CONNECTIVE TISSUES

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• CONNECTIVE TISSUES
• Most abundant type of tissue
• Fills internal spaces, provides structural
  support for other tissues, and stores energy
  reserves
• Includes tissues such as fat, bone, and blood
• Most types are well vascularized
• All types have a common origin (mesenchyme)
• Includes 3 components
• specialized cells
• extracellular protein fibers
• ground substance
• fluid or semi-solid which surrounds cells

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3 Major Cell Types

• Fibroblast
• Most common fixed cell
• Large, star shaped
• Produces fibers by secreting protein into matrix

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• Macrophages
• Wandering Cells that originate as WBCs
• Function as scavengers that clear foreign
  particles ? Phagocytosis
• Also, play a role in immunity by allerting other
  WBCs of foreign particles

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• Mast Cells
• Large, widely distributed cells
• Associated with inflammation
• Releases heparin and histamine

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CLASSIFICATION

• 3 CATEGORIES
• Connective tissue proper
• tissue with many types of cells and extracellular
  fibers in a syrupy ground substance ex.
  Adipose tissue
• Fluid connective tissue
• cells suspended in a watery matrix that contains
  dissolved proteins ex. Blood
• Supporting connective tissue
• low diverse cell population and a matrix of
  closely packed fibers ex. Bone and cartilage

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CONNECTIVE TISSUE PROPER

• Composed of many kinds of cells
• Fibroblasts, Macrophages, Adipocytes
• 3 types of fibers
• Collagen - long, straight unbranched flexible
  but strong ex tendons, ligaments
• Reticular cells suspended in a watery matrix
  that contains dissolved proteins Bone
  Cartilage stabilizes cells vessels
• Elastic - contains the protein elastin.
  Branched, wavy, will contract after stretching
  ex elastic ligaments
• Ground Tissue -
• high viscosity slows the spread of pathogens to
  make them easier for phagocytes to catch

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Real life apps
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Connective Tissue Proper

• Loose connective tissue (areolar)
• characterized by white and yellow fibers between
  fibroblasts
• packing material of the body, cushions, attaches
  skin to the body, supports blood vessels

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• Adipose tissue
• dominated by adipocytes
• energy storage, brown fat in infants (highly
  vascularized)
• each cell consists of large vacuole filled with
  triglycerides

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• Reticular Connective Tissue
• complex open framework of reticular fibers
• supports walls of organs such as liver and spleen

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• Dense Connective Tissue
• consists of many closely packed collagen fibers,
  elastin fibers, and few fibroblasts
• regular - collagen fibers are parallel to each
  other
• tendons, ligaments
• irregular - collagen fibers are randomly arranged
  and interwoven provides strength to resist
  forces applied from many directions interwoven
  meshwork
• dermis

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• Elastic Connective Tissue
• - consists of mainly yellow elastic fibers
• parallel or branching
• walls of hollow organs, large arteries, heart etc.

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FLUID CONNECTIVE TISSUES

• Ground substance plasma
• Blood contains formed elements Erythrocytes,
  leukocytes, Platelets
• Arteries carry blood from heart to capillaries,
  water and solutes move into interstitial fluid,
  Veins return blood to heart

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• Erythrocytes carry oxygen (confined to vessels)
• Leukocytes fight infection (wander)
• Platelets blood clotting

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Supportive Connective Tissue Bone Cartilage

• I. Cartilage
• Cells Chondrocytes
• Matrix Firm gel of proteoglycans
• Avascular heals slowly
• Covering Perichondrium Composed of 2 layers
• Outer layer dense irregular tissue
• Inner layer cells
• Growth Interstitial Appositional
• Appositional undergoes extensive remodeling on a
  regular basis
• Interstitial
• 3 main types

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• Hyaline - Tightly packed collagen fibers
• Most Common Type
• Looks like white glass
• Functions Reduces friction, important in growth
  and repair of bones
• Locations Between bone surfaces, nose, trachea,
  intercostal cartilage

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• Elastic - Numerous elastic fibers
• flexible
• Functions Provides support but distorts without
  damage
• Locations Ears, nose, epiglottis
• Fibrocartilage - matrix dominated by collagen
  fibers
• Extremely durable
• Functions Resists compression, limits movement
• Locations Between vertebrae, pads within knee
  joints

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• II. Bone - Most rigid connective tissue
• Cells - Osteocytes
• Matrix - 1/3 collagen fibers mixture of calcium
  salts
• Vascularized - caniculi - extensive blood vessels
  in matrix for exchange of materials
• Covering - Periosteum (2 layers)
• fibrous outer layer
• cellular inner layer
• Growth - Appositional
• undergoes extensive remodeling on a regular basis
• responds to stresses grow thicker stronger
  exercise