Most abundant tissue in the body.
Characterized by abundant intercellular material.
Highly vascular (contains blood vessels).
Has a nerve supply.
Typically located underneath epithelial tissue.
Composed of three basic elements:
Cells
Fibers
Ground substance (matrix)
Support
Protection
Attachment
Maintains strength
Insulates and stores energy
Transportation of substances
Vary according to the type of connective tissue.
Fibroblasts: Produce fibers and ground substance.
Adipose cells (Adipocytes): Store fat.
Macrophages: Phagocytic cells involved in immune response.
Reticular cells: Produce reticular fibers.
Osteocytes: Mature bone cells.
Chondrocytes: Mature cartilage cells.
Plasma cells: Produce antibodies.
Blood cells: Various types including red and white blood cells.
Collagen (white fibers):
Broadest and most widespread type.
Provide high tensile strength.
Elastic (yellow fibers):
Can be stretched and return to their original shape.
Provide elasticity.
Reticular fibers:
Form a network or mesh-like structure.
Provide support.
Also known as ground substance.
Varies in consistency:
Gel-like
Hard
Liquid
Structure:
Mesenchymal cells are stellate or spindle-shaped.
Ground substance is a viscous fluid with some immature protein fibers.
Function: Common origin for all other connective tissue types.
Location: Throughout the body of the embryo and fetus.
Structure:
Mesenchymal cells scattered within a viscous ground substance.
Immature protein fibers are more abundant here than in mesenchyme.
Function: Support of structures in the umbilical cord.
Location: Umbilical cord of the fetus.
Loose Connective Tissue
Areolar
Adipose
Reticular
Dense Connective Tissue
Dense Regular (white fibrous)
Dense Irregular
Structure:
Abundant, viscous ground substance.
Few collagen and elastic fibers.
Scattered fibroblasts.
Many blood vessels.
Function:
Protects tissues and organs.
Binds skin and some epithelia to deeper tissues.
Location:
Papillary layer of the dermis (skin).
Subcutaneous layer (deep to skin).
Surrounds organs, nerve cells, some muscle cells, and blood vessels.
Structure:
Closely packed adipocytes.
Nucleus pushed to the edge of the cell by a large fat droplet.
Contains many blood vessels.
Function:
Stores energy.
Insulates.
Cushions and protects.
Location:
Subcutaneous layer.
Surrounds and covers some organs.
Structure:
Viscous ground substance.
Meshwork of reticular fibers, leukocytes, and some fibroblasts.
Function:
Provides stroma (supportive framework) to lymphatic organs.
Location:
Spleen.
Lymph nodes.
Red bone marrow.
Structure:
Densely packed, parallel arrays of collagen fibers.
Fibroblasts squeezed between layers of fibers.
Scarce ground substance.
Limited blood supply.
Function:
Attaches bone to bone (most ligaments) as well as muscle to bone (tendons).
Resists stress applied in one direction.
Location:
Tendons (attach muscle to bone).
Ligaments (typically attach bone to bone).
Structure:
Collagen fibers randomly arranged and clumped together.
Fibroblasts in spaces among fibers.
More ground substance than in dense regular connective tissue.
Extensive blood supply.
Function:
Withstands stresses applied in all directions.
Durable
Location:
Most of the dermis of skin.
Periosteum covering bone.
Perichondrium covering cartilage.
Epineurium covering nerves.
Epimysium covering skeletal muscle.
Some organ capsules.
Structure:
Predominantly composed of elastic fibers.
Fibroblasts occupy some spaces between fibers.
Function:
Allows for stretching and recoil.
Location:
Walls of elastic arteries (such as the aorta).
Trachea.
Vocal cords.
Structure:
Glassy-appearing matrix.
Irregularly arranged chondrocytes in lacunae.
Function:
Provides support.
Forms most of the fetal skeleton.
Location:
Tip of nose.
Trachea.
Most of larynx.
Costal cartilage.
Epiphyseal (growth) plates and articular ends of long bones.
Most of fetal skeleton.
Structure:
Readily visible, numerous, parallel collagen fibers with limited ground substance.
Large chondrocytes in lacunae.
Function:
Resists compression.
Acts as a shock absorber in some joints.
Location:
Intervertebral discs.
Pubic symphysis.
Menisci of knee joints.
Structure:
Abundant elastic fibers that form weblike mesh.
Closely packed chondrocytes in lacunae.
Function:
Maintains shape while permitting extensive flexibility.
Location:
External ear.
Epiglottis of larynx.
Structure:
Calcified extracellular matrix containing osteocytes trapped in lacunae.
Compact bone organized in osteons (concentric lamellae arranged around a central canal).
Spongy bone is a meshwork with a different organization from compact bone.
Well vascularized.
Function:
Provides levers for body movement.
Supports soft structures.
Protects organs.
Stores calcium and phosphorus.
Spongy bone contains hemopoietic tissue and is the site for hemopoiesis.
Location: Bones of the body.
Location: Within blood vessels and the heart.
Main function: Transport of nutrients, gases, and wastes through the body.
Connective Tissue Notes