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Connective Tissue The most abundant type of tissue! Collagen is a major protein found in connective tissue Also the most common protein found in the body Functions: Provides protection Binds body tissues together Supports the body © 2015 Pearson Education, Inc.

Vascularity – blood supply Variations in blood supply Some are well vascularized Some have a poor blood supply or are avascular; Examples include: tendons, ligaments As a result, these take longer to heal © 2015 Pearson Education, Inc.

The Extracellular Matrix (ECM) a unique and distinguishing characteristic of connective tissue Nonliving material that surrounds living cells Gelatinous-like material Secreted by the connective tissue cells Composed of two main components: Ground Substance Fibers © 2015 Pearson Education, Inc.

Ground Substance Secreted by connective tissue cells Similar to cytosol in composition and function Composed of: mostly water adhesion proteins polysaccharides

Fibers Secreted by connective tissue cells Three types: 1. Collagen (white) fibers Allow CT to withstand pulling/tension 2. Elastic (yellow) fibers Contain elastin- allows stretching 3. Reticular fibers (a type of collagen) Short fibers that create a mesh-like network

Connective Tissue Types From most rigid to softest, (or most fluid): Bone Cartilage Dense connective tissue Loose connective tissue Blood © 2015 Pearson Education, Inc.

BONE Known as osseous tissue Produced by Osteocytes (bone cells) A Hard matrix of calcium salts Functions to protect and support the body © 2015 Pearson Education, Inc.

Figure 3.19a Connective tissues and their common body locations. Bone cells in lacunae Central canal Lacunae Lamella (a) Diagram: Bone Photomicrograph: Cross-sectional view of ground bone (165×) BONE

CARTILAGE more flexible than bone Found in only a few places in the body Produced by Chondrocytes (cartilage cell) Three types of cartilage: Hyaline (most abundant; larynx, intercostal, bone ends) Elastic (external ear and epiglottis) Fibrocartilage (intervertebral discs; pubic symphysis) © 2015 Pearson Education, Inc.

Figure 3.19b Connective tissues and their common body locations. Chondrocyte (cartilage cell) Chondrocyte in lacuna Matrix Lacunae Photomicrograph: Hyaline cartilage from the trachea (400×) (b) Diagram: Hyaline cartilage HYALINE CARTILAGE

Figure 3.19c Connective tissues and their common body locations. Chondro- cytes in lacunae Collagen fibers Chondrocytes in lacunae Collagen fiber Photomicrograph: Fibrocartilage of an intervertebral disc (150×) (c) Diagram: Fibrocartilage FIBROCARTILAGE

DENSE CONNECTIVE TISSUE Strong, ropelike structures Main matrix element is collagen fiber made by fibroblasts Locations: Tendons—attach skeletal muscle to bone Ligaments—attach bone to bone at Dermis—lower layer of the skin Found where strength of interconnection is required © 2015 Pearson Education, Inc.

Figure 3.19d Connective tissues and their common body locations. Ligament (d) Diagram: Dense fibrous Photomicrograph: Dense fibrous connective tissue from a tendon (475×) Collagen fibers Nuclei of fibroblasts Collagen fibers Tendon DENSE CONNECTIVE TISSUE: Ligament And Tendon

LOOSE CONNECTIVE TISSUE softer tissues; less fibrous provide cushioning, reduce friction, allow stretching Three types: Areolar: wraps and secures organs Lamina propria: areolar layer that underlies all mucous membranes Adipose: fat cells; energy storage; insulation Reticular: provides structural framework for organs/glands © 2015 Pearson Education, Inc.

Figure 3.19e Connective tissues and their common body locations. Mucosa epithelium Lamina propria Fibers of matrix Nuclei of fibroblasts Elastic fibers Collagen fibers Fibroblast nuclei (e) Diagram: Areolar Photomicrograph: Areolar connective tissue, a soft packaging tissue of the body (270×) AREOLAR CONNECTIVE TISSUE

Figure 3.19f Connective tissues and their common body locations. Nuclei of fat cells Vacuole containing fat droplet Nuclei of fat cells (f) Diagram: Adipose Photomicrograph: Adipose tissue from the subcutaneous layer beneath the skin (570×) ADIPOSE TISSUE

Figure 3.19g Connective tissues and their common body locations. Spleen (g) Diagram: Reticular Photomicrograph: Dark-staining network of reticular connective tissue (400×) Reticular cell Blood cell Reticular fibers White blood cell (lymphocyte) Reticular fibers RETICULAR CONNECTIVE TISSUE

BLOOD Blood cells = red and white surrounded by fluid matrix known as blood plasma Soluble fibers are visible only during clotting Function: transport vehicle for the CV system; delivers: Nutrients Wastes Respiratory gases (oxygen and carbon dioxide) © 2015 Pearson Education, Inc.

Figure 3.19h Connective tissues and their common body locations. Photomicrograph: Smear of human blood (1290×) (h) Diagram: Blood Blood cells in capillary White blood cell Red blood cells Neutrophil (white blood cell) Red blood cells Monocyte (white blood cell) BLOOD