5.4 Types of Membranes

Epithelial membrane - Thin, sheetlike structures composed of epithelium and underlying connective tissue. They cover body surfaces and line body cavities. There are 3 major types of epithelial membranes which are called serous, mucous, and cutaneous.

Serous membrane - Type of membrane that lines a cavity without an opening to the outside of the group. These membranes form the inner linings of the thorax (parietal pleura) and abdomen (parietal peritoneum), and they cover the organs in these cavities (visceral pleura and visceral peritoneum). A serous membrane consists of a layer of simple squamous epithelium and a thin layer of areolar connective tissue. The cells of a serous membrane secrete watery serous fluid, which helps lubricate membrane surfaces.

Mucous membrane - Type of membrane that lines tubes and body cavities that open to the outside of the body which includes the oral and nasal cavities and the tubes of the digestive, respiratory, urinary, and reproductive systems. The mucous membrane consists of epithelium overlying a layer of areolar connective tissue. Goblet cells within a mucous membrane secrete mucus.

Cutaneous membrane - Skin; an epithelial membrane.

Synovial membrane - Membrane that forms the inner lining of the capsule of a freely movable joint. The synovial membrane is composed entirely of connective tissue.

5.5 Muscle Tissue

Muscle tissue - Contractile tissue consisting of filaments of actin and myosin, which slide past each other, shortening cells.

Their elongated cells, called muscle fibers, shorten and thicken. As they contract, muscle fibers pull at their attached ends, which moves body parts. There are 3 types of muscle tissue: skeletal, smooth, and cardiac. 40% of the body is skeletal muscle while 10% is cardiac and smooth muscle.

Skeletal Muscle Tissue

Skeletal muscle tissue forms muscles that are attached to the bone and can be controlled by conscious effort. This tissue is a voluntary muscle tissue. The long, threadlike cells of skeletal muscle have alternating light and dark cross-markings called striations. a nerve cell must stimulate a skeletal muscle cell to contract, and then the muscle cell relaxes when simulations stop. These muscles move the head, trunk, and limbs which helps us make facial expressions, write, speak, chew, swallow, breath, etc.

Smooth Muscle Tissue

Smooth muscle tissue does not have striations. Smooth muscle cells are shorter than skeletal muscle cells and are spindle-shaped, each with a single, centrally located nucleus. This tissue composes the walls hollow organs like the stomach, intestines, urinary bladder, blood vessels, and uterus. Unlike skeletal muscle, smooth muscles can’t be stimulated to contract by conscious effort. Therefore, it’s involuntary.

Cardiac Muscle Tissue

Cardiac muscle tissue is only found in the heart. It’s cells are striated and branched, are joined end to end, forming complex network. These cardiac muscle cells have a single nucleus. Where one cell touches another cell is a specialized intercellular junction called an intercalated disc ( Connection between cardiac muscle cells). Same like smooth muscle, cardiac muscles are involuntary. This tissue makes up the bulk of the heart and plumps blood through the heart chambers and into the blood vessels.

5.6 Nervous Tissues

Nervous tissues are found in the brain, spinal cord, and peripheral nerves. the basic cells are called neurons or nerve cells. Neurons sense certain types of changes in their surroundings. Neurons may respond by conducting electrical impulses along cellular processes called axons. They can coordinate, regulate, and integrate many body functions. Nervous tissue includes neuroglia. Unlike neurons, neuroglia divide. Neuroglia supports and binds the components of nervous tissue, carries phagocytosis, and helps supply growth factors and nutrients to neurons by connecting them to blood vessels. They also play a role in cell-to-cell communication.