Chapter 8: Muscular System - Hole's Essentials of Human Anatomy & Physiology PDF

Because learning changes everything.® Chapter 08 Muscular System HOLE’S ESSENTIALS OF HUMAN ANATOMY & PHYSIOLOGY Fifteenth Edition Charles J. Welsh and Cynthia Prentice-Craver © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent o...

Because learning changes everything.® Chapter 08 Muscular System HOLE’S ESSENTIALS OF HUMAN ANATOMY & PHYSIOLOGY Fifteenth Edition Charles J. Welsh and Cynthia Prentice-Craver © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC.  8.1: Introduction to the Muscular System Muscles are organs that generate force to cause all types of movement Examples of muscle actions are walking, breathing, pumping blood, and moving food in the digestive tract The 3 types of muscle tissue in the body are skeletal, smooth, and cardiac muscle © McGraw Hill, LLC 2  8.2: Structure of a Skeletal Muscle Body contains over 600 skeletal muscles Connective tissue coverings over muscles: Layers of dense connective tissue, called fascia, surround and separate each muscle This connective tissue extends beyond the ends of the muscle, and gives rise to tendons that are fused to the periosteum of bones Sometimes muscles are connected to each other by broad sheets of connective tissue called aponeuroses © McGraw Hill, LLC 3  Connective Tissue Coverings Fascia blends with the epimysium, the layer of connective tissue around each skeletal muscle The perimysium extends inward from the epimysium; it surrounds bundles of skeletal muscle fibers, called fascicles, within each muscle Each muscle cell (fiber) is covered by a connective tissue layer called endomysium © McGraw Hill, LLC 4  Figure 8.1: A Skeletal Muscle and Its Connective Tissues Access the text alternative for these images © McGraw Hill, LLC 5  Skeletal Muscle Fibers Each muscle fiber is a single, long, cylindrical muscle cell Fibers respond to stimulation by exerting a pulling force Cell membrane of a muscle fiber is the sarcolemma Cytoplasm of a muscle cell is the sarcoplasm; it contains many mitochondria and nuclei Sarcoplasm contains parallel myofibrils, which are active in muscle contraction: Thick filaments in myofibrils consist of the protein myosin Thin filaments in myofibrils are mainly composed of the protein actin, but also contain troponin and tropomyosin The organization of these filaments produces bands called striations © McGraw Hill, LLC 6  Myofibrils and Sarcomeres Myofibrils are made up of many units called sarcomeres, joined end- to-end A sarcomere extends from one Z line to the next Striations consist of an alternating pattern of light and dark bands I bands (light bands) are made up of actin filaments, which are anchored to the Z lines A bands (dark bands) are made up of overlapping thick and thin filaments In the center of the A band is the H zone, which consists of myosin filaments only The M line, in the center of the H zone, consists of proteins that hold the myosin filaments in place © McGraw Hill, LLC 7  Figure 8.2: Structure of a Skeletal Muscle Fiber Access the text alternative for these images © McGraw Hill, LLC 8  Figure 8.3: The Structure of a Sarcomere (a): Dr. H. E. Huxley Access the text alternative for these images © McGraw Hill, LLC 9  The Sarcoplasm of a Skeletal Muscle Fiber Beneath the sarcolemma of a muscle fiber lies a network of membranous channels, called the sarcoplasmic reticulum (SR), which is the endoplasmic reticulum of a muscle cell The SR is associated with transverse (T) tubules, invaginations of the sarcolemma Each T tubule lies between 2 cisternae of the sarcoplasmic reticulum; T tubules are open to the outside of the muscle fiber The sarcoplasmic reticulum and transverse tubules activate the muscle contraction mechanism when the fiber is stimulated © McGraw Hill, LLC 10  Figure 8.4: The SR and T Tubules of the Sarcoplasm Access the text alternative for these images © McGraw Hill, LLC 11  Neuromuscular Junction 1 Skeletal muscle fibers contract only when stimulated by a motor neuron Each skeletal muscle fiber (cell) is functionally (not physically) connected to the axon of a motor neuron, creating a synapse The neuron communicates with the muscle fiber by way of chemicals called neurotransmitters, which are released at the synapse Neuromuscular junction: a synapse between a motor neuron and a muscle fiber that it regulates © McGraw Hill, LLC 12  Neuromuscular Junction 2 The cytoplasm of the distal end of the motor neuron contains numerous mitochondria and synaptic vesicles storing neurotransmitters The muscle fiber membrane in this area contains a specialized region called the motor end plate, in which the sarcolemma is tightly folded The motor end plate contains specific receptors for the neurotransmitter When an electrical impulse reaches the end of the axon of a motor neuron, synaptic vesicles release neurotransmitter into the synaptic cleft, the gap between the membranes of the neuron and muscle fiber The neurotransmitters diffuse across the cleft, bind to the motor end plate, and stimulate the muscle fiber to contract © McGraw Hill, LLC 13  Figure 8.5: A Neuromuscular Junction Access the text alternative for these images © McGraw Hill, LLC 14  8.3: Skeletal Muscle Contraction Muscle contraction involves several events, that result in the shortening of sarcomeres, and the pulling of the muscle against its attachments The pulling force is exerted by the binding of myosin molecules to actin molecules The shortening of a muscle fiber results from an increase in the overlap between actin and myosin filaments, as they slide past each other Shortening of muscle fibers results in shortening of the entire muscle, which then pulls on the attached body part to cause movement © McGraw Hill, LLC 15  Role of Myosin and Actin 1 Myosin molecules consist of two twisted strands, with globular heads projected outward along the strands A group of myosin molecules forms a thick filament Actin molecules consist of globular proteins arranged in twisted filaments (a double helix), containing myosin binding sites Troponin and tropomyosin are 2 proteins associated with the surface of the actin molecules; together, these 3 proteins form the thin filaments © McGraw Hill, LLC 16  Figure 8.6: Thin and Thick Filaments Access the text alternative for these images © McGraw Hill, LLC 17  Role of Myosin and Actin 2 According to the sliding filament model of muscle contraction, during muscle contraction, a myosin head attaches to a binding site on the actin filament, forming a cross-bridge This binding causes the head to bend, pulling on the actin filament, and moving it toward the center of the sarcomere The head then releases, and attaches to the next binding site on the actin, pulling this site toward the center As this occurs again and again, the filaments increase their overlap, and the sarcomere shortens from both ends When many sarcomeres shorten at the same time, the muscle fiber shortens Energy from the conversion of ATP to ADP is provided to the cross-bridges by the enzyme ATPase; ATP breakdown causes the heads to return to the “cocked” position, ready to bind to another actin binding site After death, skeletal muscles contract partially and become rigid, which is called rigor mortis; due to increased calcium permeability, cross-bridge formation, and decreased ATP, which prevents muscle relaxation. © McGraw Hill, LLC 18  Figure 8.7: The Sliding Filament Model Access the text alternative for these images © McGraw Hill, LLC 19  Figure 8.8: Sarcomere Shortening in Muscle Contraction (b): Dr. H. E. Huxley Access the text alternative for these images © McGraw Hill, LLC 20  Stimulus for Contraction 1 Acetylcholine is the neurotransmitter for skeletal muscle fiber contraction at the neuromuscular junctions Acetylcholine is produced in the motor neuron, and stored in the synaptic vesicles at the distal end of the neuron Acetylcholine is released into the synaptic cleft in response to an impulse in the motor neuron; it then stimulates the muscle fiber Upon receipt of the muscle impulse, the sarcoplasmic reticulum releases its stored calcium to the cytosol of the muscle fiber The high concentration of calcium in the sarcoplasm interacts with the troponin and tropomyosin molecules, which move aside, exposing the myosin binding sites on the actin filaments Cross-bridges now form, and pull on the actin filaments, using the energy of ATP; this causes the sarcomere to shorten © McGraw Hill, LLC 21  Stimulus for Contraction 2 The contraction continues as long as the nerve impulse continues After the nerve impulse stops, these events lead to relaxation of the muscle: The enzyme acetylcholinesterase, in the motor end plate, rapidly decomposes the acetylcholine Calcium is returned to the sarcoplasmic reticulum, using ATP as an energy source ATP now binds to the myosin heads, and the linkages between myosin and actin are broken The actin returns to its original position and the muscle relaxes © McGraw Hill, LLC 22  Major Events of Muscle Contraction TABLE 8.1 Major Events of Muscle Contraction and Relaxation Muscle Fiber Contraction 1. An impulse travels down a motor neuron axon. 2. The motor neuron releases the neurotransmitter acetylcholine (ACh). 3. ACh binds to ACh receptors in the muscle fiber membrane. 4. The sarcolemma is stimulated. An impulse travels over the surface of the muscle fiber and deep into the fiber through the transverse tubules. 5. The impulse reaches the sarcoplasmic reticulum, and calcium channels open. 6. Calcium ions diffuse from the sarcoplasmic reticulum into the cytosol and bind to troponin molecules. 7. Tropomyosin molecules move and expose specific sites on actin where myosin heads can bind. 8. Cross-bridges form, linking thin and thick filaments. 9. Thin filaments are pulled toward the center of the sarcomere by pulling of the cross-bridges. 10. The muscle fiber exerts a pulling force on its attachments as a contraction occurs. © McGraw Hill, LLC 23  Major Events of Muscle Relaxation TABLE 8.1 Major Events of Muscle Contraction and Relaxation Muscle Fiber Relaxation 1. Acetylcholinesterase decomposes acetylcholine, and the muscle fiber membrane is no longer stimulated. 2. Calcium ions are actively transported into the sarcoplasmic reticulum. 3. ATP breaks cross-bridge linkages between actin and myosin filaments without breakdown of the ATP itself. 4. Breakdown of ATP “cocks” the myosin heads. 5. Troponin and tropomyosin molecules block the interaction between myosin and actin filaments. 6. The muscle fiber remains relaxed, yet ready, until stimulated again. © McGraw Hill, LLC 24  Energy Sources for Contraction Energy for muscle fiber contraction comes from molecules of ATP; this chemical is in limited supply, and so must be regenerated The initial source of energy for muscle contraction is ATP that is stored in the muscle Creatine phosphate is present to initially regenerate ATP from ADP and phosphate, as it also contains high energy bonds Whenever the supply of ATP is sufficient, the enzyme creatine phosphokinase promotes the synthesis of creatine phosphate As ATP decomposes, the energy from creatine phosphate can be transferred to ADP molecules, converting them back to ATP Creatine phosphate is rapidly used up too, and as its supply declines, the cell must rely on cellular respiration to generate ATP © McGraw Hill, LLC 25  Figure 8.9: Creatine Phosphate Regenerates ATP Access the text alternative for these images © McGraw Hill, LLC 26  Oxygen Supply and Cellular Respiration Glycolysis is the first phase of cellular respiration; it is anaerobic and occurs in the cytoplasm Glycolysis is an incomplete breakdown of glucose, and yields 2 ATP per molecule of glucose Aerobic respiration is a complete breakdown of glucose; it is aerobic (requires oxygen) and occurs in the mitochondria Aerobic respiration yields 28 ATP per molecule of glucose Hemoglobin in red blood cells carries oxygen to muscle tissue The pigment myoglobin stores oxygen in muscle tissue for aerobic respiration; this increases oxygen availability © McGraw Hill, LLC 27  Figure 8.10: Overview of Cellular Respiration of Glucose Access the text alternative for these images © McGraw Hill, LLC 28  Oxygen Debt 1 During rest or moderate activity, there is enough oxygen available to support aerobic respiration Oxygen deficiency may develop during 1 to 2 minutes of strenuous exercise In this case, pyruvic acid forms, and then reacts to form lactic acid, which accumulates as an end product of anaerobic respiration in the form of lactate Lactate diffuses out of muscle cells and is carried in the bloodstream to the liver Using ATP, liver cells convert lactate back into glucose During strenuous exercise, oxygen is used to produce ATP for muscle contraction, rather than for converting lactate back to glucose As lactate builds up, an oxygen debt develops; this must be repaid © McGraw Hill, LLC 29  Oxygen Debt 2 Oxygen debt refers to the amount of oxygen that liver cells require to convert the accumulated lactate back into glucose, plus the amount that muscle cells need to resynthesize ATP and creatine phosphate to their original concentrations Oxygen debt is also called excess post-exercise oxygen consumption (EPOC) Repaying the oxygen debt may take several hours Physical training helps to increase a muscle’s capacity to improve energy production © McGraw Hill, LLC 30  Muscle Metabolism TABLE 8.2 Muscle Metabolism Type of Low to moderate intensity: Blood High intensity: Oxygen Exercise flow provides sufficient oxygen supply is not sufficient for for cellular requirements cellular requirements Pathway Glycolysis,leading to pyruvic acid Glycolysis, leading to lactic Used formation and aerobic acid formation respiration ATP 30 ATP per glucose for skeletal 2 ATP per glucose Production muscle Waste Carbon dioxide is exhaled Lactic acid accumulates Product © McGraw Hill, LLC 31  Heat Production and Muscle Fatigue Less than half of energy released in reactions of cellular respiration is used to form ATP; the rest becomes heat This heat is carried by the blood to other tissues, and helps maintain body temperature When a muscle loses its ability to contract during strenuous exercise, it is referred to as fatigue Muscle fatigue may arise from electrolyte imbalances and decreased ATP levels A decrease in pH due to lactic acid accumulation may have a role in muscle fatigue A muscle cramp, a sustained, painful, involuntary contraction, is thought to occur due to changes in the extracellular fluid around the muscle fibers, leading to uncontrolled muscle fiber stimulation by its motor neurons © McGraw Hill, LLC 32  Types of Muscle Fibers Skeletal muscle fibers are classified as fast or slow fibers Fast fibers: Make up majority of muscle fibers Rapid movements, reach maximum force quickly, fatigue quickly Large diameter Few mitochondria, store glycogen; anaerobic metabolism Powerful contractions, but best for short-term activities Slow fibers: Small diameter Takes longer to reach peak tension, but resistant to fatigue Provide prolonged contraction; used in endurance activities Many mitochondria and capillaries; aerobic metabolism © McGraw Hill, LLC 33  Exercise and Muscle Use Skeletal muscles respond to changes in activity level Hypertrophy: enlargement of a muscle due to repeated exercise Atrophy: decrease in muscle size and strength, due to disuse Type of exercise determines responses of the muscle: Low intensity exercise causes slow fibers to increase mitochondria and capillaries; they become more fatigue-resistant, but maintain size and strength Forceful exercise causes fast fibers to increase numbers of actin and myosin filaments, which enlarges fibers and entire muscle; this allows for stronger contractions. Number of skeletal muscle fibers does not change with hypertrophy or atrophy © McGraw Hill, LLC 34  8.4: Muscular Responses One method of studying muscle function is to remove a single fiber and connect it to a device that records its responses to electrical stimulation Isolated muscle fibers in a lab can be exposed to stimuli of various strengths; fibers will be unresponsive until the threshold stimulus is reached Threshold Stimulus: the minimum strength of stimulus required to generate a impulse through the muscle fiber, release calcium ions, activate cross-bridges, and contract the muscle In the body, one motor neuron impulse releases sufficient acetylcholine (ACh) in the neuromuscular junction to bring a muscle fiber to its threshold © McGraw Hill, LLC 35  Recording of a Muscle Contraction The response of a single muscle fiber to a single impulse is referred to as a twitch; a twitch consists of a cycle of contraction and relaxation A myogram is the recording of an electrically-stimulated muscle contraction The latent period is a brief delay between the stimulation and beginning of the contraction The latent period is followed by a period of contraction and a period of relaxation When a muscle fiber contracts, it contracts to its full extent, with each twitch generating the same force; this is called the all-or-none response © McGraw Hill, LLC 36  Figure 8.11: Myogram of a Single Muscle Twitch Access the text alternative for these images © McGraw Hill, LLC 37  Summation A muscle fiber receiving a series of stimuli of increasing frequency reaches a point when it is unable to relax completely, and the force of individual twitches combine by the process of summation Summation allows for a greater force of contraction than a single twitch can generate When exposed to higher frequency of stimulation, relaxation time becomes very short; this is called partial tetany If the frequency of stimulation is very high, and the sustained contraction lacks any relaxation, it is called a complete tetanic contraction Partial tetany occurs in the body, but complete tetany can only be accomplished in a lab © McGraw Hill, LLC 38  Figure 8.12: Myograms of Twitches, Summation, and Tetanic Contraction Access the text alternative for these images © McGraw Hill, LLC 39  Recruitment of Motor Units A motor neuron and the muscle fibers it controls make up a motor unit; when stimulated, the muscle fibers of the motor unit contract all at once An increase in the number of activated motor units within a muscle at higher intensities of stimulation is called motor unit recruitment Recruitment causes an increase in the strength of a contraction A muscle achieves maximum tension when all of its motor units have been recruited © McGraw Hill, LLC 40  Figure 8.13: Portions of Two Motor Units Access the text alternative for these images © McGraw Hill, LLC 41  Sustained Contractions and Muscle Tone Summation and recruitment together can produce a sustained contraction of increasing strength Sustained contraction of muscles allow for performance of daily activities Muscle tone is a continuous state of sustained contraction of a few motor units at a time within a muscle, even when at rest Muscle tone is important for maintenance of posture © McGraw Hill, LLC 42  Types of Contractions Muscles do not have to shorten to generate force Types of muscle contractions: Isotonic (“same tension”) contraction: Involves shortening of muscle Associated with movement, such as lifting a weight As muscle shortens, tension remains the same Isometric (“same measurement”) contraction: Involves force generation without shortening Force is used to resist overstretching and oppose gravity Example: holding a weight in one position Most movements are a combination of both types of contraction © McGraw Hill, LLC 43  8.5: Smooth Muscle Smooth Muscle Cells: Smooth muscle cells are elongated with tapered ends, lack striations (look “smooth”), and have a relatively undeveloped sarcoplasmic reticulum Contain thick and thin filaments, but they are arranged more randomly Types of Smooth Muscle: In multiunit smooth muscle, such as in the blood vessels and iris of the eye, fibers occur separately rather than as sheets; stimulated by neurons and some hormones Visceral smooth muscle occurs in sheets, and is found in the walls of hollow organs; these fibers can stimulate one another and display rhythmicity; these features accomplish peristalsis in tubular organs © McGraw Hill, LLC 44  Smooth Muscle Contraction Similarities to skeletal muscle contraction: Both types involve reaction between actin and myosin Both types are stimulated by membrane impulses, require an increase in calcium ions in the cells, and use ATP energy Differences from skeletal muscle contraction: Both acetylcholine (ACh) and norepinephrine stimulate and inhibit smooth muscle contraction, while only ACh stimulates skeletal muscle Hormones can stimulate or inhibit contraction of smooth muscle, but not skeletal muscle Smooth muscle is slower to contract and relax Smooth muscle maintains a contraction longer with the same amount of ATP Smooth muscle can change length without change in tautness © McGraw Hill, LLC 45  8.6: Cardiac Muscle Cardiac muscle is only found in the heart Cardiac muscle consists of branching, striated cells that interconnect in three-dimensional networks The mechanism of contraction in cardiac muscle is essentially the same as that for skeletal and smooth muscle, but with some differences: Sarcoplasmic reticulum is not well-developed; does not store much calcium Transverse tubules supply extra calcium from extracellular fluid, so cardiac muscle cell twitches last longer Cardiac muscle is self-exciting and rhythmic, creating a pattern of contraction and relaxation Complex membrane junctions, called intercalated discs, join cells and transmit the force of contraction from one cell to the next © McGraw Hill, LLC 46  Types of Muscle Tissue TABLE 8.3 Types of Muscle Tissue Skeletal Smooth Cardiac Major Location Skeletal muscles Walls of hollow viscera, Wall of the heart blood vessels Major Function Movement of bones at Movement of viscera, Pumping action of the heart joints, maintenance of peristalsis, posture vasoconstriction Cellular characteristics Striations Present Absent Present Nucleus Many nuclei Single nucleus Single nucleus Special features Well-developed Lacks transverse tubules Well-developed transverse transverse tubule system tubule system; intercalated discs separating adjacent cells Mode of Control Voluntray Involuntray Involuntary Contraction Contracts and relaxes Contracts and relaxes Network of cells contracts as Characteristics rapidly when stimulated slowly; single unit type a unit; self-exciting; by a motor neuron is self-exciting; rhythmic rhythmic © McGraw Hill, LLC 47  8.7: Skeletal Muscle Actions Origin: the less movable end of a skeletal muscle Insertion: the more movable end of a skeletal muscle Muscle contraction pulls the insertion toward the origin Some muscles have more than one insertion or origin Example: Biceps brachii in the arm “Biceps” means 2 origins or heads Both heads attach to portions of the scapula (coracoid process and tubercle above glenoid cavity) Insertion is the radial tuberosity of the radius Muscle is located on the anterior surface of humerus Action is flexion of the forearm at the elbow © McGraw Hill, LLC 48  Figure 8.14: The Biceps Brachii: Origins and Insertion Access the text alternative for these images © McGraw Hill, LLC 49  Skeletal Muscle Movements: Levers Body Movements: Bones and muscles interact as levers for movement Bending and straightening of the arm (upper limb) at the elbow is a good example of bones and muscles acting as levers Parts of a lever, using the bending of the upper limb as an example: Rigid bar or rod: forearm bones Fulcrum or pivot, on which bar turns; elbow joint Object moved against resistance: the hand is moved against the resistance of a weight being lifted Force supplying energy for movement: anterior arm muscles Bending is accomplished by the Biceps brachii muscle pulling on its tendon as it contracts; the tendon is attached to the radius, a bone of the forearm © McGraw Hill, LLC 50  Figure 8.15: Levers and Movement Access the text alternative for these images © McGraw Hill, LLC 51  Muscle Relationships Common changes in the angle & opposing movements between bones at a joint: Flexion: decrease in the angle between bones at a joint Example: flexion of the arm at the elbow bends the arm Extension: increase in the angle between bones at a joint Example: extension of the arm at the elbow straightens the arm Skeletal muscles usually function in groups: The muscle that causes an action, and does the majority of the work is the agonist (prime mover) Muscles that assist the prime mover are called synergists Muscles that oppose an action are called antagonists The relationships between muscles depends on the action; a muscle can be a synergist for one action and an antagonist for another action © McGraw Hill, LLC 52  8.8: Major Skeletal Muscles Skeletal muscles are named according to any of these: size, shape, location, action, number of attachments, direction of its fibers, or combinations of the above. Examples: Pectoralis major: named for size and location; large size, located in chest Deltoid: named for shape; shaped like a triangle Extensor digitorum: named for action; extends digits (fingers, toes) Biceps brachii: named for number of attachments and location; has 2 origins/heads, and is found in the arm (brachium) Sternocleidomastoid: named for attachments; attaches to sternum, clavicle, and mastoid process External oblique: named for location and direction of fibers; located near outside of body, and fibers run at a slant © McGraw Hill, LLC 53  Figure 8.16: Anterior View of Superficial Skeletal Muscles Access the text alternative for these images © McGraw Hill, LLC 54  Figure 8.17: Posterior View of Superficial Skeletal Muscles Access the text alternative for these images © McGraw Hill, LLC 55  Muscles of Facial Expression 1 Muscles of facial expression attach to underlying bones and overlying connective tissue of skin They are responsible for the variety of facial expressions possible in the human face, communicating anger, fear, pain, disgust, surprise, happiness Major muscles include the epicranius, orbicularis oculi, orbicularis oris, buccinator, zygomaticus, and platysma © McGraw Hill, LLC 56  Figure 8.18a: Muscles of the Face and Neck: Lateral View Access the text alternative for these images © McGraw Hill, LLC 57  Muscles of Facial Expression 2 TABLE 8.4 Muscles of Facial Expression Muscle Origin Insertion Action Epicranius Occipital bone Skin around eye Elevates eyebrow Orbicularis Maxilla and frontal Skin around eye Closes eye oculi bone Orbicularis Muscle near the Skin of lips Closes and protrudes oris mouth lips Buccinator Alveolar processes Orbicularis oris Compresses cheeks of maxilla and mandible Zygomaticus Zygomatic bone Skin and muscle at corner Elevates corner of of mouth mouth Platysma Fascia in upper Skin and muscles below Depresses lower lip chest mouth and angle of mouth © McGraw Hill, LLC 58  Muscles of Mastication 1 Chewing movements are derived from muscles attached to the mandible Chewing muscles that elevate the mandible include the masseter and temporalis © McGraw Hill, LLC 59  Muscles of Mastication 2 TABLE 8.5 Muscles of Mastication Muscle Origin Insertion Action Masseter Zygomatic arch Posterior lateral Elevates and protracts surface of mandible mandible Temporalis Temporal bone Coronoid process of Elevates and retracts mandible mandible © McGraw Hill, LLC 60  Muscles that Move the Head 1 Paired muscles in the neck and upper back cause flexion, extension, and rotation of the head Major muscles include the sternocleidomastoid, splenius capitis, semispinalis capitis, and scalenes © McGraw Hill, LLC 61  Figure 8.18b: Muscles That Move the Head Access the text alternative for these images © McGraw Hill, LLC 62  Muscles That Move the Head 2 TABLE 8.6 Muscles That Move the Head Muscle Origin Insertion Action Sternocleidomastoid Manubrium of Mastoid process of Individually: laterally flexes head and neck to the sternum and medial temporal bone same side, rotates head to the opposite side. clavicle Together: pull the head forward and down; also aid in forceful inhalation by elevating sternum and first ribs. Splenius capitis Ligamentum nuchae; Occipital bone and Individually: rotates head to the same side spinous processes of mastoid process of 7th cervical and upper temporal bone Together: bring head into an upright position thoracic vertebrae Semispinalis capitis Below the articular Occipital bone Individually: rotates head to the opposite side facets of lower cervical vertebrae; Together: extend head and neck transverse processes of upper thoracic vertebrae Scalenes Transverse processes Superior and lateral Individually: laterally flexes head and neck to the of cervical vertebrae surface of first two same side ribs Together: elevate first two ribs during forceful inhalation © McGraw Hill, LLC 63  Muscles That Move the Pectoral Girdle 1 Muscles that move the pectoral girdle are associated with those that move the arm Several chest and shoulder muscles move the scapula Major muscles include the trapezius, rhomboid major, levator scapulae, serratus anterior, and pectoralis minor © McGraw Hill, LLC 64  Figure 8.19: Muscles of the Posterior Shoulder Access the text alternative for these images © McGraw Hill, LLC 65  Figure 8.20: Muscles of Anterior Chest and Abdominal Wall Access the text alternative for these images © McGraw Hill, LLC 66  Muscles that Move the Pectoral Girdle 2 TABLE 8.7 Muscles That Move the Pectoral Girdle Muscle Origin Insertion Action Trapezius Occipital bone, ligamentum Clavicle; spine and Rotates and retracts scapula nuchae, and spinous acromion process of processes of 7th cervical and scapula Superior portion elevates scapula all thoracic vertebrae Inferior portion depresses scapula Rhomboid Spinous processes of upper Medial border of Elevates and retracts scapula major thoracic vertebrae scapula Levator Transverse processes of Superior angle and Elevates scapula scapulae cervical vertebrae medial border of scapula Serratus Anterior surfaces of ribs 1 to Medial border of Protracts and rotates scapula anterior 10 scapula Pectoralis Anterior surfaces of ribs 3 to Coracoid process of Depresses and protracts scapula, minor 5 scapula elevates ribs during forceful inhalation © McGraw Hill, LLC 67  Muscles that Move the Arm 1 Muscles connect the arm to the pectoral girdle, ribs, and vertebral column, making the arm freely movable Muscles can be grouped by action: Flexors include the coracobrachialis and pectoralis major Extensors include the teres major and latissimus dorsi Abductors include the supraspinatus and the deltoid Rotators are the subscapularis, infraspinatus, and teres minor © McGraw Hill, LLC 68  Muscles that Move the Arm 2 TABLE 8.8 Muscles That Move the Arm Muscle Origin Insertion Action Coracobrachialis Coracoid process of scapula Medial midshaft of humerus Flexes arm at shoulder, adducts arm Pectoralis major Clavicle, sternum, and costal Intertubercular sulcus of Flexes arm at shoulder, adducts and cartilages of upper ribs humerus medially rotates arm Teres major Lateral border of scapula Intertubercular sulcus of Extends arm at shoulder, adducts and humerus medially rotates arm Latissimus dorsi Spinous processes of lower Intertubercular sulcus of Extends arm at shoulder, adducts and thoracic and lumbar humerus medially rotates arm vertebrae, iliac crest, and lower ribs Supraspinatus Supraspinous fossa of scapula Greater tubercle of humerus Abducts arm Deltoid Acromion process, spine of Deltoid tuberosity of Lateral portion abducts arm scapula, and clavicle humerus Anterior portion flexes arm at shoulder Posterior portion extends arm at shoulder Subscapularis Anterior surface of scapula Lesser tubercle of humerus Medially rotates arm Infraspinatus Infraspinous fossa of scapula Greater tubercle of humerus Laterally rotates arm Teres minor Lateral border of scapula Greater tubercle of humerus Laterally rotates arm © McGraw Hill, LLC 69  Muscles that Move the Forearm 1 Most forearm movements are accomplished by muscles that arise from the humerus or pectoral girdle and connect to the ulna and radius Muscles on the anterior side of the humerus cause flexion of the elbow; one muscle on the posterior side of the humerus causes extension of the elbow Flexors are the biceps brachii, brachialis, and brachioradialis The extensor is the triceps brachii muscle Rotators include the supinator, pronator teres, and pronator quadratus © McGraw Hill, LLC 70  Figure 8.21: Muscles of the Posterior Scapula and Arm Access the text alternative for these images © McGraw Hill, LLC 71  Figure 8.22: Muscles of the Anterior Shoulder and Arm Access the text alternative for these images © McGraw Hill, LLC 72  Figure 8.23: Muscles of the Anterior Forearm Access the text alternative for these images © McGraw Hill, LLC 73  Muscles that Move the Forearm 2 TABLE 8.9 Muscles That Move the Forearm Muscle Origin Insertion Action Biceps brachii Coracoid process (short head); Radial tuberosity Flexes forearm at elbow, tubercle above glenoid cavity of supinates forearm and scapula (long head) hand Brachialis Anterior surface of humerus Coronoid process of ulna Flexes forearm at elbow Brachioradialis Distal lateral end of humerus Lateral surface of radius Flexes forearm at elbow above styloid process Triceps brachii Tubercle below glenoid cavity of Olecranon process of Extends forearm at elbow scapula(long head); lateral surface ulna of humerus(lateral head); posterior surface of humerus(lateral and medial heads) Supinator Lateral epicondyle of humerus Anterior and lateral Supinates forearm and and proximal ulna surface of radius hand Pronator teres Medial epicondyle of humerus Lateral surface of radius Pronates forearm and hand and coronoid process of ulna Pronator Anterior distal end of ulna Anterior distal end of Pronates forearm and hand quadratus radius © McGraw Hill, LLC 74  Muscles that Move the Hand 1 Hand movements are caused by many muscles Movements of the hand are caused by muscles originating from the distal humerus, the radius and the ulna Flexors (on the anterior side) include the flexor carpi radialis, flexor carpi ulnaris, palmaris longus, and flexor digitorum profundus Extensors (on the posterior side) include the extensor carpi radialis longus, extensor carpi radialis brevis, extensor carpi ulnaris, and extensor digitorum © McGraw Hill, LLC 75  Figure 8.24: Muscles of the Posterior Forearm Access the text alternative for these images © McGraw Hill, LLC 76  Muscles that Move the Hand 2 TABLE 8.10 Muscles That Move the Hand Muscle Origin Insertion Action Flexor carpi radialis Medial epicondyle of Base of second and third Flexes wrist, abducts hand humerus metacarpals Flexor carpi ulnaris Medial epicondyle of Carpal bones and fifth Flexes wrist, adducts hand humerus and olecranon metacarpal bone process of ulna Palmaris longus Medial epicondyle of Fascia of palm Flexes wrist humerus Flexor digitorum profundus Anterior and medial surface Distal phalanges of Flexes wrist and joints of of ulna fingers 2 to 5 fingers Extensor carpi radialis longus Lateral distal end of humerus Base of second Extends wrist, abducts hand metacarpal Extensor carpi radialis brevis Lateral epicondyle of humerus Base of third metacarpal Extends wrist, abducts hand Extensor carpi ulnaris Lateral epicondyle of humerus Base of fifth metacarpal Extends wrist, adducts hand and proximal, posterior ulna Extensor digitorum Lateral epicondyle of humerus Posterior surface of Extends wrist and joints of phalanges in fingers 2 to fingers 5 © McGraw Hill, LLC 77  Muscles of the Abdominal Wall 1 Abdominal wall is not supported by bone, which is unlike walls of chest and pelvic regions Abdominal wall is instead supported by broad, flattened muscles This group of muscles connects the rib cage and vertebral column to the pelvic girdle A band of tough connective tissue, the linea alba, extending from the xiphoid process to the symphysis pubis, serves as an attachment for certain abdominal wall muscles Contraction of abdominal wall muscles increases abdominal pressure and decreases size of abdominal cavity The 4 muscles of the abdominal wall are the: external oblique, internal oblique, transverse abdominis, and rectus abdominis © McGraw Hill, LLC 78  Figure 8.20: Muscles of the Abdominal Wall Access the text alternative for these images © McGraw Hill, LLC 79  Muscles of the Abdominal Wall 2 TABLE 8.11 Muscles of the Abdominal Wall Muscle Origin Insertion Action External Outer surfaces of lower 8 Outer lip of iliac Compresses abdomen, Oblique ribs crest and linea alba flexes and rotates vertebral column Internal Iliac crest and inguinal Lower 3 to 4 ribs, Compresses abdomen, oblique ligament linea alba, and crest flexes and rotates vertebral of pubis column Transversus Costal cartilages of lower Linea alba and crest Compresses abdomen abdominis 6 ribs, processes of of pubis lumbar vertebrae, lip of iliac crest, and inguinal ligament Rectus Crest of pubis and pubic Xiphoid process of Compresses abdomen, abdominis symphysis sternum and costal flexes vertebral column cartilages of ribs 5 to 7 © McGraw Hill, LLC 80  Muscles of the Pelvic Floor 1 2 muscular sheets close off the inferior outlet of the pelvis, and form floor of pelvis: The deeper pelvic diaphragm forms the outlet of the pelvic cavity; muscles include the levator ani and coccygeus The superficial urogenital diaphragm fills the space within the pubic arch; muscles include the superficial transverse perineal, bulbospongiosus, and ischiocavernosus © McGraw Hill, LLC 81  Figure 8.25: Muscles of the Pelvic Floor in Males and Females Access the text alternative for these images © McGraw Hill, LLC 82  Muscles of the Pelvic Floor 2 TABLE 8.12 Muscles of the Pelvic Floor Muscle Origin Insertion Action Levator ani Pubis and ischial Coccyx Supports pelvic viscera, spine compresses anal canal Coccygeus Ischial spine Sacrum and coccyx Supports pelvic viscera, compresses anal canal Superficial Ischial tuberosity Central tendon Supports pelvic viscera transversus perinei Bulbospongiosus Central tendon Males: Corpus cavernosa of Males: Assists emptying of penis urethra, assists erection of penis Females: Corpus cavernosa Females: Constricts vagina, assists of clitoris erection of clitoris Ischiocavernosus Ischial tuberosity Males: Corpus cavernosa of Males: Contributes to erection of penis the penis Females: Corpus cavernosa Females: Contributes to erection of clitoris of the clitoris © McGraw Hill, LLC 83  Muscles that Move the Thigh 1 The muscles that move the thigh are attached to the femur and to the pelvic girdle They are classified in anterior, medial, and posterior groups Anterior group muscles: Flex the thigh Include the psoas major and iliacus Medial group muscles: Adduct the thigh Include adductor magnus, adductor longus, gracilis Posterior group muscles: Extend, abduct, or rotate thigh Include the gluteus maximus, gluteus medius, gluteus minimus, and tensor fasciae latae © McGraw Hill, LLC 84  Figure 8.26: Muscles of the Anterior Right Thigh 1 Access the text alternative for these images © McGraw Hill, LLC 85  Figure 8.27: Muscles of the Lateral Right Thigh Access the text alternative for these images © McGraw Hill, LLC 86  Figure 8.28: Muscles of the Posterior Right Thigh Access the text alternative for these images © McGraw Hill, LLC 87  Muscles that Move the Thigh 2 TABLE 8.13 Muscles That Move the Thigh Muscle Origin Insertion Action Psoas major Bodies and transverse processes Lesser trochanter of Flexes thigh at hip of lumbar vertebrae femur Iliacus Iliac fossa of ilium Lesser trochanter of Flexes thigh at hip femur Gluteus maximus Sacrum, coccyx, and posterior Posterior surface of Extends thigh at hip, laterally surface of ilium femur and fascia of rotates thigh thigh Gluteus medius Lateral surface of ilium Greater throchanter of Abducts thigh, medially rotates femur thigh Gluteus minimus Lateral surface of ilium Greater throchanter of Abducts thigh, medially rotates femur thigh Tensor fasciae latae Anterior iliac crest Fascia of thigh Abducts thigh, medially rotates thigh Adductor longus Pubic bone near pubic symphysis Posterior surface of Adducts thigh, flexes thigh at hip femur Adductor magnus Pubis and ischial tuberosity Posterior surface of Adducts thigh, extends thigh at femur hip Gracilis Lower edge of pubis Proximal medial Adducts thigh, flexes thigh at hip, surface of tibia medially rotates thigh and leg © McGraw Hill, LLC 88  Muscles that Move the Leg 1 This muscle group connects the tibia or fibula to the femur or pelvic girdle 2 major groups: flexors and extensors of the knee: Flexors: the hamstring group (biceps femoris, semitendinosus, semimembranosus), and sartorius Extensors: the quadriceps femoris group, composed of 4 muscles: rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius © McGraw Hill, LLC 89  Figure 8.26: Muscles of the Anterior Right Thigh 2 Access the text alternative for these images © McGraw Hill, LLC 90  Figure 8.28: Muscles of the Posterior Right Thigh 2 Access the text alternative for these images © McGraw Hill, LLC 91  Muscles That Move the Leg 2 TABLE 8.14 Muscles That Move the Leg Muscle Origin Insertion Action Sartorius Anterior superior iliac Proximal medial surface of tibia Flexes leg at knee, flexes thigh spine at hip, abducts thigh, laterally rotates thigh, medially rotates leg Hamstring group Biceps femoris Ischial tuberosity and Head of fibula Flexes leg at knee, extends posterior surface of thigh at hip femur Semitendinosus Ischial tuberosity Proximal medial surface of tibia Flexes leg at knee, extends thigh at hip Semimembranosus Ischial tuberosity Medial condyle of tibia Flexes leg at knee, extends thigh at hip Quadriceps femoris group Rectus femoris Anterior inferior iliac Patella, by the tendon which continues as Extends leg at knee, flexes spine and margin of patellar ligament to tibial tuberosity thigh at hip acetabulum Vastus lateralis Greater trochanter and Patella, by the tendon which continues as Extends leg at knee posterior surface of patellar ligament to tibial tuberosity femur Vastus medialis Medial surface of femur Patella, by the tendon which continues as Extends leg at knee patellar ligament to tibial tuberosity Vastus intermedius Anterior and lateral Patella, by the tendon which continues as Extends leg at knee surfaces of femur patellar ligament to tibial tuberosity © McGraw Hill, LLC 92  Muscles that Move the Foot 1 Many muscles that move the foot are found in the leg Muscles that move the foot are attached from the femur, fibula, or tibia to bones of foot These muscle move the foot in the following directions: Upward, called dorsiflexion: tibialis anterior, fibularis (peroneus) tertius, and extensor digitorum longus Downward, called plantar flexion: gastrocnemius, soleus, and flexor digitorum longus Turn sole medially, called inversion: tibialis posterior Turn sole laterally, called eversion: fibularis (peroneus) longus, and fibularis (peroneus) brevis © McGraw Hill, LLC 93  Figure 8.29: Muscles of the Anterior Right Leg Access the text alternative for these images © McGraw Hill, LLC 94  Figure 8.30: Muscles of the Lateral Right Leg Access the text alternative for these images © McGraw Hill, LLC 95  Figure 8.31: Muscles of the Posterior Right Leg Access the text alternative for these images © McGraw Hill, LLC 96  Muscles that Move the Foot 2 TABLE 8.15 Muscles That Move the Foot Muscle Origin Insertion Action Tibialis anterior Lateral condyle and lateral Tarsal bone (medial cuneiform) and Dorsiflexion and inversion of surface of tibia first metatarsal foot Fibularis tertius Anterior surface of fibula Dorsal surface of fifth metatarsal Dorsiflexion and eversion of foot Extensor Lateral condyle of tibia and Dorsal surfaces of middle and distal Dorsiflexion of foot, extension digitorum longus anterior surface of fibula phalanges of the four lateral toes of four lateral toes Gastrocnemius Lateral and medial condyles of Posterior surface of calcaneus Plantar flexion of foot, flexion femur of leg at knee Soleus Head and shaft of fibula and Posterior surface of calcaneus Plantar flexion of foot posterior surface of tibia Flexor digitorum Posterior surface of tibia Distal phalanges of the four lateral Flexion of the four lateral toes longus toes Tibialis posterior Lateral condyle and posterior Tarsal and metatarsal bones Inversion and plantar flexion of surface of tibia, and posterior foot surface of fibula Fibularis longus Lateral condyle of tibia and Tarsal bone (medial cuneiform) and Eversion and plantar flexion of head and shaft of fibula first metatarsal foot; also supports arch Fibularis brevis Lower lateral surface of fibula Base of fifth metatarsal Eversion and plantar flexion of foot © McGraw Hill, LLC 97  Because learning changes everything. ® www.mheducation.com © McGraw Hill LLC. 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