Chapter 11 The Muscular System
Lecture slides prepared by Curtis DeFriez, Weber State University
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Naming Muscles Location tibialis anterior
Tibialis anterior
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Naming Muscles
Size gluteus maximus
• Number of Attachments o
biceps; triceps
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Naming Muscles
Location/Direction of Fibers transversus abdominus
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Naming Muscles
Hyoid bone Styloid process
• Attachments (origin & insertion) o
stylohyoid; sternocleidomastoid
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Naming Muscles Muscle action levator scapulae
adductor magnus tensor tympani Levator scapulae
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Naming Muscles Combination of above
Fibularis longus
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Origins and Insertions Muscles produce movement by exerting force on tendons which in turn pull on bones and other supporting structures like the skin. In order to produce movement around a joint, one bone must be stationary while another bone moves. The attachment of a muscle's tendon to the stationary, usually proximal bone, is called the origin.
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Origins and Insertions
Insertion of the long head of the biceps
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Origins and Insertions Biceps: Origin: Scapula Insertion: Radius Action: pronate and flex the arm Triceps: Origin: Scapula near shoulder joint Upper lateral and posterior sites of humerus Posterior surface of humerus Insertion: Back of olecranon process of ulna Action: Straighten (extend) the arm Copyright © John Wiley & Sons, Inc. All rights reserved.
Musculoskeletal Levers Muscles, tendons, bones, and joints can form three different types of levers in the body. When producing movement, bones act as levers, and joints function as the fixed point of movement called the fulcrum. In a lever, the point of movement (fulcrum) is acted on by two different forces: Effort and load. Copyright © John Wiley & Sons, Inc. All rights reserved.
Musculoskeletal Levers There are few first-class levers in the body
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Musculoskeletal Levers Second class levers always provide a distinct mechanical advantage in producing force. Like a pry bar
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Musculoskeletal Levers Third-class levers are the most common and favor speed and range of motion over maximum force.
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Coordination Among Muscles Movements are often the result of several skeletal muscles acting as a group. Most skeletal muscles are arranged in opposing (antagonistic) pairs at joints. Within opposing pairs, the prime mover or agonist (“the leader”) is the muscle primarily responsible for causing the desired movement. Copyright © John Wiley & Sons, Inc. All rights reserved.
Coordination Among Muscles The antagonist stretches and yields to the effects of the prime mover. In flexing the forearm at the elbow, the brachialis is the prime mover or agonists, and the triceps brachii is the antagonist.
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Coordination Among Muscles Synergists are muscles used to prevent unwanted movements at intermediate joints, or otherwise aid the movement of the prime mover.
The biceps acts synergistically with the brachialis. Fixator muscles are a type of synergist muscle that are used to steady the proximal joints of a prime mover. Shoulder stabilizers for the forearm flexors
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Major Skeletal Muscles Learn the origin, insertion and action of the major skeletal muscles of the body as directed by your instructor. Some of the more common muscles of the head and neck include: Orbicularis oris Extraocular muscles Sternocleidomastoid Rectus abdominus External oblique Copyright © John Wiley & Sons, Inc. All rights reserved.
Major Skeletal Muscles The muscles of facial expression move skin rather than bones around a joint. Orbicularis oris
Action: Closes and protrudes lips for kissing Origin: Surrounding the opening of the mouth Insertion: The skin at the corner of the mouth
Orbicularis oris
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Major Skeletal Muscles Muscles that move the mandible (lower jaw) Also called muscles of mastication Masseter Origin: Maxilla and zygomatic arch Insertion: Mandible Action: Closes the mouth
Masseter Copyright © John Wiley & Sons, Inc. All rights reserved.
Major Skeletal Muscles The Extraocular muscles 3 pair give each eye very precise movement Origin: Back of the orbit Insertion: Different parts of the eyeball Action: Precise and rapid movement of the eyes Copyright © John Wiley & Sons, Inc. All rights reserved.
Major Skeletal Muscles Muscles that move the head Sternocleidomastoid (commonly abbreviated as SCM) Origin: Clavicle and sternum
Insertion: Mastoid process of temporal bone Action: Flex and rotate the head Sternocleidomastoid Copyright © John Wiley & Sons, Inc. All rights reserved.
Major Skeletal Muscles Some of the more common muscles that originate on the trunk include: Pectoralis major and
minor Anterior abdominal muscle group Latissimus dorsi
Biceps brachii Diaphragm Trapezius Deltoid Copyright © John Wiley & Sons, Inc. All rights reserved.
Major Skeletal Muscles Muscles that move the pectoral girdle (shoulder) Pectoralis major
Pectoralis minor
Origin: Clavicle and
Origin: Ribs 3–5
sternum
Insertion: Coracoid
Insertion: Proximal
process of the scapula
humerus
Action: Internally rotates
Action: Adducts and
the shoulder
medially rotates the arm at the shoulder joint Copyright © John Wiley & Sons, Inc. All rights reserved.
Major Skeletal Muscles Muscles that move the pectoral girdle (shoulder) Deltoid Muscle Origin: Lateral clavicle and upper scapula Insertion: Deltoid tuberosity
Deltoid
on the shaft of the humerus Action: Abducts, flexes, and medially rotates the upper arm at the shoulder joint Copyright © John Wiley & Sons, Inc. All rights reserved.
Major Skeletal Muscles Muscles that move the pectoral girdle (shoulder) Trapezius Origin: Occipital bone and cervical spine
Trapezius
Insertion: Clavicle, scapula and lower thoracic vertebrae Action: Supports the arm and moves the scapula up, down,
in, and out Copyright © John Wiley & Sons, Inc. All rights reserved.
Major Skeletal Muscles Muscles that move the pectoral girdle (shoulder) Latissimus dorsi Origin: Thoracic and lumbar vertebrae and the iliac bone Insertion: Mid-humerus Action: Drives arm inferiorly
and posteriorly (the
Latissimus dorsi
swimmer’s muscle) Copyright © John Wiley & Sons, Inc. All rights reserved.
Major Skeletal Muscles Anterior abdominal wall
Rectus abdominis Origin: Pubic bone Insertion: Ribs and sternum External oblique Origin: Ribs 5–12 Insertion: Iliac crest and
linea alba Actions: Flexes vertebral column and compresses abdomen Copyright © John Wiley & Sons, Inc. All rights reserved.
Major Skeletal Muscles The main muscle of inspiration is the diaphragm. Origin: Inferior 6 ribs (anteriorly) and lumbar vertebrae (posteriorly) Insertion: Central tendon Diaphragm
Central tendon
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Major Skeletal Muscles Some of the more common muscles of the extremities include: Triceps brachii
Quadriceps group: Rectus
Brachioradialis
femoris, along with the vastus
Thenar muscles
lateralis, vastus intermedius,
Hypothenar muscles
and vastus medialis
Gluteus maximus
Tibialis anterior
Biceps femoris
Gastrocnemius Soleus Copyright © John Wiley & Sons, Inc. All rights reserved.
Major Skeletal Muscles Muscles that move the Radius and Ulna Biceps brachii Origin: Scapula Insertion: Radius Action: Flexes and
Brachialis
Origin: Distal anterior surface of humerus Insertion: Ulna
supinates forearm at
Action: Flexor of forearm
elbow joint and flexes
at elbow
arm at shoulder joint Copyright © John Wiley & Sons, Inc. All rights reserved.
Major Skeletal Muscles Muscles that move the Radius and Ulna Triceps brachii Origin: Scapula and posterior surface of humerus Insertion: Olecranon
process of ulna Action: Extends forearm at elbow joint and arm at shoulder joint Copyright © John Wiley & Sons, Inc. All rights reserved.
Major Skeletal Muscles Muscles that move the Radius and Ulna Brachioradialis Origin: Humerus Insertion: Distal radius Action: Supinates the forearm at the radioulnar joint
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Major Skeletal Muscles Muscles that move the wrist, hand, thumb, and finger
Thenar: lateral aspect of palm Hypothenar: medial aspect of palm Action: Oppose thumb against other 4 fingers
Thenar Hypothenar
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Major Skeletal Muscles Muscles that move the femur
Gluteus maximus Origin: Iliac crest, sacrum, and coccyx Insertion: Femur Action: Extends and
Gluteus maximus
laterally rotates thigh at hip joint
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Major Skeletal Muscles Muscles that move the femur, tibia,
and fibula Quadricep group (Rectus femoris, vastus lateralis, vastus intermedius, and vastus medialis) Origin: Iliac spine and proximal femur
Insertion: Patella and proximal tibia Action: Flexes thigh at high joint and extends leg at knee joint Copyright © John Wiley & Sons, Inc. All rights reserved.
Major Skeletal Muscles Muscles that move the
femur, tibia, and fibula Hamstring group: (Biceps femoris, Semitendinosus, and Semimembranosus) Origin: Ischial tuberosity Insertion: Proximal tibia and fibula Copyright © John Wiley & Sons, Inc. All rights reserved.
Major Skeletal Muscles Muscles that move the femur, tibia, and fibula Tibialis anterior Origin: Tibia Insertion: First cuneiform and first metatarsal
Action: Dorsiflexes and inverts the foot Copyright © John Wiley & Sons, Inc. All rights reserved.
Major Skeletal Muscles Muscles that plantar flex the foot at the ankle joint (standing on “tip toes”) Gastrocnemius and soleus muscles
function as one – often called the gastrocsoleus muscle Origin: Femur, capsule of knee, and head of fibula Insertion: Calcaneus by way of calcaneal (Achilles) tendon Copyright © John Wiley & Sons, Inc. All rights reserved.
Major Skeletal Muscles
Copyright © John Wiley & Sons, Inc. All rights reserved.
Major Skeletal Muscles
Copyright © John Wiley & Sons, Inc. All rights reserved.
Imbalances of Homeostasis Exercise-induced muscle damage After intense exercise, electron micrographs reveal considerable muscle damage including torn sarcolemmas and disrupted Z-discs. Blood levels of proteins normally confined only to
muscle (including myoglobin and the enzyme, creatine kinase) increase as they are released from damaged muscle.
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Imbalances of Homeostasis Spasm A sudden involuntary contraction of a single muscle within a large group of muscles – usually painless Cramp Involuntary and often painful muscle contractions Caused by inadequate blood flow to muscles (such as in
dehydration), overuse and injury, and abnormal blood electrolyte levels Copyright © John Wiley & Sons, Inc. All rights reserved.
Imbalances of Homeostasis Disease States and Disorders Fibrosis (myofibrosis) Replacement
of muscle fibers by excessive amounts
of connective tissues (fibrous scar tissue) Myosclerosis Hardening
of the muscle caused by calcification
Both myosclerosis and muscle fibrosis occur as a result of trauma and various metabolic disorders. Copyright © John Wiley & Sons, Inc. All rights reserved.
Imbalances of Homeostasis Aging In part due to decreased levels of physical activity, with aging, humans undergo a slow, progressive loss of
skeletal muscle mass that is replaced largely by fibrous connective tissue and adipose tissue. Muscle strength at 85 is about half that at age 25. Compared to the other two fiber types, the relative number of slow oxidative fibers appears to increase. Copyright © John Wiley & Sons, Inc. All rights reserved.
