Muscle Tissue and Joints Lecture Notes PDF

Skeletal muscle Cardiac muscle Smooth muscle tissue tissue tissue Skeletal Walls of the Walls of muscle heart hollow organs Voluntary Involuntary Involuntary Cells are Striated Lack striations st...

Skeletal muscle Cardiac muscle Smooth muscle tissue tissue tissue Skeletal Walls of the Walls of muscle heart hollow organs Voluntary Involuntary Involuntary Cells are Striated Lack striations striated Makes up 40% of body weight Functions of skeletal muscle tissue Movement Skeletal muscle - attached to skeleton Moves body by moving the bones Maintenance of posture – enables the body to remain sitting or standing Joint stabilization (support) Temperature regulation– if you are cold you will shiver Helps maintain normal body temperature Functional features Contractility Ability of cells to be forcefully shortened (flex) Excitability Ability to respond to stimulation. (motor neuron) Extensibility Ability of cells to be stretched (extension) Elasticity can recoil or bounce back after being stretched  Gross anatomy of skeletal muscle Each muscle is comprised of muscle fibers (individual cells) organized into bundles called fascicles Muscle fibers contain myofibrils (bundle of proteins that contract) Myofibrils are composed of myofilaments  Microscopic anatomy of skeletal muscle Skeletal muscle fibers have many of the same components of a typical cell, but some are named differently (sarco = root for muscle) Examples: – Sarcolemma: Plasma membrane – Sarcoplasm: Cytoplasm – Sarcoplasmic reticulum: Smooth ER  Connective Tissue Components Epimysium: Surrounds the entire muscle -Dense irregular connective tissue Perimysium: Surrounds the fascicles -Dense irregular connective tissue Endomysium: Innermost layer that surrounds and insulates each muscle fiber -Areolar connective tissue  Muscle Attachments At the ends of each muscle, all of the connective tissue merge to form a tendon which attaches the muscle to bone, skin or another muscle A tendon is usually cordlike in appearance, but some appear as a sheet, termed aponeurosis  Muscle attachments Most muscles extend over a joint and have attachments to both articulating bones of that joint Upon contraction of the muscle, one of the articulating bones moves and the other one does not The less moveable point of attachment is called the origin The more moveable point of attachment is the insertion The point of origin does not move while the insertion point does move Muscle inserts onto the radius and therefore forearm is the moveable part Skeletal Muscle Histology Cardiac muscle Exclusively in heart wall One or two nuclei Striated like skeletal muscle with a branched shape Join other adjacent cells to form junctions termed intercalated discs comprised of gap junctions Autorhythmic: Able to generate a muscle impulse without nervous stimulation Under involuntary control Cardiac muscle contracts the same way that skeletal muscle does but the signal does not depend on nerve innervation  Smooth muscle Cells Found in the walls of Non-striated and visceral organs contain no sarcomeres Circulatory vessels One nucleus (blood vessels) Respiratory tubes Entry of Ca2+ into the Digestive tubes cytoplasm signals Urinary organs contraction of the Reproductive organs smooth muscle fiber Inside the eye Introduction to Joints  Articulations (Joints) An articulation, or joint, is the place where a bone meets another bone, cartilage or teeth – Only points at which movements of bones can occur Joints allow mobility while preserving bone strength Amount of movement allowed is determined by anatomical structure Not all joints permit movement! Articulations vary in stability and mobility, and are classified into categories based on these qualities – Determined by joint structure – More mobility = less stability and vice versa  Classification of Joints Classification by structure (what holds bones together): – Bony: Bones are fused together – Fibrous: Bones held together by dense regular connective tissue – Cartilaginous: Bones joined by cartilage – Synovial: Bones separated by fluid-filled cavity Classification by function: – Synarthrosis: Immobile joint, no movement – Amphiarthrosis: Slightly moveable joint – Diarthrosis: Freely moveable joint = synovial  Fibrous joints Bones joined by dense regular CT Three specific types: – Gomphosis: Joints between teeth and maxilla and mandible; synarthrosis (immobile) – Sutures: Joints between skull bones; synarthrosis – Syndesmoses: Joints between parallel bones in the forearm and leg (radius and ulna, tibia and fibula); amphiarthrosis (slightly moveable)  Cartilaginous Joints Bones attached by cartilage Two specific types: – Synchondroses: Bones joined by hyaline cartilage; synarthrosis (immobile) – Symphyses: Bones joined by pad of fibrocartilage; amphiarthrosis (slightly moveable)  Synovial Joints Freely mobile diarthrosis Articulating bones separated by a joint cavity General anatomy: – Articular capsule – Joint cavity – Synovial fluid – Articular cartilage – Ligaments – Nerves and blood vessels  A typical synovial joint Richly supplied with sensory nerves Detect pain Most monitor how much the capsule is being stretched Have a rich blood supply Most supply the synovial membrane Extensive capillary beds produce basis of synovial fluid  Joint stability Articular surfaces Size, shape and arrangement of the surface seldom play a major role in joint stability Ligaments the more ligaments in a joint, the stronger it is Muscle tone the most important factor in joint stability Keeps tension on muscle tendons Arthritis describes over 100 kinds of joint- damaging diseases Osteoarthritis most common type: degeneration of cartilage “wear and tear” arthritis Rheumatoid arthritis Autoimmune Inflammatory disorder 2:1 prevalence in women (may be as high as 3:1) Gouty arthritis (gout) Uric acid build-up (from the blood stream) causes pain in joints More prevalent in men