Muscle Architecture Muscle architecture or the shape of skeletal muscles helps to shape their external appearance and determines their range of movement. Spiral muscles, as found in the trapezius muscle of the back, produce a twisting action at joints, Triangular bundles of muscle fibers, which appear fan-shaped, are arranged at an angle to the line of pull, as for example the temporalis muscles involved in chewing. Strap-like muscles, such as the sartorius of the leg and the sternohyoid of the neck, have parallel arrangement of fiber bundles. They are capable of both subtle and powerful contractions. Multipennate muscles, like the deltoid of the arm, are composed of many short bundles of fibers. Despite a limited range of shortening, these muscles are powerful in their actions. [More] [Less]
Skeletal Muscles The voluntary or skeletal muscle system consists of more than 650 muscles, which produce body movement and help maintain an upright posture. Voluntary muscles are The voluntary or skeletal muscle system consists of more than 650 muscles, which produce body movement and help maintain an upright posture. built onto the skeletal framework in several layers; the ones shown here are those directly under the skin. Facial muscles are involved in speech, eating, and expression. Muscles across the chest and the top of the back function in respiration and are also responsible for shoulder and arm movements. Muscles in the lower back help to maintain an erect posture. Abdominal muscles protect the internal organs. Arm and leg muscles, among the most powerful in the body, produce limb movements. Acting like cables, muscles pull on bones to produce movement. This involves the contraction and shortening of individual muscle fibers. Most of the body\\\\\\\\\\\\\\\'s voluntary muscles are arranged in opposing groups-as one muscle contracts the opposing muscle relaxes. Even when the body is being maintained in a relaxed position the muscles contract partially, but do not shorten. This maintains tone. [More] [Less]
The Stomach The stomach acts as a reservoir for food and has a capacity of two and a half pints. Within the stomach, solid food material is churned and kneaded for about three hours until it becomes a semiliquid mass known as chyme. The chyme is then forced into the small intestine, where the process of digestion is completed. The wall of the stomach has three muscular layers, an outer longitudinal layer, a middle circular layer and an inner oblique layer. As the stomach fills with food, wavelike contractions of the wall begin, and as these waves move along the stomach wall some of the food is passed through the relaxed muscle valve at the base and into the duodenum, the first part of the small intestine, where it is further digested before being absorbed into the body. [More] [Less]
The Small Intestine The small intestine, a twenty-one-foot tube, lies in coils in the abdomen. The first ten to twelve inches are called the duodenum, which is the U-shaped section of the small intestine that joins the stomach and the jejunum. The next eight feet, the jejunum and the remaining twelve feet the ileum, join the duodenum with the large intestine. The muscle layers of the small intestine are arranged longitudinally on the outside and circularly on the inside. Between the muscle layers are a series of nerve fibers which control the muscular movements that mix and move food along. The common bile duct is the opening through which bile and pancreatic juices enter the small intestine. As food reaches the duodenum from the stomach, it is mixed with these juices and further digested. At the base of the duct is a ring of smooth muscle, the sphincter, which regulates the outflow of fluid. Digested food is absorbed into the cells through the fingerlike projections lining the small intestine called the villi. The Crypts of Lieberkuhn, numerous tubular glands which open into the intestine from between the villi, secrete an alkaline fluid rich in digestive enzymes and mucus. The mucus protects the tissues of the small intestine from being digested by it\\\\\\\\\\\\\\\'s own enzymes. Brunner\\\\\\\\\\\\\\\'s glands pour out an alkaline juice to neutralize the acid chyme reaching the small intestine and to create the necessary conditions for further digestion. Tributaries of the portal vein carry digested materials away from the small intestine to the liver. The major function of the small intestine is to complete the digestion of food passing into it from the stomach and to absorb the final products of digestion. [More] [Less]
Inside the Heart The heart is a muscular pumping organ which beats nonstop to circulate blood around the body. It functions as two halves, each consisting of a holding chamber, or atrium, and a pumping center, or ventricle. After circulating around the body, blood, now deoxygenated, returns to the right atrium through large veins, the superior vena cava and the inferior vena cava. When the atrium is full, blood is forced through the tricuspid valve into the right ventricle. It is then pumped to the lungs through the pulmonary valve into the pulmonary artery. The oxygenated blood returns via the pulmonary veins to the left atrium. After flowing through the mitral valve it is pumped out of the left ventricle into the aorta to return to the general circulation. [More] [Less]
http://www.PreOp.com Patient ED @ 617-379-1582 INFO Laser Eye Surgery is a relatively simple and nonintrusive procedure that is designed to reduce or eliminate the need for glasses or contact lenses. Patient Education LASIK laser surgery generally does not have any effect on a patient\'s overall health and there are no risks in choosing not to have the surgery. Patient Education LASIK Laser Eye Surgery [More] [Less]
