Muscular System PDF

# Muscular System ## Zaitunnatakhin Zamli @wu.edu.my ## Learning Outcomes The student should be able to: - Describe the general features and functions of the muscular system. - Elaborate how skeletal muscles are classified and organized. - Name the various types of skeletal muscle fascicles, thei...

# Muscular System ## Zaitunnatakhin Zamli @wu.edu.my ## Learning Outcomes The student should be able to: - Describe the general features and functions of the muscular system. - Elaborate how skeletal muscles are classified and organized. - Name the various types of skeletal muscle fascicles, their arrangement, and give an example of each. - Differentiate the types of muscular tissues. - Describe the microscopic organization of a muscle fiber. ## The Skeletal Muscle System ### Introduction #### Major Components - Skeletal muscles - Associated tendon #### General Features - Electrical excitability - Contractibility - Extensibility - Elasticity #### Functions - Produce body movements - Stabilize posture and body position - Support soft tissues - Guard entrances and exits - Maintain body temperature ### Classification #### Based on Individual Muscle Action - Extensor, flexor, abductor, adductor, rotator, pronator, supinator, eversion, inversion, circumduction, protraction, elevation, and depression. #### Based on Integration of Muscle Action - **Prime mover**: A chief muscle or group of muscles responsible for causing movement. - **Antagonist**: A muscle that opposes the movement of the prime mover. - **Fixator**: A muscle that contracts to stabilize the origin of the prime mover. - **Synergist**: A muscle whose contraction controls the movement of a part, usually the joint, to aid the action of the prime mover in moving the other part. **Diagram of Muscle Action** The image shows an example of the different muscle actions: - **Prime mover**: Brachialis muscle - **Synergist**: Biceps muscle - **Antagonist**: Triceps muscle - **Fixator**: Rhomboid major and minor muscles ### Parts & Muscle Attachment Sites - **Contractile/Fleshy part**: "Belly" or body part - **Non-contractile part/Tendon**: Aponeurosis and raphe - **Origin**: Attachment of the muscle's tendon to the stationary bone, typically proximal. - **Insertion**: Attachment of the muscle's tendon to the movable bone, typically distal. ### Structural organization of a Muscle #### Muscle Cell/Fiber - A muscle comprises thousands of muscle cells/fibers. #### Connective Tissue Components - They protect muscular tissue and provide a pathway for nerves, blood, and lymphatic vessels. #### Types of Connective Tissue ##### Superficial Fascia/Subcutaneous Layer/Hypodermis - Composed of areolar connective tissue and adipose tissue. - Separates muscle from the skin and stores fats. ##### Deep Fascia - A dense sheet of irregular connective tissue that lines the body wall and limbs. - Holds muscles of similar function and, thus, allows free movement of those muscles. - Extension of deep fascia: - Epimysium - Perimysium - Endomysium The perimysium and endomysium form the **tendon** or **aponeurosis**. **Diagram of Fasciae** The image shows a cross section of the body illustrating the superficial fascia, deep fascia, and subserous fascia. **Diagram of Aponeurosis** The image shows a muscle labeled **aponeurosis**, highlighting the way connective tissue can connect to muscles. #### Diagram of Muscle Structure The image shows a zoomed-in view of muscle structure. - **Skeletal Muscle:** The outer layer of muscle (organ). - **Muscle Fascicle:** A bundle of muscle cells. - **Muscle Fiber:** An individual muscle cell. The fascicle contains blood vessels and nerves. The fiber contains mitochondria, sarcolemma, endomysium, a capillary, myosatellite cells, a myofibril, an axon, and a nucleus. #### Nerve and Blood Supply - An artery and one or two veins accompany each nerve that penetrates a skeletal muscle. - Rich in microscopic capillaries. #### Nerve Supply - Mixed nerves consisting of: - Motor nerves (60%) - Sensory nerves (40%) #### Nerve End - **Motor**: Motor-end-plate - **Sensory**: Specialized nerve endings arise from muscle and tendon spindles. #### Diagram of Nerve and Muscle Connection: **a) Motor neuron:** The image shows a motor neuron with an axon connected to a muscle fiber, showing the path of action potential from the motor neuron to the muscle fiber. **b) Motor end plate:** The image shows a more detailed view of the synaptic terminal of the motor neuron with a supporting cell and a mitochondrion within the muscle fiber. The image also shows a portion of the sarcoplasm, sarcolemma, and myofibril. **c) Muscle:** The image shows a zoomed-in view of multiple muscle fibers with axons connecting to the fibers at the motor end plate. ## Arrangement of Muscle Fascicles - **Parallel arrangement**: - Attachment of muscle's tendon to stationary bone. - Types: Parallel and fusiform muscles. - **Triangular arrangement**: - Type: Convergent muscle. - **Oblique arrangement**: - Types: Unipennate, bipennate, and multipennate. - **Circular arrangement**: - Type: Circular muscle. **Diagram of Muscle Fascicle Arrangements**: The image shows diagrams of different muscle arrangements: - **a) Fusiform muscle:** Biceps Brachii - **b) Convergent muscle:** Pectoralis muscles - **c) Unipennate muscle:** Extensor digitorum muscle - **d) Bipennate muscle:** Rectus Femoris muscle - **e) Multipennate muscle:** Deltoid muscle - **f) Circular muscle:** Orbicularis oris muscle ### Revision **Diagram of the Rectus Femoris Muscle.** The image shows a cross-section of the thigh and asks the viewer to: - Classify the Rectus Femoris muscle based on: - Individual action - Integration of muscle action - Arrangement of muscle fascicles - Identify the different parts of the Rectus Femoris muscle and its attachment. - Label points A, B, and C. ## Histology of Muscle ## Classification of Muscle Tissues #### Morphologically - Skeletal muscle - Cardiac muscle - Smooth muscle #### Functionally - Voluntary muscle - Involuntary muscle **Diagram of Three types of Muscle Tissues:** The image shows the different types of muscle tissue under the microscope. - **A**: Cardiac muscle - **B**: Skeletal muscle - **C**: Smooth muscle **Diagram of Muscle Tissue Formation:** The image on the left illustrates the process of myoblast fusion to form a skeletal muscle fiber. Two stages are shown: - **1**: Myoblasts fuse to form a skeletal muscle fiber. - **2**: A single muscle fiber. The image on the right shows a cross-section of cardiac muscle tissue: - **a)** A relaxed cardiac muscle cell. - **b)** A contracted cardiac muscle cell. ## Describe the distinctions between the three types of muscular tissue - **Microscopic features**: The image for each type of muscle tissue can be used to describe the features, including the shape, location, and size of the nuclei. - **Function**: For example, skeletal muscle is responsible for voluntary movement, while cardiac muscle is responsible for involuntary movement of the heart. - **Location**: Skeletal muscle is found attached to bones. Cardiac muscle is found in the heart. Smooth muscle is found in the walls of hollow organs and blood vessels. ## Microscopic Organization of a Muscle Fiber - **Sarcolemma**: The plasma membrane of a muscle cell. - **Sarcoplasm**: The cytoplasm of a muscle cell. - **Transverse/T-tubule**: - Invagination of the sarcolemma extending into the sarcoplasm at a right angle to the muscle cell surface. - Structurally similar to sarcolemma. - Filled with extracellular fluid. - **Myofibrils**: Consists of myofilaments. - **Sarcoplasmic reticulum**: A tubular network similar to smooth endoplasmic reticulum. - Encircles each myofibril. - Dilated end tube of sarcoplasmic reticulum is known as **terminal cisterns**. - **Triad**: A pair of terminal cisternae + T-tubule. **Diagram of Muscle Structure:** The image shows a cross-section of a muscle fiber. - **Myofibrils and Sarcoplasmic Reticulum:** The image highlights the sarcoplasmic reticulum, terminal cisternae, and T-tubule. - **Myofilaments and Sarcomeres**: The image highlights the thick and thin filaments and the sarcomere structure. - **Myofilaments**: Protein filaments involved in muscle contraction: - **Thin filament**: Mainly actin. - **Thick filament**: Mainly myosin. - **Sarcomeres**: The functional unit of a myofibril. **Diagram of Sarcomere Structure:** The image shows the structure of a muscle fiber from the myofibril to the myofilaments to sarcomeres. It also shows: - **Myofibrils:** - The source of a muscle fiber's striations. - Composed of myofilaments. - **Sarcomeres:** - The repeating functional units of myofilaments. - They form the striated pattern of a muscle fiber. The image shows a visual of sarcomere structure with the following components labelled: - **Z line**: Marks the boundary between sarcomeres. - **I Band**: The region of thin filaments only. - **A Band**: The region where the thick filaments overlap the thin filaments. - **H Zone**: The region of thick filaments only - **M Line**: Center of the A band. **Diagram of Sarcomere:** The image highlights the parts of the sarcomere: - **Sarcomere** - **A Band** - **I Band** - **H Band** - **M Line** - **Z Line** ## What is a sarcomere? Sketch the arrangement of thick and thin filaments that account for the striations. - **Sarcomere**: The functional unit of a muscle. It is composed of a repeating unit of thick and thin filaments. - **Arrangement:** The thick and thin filaments overlap within each sarcomere. This creates a striated pattern. ## Muscle Innervation - Motor End Plate - **General Features:** - Also known as the neuromuscular junction. - **Motor unit**: A motor neuron + all of the muscle fibers it innervates. **Diagram of Motor Neuron and Muscle Connection:** The image shows a zoomed-in view of how a motor neuron interacts with a muscle fiber at a motor end plate. The top image shows: - **Axonal terminal of the motor neuron** - **Mitochondrion** - **Synaptic cleft** - **Junctional folds of the sarcolemma at the motor end plate** - **Part of a myofibril** **Diagram of Motor End Plate:** The image shows the motor end plate at the neuromuscular junction. - **Axon terminus** - **Synaptic vesicle** - **Sarcomere** - **Muscle cell** - **Basal lamina** ## Revision **Diagram of Muscle Structure:** The image shows a cross section of muscle tissue under a microscope. - **A:** Muscle fiber - **B:** A circular structure within the cell, but the image is too small to tell what it is. - **C:** A nerve ending - **D:** A blood vessel - **E:** A muscle fiber - **F:** A circular area containing multiple small circles, but the image is too small to discern. ## Diagram of Sarcomere: The image shows a diagram of how the T-tubule connects with the terminal cisternae. - **A:** Portion of T-tubule (transverse tubule) - **B:** Portion of sarcoplasmic reticulum ## Abu Huraira reported Allah’s Messenger (may peace be upon him) as saying: A strong believer is better and is more lovable to Allah than a weak believer, and there is good in everyone, ***(but)*** cherish that which gives you benefit ***(in the Hereafter)*** and seek help from Allah and do not lose heart, and if anything ***(in the form of trouble)*** comes to you, don’t say: If I had not done that, it would not have happened so and so, but say: Allah did that what He had ordained to do and your “if” opens the ***(gate)*** for the Satan. - Sahih Muslim 2664 ## Thanks!