connective tissues 1-2

Connective Tissues Overview

Page 4: General Features

• Origin: Connective tissue (C.T) originates from the mesoblast of the embryo.

• Composition:

  • Consists of fibers, cells, and ground substance.

  • Cells are widely separated by the extracellular matrix (ECM).

• Types of ECM:

  • Soft in connective tissue proper.

  • Firm in cartilage.

  • Hard in bone.

  • Fluid in blood.

Page 5: Functions of Connective Tissues

• Binding and Support: Connects and supports most body organs.

• Defense: Contains phagocytic cells and antibodies for defense.

• Nutrition and Storage: Stores lipids, water, electrolytes, and plasma proteins.

• Transport Medium: Facilitates transport of vital materials between blood and connective tissues.

Page 6: Types of Connective Tissue Cells

• Fixed Cells:

  1. Undifferentiated mesenchymal cells.

  2. Reticular cells.

  3. Endothelial cells.

  4. Pericytes.

  5. Macrophages.

  6. Fibroblasts.

  7. Fat cells.

Page 7: Free Cells

• Types:

  1. Free macrophages.

  2. Mast cells.

  3. Leucocytes.

  4. Pigment cells.

  5. Plasma cells.

Page 8: Fixed Cells - Undifferentiated Mesenchymal Cells

• LM: Stem cells with small irregular, branched, star-shaped appearance.

• EM:Few organelles many ribosomes

• Function:

  • Differentiate into other types of connective tissue cells.

  • Produce blood cells in bone marrow.

Page 9: Fixed Cells - Pericytes

• Location: Present around blood capillaries.

• Function:

  • Similar to undifferentiated mesenchymal cells but postnatally.

  • Differentiate into fibroblasts, endothelial, and smooth muscle cells.

  • Contraction leads to vasoconstriction.

Page 10: Fixed Cells - Endothelial Cells

• Location: Lining all blood vessels and the heart.

• Functions:

  • Divide to produce new endothelial cells.

  • Produce basement membrane and antithrombotic factors.

  • Synthesize collagen type IV.

Page 11: Fixed Cells - Fibroblasts

• Origin: Derived from undifferentiated mesenchymal cells and pericytes.

• Functions:

  • Formation of connective tissue fibers and ground substance.

  • Healing and repair of wounds.

Page 12: Fibrocytes

• Description: Inactive fibroblasts with fewer processes and less basophilic cytoplasm.

• Function: Maintenance of extracellular components of connective tissue.

Page 13: Fixed Cells - Fat Cells

• Types:

  • Unilocular adipocytes (white fat).

  • Multilocular adipocytes (brown fat).

• Functions:

  • Store fat, support organs, and provide heat insulation.

Page 14: Multilocular Adipocytes (Brown Fat)

• Location: Present in brown adipose connective tissue.

• Function: Heat generation.

Page 15: Fixed Cells - Macrophages

• Origin: Derived from monocytes.

• Functions:

  • Phagocytic activity.

  • Antigen presentation.

Page 16: Fixed Cells - Reticular Cells

• Location: Stroma of glands or organs.

• Functions:

  • Provide support.

  • Exhibit phagocytic activity.

Page 18: Free Cells - Plasma Cells

• Origin: Derived from B lymphocytes.

• Functions:

  • Responsible for humoral immunity.

  • Present in the submucosa of the gastrointestinal tract.

Page 19: Free Cells - Mast Cells

• Description: Ovoid cells filled with basophilic granules.

• Functions:

  • Secrete histamine and other chemicals involved in immune responses.

  • Act as paracrine cells affecting surrounding cells.

Page 23: Free Cells - Pigment Cells (Melanophores)

• Origin: Derived from macrophages that phagocytose melanin.

• Functions:

  • Carry melanin pigments for skin color.

  • Absorb ultraviolet rays for skin protection.

Page 24: Connective Tissue Fibers

• Types:

  1. White (collagen) fibers.

  2. Yellow (elastic) fibers.

  3. Reticular fibers.

Page 25: White Collagenous Fibers

• Characteristics:

  • White in color, tough, and resistant to stretch.

  • Form wavy bundles.

• Composition: Composed of fibrils formed from type-I tropocollagen molecules synthesized by fibroblasts.

Page 26: Yellow Elastic Fibers

• Characteristics: Yellow in color, elastic, and can stretch and recoil.

• Composition: Composed of elastin and oxytalan fibers.

• Locations: Found in arterial walls, trachea, bronchi, and ligamentum flavum.

Page 27: Reticular Fibers

• Characteristics: Very thin, branched fibers forming a network.

• Composition: Composed of type-III collagen coated with glycoprotein.

• Locations: Present in the stroma of organs like the liver, spleen, and lymph nodes.

Page 28: Ground Substance

• Description: Found in cavities and clefts between fibers and cells.

• Composition: Contains water, salts, and low molecular substances; primarily made of proteoglycans.

• Visibility: Not visible in ordinary histological sections due to solubility.

Page 29: Proteoglycans and Glycoproteins

• Proteoglycans: Composed of proteins (5%) and polysaccharide chains (95%).

• Glycoproteins: Composed of 90% protein and 10% monosaccharides.

• Components: Include hyaluronic acid, chondroitin sulfate, dermatan sulfate, keratan sulfate, and heparan sulfate