![]() ![]() size – maximus (largest), minimus (smallest).divisions – biceps, triceps, quadriceps.There are many nomenclatures for naming muscles. If all the muscles in the jaw worked together, it could close the teeth with a force as great as 200 pounds on the molars (Science Reference Section, 2019). ![]() An intercalated disc allows the cardiac muscle cells to contract in a wave-like pattern so that the heart can work as a pump. Cardiac muscle fibers cells also are extensively branched and are connected to one another at their ends by intercalated discs. Similar to skeletal muscle, cardiac muscle is striated and organized into sarcomeres, possessing the same banding organization as skeletal muscle (see Figure 7.1). Highly coordinated contractions of cardiac muscle pump blood into the vessels of the circulatory system. Cardiac MuscleĬardiac muscle tissue is only found in the heart. Smooth muscle is also present in the eyes, where it functions to change the size of the iris and alter the shape of the lens and in the skin where it causes hair to stand erect in response to cold temperature or fear. Smooth muscle, so named because the cells do not have striations, is present in the walls of hollow organs like the urinary bladder, uterus, stomach, intestines, and in the walls of passageways, such as the arteries and veins of the circulatory system, and the tracts of the respiratory, urinary, and reproductive systems. The gluteus maximus is the largest muscle and the heart is the hardest working muscle. This heat is very noticeable during exercise, when sustained muscle movement causes body temperature to rise, and in cases of extreme cold when shivering produces random skeletal muscle contractions to generate heat. Skeletal muscles contribute to the maintenance of homeostasis in the body by generating heat. Skeletal muscles also protect internal organs (particularly abdominal and pelvic organs) by acting as an external barrier or shield to external trauma and by supporting the weight of the organs. These muscles allow functions, such as swallowing, urination, and defecation, to be under voluntary control. Skeletal muscles are located throughout the body at the openings of internal tracts to control the movement of various substances. Muscles also prevent excess movement of the bones and joints, maintaining skeletal stability and preventing skeletal structure damage or deformation. Small, constant adjustments of the skeletal muscles are needed to hold a body upright or balanced in any position. Skeletal muscles act not only to produce movement but also to stop movement, such as resisting gravity to maintain posture. Its appearance is similar to a skeletal muscle and is responsible for the pumping of blood. Also known as visceral muscles, they are responsible for involuntary muscle movement, such as breathing, et cetera. Smooth – mainly associated with the walls of the internal organs.Also known as striated muscles, they are responsible for voluntary muscle movement, such as swallowing, et cetera. Skeletal – closely associated with the skeletal system.(Micrographs provided by the Regents of University of Michigan Medical School © 2012). The body contains three types of muscle tissue: (a) skeletal muscle, (b) smooth muscle, and (c) cardiac muscle. Figure 7.1 The Three Types of Muscle Tissue. Fascia is fibrous connective tissue that encloses muscles. All three muscle tissues have some properties in common they all exhibit a quality called excitability as their plasma membranes can change their electrical states (from polarized to depolarized) and send an electrical wave called an action potential along the entire length of the membrane. The body contains three types of muscle tissue: skeletal muscle, cardiac muscle, and smooth muscle (see Figure 7.1). Muscle is one of the four primary tissue types of the body, and it is made up of specialized cells called fibers. Anatomy (Structures) of the Muscular System ![]()
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