mod 3

• Connective Tissues:
• Importance:

  • Provides a matrix that supports and physically connects other tissues and cells together to form the organs of the body
  • Gives metabolic support to cells as the medium for diffusion of nutrients and waste products
• Functions:

  • Binding and packing material of other tissues
  • Vehicle for transport of gases and substances to and from the various tissues of the body
  • Forms the structural framework of many organs
  • Venue for the exchange of gases and substances from the basic tissues and the blood
  • Comprise the skeletal system
  • Storage area for fat
• Types:

  • Embryonic Connective Tissue
  • Mesenchyme
  • Mucous Connective Tissue
  • Proper Loose (areolar)
  • Dense regular CT
  • Dense irregular CT
  • Specialized Connective Tissue
  • Reticular CT
  • Adipose
  • Cartilage
  • Hyaline
  • Fibrous
  • Elastic
  • Bone
  • Compact
  • Spongy/Cancellous
  • Blood
• Components:

  • Major constituent is the Extracellular matrix (ECM)
  • Which consists of different combinations of protein fibers and ground substance
• Types of Fibers:

  • Collagen Fiber
  • Reticular Fiber
  • Elastic Fiber
• Categories of Cells Present:

  • Fibroblast
  • Adipocytes
  • Macrophages
  • Plasma Cells
  • Mast Cells
  • Leukocytes
• Macrophages:

  • Size and shape vary considerably (state of functional activity)
  • 10-30μm in diameter; eccentrically located oval or kidney-shaped nucleus
  • Present in the CT of most organs, also known as "Histiocytes"
  • Highly developed phagocytic activity
  • Specialize in turnover of protein fibers and removal of apoptotic cells/tissue debris (especially abundant in sites of inflammation)
  • Secrete growth factors important for tissue repair
  • Important in the uptake, processing, and presentation of antigens for lymphocyte activation
• Mast cells:

  • Oval, irregularly shaped; 7-20μm in diameter
  • Filled with basophilic secretory granules that obscure the nucleus
  • Localized release of bioactive substances important in local inflammatory response, innate immunity, and tissue repair
  • Granules are electron dense and display metachromasia
  • Bioactive substances include heparin, histamine, serine proteases, eosinophil and neutrophil chemotactic factors, cytokines, and phospholipid precursors
• Plasma cells:

  • B lymphocyte-derived, antibody-producing cells
  • Large ovoid cells with basophilic cytoplasm rich in RER and large Golgi apparatus near the nucleus
  • Nucleus is spherical, eccentrically placed, and contains compact, peripheral regions of heterochromatin alternating with lighter areas of euchromatin
  • Lifespan of 10-20 days
  • Synthesize immunoglobulin antibodies
• Leukocytes:

  • White blood cells derived from circulating WBCs
  • Most WBCs stay in the CT for a few hours or days then undergo apoptosis
  • Vascular and defensive response to injury or foreign substances including pathogenic bacteria or irritating chemical substances
• • Fibrocyte is quiescent with smaller, spindle-shaped morphology, less RER, darker, more heterochromatic nucleus
• Fibroblast:

  • Most common cell in CT; produce and maintain most of the tissues' extracellular components
  • Synthesize and secrete collagen and elastin
  • Target of growth factors influencing cell growth and differentiation
  • Involved in wound healing with well-developed contractile function
  • Fibroblast vs Fibrocyte:
  • Fibroblast is active with more abundant and irregularly branched cytoplasm, more RER, well-developed Golgi apparatus, large ovoid euchromatic nucleus, and prominent nucleolus
• Adipocytes:

  • Fat cells; large mesenchymally derived cells
  • Have major metabolic significance and considerable metabolic significance
  • Specialized for cytoplasmic storage of lipid as "neutral fats"
  • Serve to cushion, insulate the skin, and other organs
  • Types include white adipose tissue (unilocular) and brown adipose tissue (multilocular)
• Connective Tissue Proper:

  • Loose Connective (Areolar):
  • Contains cells, fibers, and ground substance in roughly equal parts
  • Fibroblasts are most numerous cells with collagen fibers predominating
  • Forms a layer beneath epithelial lining of many organs and fills the spaces between fibers of muscle and nerve
  • Dense Regular CT:
  • Consists mainly of Type I collagen bundles and aligned fibroblasts
  • Great resistance to prolonged and repeated stresses from the same direction
  • Dense Irregular CT:
  • Bundles of collagen fibers appear randomly interwoven with no definite orientation
• • Protects organs and strengthens them structurally
• Specialized CT:

  • Reticular CT:
  • Characterized by abundant fibers of type III collagen forming a delicate network
  • Macrophages and dendritic cells monitor cells passing through and remove debris
  • Provides a framework for hematopoietic tissues in bone marrow and lymphoid organs
  • Adipose Tissue:
  • Fat-storing cells or adipocytes predominate
  • White adipose tissue has a unilocular appearance, while brown adipose tissue is multilocular and found in scattered areas
• Cartilage is a tough, durable form of supporting connective tissue
• It has a firm consistency, resilient, smooth, lubricated surface
• Consists of chondrocytes in extracellular matrix (ECM)
• Cartilage allows tissue to bear mechanical stress without permanent distortion
• It provides cushioning and sliding regions within skeletal joints
• Facilitates bone movement
• Guides development and growth of long bones before and after birth
• Cartilage lacks vascular supplies
• Chondrocytes receive nutrients by diffusion from capillaries
• Perichondrium is a sheath of dense connective tissue that surrounds cartilage
• Hyaline cartilage is the most common type
• It is homogenous and semitransparent
• Found in articular surfaces of movable joints, walls of larger respiratory passages, ventral ends of ribs, and epiphyseal plates of long bones
• Elastic cartilage contains an abundant network of elastic fibers in addition to collagen type II fibrils
• More flexible than hyaline cartilage
• Found in the auricle of the ear, walls of the external auditory canals, the auditory tubes, epiglottis, and upper respiratory tract
• Fibrous cartilage is a mingling of hyaline cartilage and dense connective tissue
• Found in intervertebral discs, attachments in certain ligaments, and pubic symphysis
• Serves as tough yet cushioning support for the bone
• Bone is the main constituent of the adult skeleton
• It provides solid support for the body
• Protects vital organs in the cranial and thoracic cavities
• Encloses internal cavities containing bone marrow where blood cells are formed