Essentials of Human Anatomy & Physiology Chapter 6 PDF

Chapter 6 The Muscular System Lecture Presentation by Patty Bostwick-Taylor Florence-Darlington Technical C...

Chapter 6 The Muscular System Lecture Presentation by Patty Bostwick-Taylor Florence-Darlington Technical College © 2018 Pearson Education, Inc.  The Muscular System ▪ Muscles are responsible for all types of body movement ▪ Three basic muscle types are found in the body 1. Skeletal muscle 2. Cardiac muscle 3. Smooth muscle © 2018 Pearson Education, Inc.  Muscle Types ▪ Skeletal and smooth muscle cells are elongated (muscle cell = muscle fiber) ▪ Contraction and shortening of muscles are due to the movement of microfilaments ▪ All muscles share some terminology ▪ Prefixes myo- and mys- refer to ―muscle‖ ▪ Prefix sarco- refers to ―flesh‖ © 2018 Pearson Education, Inc. Table 6.1 Comparison of Skeletal, Cardiac, and Smooth Muscles © 2018 Pearson Education, Inc. Table 6.1 Comparison of Skeletal, Cardiac, and Smooth Muscles (1 of 2) © 2018 Pearson Education, Inc. Table 6.1 Comparison of Skeletal, Cardiac, and Smooth Muscles (2 of 2) © 2018 Pearson Education, Inc.  Muscle Types ▪ Skeletal muscle ▪ Most skeletal muscle fibers are attached by tendons to bones ▪ Skeletal muscle cells are large, cigar-shaped, and multinucleate ▪ Also known as striated muscle because of its obvious stripes ▪ Also known as voluntary muscle because it is the only muscle tissue subject to conscious control © 2018 Pearson Education, Inc.  Muscle Types ▪ Skeletal muscle cells are surrounded and bundled by connective tissue ▪ Endomysium— encloses a single muscle fiber ▪ Perimysium—wraps around a fascicle (bundle) of muscle fibers ▪ Epimysium—covers the entire skeletal muscle ▪ Fascia—on the outside of the epimysium © 2018 Pearson Education, Inc.  Muscle Types ▪ The epimysium of skeletal muscle blends into a connective tissue attachment ▪ Tendons—cordlike structures ▪ Mostly collagen fibers ▪ Often cross a joint because of their toughness and small size ▪ Aponeuroses—sheetlike structures ▪ Attach muscles indirectly to bones, cartilages, or connective tissue coverings © 2018 Pearson Education, Inc.  Muscle Types ▪ Smooth muscle ▪ No striations ▪ Involuntary—no conscious control ▪ Found mainly in the walls of hollow visceral organs (such as stomach, urinary bladder, respiratory passages) ▪ Spindle-shaped fibers that are uninucleate ▪ Contractions are slow and sustained © 2018 Pearson Education, Inc.  Muscle Types ▪ Cardiac muscle ▪ Striations ▪ Involuntary ▪ Found only in the walls of the heart ▪ Uninucleate ▪ Branching cells joined by gap junctions called intercalated discs ▪ Contracts at a steady rate set by pacemaker © 2018 Pearson Education, Inc.  Muscle Functions ▪ Whereas all muscle types produce movement, skeletal muscle has three other important roles: ▪ Maintain posture and body position ▪ Stabilize joints ▪ Generate heat © 2018 Pearson Education, Inc.  Microscopic Anatomy of Skeletal Muscle ▪ Sarcolemma—specialized plasma membrane ▪ Myofibrils—long organelles inside muscle cell ▪ Light (I) bands and dark (A) bands give the muscle its striated (banded) appearance © 2018 Pearson Education, Inc.  Microscopic Anatomy of Skeletal Muscle ▪ Banding pattern of myofibrils ▪ I band = light band ▪ Contains only thin filaments ▪ Z disc is a midline interruption ▪ A band = dark band ▪ Contains the entire length of the thick filaments ▪ H zone is a lighter central area ▪ M line is in center of H zone © 2018 Pearson Education, Inc.  Microscopic Anatomy of Skeletal Muscle ▪ Sarcomere—contractile unit of a muscle fiber ▪ Structural and functional unit of skeletal muscle ▪ Organization of the sarcomere ▪ Myofilaments produce banding (striped) pattern ▪ Thick filaments = myosin filaments ▪ Thin filaments = actin filaments © 2018 Pearson Education, Inc.  Microscopic Anatomy of Skeletal Muscle ▪ Thick filaments = myosin filaments ▪ Composed of the protein myosin ▪ Contain ATPase enzymes to split ATP to release energy for muscle contractions ▪ Possess projections known as myosin heads ▪ Myosin heads are known as cross bridges when they link thick and thin filaments during contraction © 2018 Pearson Education, Inc.  Microscopic Anatomy of Skeletal Muscle ▪ Thin filaments = actin filaments ▪ Composed of the contractile protein actin ▪ Actin is anchored to the Z disc ▪ At rest, within the A band there is a zone that lacks actin filaments called the H zone ▪ During contraction, H zones disappear as actin and myosin filaments overlap © 2018 Pearson Education, Inc. Figure 6.3c Anatomy of a skeletal muscle fiber (cell). Sarcomere M line Z disc Z disc Thin (actin) myofilament Thick (myosin) myofilament (c) Sarcomere (segment of a myofibril) © 2018 Pearson Education, Inc.  Microscopic Anatomy of Skeletal Muscle ▪ Sarcoplasmic reticulum (SR) ▪ Specialized smooth endoplasmic reticulum ▪ Surrounds the myofibril ▪ Stores and releases calcium © 2018 Pearson Education, Inc.  Stimulation and Contraction of Single Skeletal Muscle Cells ▪ Special functional properties of skeletal muscles ▪ Irritability (also called responsiveness)—ability to receive and respond to a stimulus ▪ Contractility—ability to forcibly shorten when an adequate stimulus is received ▪ Extensibility—ability of muscle cells to be stretched ▪ Elasticity—ability to recoil and resume resting length after stretching © 2018 Pearson Education, Inc.  The Nerve Stimulus and Action Potential ▪ Skeletal muscles must be stimulated by a motor neuron (nerve cell) to contract ▪ Motor unit—one motor neuron and all the skeletal muscle cells stimulated by that neuron © 2018 Pearson Education, Inc. Figure 6.4a Motor units. Axon terminals at neuromuscular junctions Spinal cord Motor Motor unit 1 unit 2 Nerve Axon of Motor motor neuron neuron cell bodies Muscle Muscle fibers (a) © 2018 Pearson Education, Inc. Figure 6.4b Motor units. Axon terminals at Muscle neuromuscular junctions fibers Branching axon to motor unit (b) © 2018 Pearson Education, Inc.  The Nerve Stimulus and Action Potential ▪ Neuromuscular junction ▪ Association site of axon terminal of the motor neuron and sarcolemma of a muscle ▪ Neurotransmitter ▪ Chemical released by nerve upon arrival of nerve impulse in the axon terminal ▪ Acetylcholine (ACh) is the neurotransmitter that stimulates skeletal muscle © 2018 Pearson Education, Inc.  The Nerve Stimulus and Action Potential ▪ Synaptic cleft ▪ Gap between nerve and muscle filled with interstitial fluid ▪ Although very close, the nerve and muscle do not make contact © 2018 Pearson Education, Inc.  The Nerve Stimulus and Action Potential ▪ When a nerve impulse reaches the axon terminal of the motor neuron, Step 1: Calcium channels open, and calcium ions enter the axon terminal Step 2: Calcium ion entry causes some synaptic vesicles to release acetylcholine (ACh) Step 3: ACh diffuses across the synaptic cleft and attaches to receptors on the sarcolemma of the muscle cell © 2018 Pearson Education, Inc.  The Nerve Stimulus and Action Potential Step 4: If enough ACh is released, the sarcolemma becomes temporarily more permeable to sodium ions (Na+) ▪ Potassium ions (K+) diffuse out of the cell ▪ More sodium ions enter than potassium ions leave ▪ Establishes an imbalance in which interior has more positive ions (depolarization), thereby opening more Na+ channels © 2018 Pearson Education, Inc.  The Nerve Stimulus and Action Potential Step 5: Depolarization opens more sodium channels that allow sodium ions to enter the cell ▪ An action potential is created ▪ Once begun, the action potential is unstoppable ▪ Conducts the electrical impulse from one end of the cell to the other Step 6: Acetylcholinesterase (AChE) breaks down acetylcholine into acetic acid and choline ▪ AChE ends muscle contraction ▪ A single nerve impulse produces only one contraction © 2018 Pearson Education, Inc.  The Nerve Stimulus and Action Potential ▪ Cell returns to its resting state when: 1. Potassium ions (K+) diffuse out of the cell 2. Sodium-potassium pump moves sodium and potassium ions back to their original positions © 2018 Pearson Education, Inc. Figure 6.5 Events at the neuromuscular junction. Slide 2 Myelinated axon Nerve of motor neuron impulse Axon terminal of Nucleus neuromuscular junction Sarcolemma of the muscle fiber Synaptic vesicle containing ACh 1 Nerve impulse reaches axon terminal of motor neuron. Axon terminal of motor neuron Mitochondrion Ca2+ Ca2+ Synaptic cleft Sarcolemma Fusing synaptic vesicle Sarcoplasm ACh of muscle fiber ACh Folds of receptor sarcolemma © 2018 Pearson Education, Inc. Figure 6.5 Events at the neuromuscular junction. Slide 3 Synaptic vesicle containing ACh 1 Nerve impulse reaches axon terminal of motor neuron. Axon terminal of motor neuron Mitochondrion 2 Calcium (Ca2+) channels Ca2+ Ca2+ open, and Ca2+ enters the Synaptic axon terminal. cleft Sarcolemma Fusing synaptic vesicle Sarcoplasm ACh of muscle fiber ACh Folds of receptor sarcolemma © 2018 Pearson Education, Inc. Figure 6.5 Events at the neuromuscular junction. Slide 4 Synaptic vesicle containing ACh 1 Nerve impulse reaches axon terminal of motor neuron. Axon terminal of motor neuron Mitochondrion 2 Calcium (Ca2+) channels Ca2+ Ca2+ open, and Ca2+ enters the Synaptic axon terminal. cleft Sarcolemma Fusing synaptic vesicle Sarcoplasm 3 Ca2+ entry causes some ACh of muscle fiber synaptic vesicles to release their Folds of contents (the neurotransmitter ACh receptor sarcolemma acetylcholine) by exocytosis. © 2018 Pearson Education, Inc. Figure 6.5 Events at the neuromuscular junction. Slide 5 Synaptic vesicle containing ACh 1 Nerve impulse reaches axon terminal of motor neuron. Axon terminal of motor neuron Mitochondrion 2 Calcium (Ca2+) channels Ca2+ Ca2+ open, and Ca2+ enters the Synaptic axon terminal. cleft Sarcolemma Fusing synaptic vesicle Sarcoplasm 3 Ca2+ entry causes some ACh of muscle fiber synaptic vesicles to release their Folds of contents (the neurotransmitter ACh receptor sarcolemma acetylcholine) by exocytosis. 4 Acetylcholine diffuses across the synaptic cleft and binds to receptors in the sarcolemma. © 2018 Pearson Education, Inc. Figure 6.5 Events at the neuromuscular junction. Slide 6 Ion channel in 5 ACh binds and opens channels Na+ K+ sarcolemma opens; that allow simultaneous passage ions pass. of Na+ into the muscle fiber and K+ out of the muscle fiber. More Na+ ions enter than K+ ions leave, producing a local change in the electrical conditions of the membrane (depolarization). This eventually leads to an action potential. © 2018 Pearson Education, Inc. Figure 6.5 Events at the neuromuscular junction. Slide 7 ACh Degraded ACh Ion channel closes; Na+ ions cannot pass. 6 The enzyme acetylcholinesterase breaks down ACh in the synaptic cleft, ending the process. Acetylcholinesterase K+ © 2018 Pearson Education, Inc. Figure 6.5 Events at the neuromuscular junction. Slide 8 Myelinated axon Nerve of motor neuron impulse Axon terminal of Nucleus neuromuscular junction Sarcolemma of the muscle fiber Synaptic vesicle containing ACh 1 Nerve impulse reaches axon terminal of motor neuron. Axon terminal of motor neuron Mitochondrion 2 Calcium (Ca2+) channels Ca2+ Ca2+ open, and Ca2+ enters the Synaptic axon terminal. cleft Sarcolemma Fusing synaptic vesicle Sarcoplasm 3 Ca2+ entry causes some ACh of muscle fiber synaptic vesicles to release their Folds of contents (the neurotransmitter ACh receptor sarcolemma acetylcholine) by exocytosis. 4 Acetylcholine diffuses across the synaptic cleft and binds to receptors in the sarcolemma. Ion channel in 5 ACh binds and opens channels Na+ K+ sarcolemma opens; that allow simultaneous passage ions pass. of Na+ into the muscle fiber and K+ out of the muscle fiber. More Na+ ions enter than K+ ions leave, producing a local change in the electrical conditions of the membrane (depolarization). This eventually leads to an action potential. ACh Degraded ACh Ion channel closes; Na+ ions cannot pass. 6 The enzyme acetylcholinesterase breaks down ACh in the synaptic cleft, ending the process. Acetylcholinesterase K+ © 2018 Pearson Education, Inc. Figure 6.6 Comparing the action potential to a flame consuming a dry twig. Small twig Match flame 1 Flame ignites 2 Flame spreads the twig. rapidly along the twig. (a) Neuromuscular junction Muscle fiber Nerve (cell) Striations fiber 1 Na+ diffuses into the cell. 2 Action potential spreads rapidly along the sarcolemma. (b) © 2018 Pearson Education, Inc.  Providing Energy for Muscle Contraction ▪ ATP ▪ Only energy source that can be used to directly power muscle contraction ▪ Stored in muscle fibers in small amounts that are quickly used up ▪ After this initial time, other pathways must be utilized to produce ATP © 2018 Pearson Education, Inc.  Providing Energy for Muscle Contraction ▪ Three pathways to regenerate ATP 1. Direct phosphorylation of ADP by creatine phosphate 2. Aerobic pathway 3. Anaerobic glycolysis and lactic acid formation © 2018 Pearson Education, Inc.  Providing Energy for Muscle Contraction ▪ Direct phosphorylation of ADP by creatine phosphate (CP)—fastest ▪ Muscle cells store CP, a high-energy molecule ▪ After ATP is depleted, ADP remains ▪ CP transfers a phosphate group to ADP to regenerate ATP ▪ CP supplies are exhausted in less than 15 seconds ▪ 1 ATP is produced per CP molecule © 2018 Pearson Education, Inc.  Providing Energy for Muscle Contraction ▪ Aerobic respiration ▪ Supplies ATP at rest and during light/moderate exercise ▪ A series of metabolic pathways, called oxidative phosphorylation, use oxygen and occur in the mitochondria ▪ Glucose is broken down to carbon dioxide and water, releasing energy (about 32 ATP) ▪ This is a slower reaction that requires continuous delivery of oxygen and nutrients © 2018 Pearson Education, Inc. Figure 6.10b Methods of regenerating ATP during muscle activity. (b) Aerobic pathway Aerobic cellular respiration Energy source: glucose; pyruvic acid; free fatty acids from adipose tissue; amino acids from protein catabolism Glucose (from glycogen breakdown or delivered from blood) Pyruvic acid Fatty acids O2 Aerobic respiration Amino in mitochondria acids 32 ATP CO2 H2O net gain per glucose Oxygen use: Required Products: 32 ATP per glucose, CO2, H2O Duration of energy provision: Hours © 2018 Pearson Education, Inc.  Providing Energy for Muscle Contraction ▪ Anaerobic glycolysis and lactic acid formation ▪ Reaction that breaks down glucose without oxygen ▪ Glucose is broken down to pyruvic acid to produce about 2 ATP ▪ Pyruvic acid is converted to lactic acid, which causes muscle soreness ▪ This reaction is not as efficient, but it is fast ▪ Huge amounts of glucose are needed © 2018 Pearson Education, Inc. Figure 6.10c Methods of regenerating ATP during muscle activity. (c) Anaerobic pathway Glycolysis and lactic acid formation Energy source: glucose Glucose (from glycogen breakdown or delivered from blood) Glycolysis in cytosol 2 ATP Pyruvic acid net gain Released Lactic acid to blood Oxygen use: None Products: 2 ATP per glucose, lactic acid Duration of energy provision: 40 seconds, or slightly more © 2018 Pearson Education, Inc.  Muscle Fatigue and Oxygen Deficit ▪ If muscle activity is strenuous and prolonged, muscle fatigue occurs ▪ Suspected factors that contribute to muscle fatigue include: ▪ Ion imbalances (Ca2+, K+) ▪ Oxygen deficit and lactic acid accumulation ▪ Decrease in energy (ATP) supply ▪ After exercise, the oxygen deficit is repaid by rapid, deep breathing © 2018 Pearson Education, Inc.  Types of Muscle Contractions ▪ Isotonic contractions ▪ Myofilaments are able to slide past each other during contractions ▪ The muscle shortens, and movement occurs ▪ Example: bending the knee; lifting weights, smiling ▪ Isometric contractions ▪ Muscle filaments are trying to slide, but the muscle is pitted against an immovable object ▪ Tension increases, but muscles do not shorten ▪ Example: pushing your palms together in front of you © 2018 Pearson Education, Inc.  Muscle Tone ▪ Muscle tone ▪ State of continuous partial contractions ▪ Result of different motor units being stimulated in a systematic way ▪ Muscle remains firm, healthy, and constantly ready for action © 2018 Pearson Education, Inc.  Effect of Exercise on Muscles ▪ Exercise increases muscle size, strength, and endurance ▪ Aerobic (endurance) exercise (biking, jogging) results in stronger, more flexible muscles with greater resistance to fatigue ▪ Makes body metabolism more efficient ▪ Improves digestion, coordination ▪ Resistance (isometric) exercise (weight lifting) increases muscle size and strength ▪ Individual muscle fibers enlarge © 2018 Pearson Education, Inc.  Types of Body Movements ▪ Flexion ▪ Decreases the angle of the joint ▪ Brings two bones closer together ▪ Typical of bending hinge joints (e.g., knee and elbow) or ball-and-socket joints (e.g., the hip) ▪ Extension ▪ Opposite of flexion ▪ Increases angle between two bones ▪ Typical of straightening the elbow or knee ▪ Extension beyond 180º is hyperextension © 2018 Pearson Education, Inc.  Types of Body Movements ▪ Rotation ▪ Movement of a bone around its longitudinal axis ▪ Common in ball-and-socket joints ▪ Example: moving the atlas around the dens of axis (i.e., shaking your head ―no‖) © 2018 Pearson Education, Inc.  Types of Body Movements ▪ Abduction ▪ Movement of a limb away from the midline ▪ Adduction ▪ Opposite of abduction ▪ Movement of a limb toward the midline ▪ Circumduction ▪ Combination of flexion, extension, abduction, and adduction ▪ Common in ball-and-socket joints ▪ Proximal end of bone is stationary, and distal end moves in a circle © 2018 Pearson Education, Inc.  Special Movements ▪ Dorsiflexion ▪ Lifting the foot so that the superior surface approaches the shin (toward the dorsum) ▪ Plantar flexion ▪ Pointing the toes away from the head © 2018 Pearson Education, Inc.  Special Movements ▪ Inversion ▪ Turning sole of foot medially ▪ Eversion ▪ Turning sole of foot laterally © 2018 Pearson Education, Inc.  Special Movements ▪ Supination ▪ Forearm rotates laterally so palm faces anteriorly ▪ Radius and ulna are parallel ▪ Pronation ▪ Forearm rotates medially so palm faces posteriorly ▪ Radius and ulna cross each other like an X © 2018 Pearson Education, Inc.  Special Movements ▪ Opposition ▪ Moving the thumb to touch the tips of other fingers on the same hand © 2018 Pearson Education, Inc. Naming Skeletal Muscles 1– Location of the muscle 2– Shape of the muscle 3– Size of the muscle 4– Direction/Orientation of the muscle fibers/cells 5 – Number of Origins 6 – Location of the Attachments 7 – Action of the muscle  Muscles Named by Location Location: ⚫ frontalis – frontal bone ⚫ lateralis – lateral or on the side ⚫ tibialis anterior – front of tibia ⚫ fibularis longus – near fibula ⚫ supra – above ⚫ infra – below ⚫ sub - underneath  Muscles Named by Shape Shape: ⚫ deltoid – triangle ⚫ Latissimus – wide ⚫ teres - round ⚫ trapezius – trapezoid ⚫ serratus –saw-toothe ⚫ orbicularis – circular  Muscles Named by Size Size: ⚫ maximus – largest ⚫ minimis – smallest ⚫ vastus - huge ⚫ longus – longest ⚫ brevis – short ⚫ major – large ⚫ minor – small Example: Pectoralis Major  Muscles Named by Direction of Fibers Direction/Orientation: ⚫ rectus (straight) - parallel to the muscle’s long axis ex: rectus abdominis ⚫ transversus (transverse) – at right angles to the muscle’s long axis ⚫ oblique – diagonal Muscles Named for Number of Origins Number of Origins: ⚫ biceps – two origins ex: biceps brachii ⚫ triceps – three origins ex: triceps brachii ⚫ quadriceps – four origins  Muscles Named for Origin and Insertion Points Origin and Insertion: sterno = sternum cleiodo = clavicle mastoid = location on the temporal bone sternocleiodomastoid muscle Muscles Named for Action Action: ⚫ flexor carpi radialis – flexes wrist ⚫ abductor magnus – abducts the thigh ⚫ extensor digitorum – extends the fingers ⚫ levator – lifts a structure  Figure 6.15 Relationship of fascicle arrangement to muscle structure. (a) (b) (e) (c) (a) Circular (b) Convergent (e) Multipennate (orbicularis oris) (pectoralis major) (deltoid) (d) (f) (f) Bipennate (rectus (g) femoris) (c) Fusiform (d) Parallel (g) Unipennate (biceps brachii) (sartorius) (extensor digitorum longus) © 2018 Pearson Education, Inc. Figure 6.16a Superficial muscles of the head and neck. Figure 6.16b Superficial muscles of the head and neck. Cranial Frontalis aponeurosis Temporalis Orbicularis oculi Occipitalis Zygomaticus Buccinator Masseter Orbicularis oris Sternocleidomastoid Trapezius Platysma Posterior muscles of the neck. Figure 6.17a Clavicle Muscles of the anterior trunk, shoulder, and Deltoid arm. Sternum Pectoralis major Biceps brachii Brachialis Brachio- radialis  Figure 6.19 The fleshy deltoid muscle is a favored site for administering intramuscular injections. Deltoid muscle Humerus © 2018 Pearson Education, Inc. Figure 6.17b Muscles of the anterior trunk, shoulder, and arm. Pectoralis Serratus major anterior Rectus abdominis Transversus abdominis Internal oblique External oblique Aponeurosis  Occipital bone Figure 6.18a Sternocleidomastoid Muscles of Spine of scapula Trapezius the posterior Deltoid (cut) neck, trunk, Deltoid and arm. Triceps brachii Latissimus dorsi Humerus Olecranon process of (a) ulna (deep to tendon)  Occipital bone Figure Sternocleidomastoid 6.18a Spine of scapula Muscles of Trapezius Deltoid (cut) the Deltoid posterior neck, trunk, and arm. Triceps brachii Latissimus dorsi Humerus Olecranon process of ulna (deep to tendon)  12th Figure 6.20c Pelvic, 12th rib thoracic vertebra hip, and thigh muscles of the right Iliac crest side of the body. Iliopsoas Psoas major Iliacus 5th lumbar vertebra Anterior superior iliac spine Tensor Fasciae Latae Sartorius Adductor group Rectus femoris Quadriceps* Vastus lateralis Vastus medialis Patella Patellar ligament (c) © 2018 Pearson Education, Inc. © 2018 Pearson Education, Inc. Figure 6.20d Pelvic, hip, and thigh muscles of the right side of the body. Inguinal ligament Adductor muscles Sartorius Vastus lateralis (d) © 2018 Pearson Education, Inc.  Figure 6.21a Superficial muscles of the right leg. Fibularis longus Tibia Fibularis brevis Soleus Tibialis anterior Extensor digitorum longus Fibularis tertius (a) © 2018 Pearson Education, Inc. Muscles of the Lower Leg Superficial Muscles: Anterior Superficial Muscles: Posterior Figure 6.22  Facial Major superficial Facial Frontalis Orbicularis oculi muscles of the Temporalis Masseter Zygomaticus Orbicularis oris anterior surface of the Shoulder Trapezius Neck Platysma Sternocleidomastoid body. Deltoid Thorax Pectoralis minor Pectoralis major Arm Serratus anterior Triceps brachii Biceps brachii Intercostals Brachialis Abdomen Rectus abdominis Forearm External oblique Brachioradialis Internal oblique Flexor carpi radialis Transversus abdominis Pelvis/thigh Iliopsoas Thigh Sartorius Adductor muscles Thigh (Quadriceps) Rectus femoris Vastus lateralis Vastus medialis Vastus intermedius (not shown, deep to rectus femoris) Leg Fibularis longus Leg Extensor digitorum longus Gastrocnemius Tibialis anterior Soleus © 2018 Pearson Education, Inc. Major superficial Neck Occipitalis muscles of the Sternocleidomastoid Trapezius posterior surface of Shoulder/Back Deltoid the body. Arm Triceps brachii Brachialis Forearm Latissimus dorsi Brachioradialis Extensor carpi radialis longus Flexor carpi ulnaris Hip Extensor carpi ulnaris Gluteus medius Extensor digitorum Gluteus maximus Thigh Iliotibial tract Adductor muscle Hamstrings: Biceps femoris Semitendinosus Semimembranosus Leg Gastrocnemius Soleus Fibularis longus Calcaneal (Achilles) tendon © 2018 Pearson Education, Inc.  Table 6.3 Superficial Anterior Muscles of the Body (See Figure 6.22) (2 of 3) © 2018 Pearson Education, Inc.  Table 6.3 Superficial Anterior Muscles of the Body (See Figure 6.22) (1 of 3) © 2018 Pearson Education, Inc.  Table 6.3 Superficial Anterior Muscles of the Body (See Figure 6.22) (3 of 3) © 2018 Pearson Education, Inc.  Table 6.4 Superficial Posterior Muscles of the Body (Some Forearm Muscles Also Shown) (See Figure 6.23) (1 of 3) © 2018 Pearson Education, Inc.  Table 6.3 Superficial Anterior Muscles of the Body (See Figure 6.22) (2 of 3) © 2018 Pearson Education, Inc.  Table 6.4 Superficial Posterior Muscles of the Body (Some Forearm Muscles Also Shown) (See Figure 6.23) (2 of 3) © 2018 Pearson Education, Inc.  Table 6.4 Superficial Posterior Muscles of the Body (Some Forearm Muscles Also Shown) (See Figure 6.23) (3 of 3) © 2018 Pearson Education, Inc.  Developmental Aspects of the Muscular System ▪ Increasing muscular control reflects the maturation of the nervous system ▪ Muscle control is achieved in a superior/inferior and proximal/distal direction © 2018 Pearson Education, Inc.  Developmental Aspects of the Muscular System ▪ To remain healthy, muscles must be exercised regularly ▪ Without exercise, muscles atrophy ▪ With extremely vigorous exercise, muscles hypertrophy © 2018 Pearson Education, Inc.  Developmental Aspects of the Muscular System ▪ As we age, muscle mass decreases, and muscles become more sinewy ▪ Exercise helps retain muscle mass and strength © 2018 Pearson Education, Inc.