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NAME: ALADE ADETUTU SEFINAT MATRIC NO: 14/MHS02/008 DEPT: NURSING SCIENCE LEVEL: 200L COURSE: HISTOLOGY MUSCLES TISSUES Structure of muscles tissues all muscles tissues have a superficial covering of vary thickness called fascia, made of connective tissue and laced with adipose tissue inside the facia, the muscles tissue is surrounded by epimysium and individual muscles bundles or faciculus are surrounded by perimysium. There are three types of muscles tissue which can be described from the level of details of the muscles fibre (muscles cells) through all the other muscles structures and parts of structures that bind muscles cells together enabling them to perform their functions. They are: SKELETAL MUSCLE TISSUE Structure: A skeletal muscles is called “striated” because of its appearance consisting of light and dark bands visible using a light microscope. A single cell skeletal muscle cell is long and approximately cylindrical in shape, with many nuclei located at the edges (periphery) of the cells. Functions: Movement of the skeleton: under conscious control including movement of limbs, fingers, toes, neck, etc. Movement of tissue: of facial expression under conscious control, e.g ability to smile and to frown. CARDIAC MUSCLE TISSUE Structure: found in the heart and responsible for contraction of cardiac tissue and distribution of blood cardiac muscles fibers are striated, branched (sometimes described as y-shaped), and have single central nucleus. these fibers are attached at their ends to adjoining fibers by thick plasma membranes called intercalated discs. Function Pumping of blood through the heart: Alternate contraction and relaxation of cardiac muscle pumps (de-oxygenated blood through the right atrium and right ventricle to the lungs and oxygenated blood through the left atrium and left ventricle to the aorta, then the rest of the body) SMOOTH MUSCLES TISSUE Structure: unlike skeletal and cardiac muscle tissue, smooth muscles “Is nonstriated, anucleated”, but similar to cardiac tissue relative to functional spontaneity and long sustained contraction. Smooth muscle fibers are small and tapered with the ends reducing in size, in contrast to the cylindrical shape of skeletal muscle. Each smooth muscle fiber has a single centrally located nucleus. It is found in the lining of blood vessels, urinary bladder, kidneys, esophagus and small intestines. FUNCTION Contraction of smooth muscle constrict (i.e narrow= reduce the diameter of) the vessels they surround. This is particularly important in the digestive in which the action of smooth muscles helps to move food along the gastrointestinal tract as well as breaking the food down further. Smooth muscles also contributes to the moving fluids through the body and to the elimination of indigestible matter from the gastrointestinal system. COMPARISM OF THE 3 TYPES OF MUSCLES TISSUE LOCATIONS OF MUSCLE TYPE Voluntary or involuntary Striations Cell nuclei SKELETAL MUSCLE TISSSUE Attached to bones, in the case of facial muscles CARDIAC MUSCLE TISSUE Wall of the heart voluntary involuntary striated Many nuclei (located at the periphery of long cylindrical muscle fiber striated one SMOOTH MUSCLE TISSUE Wall of hollow internal structure(blood vessels, stomach, urinary bladder, airways to the lungs, intestines) involuntary nonstriated One( centrally located) nucleus BANDS AND LINES Muscle contraction based on sliding filament hypothesis The sarcomeres are what give skeletal and cardiac muscles their striated appearance. [1] · A sarcomere is defined as the segment between two neighbouring Z-lines (or Z-discs, or Z bodies). In electron micrographs of cross-striated muscle, the Z-line (from the German "Zwischenscheibe", the disc in between the I bands) appears as a series of dark lines. · · · · Surrounding the Z-line is the region of the I-band (for isotropic). I-band is the zone of thin filaments that is not superimposed by thick filaments. Following the I-band is the A-band (for anisotropic). Named for their properties under a polarizing microscope. An A-band contains the entire length of a single thick filament. Within the A-band is a paler region called the H-zone (from the German "heller", brighter). Named for their lighter appearance under a polarization microscope. H-band is the zone of the thick filaments that is not superimposed by the thin filaments. Inside the H-zone is a thin M-line (from the German "Mittelscheibe", the disc in the middle of the sarcomere) formed of cross-connecting elements of the cytoskeleton. The relationship between the proteins and the regions of the sarcomere are as follows: · Actin filaments, the thin filaments, are the major component of the I-band and extend into the A-band. · Myosin filaments, the thick filaments, are bipolar and extend throughout the A-band. They are cross-linked at the centre by the M-band. · The giant protein titin (connectin) extends from the Z-line of the sarcomere, where it binds to the thick filament (myosin) system, to the M-band, where it is thought to interact with the thick filaments. Titin (and its splice isoforms) is the biggest single highly elasticated protein found in nature. It provides binding sites for numerous proteins and is thought to play an important role as sarcomeric ruler and as blueprint for the assembly of the sarcomere. Another giant protein, nebulin, is hypothesised to extend along the thin filaments and the entire I-Band. Similar to titin, it is thought to act as a molecular ruler along for thin filament assembly. Several proteins important for the stability of the sarcomeric structure are found in the Z-line as well as in the M-band of the sarcomere. Actin filaments and titin molecules are cross-linked in the Z-disc via the Zline protein alpha-actinin. The M-band proteins myomesin as well as C-protein crosslink the thick filament system (myosins) and the M-band part of titin (the elastic filaments). The interaction between actin and myosin filaments in the A-band of the sarcomere is responsible for the muscle contraction (sliding filament model).[1] · · · · · REFERENCES Ivyrose holistic health 2003-2015 google