The structure and function of loose/dense connective tissue

• What is the shape of the nucleus in fibroblasts?


  Elongated cigar-shaped nucleus
• What do fibroblasts deposit in connective tissue?


  All extracellular matrix components including fibers and ground substance
• What do fibroblasts secrete?


  Precursors of GAGs, collagen, and elastin
• What happens to the cytoplasm of fibroblasts during the synthesis of extracellular fibers?


  It expands and rER and Golgi become more apparent
• What is the role of fibroblasts in the extracellular matrix?


  They maintain the continuous slow turnover of ECM components
• What is a fibrocyte?


  The inactive state of a fibroblast
• What is the appearance of plasma cells' nucleus?


  Clock face nucleus
• What is the primary function of adipocytes?


  To store energy as fat
• What is the characteristic feature of macrophages?


  They have ingested particles in their cytoplasm
• What type of cells are eosinophils, neutrophils, and lymphocytes?


  White blood cells used in the immune response
• What do mast cells contain that is released during allergic reactions?


  Basophilic granules containing histamine and proteoglycans
• Which cells are considered fixed cells in connective tissue?

  Fibroblast, fibrocyte, adipocyte, and macrophage
• Which cells are considered wandering cells in connective tissue?


  Plasma cells, eosinophils, neutrophils, lymphocytes, and mast cells
• What role do monocytes play in the defense of connective tissue?


  They secrete cytokines to attract other immune cells
• How do mast cells contribute to the immune response?


  They produce histamines that make blood vessels leaky
• What is the function of macrophages in connective tissue defense?


  They begin engulfing pathogens
• How do plasma cells, eosinophils, neutrophils, and lymphocytes arrive at the site of infection?


  They arrive via blood vessels
• What is the main and most abundant fiber type in the human body?

  Collagen fibers
• How is collagen secreted by fibroblasts?


  In the form of tropocollagen, which polymerizes to form collagen
• What happens to collagen fibers when stretched over 3% of their original length?


  They will break
• What is the appearance of collagen fibers?


  Thick bundled fibers that do not branch and are flexible
• What type of collagen is found in the dermis, ligaments, tendons, and bones?

  Type 1 collagen
• What type of collagen is found in cartilage?

  Type 2 collagen
• What are reticular fibers made of?


  Type 3 collagen fibers
• What is the function of reticular fibers?


  To form a meshwork supporting the liver, spleen, bone marrow, and lymph nodes
• What do elastin fibers allow in connective tissue?


  Stretching and recoil to original shape
• What is the precursor form of elastin secreted by fibroblasts?

  Tropoelastin
• What happens to elastic fibers in the dermis of the skin as they age?


  Loss of elastic fibers leads to wrinkling
• What is ground substance in connective tissue?


  A viscous clear substance occupying space between fibers and cells
• What is the composition of ground substance?


  Glycoproteins, proteoglycans, and glycosaminoglycans (GAGs)
• How do proteoglycans attract water in the ground substance?


  Charged side chains are hydrophilic, attracting water and ions
• What is the main GAG backbone in loose connective tissue?


  Hyaluronic acid
• What GAG is bound to proteoglycans in cartilage?


  Chondroitin sulfate
• What GAG is bound to proteoglycans in the dermis of the skin?


  Dermatan sulfate
• What is the function of tissue fluid associated with ground substance?


  Allows passage of molecules and exchange of metabolites
• What are the characteristics of loose connective tissue?


  • Plenty of ground substance
  • Loose fibers (type 1 and 3 collagen and elastin)
  • Scattered cells
  • Found in lamina propria and surrounding blood vessels
  • Functions: Attaches epithelia to underlying tissue, forms passages for blood vessels, nerves, and lymphatics
• What are the characteristics of dense connective tissue?


  • Less ground substance and fibroblasts
  • Closely packed collagen fibers
  • Dense regular: Type 1 collagen fibers run in one direction (found in tendons and ligaments)
  • Dense irregular: Collagen fibers run transversely and longitudinally (found in dermis of skin and joint capsules)
  • Resists tensile forces
• What are the functions of adipose tissue?


  • White adipose tissue: Stores energy, acts as thermal insulator, shock absorber
  • Brown adipose tissue: Generates heat, key in body temperature regulation
• What is a lipoma?


  A benign non-malignant harmless swelling due to swelling of adipocyte cells
• What is edema?


  Excess accumulation of fluid within tissue spaces