Connective Tissues PDF

Connective Tissues Section 5.3  Connective Tissues - Overview  Lots of ECM (ground substance + fibers), relatively few cells  Most abundant, widely distributed tissue type  Highly variable  General Functions  Binding/Connecting  Supp...

Connective Tissues Section 5.3  Connective Tissues - Overview  Lots of ECM (ground substance + fibers), relatively few cells  Most abundant, widely distributed tissue type  Highly variable  General Functions  Binding/Connecting  Support  Protection (physical and immunity)  Movement  Storage  Heat Production  Transport  Cell Name Suffixes  -blasts = produce (build) the ECM (fibers & ground substance)  -clasts = break down extracellular matrix for remodeling  -cytes = maintain extracellular matrix  Ex. Bone (osteo-) Fibroblasts – most  Osteoblast – forms bone matrix common cell in connective  Osteoclast – breaks down bone matrix tissue secrete collagen  Osteocyte – maintains bone matrix  Connective Tissue – Fibers Collagen  Collagen  Most common fiber  Extremely strong  Dense in tendons & ligaments  Connective Tissue – Fibers Elastic fiber  Elastic  Long, thin fibers  Contain elastin (protein)  Allows stretch & recoil  Marfan Syndrome  Mutation in gene that makes elastic fibers  Symptoms vary & are widespread  Connective Tissue – Fibers  Reticular  Thin collagen fibers Reticular fiber  Short, thin, branching networks  Sponge-like framework to support other tissues Classification of Connective Tissues (fibrous)  Loose vs. Dense Fibrous Connective Tissue  Loose – fewer fibers (more ground substance)  Dense – more fibers (less ground substance) Loose Dense Classification of Connective Tissues (fibrous)  Fibrous CT: Loose – Areolar  Most abundant  Cells:  Mainly fibroblasts  Fibers:  All but mainly collagen  Binds epithelia to deeper structures  Locations (some):  Below epithelia  Between muscles (fascia)  Pleurae and pericardium  Fibrous CT: Loose – Reticular  Cells:  Fibroblasts and leukocytes (white blood cells)  Fibers:  Mesh-like organization of reticular fibers  Supportive framework  Locations (some):  Lymph-nodes  Spleen  Fibrous CT: Loose – Adipose  Adipocytes (fat cells)  Very little matrix  White fat – inert adipocytes  Energy storage  Cushioning  Thermal insulation  Brown fat – adipocytes that burn fat to create heat  Abundant in infants & young children  Locations:  Beneath skin (subcutaneous fat)  Around organs (e.g., kidneys, heart, eyes) TopHat Classification of Connective Tissues (fibrous)  Fibrous CT: Dense  Much more collagen than loose CT  Little ground substance  Nearly avascular  Main function = withstand physical stress  3 types  Regular  Elastic  Irregular  Fibrous CT: Dense – Regular  Collagen fibers parallel to each other  strength in one direction  Tensile strength (resist force that would pull apart)  Wavy  slight give to the tissue as it straightens out  Locations:  tendons (bind muscle to bone)  ligaments (bind bone to bone)  Fibrous CT: Dense – Irregular  No consistent pattern to fiber arrangement  Strength in many directions  Locations:  Deep dermis (skin)  Fibrous sheaths around cartilage (perichondrium) and bone (periosteum) TopHat Classification of Connective Tissues (fibrous) Will be covered in A&P II Classification of Connective Tissues (fibrous) Supportive CT: Cartilage  Stiff connective tissue with rubbery ECM  Avascular  Cells:  Chondroblasts (secrete matrix)  Chondrocytes – trapped in lacunae  Fibers – collagen & elastic  3 types  Hyaline  Elastic  Fibrocartilage  Supportive CT: Bone  Calcified; highly vascular  More support, less flexible  Osteoblasts – secrete matrix  Osteocytes – trapped in lacunae  Osteoclasts – break down calcified matrix  Functions:  Physical support for body  Leverage for muscle action  Reservoir for calcium and phosphorus