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Unit 1 Human Anatomy Key to the Exercises I. Preparation Enjoy a video clip. You may watch it twice to achieve a good understanding. After watching��please fill in each of the following blanks with one word. 1) Cardiac 2) conscious 3) unstriated 4) clongatcd�� striatcd �� voluntary Script I tell you��working in a place like this��you can sure learn a lot about muscles. Hah. I mean sure there are three different types of muscles:cardiac��smooth��and skeletal. And skeletal is the only type you can see but. what you can't. see? Pretty impressive. Hey�� thanks��Rex. Thcrc arc thrcc fundamcntal typcs of musclc tissuc:cardiac��smooth and skclctal. Cardiac musclc forms the walls of the hcart and contracts to propcl blood through the blood vessels of the body. Cardiac muscles are involuntary. Involuntary muscles are muscles we have no conscious control over. Cardiac muscles are striated��which means the muscle tissue has obvious st.ripes or striat.ions. Smooth muscle forms the walls of hollow structures like the digestive tract. It's also responsible for changing the diameter of these tubes to move stuff like food through them. Smooth muscle is controlled by the autonomic nervous system. Basically that means the smooth muscle works without any conscious help from us. It's on autopilot. Smooth muscle cells are unstriated. That means they don't have the stripes that cardiac and skeletal muscles have�� but like cardiac muscles�� smooth muscles are involuntary. We can't control them consciously. Skeletal muscles�� the final division�� are typically attached to the skeletal system�� cover name-skeletal muscles. The skclctal musclcs arc also rcsponsiblc for body movcmcnts and facial expressions. Throwing balls�� running from the police�� frowning in disgust�� all these things are the bread and butter of skeletal muscles.Skeletal muscle cells are elongated��striated and under voluntary control. So when you think skeletal muscles��think striated and voluntary. Apart from movement��skeletal muscles have a number of other responsibilities. Skeletal muscles help you stand. They maintain posture by resisting the pull of gravity. Nothing can resist the downward pull of gravity. Just watch ! Hah ! It's impossible�� I tell you. II.Reading Text A Comprehension Check Pair work:Discuss and answer the following questions. Try not to look back at the text. l)The ability to change shape has become the most important property of muscle cells. (Para. 2) 2)The prefixes myo- and sarco- are frequently used in naming structures associated with muscle. (Para. 3) 3)Striated muscle is composed of regular�� repeating elements which give the cells a finely cross-striated appearance when they are viewed microscopically. Smooth muscle��in contrast��lacks such repeating elements and thus has no striations. (Para. 3) 4)The advantage of skeletal muscle is that it is capable of powerful contractions (about 100 watts per kilogram) because of the regular organization of its contractile proteins. Its disadvantage is that its contractile range is limited:wherever a larger range of movement is required��it is achieved through the amplification provided by the lever systems of the skeleton to which the muscle is attached (hence the name skeletal muscle). (Para. 5) 5)Because skeletal muscle is involved in many movements��such as breathing��blinking�� swallowing��and the actions of the muscles of the perineum and in the middle ear�� which are usually or exclusively driven at an unconscious level. (Para. 6) 6)Because cardiac muscle is provided with a continuous supply of energy by numerous blood vessels around the fibers��and abundant mitochondria within them. (Para. 7) 7)Smooth muscle is found in all systems of the body��in the walls of the viscera�� including most of the gastrointestinal��respiratory�� urinary and reproductive tracts��in the tunica media of blood vessels��in the dermis (as the arrector pili muscles)��in the intrinsic muscles of the eye��and the dartos muscular layer of the scrotum. In some places��smooth muscle fasciculi are associated with those of skeletal muscle��e.g. the sphincters of the anus and the urinary bladder��the tarsal muscles of the upper and lower eyelids�� the suspensory muscle of the duodenum�� a transitional zone in the esophagus��and fasciae and ligaments on the pelvic aspect of the pelvic diaphragm. (Para. 8) 8)These features are well illustrated by the role of smooth muscle in the walls of tubes and sacs��where its action regulates the size of the enclosed lumen and��in some cases�� the consequent movement of luminal contents. (Para. 9) Language Practice 1.Read the text carefully and then fill out the missing information in the following short passage.The beginning letter of each missing word has been given. 1)mechanical2)inflate 3)pump4)tissue 5)mass 6)cardiac 7)Cardiac 8)bulk 9) striatedlO)involuntary11)