Connective tissue is made of scattered cells inside a material they produce, called the matrix. The type of fibers and how dense the matrix is decide whether the tissue is soft, tough, firm or fluid.
Fibers and matrix
Collagen fibers resist pulling, elastic fibers let tissue stretch and recoil, and a gel-like ground substance fills the space between them. Fibroblasts are the main cells that build and repair this matrix.
Loose tissue and fat
Loose connective tissue packs around organs, vessels and nerves. Adipose tissue stores energy, insulates and cushions, and it forms most of the layer under the skin.
Dense tissue
Tendons join muscle to bone and ligaments join bone to bone. Their tightly packed collagen makes them strong, but their poor blood supply makes them slow to heal.
Cartilage, bone and blood
Cartilage is firm and smooth and has no blood vessels, so damaged joint cartilage repairs poorly. Bone has a mineral-hardened matrix, and blood is a connective tissue with a liquid matrix, the plasma.
| Type | Where | Healing |
|---|---|---|
| Adipose | Under the skin, around organs | Good blood supply |
| Dense regular | Tendons and ligaments | Slow, weeks to months |
| Cartilage | Joint surfaces, ear, airway rings | Very poor |
| Bone | Skeleton | Good, about 6 to 8 weeks for many fractures |
At the bedside
Subcutaneous injections go into the fatty layer, and intramuscular injections pass through it into muscle. When you examine a joint, pain on stressing a ligament points to a sprain rather than a fracture or muscle injury.
Related guides
Written by Making Synapses. Topic reference: OpenStax, Anatomy and Physiology 2e (no text adapted).