Muscle Tissue-Structure And Functions
DIAGNOSTIC RADIOGRAPHY · NTA LEVEL 4 · SEMESTER ONE Muscle Tissue-Structure And Functions CRT04101 · Anatomy, Physiology and Pathology START READING NOTES Study Muscle Tissue-Structure And Functions using the sections below. Use the topic navigation to continue through Anatomy, Physiology and Pathology. Contents of This Topic Muscle Tissue Skeletal Muscles- 6 Functions of Skeletal Muscles Muscles serve specific functions in moving and positioning the body. How is muscle tissue organized at the tissue level? Organization of Connective Tissues 3. Endomysium Muscle Attachments Nerves What are the characteristics of skeletal muscle fibers? Skeletal Muscle Fibers Organization of Skeletal Muscle Fibers The Sarcolemma Transverse Tubules (T tubules) Muscle Striations Figure 10–6 (1 of 5) Muscle Contraction Skeletal Muscle Contraction The Process of Contraction Structure of Cardiac Tissue 7 Characteristics of Cardiocytes 4 Functions of Cardiac Tissue Role of Smooth Muscle in Body Systems Structure of Smooth Muscle 8 Characteristics of Smooth Muscle Cells Functional Characteristics of Smooth Muscle Muscle Tissue Muscle Tissue One of 4 primary tissue types, divided into: skeletal muscle cardiac muscle smooth muscle Without these muscles, nothing in the body would move and no body movement would occur Skeletal Muscles- Organs of skeletal muscle tissue are attached to the skeletal system and allow us to move Muscular System- Includes only skeletal muscles Skeletal Muscle Structures Muscle tissue (muscle cells or fibers) Connective tissues Nerves Blood vessels 6 Functions of Skeletal Muscles Produce skeletal movement Maintain body position and posture Support soft tissues Guard body openings (entrance/exit) Maintain body temperature Store Nutrient reserves Muscles serve specific functions in moving and positioning the body. The same muscle may act as a prime mover, antagonist, synergist, or fixator under specific conditions. The functions include. A prime mover or agonist is the main muscle responsible for producing a specific movement of the body (e.g. concentric contraction). Fixators steady the proximal parts of a limb while movements are occurring in distal parts. A synergist complements the action of prime mover for example, by preventing movement of the intervening joint when a prime mover passes over more than one joint. An antagonist is a muscle that opposes the action of a prime mover. As a prime mover contracts, the antagonist progressively relax, producing a smooth movement How is muscle tissue organized at the tissue level? Organization of Connective Tissues Figure 10–1 Organization of Connective Tissues Muscles have 3 layers of connective tissues: Epimysium-Exterior collagen layer Connected to deep fascia Separates muscle from surrounding tissue perimysium- Surrounds muscle fiber bundles (fascicles) Contains blood vessel and nerve supply to fascicles endomysium 3. Endomysium Surrounds individual muscle cells (muscle fibers) Contains capillaries and nerve fibers contacting muscle cells Contains satellite cells (myogenic stem cells) that repair damage Muscle Attachments Endomysium, perimysium, and epimysium come together: at ends of muscles to form connective tissue attachment to bone matrix i.e., tendon (bundle) or aponeurosis (sheet) Nerves Skeletal muscles are voluntary muscles, controlled by nerves of the central nervous system Blood Vessels Muscles have extensive vascular systems that: supply large amounts of oxygen supply nutrients carry away wastes What are the characteristics of skeletal muscle fibers? Skeletal muscle cells are called fibers Figure 10–2 Skeletal Muscle Fibers Are very long Develop through fusion of mesodermal cells (myoblasts- embryonic cells)) Become very large Contain hundreds of nuclei –multinucleate Unfused cells are satellite cells- assist in repair after injury Germ layers Structures originating from germ layers Organization of Skeletal Muscle Fibers Figure 10–3 The Sarcolemma The cell membrane of a muscle cell Surrounds the sarcoplasm (cytoplasm of muscle fiber) A change in transmembrane potential begins contractions All regions of the cell must contract simultaneously Transverse Tubules (T tubules) Transmit action potential – impulses through cell Allow entire muscle fiber to contract simultaneously Have same properties as sarcolemma Filled with extracellular fluid Muscle Striations A striped or striated pattern within myofibrils: alternating dark, thick filaments (A bands) and light, thin filaments (I bands) Figure 10–6 (1 of 5) Level 1: Skeletal Muscle Level 2: Muscle Fascicle Muscle Contraction Is caused by interactions of thick and thin filaments Structures of protein molecules (actin and myosin) detemine interactions Skeletal Muscle Contraction Figure 10–9 (Navigator) The Process of Contraction Neural stimulation of sarcolemma: causes excitation–contraction coupling Cisternae of Sarcoplasmic reticulum(SR) release Ca2+: which triggers interaction of thick and thin filaments consuming ATP and producing tension What are the structural and functional differences between skeletal muscle fibers and cardiac muscle cells? Structure of Cardiac Tissue Cardiac muscle is striated-involuntary muscle, found only in the heart Figure 10–22 7 Characteristics of Cardiocytes Unlike skeletal muscle, cardiac muscle cells (cardiocytes): are small have a single nucleus have short, wide T tubules 7 Characteristics of Cardiocytes have no triads have SR with no terminal cisternae are aerobic (high in myoglobin, mitochondria) have intercalated discs 4 Functions of Cardiac Tissue 1. Automaticity: – contraction without neural stimulation controlled Variable contraction tension: – controlled Extended contraction time Prevention of wave summation and tetanic contractions Role of Smooth Muscle in Body Systems Forms around other tissues In blood vessels: regulates blood pressure and flow In reproductive and glandular systems: produces movements In digestive and urinary systems: forms sphincters produces contractions In integumentary system: arrector pili muscles cause goose bumps Structure of Smooth Muscle Nonstriated tissue Figure 10–23 8 Characteristics of Smooth Muscle Cells Long, slender, and spindle shaped Have a single, central nucleus Have no T tubules, myofibrils, or sarcomeres Have no tendons or aponeuroses 8 Characteristics of Smooth Muscle Cells Have scattered myosin fibers Myosin fibers have more heads per thick filament Have thin filaments attached to dense bodies Dense bodies transmit contractions from cell to cell Functional Characteristics of Smooth Muscle Excitation–contraction coupling Length–tension relationships Control of contractions Smooth muscle tone ← PREVIOUS TOPICNEXT TOPIC →VIEW ALL MODULE NOTESVIEW SEMESTER NOTESVIEW ALL LEVEL NOTESALL DIAGNOSTIC RADIOLOGY NOTES Need These Notes as PDF? 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