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Muscular System Chapter 6 Muscle Types Skeletal muscles – attach to the body’s skeleton Cardiac – heart Smooth – walls of hollow organs such as the stomach, urinary bladder, intestines, and respiratory tract Muscle Types (cont.) Nuclei Striations Intercalated Disks Voluntary or Involuntary Movement Cardiac Uninucleated Yes Yes Involuntary Skeletal Multinucleated Yes No Voluntary Smooth Uninucleated No No Involuntary Tendons and Ligaments Tendon – connective tissue that attaches muscle to bone Ligament – connective tissue that attaches bone to bone Tendons and Ligaments (cont.) Muscle Functions Produces movement Generates heat Maintains posture Stabilizes joints Microscopic Anatomy of Skeletal Muscle Myofibrils – long ribbon-like organelles Have striations A band – dArk color I band – light color Sarcomere – a segment of a myofibril Myofilaments – threadlike proteins consisting of actin and myosin Actin – thin filaments Myosin – thick filaments Microscopic Anatomy of Skeletal Muscle Skeletal Muscle Activity Electronic impulses originate in the brain Electricity travels through the nervous system Nerves attach to muscle fibers Skeletal Muscle Activity Electricity causes SR to release Ca2+ ions which start myosin heads to bind with actin tails Sarcoplasmic reticulum (SR) – a specialized smooth ER that store calcium (Ca2+) Example: myosin - fish hooks actin - chains The end result is muscle contraction Skeletal Muscle Activity Types of Body Movements Origin – attached to the immovable or less movable bone Insertion – attached to the movable bone When the muscle contracts, the insertion moves toward the origin. Types of Body Movements Flexion – a movement that decreases the angle of the joint and brings two bones closer together Types of Body Movements Extension – a movement that increases the angle, or distance, between two bones or parts of the body Types of Body Movements Adduction – moving a limb toward the body midline Abduction – moving a limb away (generally on the frontal plane) from the midline Types of Body Movements Rotation – movement of a bone around its longitudinal axis Ex. – Shoulder and head Types of Body Movements Circumduction – a combination of flexion, extension, abduction, and adduction commonly seen in ball-and-socket joints such as the arm The limb as a whole outlines a cone Gross Anatomy of Skeletal Muscles Head Muscles Facial Muscles Frontalis – Covers the frontal bone Raises eyebrows and wrinkles forehead Frontalis Temporalis Zygomaticus Masseter Buccinator Orbicularis oris Platysma Orbicularis oculi Facial Muscles Orbicularis Oculi Close eyes, squint, blink, and wink Orbicularis oculi Frontalis Temporalis Zygomaticus Masseter Buccinator Orbicularis oris Platysma Facial Muscles Orbicularis oris Closes the mouth and protrudes the lips Frontalis Temporalis Zygomaticus Masseter Buccinator Orbicularis oris Platysma Orbicularis oculi Facial Muscles Buccinator Flattens the cheek (as in whistling) Aids in chewing Orbicularis oculi Frontalis Temporalis Zygomaticus Masseter Buccinator Orbicularis oris Platysma Facial Muscles Zygomaticus “Smiling” muscle Orbicularis oculi Raises the corners of the mouth upward Frontalis Temporalis Zygomaticus Masseter Buccinator Orbicularis oris Platysma Facial Muscles Masseter Closes the jaw Orbicularis oculi Frontalis Temporalis Zygomaticus Masseter Buccinator Orbicularis oris Platysma Facial Muscles Temporalis Helps close the jaw Orbicularis oculi Frontalis Temporalis Zygomaticus Masseter Buccinator Orbicularis oris Platysma Gross Anatomy of Skeletal Muscles Trunk and Neck Muscles Anterior Muscles Platysma Pulls the corners of the mouth inferiorly Frontalis Temporalis Zygomaticus Masseter Buccinator Orbicularis oris Platysma Orbicularis oculi Anterior Muscles Sternocleidomastoid One head of the muscle arises from the sternum and the other arises from the clavicle When both muscles contract, they flex the neck When one muscle contracts, the head rotates toward the opposite side Anterior Muscles Pectoralis Major Covers the upper part of the chest Adduct and flex the arm Anterior Muscles Pectoralis Minor Lies deep to the pectoralis major Draws down the scapula or raises the ribs Anterior Muscles Intercostal Muscles Deep muscles found between the ribs Help raise and depress the rib cage for breathing Anterior Muscles Transverse abdominis Aponeurosis Rectus Abdominis The most superficial muscles of the abdomen Flex the vertebral column Compress the abdominal contents during defecation and childbirth Involved with forced breathing Internal oblique External oblique Rectus abdominis Anterior Muscles Transverse abdominis Aponeurosis External oblique Make up the lateral walls of the abdomen Flex the vertebral column Rotate the trunk and bend it laterally Internal oblique External oblique Rectus abdominis Anterior Muscles Transverse abdominis Aponeurosis Internal oblique Deep to the external oblique Same functions as the external oblique Internal oblique External oblique Rectus abdominis Anterior Muscles Transverse abdominis Aponeurosis Transverse abdominis The deepest muscle of the abdominal wall Compresses the abdominal contents Internal oblique External oblique Rectus abdominis Anterior Muscles Transverse abdominis Aponeurosis Aponeurosis A sheetlike tendinous expansion, mainly serving to connect a muscle with the parts it moves Internal oblique External oblique Rectus abdominis Posterior Muscles Trapezius Most superficial muscles of the posterior neck and upper trunk Extend the head Elevate, depress, and adduct the scapula Posterior Muscles Latissimus Dorsi The large, flat muscle pair that covers the lower back Extends and adducts the humerus Important when executing a power stroke (swimming) or striking a blow Posterior Muscles Deltoid The main muscles for arm abduction A favored injection site of medication less than 5ml (must be given intramuscularly) Gross Anatomy of Skeletal Muscles Muscles of the Humerus Biceps brachii The main muscle for flexion of the forearm The best way to remember its action is that “it turns the corkscrew and pulls the cork” Triceps brachii The main muscle for elbow extension Called the “boxer’s” muscle because it can deliver a straight-arm knockout punch
