Connective and Muscle Tissue

Connective Tissue

Where found? Most abundant type of tissue everywhere in the body

Purposes 1. Binds body parts together (tendons, ligaments) 2. Provide support and protection 3. Serve as frameworks (bone) 4. Fills spaces 5. Stores fat 6. Produces blood cells 7. Protects against infections (white blood cells) 8. Helps repair tissue damage

Characteristics 1. Cells are further apart than epithelial cells and have abundant 2. Major components: a. cells b. Extracellular matrix (ECM) extracellular matrix (ECM) is between the cells Extracellular matrix is made of protein fibers and ground substance; consistency varies from fluid to semisolid to solid 3. Most of this tissue is well vascularized = good blood supply except tendons and ligaments (which means they heal slowly) 4. Most connective tissue cells can divide

Extracellular Matrix= fibers + ground substance Ground Substance is made of: Interstitial fluid Cell adhesion proteins = glues cells to matrix Proteoglycans= proteins + glycosaminoglycans (GAG) = traps water and forms fluids of various viscocities Fibers- 3 types Collagen Elastic Reticular

Collagen fiber Actin filament Proteoglycan

Major Cell Types of Connective Tissue Fibroblasts: Most common fixed cell Large star-shaped cell Secrete fibers into extracellular matrix Macrophages: Usually attached to fibers, but can detach and wander Conduct phagocytosis Defend against infection

Major Cell Types of Connective Tissue Mast Cells: Large, fixed cells Release heparin to prevent blood clotting Release histamine, which causes inflammatory response

Connective Tissue Fibers Fibroblasts produce 3 types of fibers in connective tissue: Collagen Fibers: Thick, bundled, tough threads, the body’s main structural protein Provide high tensile strength to the matrix; flexible, slightly elastic Found in ligaments and tendons, bone, skin Elastic (Yellow) Fibers: Composed of branching elastin protein Can stretch and return to original shape Not as strong as collagen fibers Found in skin, lungs, blood vessels Reticular Fibers: Short, branching fibers; collagen-like Form delicate, supporting networks Found in spleen, liver, basement membrane

Categories of Connective Tissue Connective tissues can be classified in 2 major categories: A. Connective Tissue Proper: 1. Loose connective tissues: - Areolar - Adipose - Reticular 2. Dense connective tissues: - Dense Regular - Dense Irregular - Elastic B. Specialized connective tissues: Cartilage Bone Blood

Adipocytes (white adipose cells) Areolar Tissue LOCATIONS: Within and deep to the dermis of skin, and covered by the epithelial lining of the digestive, respiratory, and urinary tracts; between muscles; around joints, blood vessels, and nerves Fibrocytes Macrophage Collagen fibers FUNCTIONS: Cushions organs; provides support but permits independent movement; phagocytic cells provide defense against pathogens Mast cell Loose Connective Tissue Elastic fibers Areolar tissue from pleura LM × 380 a Areolar tissue Adipose Tissue LOCATIONS: Deep to the skin, especially at sides, buttocks, and breasts; padding around eyes and kidneys FUNCTIONS: Provides padding and cushions shocks; insulates (reduces heat loss); stores energy Adipocytes (white adipose cells) LM × 300 b Adipose tissue Reticular Tissue LOCATIONS: Liver, kidney, spleen, lymph nodes, and bone marrow FUNCTIONS: Provides supporting framework Reticular fibers Reticular tissue from liver LM × 375 c Reticular tissue

Collagen fiber bundles Dense Regular Connective Tissue LOCATIONS: Between skeletal muscles and skeleton (tendons and aponeuroses); between bones or stabilizing positions of internal organs (ligaments); covering skeletal muscles; deep fasciae Dense Connective Tissue Collagen fibers FUNCTIONS: Provides firm attachment; conducts pull of muscles; reduces friction between muscles; stabilizes positions of bones Fibroblast nuclei a Tendon LM × 440 Dense Irregular Connective Tissue LOCATIONS: Capsules of visceral organs; periostea and perichondria; nerve and muscle sheaths; dermis FUNCTIONS: Provides strength to resist forces from many directions; helps prevent overexpansion of organs, such as the urinary bladder Collagen fiber bundles b Deep dermis LM × 111 Elastic Tissue LOCATIONS: Between vertebrae of the spinal column (ligamentum flavum and ligamentum nuchae); ligaments supporting penis; ligaments supporting transitional epithelia; in blood vessel walls Elastic fibers FUNCTIONS: Stabilizes positions of vertebrae and penis; cushions shocks; permits expansion and contraction of organs Fibroblast nuclei c Elastic ligament LM × 887

Human Skin

Specialized Connective Tissue Bone (Osseous Tissue): Most rigid connective tissue Solid matrix, composed of mineral (calcium) salts & collagen Contain osteocytes (bone cells) in lacunae (chambers)

Specialized Connective Tissue Blood: Cells suspended in fluid matrix called plasma

Specialized Connective Tissue Cartilage Made of: Chondrocytes (cartilage cells) in lacunae (chambers), surrounded by the extracellular matrix Covered by perichondrium (connective tissue), which contains blood vessels and provides some nutrients to the cartilage 3 types of cartilage: Hyaline, Elastic, and Fibrocartilage

Types of cartilage

Muscles

Where found? attached to skeleton in the heart in the walls of hollow organs

Purpose contract and shorten to produce movement

Types and Characteristics

Skeletal 1. Voluntary 2. Multinucleate 3. contains many striations

Skeletal Muscle

Cardiac 1. involuntary 2. uninucleate 3. branching fibers 4. many striations with intercalated discs

Cardiac Muscle

Smooth 1. involuntary 2. uninucleate 3. no striations 4. spindle-like appearance

Smooth Muscle