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CHAPTER 11
LECTURE OUTLINE
INTRODUCTION
1. Distinguish the tissues that constitute the skeletal system.
HOW SKELETAL MUSCLES PRODUCE MOVEMENT
Muscle Attachment Sites: Origin and Insertion
2. Define the terms origin and insertion.
3. Show the relationship between the usual location of the belly of a muscle and
the more mobile bones of its insertion.
4. Describe tenosynovitis and its possible causes.
Lever System and Leverage
5. Define lever, fulcrum and mechanical advantage. Compare the three classes of
levers on the basis of placement of the fulcrum, effort, and resistance, with
respect to examples of muscle systems on the body.
Effects of Fascicle Arrangement
6. Identify the various arrangements of muscle fibers in a skeletal muscle and
relate the arrangements to the strength of contraction and range of motion.
7. Compare the advantages and disadvantages of intramuscular injection to
subcutaneous injection and oral medications.
Coordination Within Muscle Groups
8. Discuss most body movements as activities of groups of muscles by explaining
the roles of the prime mover, antagonist, synergist, and fixator.
9. Examine the effects of stretching for range of motion and mobility of soft
tissues.
HOW SKELETAL MUSCLES ARE NAMED
10. Define the criteria employed in naming skeletal muscles.
PRINCIPAL SKELETAL MUSCLES
11. Identify the principal skeletal muscles in different regions of the body by
name, origin, insertion, and action.
12. Identify and discuss the various clinical problems associated with the different
muscle groups.
DISORDERS: HOMEOSTATIC IMBALANCES
13. Describe the prevalence and cause of common injuries related to running.
14. Describe compartment syndrome, its causes and untreated outcome.
Suggested Lecture Outline
I. INTRODUCTION
A. The muscular system specifically concerns skeletal muscles and associated
connective tissue that make individual muscle organs.
B. This chapter discusses how skeletal muscles produce movement and describes
the principal skeletal muscles.
II. HOW SKELETAL MUSCLES PRODUCE MOVEMENT
A. Muscle Attachment Sites: Origin and Insertion
1. Skeletal muscles produce movements by exerting force on tendons,
which in turn pull on bones or other structures, such as skin.
2. Most muscles cross at least one joint and are attached to the
articulating bones that form the joint (Figure 11.1a).
3. When such a muscle contracts, it draws one articulating bone toward
the other.
a. The attachment to the stationary bone is the origin.
b. The attachment to the movable bone is the insertion.
4. Tenosynovitis is an inflammation of the tendons, tendon sheaths, and
synovial membranes surrounding certain joints (Clinical Connection).
B. Lever Systems and Leverage
1. Bones serve as levers and joints serve as fulcrums.
2. The lever is acted on by two different forces: resistance (load) and
effort (Figure 11.1b).
3. Levers are categorized into three types, according to the position of the
fulcrum, effort, and load
a. first-class (EFL) (Figure 11.2a)-the fulcrum is between the effort
and the load. An example is pair of scissors.
b.
second-class (FLE) (Figure 11.2b)- the load is between the
fulcrum and effort. An example is a wheelbarrow.
c. third-class (FEL) (Figure 11.2c).-the effort is between the fulcrum
and the load. An example is a pair of forceps.
4. Leverage, the mechanical advantage gained by a lever, is largely
responsible for a muscle’s strength and range of motion (ROM), i.e.,
the maximum ability to move the bones of a joint through an arc.
C. Effects of Fascicle Arrangement
1. Skeletal muscle fibers (cells) are arranged within the muscle in
bundles called fasciculi.
2. The muscle fibers are arranged in a parallel fashion within each
bundle, but the arrangement of the fasciculi with respect to the tendons
may take one of four characteristic patterns: parallel, fusiform,
pennate, and circular (Table 11.1).
3. Fascicular arrangement is correlated with the power of a muscle and
the range of motion.
4. Intramuscular injections have advantages, and disadvantages, over
oral or subcutaneous delivery of medications (Clinical Connection)
D. Coordination Within Muscle Groups
1. Most movements are coordinated by several skeletal muscles acting in
groups rather than individually, and most skeletal muscles are arranged
in opposing (antagonistic) pairs at joints.
2. A muscle that causes a desired action is referred to as the prime mover
(agonist); the antagonist produces an opposite action.
3. Most movements also involve muscles called synergists, which serve
to steady a movement, thus preventing unwanted movements and
helping the prime mover function more efficiently.
4. Some synergist muscles in a group also act as fixators, which stabilize
the origin of the prime mover so that it can act more efficiently.
5. Under different conditions and depending on the movement and which
point is fixed, many muscles act, at various times, as prime movers,
antagonists, synergists, or fixators.
6. Some of the benefits of stretching (Clinical Connection) include:
improved physical performance, decreased risk of injury, reduced
muscle soreness, improved posture, increased synovial fluid, and
increased neuromuscular co-ordination.
III. HOW SKELETAL MUSCLES ARE NAMED
A. Muscle naming involves many categories such as:
1.
Location
2.
Size
3.
Number or origins
4.
Appearance
5.
Direction of fibers
6.
Origin and insertion
7.
Muscle action
8.
Combinations
B. Origins and insertions
1. Muscles exert force by pulling on tendons and moving bones
a.
Insertion: moves toward the origin
b.
Origin: stationary
2. Show examples of insertions on cadaver and illustration of the biceps brachii.
C. Musculoskeletal Levers
1.
First class lever
2.
Second class lever
3.
Third class lever
D. Coordination among muscles
1.
Prime mover (agonist)
a.
2.
Primarily responsible for causing the desired movement
Antagonist
a.
Stretches and yields to the effects of the prime mover
a.
Prevent unwanted movements of intermediate joints
b.
aid movement of the primer mover
3.
4.
Fixator
a. Steady proximal joints of prime mover
IV. PRINCIPAL SKELETAL MUSCLES
A. Exhibits 11.A through 11.T list the principle skeletal muscles in various
regions of the body.
B. Discuss the origin, insertion and action of the major skeletal muscles
listed in the PowerPoint
1. Muscles of facial expression
a. Orbicularis oris
(1)
action: closes and protrudes lips
(2)
origin: surrounding opening of mouth
(3)
insertion: corner of mouth
b. Extraoccular
(1)
Action: precise and rapid eye movement
(2)
Origin: back of orbit
(3)
Insertion: different parts of eyeball
2. Muscles that move the jaw
a.
Masseter
(1) Action: closes the mouth
(2) Origin: maxilla and zygomatic arch
(3) Insertion: mandible
3. Muscles that move the head
a.
Sternocleidomastoid
(1) Action: tilt head forward
(2) Origin: clavicle and sternum
(3) Insertion: mastoid process of temporal bone
4. Muscles that act on the abdominal wall
a.
Recuts abdominis
(1) Action: flexes vertebral column, compresses abdomen
(2) Origin: pubic bone
(3) Insertion: ribs and sternum
b.
External oblique
(1) Action: Flexes vertebral column, compresses abdomen
(2) Origin: ribs 5-12
(3) Insertion: iliac crest and linea alba
5. Muscles used in breathing
a.
Diaphragm
(1) Action: pull down on lungs
(2) Origin: inferior 6 ribs (anteriorly), lumbar vertebrae (posteriorly)
(3) Insertion: central tendon
6. Muscles of the pelvic floor and perineum
a.
Show diagram
(1) Action: assist in urination, erection of the penis, clitoris,
ejaculation and defecation
7. Muscles that move the pectoral girdle (shoulder)
a.
Trapezius
(1) Action: moves scapula up, down, in and out
(2) Origin: occipital bone and cervical spine
(3) Insertion: clavicle and scapula
8. Muscles that move the humerus
a.
Pectoralis major
(1) Action: adducts and medially rotates humerus
(2) Origin: clavicle and upper ribs
(3) Insertion: proximal humerus
b.
Deltoid
(1) Action: abduct, flex and medially rotate humerus
(2) Origin: lateral clavicle and upper scapula
(3) Insertion: humerus
c.
Latissimus dorsi
(1) Action: drives arm interiorly and posteriorly
(2) Origin: thoracic and lumbar vertebrae and iliac bone
(3) Insertion: proximal humerus
9. Muscles that move the radius and ulna
a.
Biceps brachii
(1) Action: flexes and supinates forearm
(2) Origin: scapula
(3) Insertion: radius
b.
Brachialis
(1) Action: flexes forearm at elbow
(2) Origin: distal anterior surface of humerus
(3) Insertion: ulna
c.
Triceps brachii
(1) Action: extends forearm
(2) Origin: scapula and posterior
(3) Insertion: olecranon process of ulna
d.
Brachioradialis
(1) Action: supinates the forearm
(2) Origin: humerus
(3) Insertion: distal radius
10. Muscles that move the wrist, hand, thumb and finger
a.
See diagram
(1) Action: oppose thumb against other fingers
(2) Thenar: lateral aspect of palm
(3) hypothenar: medial aspect of palm
11. Muscles that move the femur
a.
Gluteus maximus
(1) Action: extends and laterally rotates thigh at hip joint
(2) Origin: iliac crest, sacrum and coccyx
(3) Insertion: femur
12. Muscles that move the femur, tibia and fibula
a.
Quadriceps femoris (recuts femoris, vastus lateralis, intermedius
and, medialis)
(1) Action: flexes thigh and extends knee
(2) Origin: iliac spine and proximal femur
(3) Insertion: patella and proximal tibia
b.
Hamstrings (biceps femoris, semitendinosus, and
semimembranosus)
(1) Action: flexes knee
(2) Origin: ischical tuberosity
(3) Insertion: proximal fibula and tibia
c.
Tibialis anterior
(1) Action: dorsiflexes and inverts foot
(2) Origin: tibia
(3) Insertion: first cuniform and first metatarsal
d.
Gastocnemius
(1) Action: plantar flexes foot
(2) Origin: femur
(3) Insertion: calcaneus
e.
Soleus
(1) Action: plantar flexes foot
(2) Origin: head of fibula and medial tibia
(3) Insertion: calcaneus
V. DISORDERS: HOMEOSTATIC IMBALANCES
A. Running Injuries
1. Most running injuries involve the knee. Other commonly injured sites
are the calcaneal (Achilles) tendon, medial aspect of the tibia, hip area,
groin area, foot and ankle, and back.
2. Running injuries are frequently related to faulty training techniques.
3. Running injuries can be treated initially (first 2-3 days) with rest, ice,
compression, and elevation (RICE therapy). Alternating moist heat and
ice massage may be used as a follow-up treatment. Sometimes,
nonsteroidal anti-inflammatory drugs (NSAIDS) or local injections of
corticosteroids are needed; an alternate fitness program is necessary to
keep active during the recovery period followed by careful
rehabilitative exercise.
B. Compartment Syndrome
1. Skeletal muscles in the limbs are organized in units called
compartments.
2. In compartment syndrome, some external or internal pressure
constricts the structures within a compartment, resulting in damaged
blood vessels and subsequent reduction of the blood supply to the
structures within the compartment.
3. Without intervention, nerves suffer damage, and muscle develop scar
tissue that results in permanent shortening of the muscles, a condition
called contracture.