What are the special features of the smooth muscle?

Answer 1

Smooth muscle cells range from 5 to 10 µm in diameter and from 30 to 200 µm in length. Each cell is spindle-shaped and has a single, centrally located nucleus. Figure 10-22a shows typical smooth muscle fibers as seen by light microscopy, and Figure 10-22b shows diagrammatic views of relaxed and contracted smooth muscle cells.

Smooth muscle tissue occurs within almost every organ, forming sheets, bundles, or sheaths around other tissues. Smooth muscles around blood vessels regulate blood flow through vital organs. In the digestive and urinary systems, rings of smooth muscle, called sphincters, regulate the movement of materials along internal passageways. Smooth muscles in bundles, layers, or sheets play a variety of other roles:

• Integumentary system. Smooth muscles around blood vessels regulate the flow of blood to the superficial dermis; smooth muscles of the arrector pili elevate hairs.
• Cardiovascular system. Smooth muscles encircling blood vessels control the distribution of blood and help regulate blood pressure.
• Respiratory system. Smooth muscle contraction or relaxation alters the diameters of the respiratory passageways and changes the resistance to airflow.
• Digestive system. Extensive layers of smooth muscle in the walls of the digestive tract play an essential role in moving materials along the tract. Smooth muscle in the walls of the gallbladder contract to eject bile into the digestive tract.
• Urinary system. Smooth muscle tissue in the walls of small blood vessels alters the rate of filtration at the kidneys. Layers of smooth muscle in the walls of the ureters transport urine to the urinary bladder; the contraction of the smooth muscle in the wall of the urinary bladder forces urine out of the body.
• Reproductive system. Layers of smooth muscle help move sperm along the reproductive tract in males and cause the ejection of glandular secretions from the accessory glands into the reproductive tract. In females, layers of smooth muscle help move oocytes (and perhaps sperm) along the reproductive tract, and contraction of the smooth muscle in the walls of the uterus expels the fetus at delivery

Answer 2

Peristalsis is a manifestation of two major reflexes within the enteric nervous system that are stimulated by a bolus of foodstuff in the lumen. Mechanical distension and perhaps mucosal irritation stimulate afferent enteric neurons.

Answer 3

They contract involuntarily.

Answer 4

okay that is a wierd question