Answer
Membranes are sheets of tissues that cover surfaces, line surfaces, separate organs and secrete a variety of chemical substances. Four kinds of membranes are usually described --mucous, serous, cutaneous, and synovial membranes.
A mucous membrane is is an epithelial sheet of tissue that lines a body cavity which opens to the exterior. This kind of membrane also secretes a mucous fluid.Mucous membranes of various kinds line certain sections of the respiratory, the digestive and the reproductive tracts.. The lubricating action of mucous fluid facilitates the passage of food along the digestive tract, and the removal of dust particles, and microbes from the respiratory tract.
Serous membranes also line body cavities, as well as cover organs in cavities. However, in this case only closed body cavities-- cavities that do not have openings to the exterior environment-- are line or covered by this kind of membrane. The pleura, the pericardium, and the peritoneum are examples of serosal membranes. Serosal fluid is less viscous that mucous secretion, but it also lubricates surfaces and reduces friction, as well as supply moisture and prevent dehydration of organs and surfaces. Serosal membranes often present in two layers, the visceral layer ( e.g. visceral pleura that covers and invests the lung, and a parietal layer that covers the walls of a cavity for example. the thoracic cavity.
Cutaneous membranes is the third class of membranes. This is , of course the skin. It comprises epidermis ( outer epithelial layers ) and a lower connective tissue dermis . The epidermis is made up of four layers of largely keratinized squamous epithelial cells, while the dermis is largely connective tissue --partly areolar and partly dense irregular connective tissue. The cutaneous membrane is much more expansive than the other membranes of the body. It is largely an external covering that provides physical protection, helps in body temperature homeostasis, has some secretory and excretory functions, and synthesizes vitamin D.
Synovial membranes membranes are connective tissue membranes with no epithelium.The cells, or synovicytes,exist in a mixture of areolar and adipose tissues. These membrane are found lining the cavities of freely movable joints ( diarthroses). Examples of these joints are the hip, and shoulder joints, the interphalangeal joints, and the pivot joint between atlas and axis vertebrae.
Work Step by Step
Synovial membranes secrete a viscous slippery fluid which lubricates joint articular surfaces and nourishes the cartilage of which they are made, Like most other connective tissue membranes synovial membranes also have macrophages that phagocytose microbes, and eliminate detritus and dead or damaged cells.
