance 2. Heterogeneous populations of cells. Resident. Transient 3. Low cellular density (compared to epithelia) 4. Vascularized 5. Innervated Extracellular Matrix a. Stroma: made up of fibrous proteins: Collagen and elastin ( they resist stretch) 1. COLLAGEN Unbranched Acidophilic Most ubiquitous protein in the body A structural glycoprotein Collagen Synthesis Collagen Synthesis SEM of bundles of human collagen fibers Types of Collagen  Reticular Fibers Properties ❏ Type of loose CT ❏ Made up of type III collagen ( very thin fibril) ❏ Found in lymphoid organs and bone marrow ❏ Not observed with H&E staining ❏ Silver staining is used to view reticular fibers  Elastin ❏ Secreted by fibroblasts ❏ Accompany collagen where fibrous CT is found ❏ Stretchable fibers hence their name elastic fibers ❏ Composed of microfibrils (fibrillar glycoprotein) AND the globular protein elastin. ❏ Lack the banding pattern. ❏ Thin, branched, and maybe coiled. Ground Substance ❏ Defined as the aqueous medium for cells and CT fibrous components. ❏ Gel- like amorphous substance. ❏ Not observed with H&E staining Ground substance components 1. Water (extracellular or intercellular fluid) 2. GAGs (glycosaminoglycans) Polymers with high molecular weights, composed of repeating disaccharide units. Sometimes called mucopolysaccharides. Types of GAGs: a. Hyaluronic acid b. Chondrotin sulfates c. Dermatan sulfate d. Heparin sulfate e. Keratan sulfate Ground substance components 3. Proteoglycans Complexed GAGs form large proteins called proteoglycans. GAGs Ground substance components 4. Proteoglycan aggregates Ex. cartilage Heterogeneous populations of cells 1. Resident or (Fixed) Cells a. Mesenchymal cells b. Fibroblasts Resident cells c. Reticular cells…. They are considered fibroblasts since they secrete type III collagen. Found in lymphatic tissues and bone marrow. Function: Forms a supportive network for developing lymphocytes and blood cells Resident cells d. Macrophages…..these are monocytes and function as phagocytes , fused macrophages are called “giant cells” to become chondroclasts and osteoclasts. Functions: Removes bacteria and cell debris Immune response by presenting antigens to lymphocytes Resident cells e. Mast cells…. Large cells located near blood vessels Found in the skin and mucous membranes. Granulated cells that mediate inflammation and increase sensitivity of nociceptors. Mast cells contain; leukotrienes, heparin, histamine, serotonin, and arachadonic acid. Resident cells f. Pericyte……..undifferentiated cells located near small vessels, might be stem cells for muscle cells. g. Adipocytes (fat cells)......they don't secrete extracellular fibers Have its own basement membrane. There are brown and white adipocytes. Transient (wandering) cells Cells that migrate in/out of CTs. a. White Blood Cells…… monocytes, lymphocytes, plasma cells, eosinophils. b. Transient (wandering) cells b. Pigment cells…..melanocytes produce melanin because of tyrosinase. Melanophage lack tyrosinase, so cannot produce melanin.