The skin; forms the outer covering of the body.

What are membranes?

Line joint cavities and are composed of connective tissue. They secrete synovial fluid into the joint cavity so that the bones can move freely.

Line cavities, including the thoracic cavity and internal organs (e.g. heart). The pleura covers the lungs; the heart is covered by the pericardium; the peritoneum lines the abdominopelvic cavity and covers the organs within.

Composed of three connective tissue membranes found within the dorsal cavity and serve as a protective covering of the brain and spinal cord. Dura mater, arachnoid, and pla mater.

Line the interior walls of the organs and tubes that open to the outside of the body, such as those of the digestive, respiratory, urinary, and reproductive systems.