Study Question Seven

• Q7. What are the major characteristics of connective tissue?
• All connective tissue have three basic components:

  • specialized cells
  • extracellular protein fibers
  • fluid known as the ground substance
  • matrix
• Connective tissue functions:

  • establish a structural framework for the body
  • transport fluids and dissolved materials from one region of the body to another
  • protect delicate organs
  • support, surround, and interconnect other tissue types
  • store energy, especially in the form of lipids
  • defend the body from invasion by microorganisms
• Three types of connective tissue:

  • Connective Tissue Proper
  • Fluid Connective Tissue
  • Supporting Connective Tissue
• Fixed Cells are stationary and involved with local maintenance, repair, and energy storage
• Fixed Cells include:

  • Mesenchymal Cells
  • Fibroblasts
  • Fibrocytes
  • Fixed Macrophages
  • Adipocytes
  • Melanocytes
• Mesenchymal Cells respond to local injury or infection by dividing and differentiating into fibroblasts, macrophages, others
• Fibroblasts are one of two most abundant fixed cells. Produce all connective tissue fibers. Manufactures and secretes protein subunits that interact to form large extracellular fibers
• Fibrocytes differentiate from fibroblasts and are second most abundant fixed cell. Maintain connective tissue fibers of connective tissue proper
• Fixed Macrophages engulf damaged cells, dead cells, and pathogens
• Adipocytes contain a single lipid droplet that occupies almost the entire cell, they provide storage and insulation as well as cushioning
• Melanocytes synthesize melanin
• Wandering Cells help defend and repair damaged tissues
• Wandering Cells include:

  • Free Macrophages
  • Mast Cells
  • Lymphocytes
  • Neutrophils and Eosinophils
• Free Macrophages, also known as monocytes, is the backup for Fixed Macrophages
• Mast Cells found near blood vessels, release histamine and heparin after injury or infection to stimulate inflammation
• Lymphocytes whenever tissue damage occurs and some develop into plasma cells to produce antibodies
• Neutrophils and Eosinophils are for infection and injury
• Collagen Fibers are the strongest and most common fibers in connective tissue proper. Long, straight, unbranched
• Reticular Fibers contain protein subunits. Thinner, form branching interwoven framework that is tough but flexible. Common around organs
• Elastic Fibers are branching and wavy, contain elastin, recoil and stretch
• Ground Substance is a solution which surrounds the cellular and fibrous components of connective tissue proper
• Loose Connective Tissues are the packing material of the body, fill spaces, cushion, support epithelia
• Loose Connective Tissue types:

  • Areolar
  • Adipose
  • Reticular
• Loose Connective Tissue type Areolar open framework and mostly ground substance so cushions shock, can be distorted, resilient due to elastic fibers
• Loose Connective Tissue type Adipose mostly made of adipocytes. White fat common in adults, brown fat common in children. Insulates and stores energy
• Loose Connective Tissue type Reticular have reticular fibers, macrophages, fibroblasts, fibrocytes. Provides support for organs
• Dense Connective Tissue consists mainly of fibers, also called collagenous tissues
• Dense Regular Connective Tissue where collagen fibers are packed tightly and aligned parallel to applied forces. Examples include tendons, aponeuroses, elastic tissue, ligaments
• Dense Irregular Connective Tissue form an interwoven meshwork and do not show any consistent pattern. Strengthens and supports areas due to stress from many direction except at joints
• Blood and lymph are fluid connective tissues that contain plasma
• Red Blood Cells, also known as erythrocytes, account for half volume of blood, also transport
• White Blood Cells, also known as leukocytes, protect against infection
• Platelets are tiny membrane-enclosed packets of cytoplasm with enzymes and proteins, clot and seal
• Cartilage cells, or chondrocytes, are only cells within the cartilage matrix
• Chondrocytes live in small chambers known as lacunae
• A fibrous perichondrium usually separates cartilage from the surrounding tissues
• The perichondrium contains two layers: outer fibrous layer of dense irregular connective tissue and an inner cellular layer
• Cartilage grows by two mechanisms including appositional growth and interstitial growth
• Appositional growth gradually increases the dimensions of the cartilage by adding to its surface