Connective Tissue

• Connective tissues maintain body and organ form and provide cohesion and internal support.
• Types of connective tissues vary in density, cellularity, and specialization.

Overview of Connective Tissue

• Key components include water, cells, extracellular matrix, and fibers.
• Cells include fibroblasts, adipocytes, macrophages, mast cells, plasma cells, and eosinophils.
• The matrix is composed of glycoproteins, fibrous proteins, and glycosaminoglycans.
• Extracellular matrix is a main feature in tissues with a mechanical function like ligaments, tendons, and bones.
• Cells are the main feature in tissues specialized for protection or metabolic maintenance.

Connective Tissue Cells

• Fixed cells: fibroblasts, adipocytes, macrophages, mast cells.
• Transient cells: plasma cells, eosinophils.

Non-Cellular Substrate (Extracellular Matrix)

• Also known as ground substance.
• It has amorphous and gelatinous consistency and is transparent and colorless.
• Fills spaces between cells and fibers, enabling metabolite transportation.
• Large protein molecules called glycosaminoglycans (GAGs) link together to form proteoglycans, which absorb water.
• The matrix is good at resisting compressive forces.

Fibers

• Fibroblasts secrete fibers that form a supporting network for cell attachment.
• Three types exist: elastic, collagen, and reticular.
• Different combinations of these fibers create different connective tissue types.

Classification of Connective Tissue

• Connective Tissue Proper divides into Loose and Dense types.
• Specialized Connective Tissue divides into Supporting (Cartilage, Bone) and Fluid (Blood, Lymph) types.

Connective Tissue Proper

• Composed of loose and dense connective tissue.

Loose Connective Tissue

• Has numerous cells, loose fibers (thin elastin, thicker collagen), and slightly viscous fluid.
• Supports and connects other tissues to acting as framework throughout the human body.

Types of Loose Connective Tissue

• Areolar connective tissue covers muscle fibers, is under the epidermis, is in/around mucous membranes, and surrounds nerves and blood vessels.
• Adipose connective tissue that is in matrix of areolar tissue, with white and brown adipose tissues.
  • White adipose tissue is 20-25% body weight, supports, thermally insulates, and stores energy.
  • Brown adipose tissue generates heat and is vital for newborns.
• Reticular connective tissue contains branching reticular fibers in a semi-solid matrix.
  • It contains reticular cells, monocytes, and lymphocytes.
  • It is found in lymph nodes and lymphatic organs.
• Areolar connective tissue is found in skin and dental pulp.

Dense Connective Tissue

• Has elastic, dense irregular, and dense regular.

Cartilage

• Firmer than other connective tissues with cells, known as chondrocytes, within matrix of collagen and elastic fibres.
• Three types: hyaline, fibrocartilage, and elastic.

Bone

• Two types: compact and spongy.

Blood

• Composed of highly specialized watery fluid: plasma.
• Constantly circulates.
• Contains various blood cells: erythrocytes, leucocytes and platelets.