1. Chapter 11 The Muscular System

2. An Introduction to the Muscular System
The Muscular System consists only approximately 600 human skeletal muscles
Muscle organization affects power, range, and speed of muscle movement
Muscle cells (fibers) are organized in bundles called (fascicles) specific arrangement based on muscle function
Skeletal muscles are classified by the way fascicles are organized – the relationships of fascicles to tendons
4 patterns of fascicle organization
Parallel, Convergent, Pennate, Circular
Each fascicle fibers are parallel and surrounded by perimysium
The strength (power) of the muscle and the direction (range of motion) of its pull are determined partly by the orientation or shape of its fascicles
Longer fibers: have greater range of motion & cover greater distance
Short muscles with higher cross-sectional area have more force (tension)

3. Sarcolemma with transverse tubules (T-tubules)
Muscle fiber
Myofibril
Myofilaments

5. Fascicle Arrangement Parallel Muscles
Fibers parallel to the long axis of muscle
Most skeletal muscles are this shape
The tension developed during contractions depends on total # of myofibrils
When parallel muscle contracts it shortens and get large in diameter.
Some are broad flat bands, others are plump and cylindrical with tendons at both ends. Spindle shaped with a belly in the center
For example, biceps brachii, rectus abdominus

6. Fascicle Arrangement - Convergent Muscles
A broad area converges on attachment site (tendon, aponeurosis, or raphe-slender band of collagen fibers)
Muscle fibers pull in DIFFERENT DIRECTIONS, depending on stimulation. This allows for wider versatility. When entire muscle contracts fibers do not pull as hard as the parallel type
fan-shaped, broad at origin and tapering to a narrower insertion; more fibers
For example, pectoralis muscles, temporalis

7. Fascicle Arrangement - Pennate Muscles
Form an angle with the tendon
Do not move as far as parallel muscles
Contain more muscle fibers than parallel muscles producing more tension or force but smaller range of motion
Unipennate
Fibers on one side of tendon
For example, extensor digitorum
Bipennate
Fibers on both sides of tendon
For example, rectus femoris
Multipennate
Tendon branches within muscle
For example, Deltoid

8. Fascicle Arrangement - Circular Muscles
Also called sphincters
Open and close to guard entrances of body
Form ring around body opening
orbicularis oris orbicularis oculi, urethral and anal sphincters

9. Skeletal Motion and Levers
Skeletal muscles attach to skeleton, produce motion
Attaching a muscle to a lever can modify the direction, force, speed and distance of the movement produced by the muscle contraction.
A lever moves when pressure (applied force) is sufficient to overcome resistance (load).
Levers:
Mechanically bones operates as levers (rigid, moving structure)
Move around a fixed point called the FULCRUM (F) which is a JOINT
MUSCLES provide APPLIED FORCE / EFFORT (AF) on lever
Required to overcome LOAD (L) = the RESISTANCE that opposes the movement
The three classes of levers Depend on the relationship between applied force, fulcrum, and resistance
First-class lever Bones = levers
Second-class lever Muscles = effort/Force
Third-class lever Fulcrum= joint
Moves the Load

10. First- Class Levers Example 3: Scissors Example 4: Car Jack
Center fulcrum between applied force and load
Force and load are balanced
Example 1: head on the vertebral column
Load: weight of face, car
Fulcrum: joint between skull and atlas, jack
Applied force (Effort) : posterior neck muscles
Example 2: Seesaw or teeter-totter
Example 3: Scissors
Example 4: Car Jack

12. Second-Class Levers
Center resistance between applied force and fulcrum
If the applied force is further from the fulcrum than the load, a strong resistance can be moved
A small force moves a large weight
Sacrifices speed
Example 1:using the calf muscles to rise up on the toes
Example 2: Wheelbarrow is an example
Load is body weight
Fulcrum is ball of Foot (metatarsal phalangeal joint)
Applied force (effort) is contraction of the calf muscles

13. Second-Class Levers

14. Third-Class Levers MOST COMMON levers in the body
Center applied force between load and fulcrum
Greater force moves smaller load
Maximizes speed and distance traveled
Example 1: muscles like the biceps brachii that flex the forearm
Load is the weight of the forearm and hand (plus whatever is held in the hand)
Fulcrum is elbow
Applied force (effort): contraction of biceps brachii muscle
Example 2: tweezers

15. Third-Class Levers

17. https://lifescitpjhs. wikispaces. com/file/view/Levers

18. Muscle Attachments to Other Tissues
Origin
ORIGIN – bony attachment at STATIONARY end of muscle-does not move
one fixed point of attachment
INSERTION- bony attachment to MOVABLE END of muscle
And one moving point of attachment
Most muscles originate or insert on the skeleton
Skeletal muscles shorten & pull on the two skeletal elements to which they are attached.
Origin is usually proximal to insertion
Insertion

19. Tendons and Aponeuroses
Collagen fibers of the endomysium, perimysium, and epimysium join at ends of muscles to form CT attachment to periosteum of bone.
When muscles contract they pull on the tendon that then moves the bone
“Cable-like” cord of dense CT collagen fibers and elastic fibers (Ex: back of your hand).
Direct very little separation between bone and muscle (brachialis)
Indirect larger separation (biceps brachii)
Biceps brachii
Brachialis
Aponeurosis: broad flat tendon.
Sparingly supplied with blood vessels and nerves.
Formation of rectus sheath from aponeuroses of the abdominal muscles.

20. Muscle Interactions Muscles work in groups to maximize efficiency
action – the effects to produce or prevent movement
Agonist (Prime Mover)
muscle that produces most of force during a joint action
produces a particular movement
Synergist
A smaller muscle that assists a larger agonist
Helps start motion or stabilize origin of agonist (fixator)
stabilizes the nearby joint
modifies the direction of movement
Antagonist
Opposes movement of a particular agonist
relaxes to give prime mover control over an action
prevents excessive movement and injury
antagonistic pairs – muscles that act on opposite sides of a joint; flexors–extensors, abductors–adductors

21. Muscle Actions Across Elbow
prime mover
Brachialis
synergist
biceps brachii
fixator - muscle that holds scapula firmly in place
Rhomboids
antagonist
triceps brachii

22. Naming Skeletal Muscles
LOCATION in the Body
Identifies body regions
For example, temporalis, frontalis, tibialis anterior,
ORIGIN AND INSERTION
First part of name indicates origin
Second part of name indicates insertion
Ex: Sternocleidomastoid
FASCICLE ORGANIZATION (Direction)
Describes fascicle orientation within muscle
rectus (straight), transversus, oblique
Ex: rectus abdominus
POSITION
Extrinsic -Muscles outside an organ (Hypoglossus-tongue from the mandible)
Intrinsic- Muscles inside an organ (inferior longitudinal muscle lines the sides of the tongue)

23. Naming Skeletal Muscles
STRUCTURAL CHARACTERISTICS
Number of tendons origins
Biceps (biceps femoris)
Triceps (triceps brachii)
Quadriceps (quadraceps femoris)
Shape
Trapezius, deltoid, rhomboid, orbicularis
Size
maximus, minimus, longus, brevis
ACTION
Flexor and Extensor (extensor digitorum)
Abductor and Adductors (adductor magnus)
Levator and Depressor (levator scapulae)
Supinator and Pronator (pronator teres)

24. Naming Exercises Extensor carpi radialis longus Biceps brachii
Adductor longus
Occipitalis
Orbicularis oris
Quadriceps femoris
Gluteus maximus
Rectus abdominus

25. Naming Skeletal Muscles
Terms Indicating Specific Regions of the Body
Abdominis (abdomen)
Brachialis (brachium)
Carpi (wrist)
Cleido-/-clavius
Cutaneous (skin)
Femoris (femur)
Radialis (radius)
Scapularis (scapula)
Temporalis (temples)
Thoracis (thoracic region)
Tibialis (tibia)
Sartorius (like a tailor)
Buccinator (trumpeter)
Costalis (ribs)
Glosso-/-glossal (tongue)
Inguinal (groin)
Oculo- (eye)
Oris (mouth)
Popliteus (posterior knee)
Uro- (urinary)
Gracilis (slender)
Latissimus (widest
Vastus (great)
Major (larger)
Minor (smaller)

26. Extrinsic Muscles of the Eyeball
Originate on skull, insert onto white (sclera) of eye
Four muscles are rectus (straight) and two are oblique
Fastest contracting and most precisely controlled muscles
Superior rectus, inferior rectus, medial rectus, lateral rectus
Superior oblique, inferior oblique

27. Muscles of Facial Expression
Originate on skull or within the skin and insert into the skin
Express emotions, assist in chewing, whistling, blowing, sucking
Examples: Occipitalis, frontalis, zygomaticus major/minor, buccinator, orbicularis oris (orb= circle; oris=mouth), orbicularis oculi (oculi=eye)

28. Dimples are a deformity of the zygomaticus MAJOR muscle
Dimples are a deformity of the zygomaticus MAJOR muscle. Generally thought to be a birth defect where this muscle is shorter than normal.

30. Muscles of Mastication
Originate from skull and insert on the mandible
Masseter
The strongest jaw muscle; elevates the mandible
Temporalis
Helps elevate and retract the mandible
Pterygoid muscles
Medial/lateral
Position mandible for chewing; elevation and depression of mandible; helps to protrude the jaw

31. Muscles of the neck that move the head
Sternocleidomastoid: originates from sternum and clavicle and inserts on mastoid process
If both left and right are contracted, the cervical vertebrae flex and head extends
Contraction of one flexes the neck laterally and rotates the face in the opposite direction
Scalene muscles
Cervical oblique muscles that flex the neck

32. Scalene muscles

33. Muscles of the Abdominal Wall
Oblique and Rectus Muscles
Function in abdominal compression needed for forced breathing (exercise), urination, defecation, childbirth, for bending the trunk
Lie within the body wall
Oblique muscles- external and internal obliques and transversus abdominis
Compress underlying structures
Rotate vertebral column
Rectus muscles- vertically oriented (six-pack)
Flex vertebral column
Between xiphoid process and pubic symphysis
Divided longitudinally by linea alba (medial collagenous partition)
Diaphragmatic muscle

34. Muscles of the Abdominal Wall
Linea alba
External oblique
Rectus abdominis
Stabilized vertebral column
Aids in compression of abdominal wall
Trunk rotation
Rotates lumbar vertebrae
Stabilized pelvis for walking
Internal oblique
Transverse abdominis
Same function as External oblique
Compresses abdominal contents

35. Muscles of Respiration - diaphragm
relaxation
contraction flattens diaphragm
enlarges thoracic cavity (inspiration)
in relaxation of diaphragm it rises
shrinks the thoracic cavity (expiration)
contraction

36. Muscles Used in Breathing
external intercostals
elevates ribs
expand thoracic cavity
create partial vacuum causing inflow of air- Inspiration
internal intercostals
depresses and retracts ribs
compresses thoracic cavity
expelling air- Expiration

37. Muscles of the Shoulders and Upper Limbs
Muscles that position the pectoral girdle
trapzius, rhomboid, levator scapulae, serratus anterior, pectoralis minor
Muscles that move the arm
deltoid, teres major and minor, pectoralis major, latissimus dorsi,
Muscles involved in shoulder rotation
the Rotator Cuff
Muscles that move the forearm and hand
Extensors- Mainly on posterior and lateral surfaces of arm
Flexors- Mainly on anterior and medial surface
Muscles that move the hand and fingers

38. Muscles That Position the Pectoral Girdle
trapezius
stabilizes scapula/ shoulder
elevates/depresses shoulder apex
levator scapulae
elevates scapula
flexes neck laterally
rhomboideus major/minor
retracts scapula and braces shoulder
trapzius, rhomboid, levator scapulae, serratus anterior, pectoralis minor

39. Muscles That Position the Pectoral Girdle
Pectoralis Minor
ribs to coracoid process of scapula
protracts and depresses scapula
lifts ribs during forced expiration
Serratus anterior
On the chest
Originates along ribs
They help us move our arms multi- dimensionally and with great speed.

40. Axial Muscles that Move the Arm
Pectoralis major
makes up the bulk of the chest muscles in the male and lies under the breast in the female.
has four actions which are primarily responsible for movement of the shoulder joint in flexion.
Deltoid
The major abductor
originates from the acromion and spine of the scapula
inserts on humerus
Abducts, flexes and extends arm

41. Axial Muscles that Move the Arm - Posterior
Teres Major/Minor
Produce medial rotation at shoulder
Latissimus dorsi
Produces extension at shoulder joint

42. The Rotator Cuff Muscles involved in shoulder rotation Supraspinatus
Subscapularis
Anterior
Infraspinatus
Posterior
Teres minor
their tendons

43. Muscles that Move the FOREARM: FLEXORS
Humerus
Biceps brachii, short head
Biceps brachii, long head
Biceps brachii: originates on scapula; inserts on radial tuberosity. Flexes shoulder and elbow; supinates hand
Triceps brachii, long head
Triceps brachii, medial head
Brachialis
Brachialis: originates on humerus; inserts on ulna. Flexion of elbow
Brachioradialis
Brachioradialis: originates on humerus; inserts on radius. Flexes elbow
Anterior view, superficial layer 43

44. Muscles Acting on Elbow
Principal flexors
biceps brachii
inserts on radius
brachialis
inserts on ulna
Synergistic flexor
brachioradialis
Prime extensor
triceps brachii
inserts onto ulna
3 origins on the humerus

45. Supination/ Pronation Forearm
Pronator teres -pronates the forearm, turning the hand posteriorly. Articulates with the humerus and ulna
Supinator- supinates the forearm, turning the hand anteriorly. Articulates with the humerus and the radial tuberosity. Lies beneath brachialradialis

46. The extensor digitorum muscle of the posterior forearm extends the medial four digits of the hand.

47. Tendon Sheaths Flexor retinaculum
bracelet-like fibrous sheet flexes the wrist
Anterior surface of wrist
Stabilizes tendons of flexor muscles
Extensor retinaculum
Wide band of connective tissue
Posterior surface of wrist
Stabilizes tendons of extensor muscles
Tight space between the flexor retinaculum and the carpal flexor tendons is called the carpal tunnel. Inflammation of the retinaculum and synovial tendon sheaths can restrict movement and irritate the distal portions of the median nerve that innervates the hand. This condition is known as carpal tunnel syndrome.

50. Appendicular Musculature
Compartments –spaces in which muscles are organized and separated by fibrous connective tissue sheets called facia.
Three compartments each with unique innervation:
Anterior compartment: quadriceps femoris; sartorius
Medial compartment: adductors; obturator nerve
Posterior compartment: hamstrings (biceps femoris, semimembranosus, semitendinosus); sciatic nerve
Muscles That Move the Thigh
Gluteal muscles
Adductors

51. Gluteal Muscles Deeper muscles of the hip - rotate femur
Gluteus maximus
Largest, most posterior gluteal muscle
Produces extension and lateral rotation at hip; extends hip
Gluteus medius and gluteus minimus
Originate anterior to gluteus maximus
Insert on trochanter; abduct hip

53. Medial Adductors / Lateral Rotators
Adductor Group
Adductor magnus
Produces adduction, extension, and flexion
Adductor brevis
Hip flexion and adduction
Adductor longus
Pectineus
Gracilis
Lateral group
Piriformis
Hip extension and flexion.
Attaches to sacrum and femur
Piriformis syndrome occurs when the piriformis irritates the sciatic nerve which comes into the gluteal region beneath the muscle, causing pain in the buttocks and referred pain along the sciatic nerve.

55. Posterior Muscles of the Thigh
Extend hip and flex knee
Hamstrings
Biceps femoris
Semimembranosus
Semitendinosus

56. Anterior Muscles that Cross the Hip Joint
Extensors of the Knee
Four muscles of the quadriceps femoris
3 heads originate from femur; all heads insert on quadriceps tendon above patella
vastus lateralis, vastus medialis, vastus intermedius
Rectus femoris muscle
Sartorius
Originates superior to the acetabulum
longest muscle in the body- obliquely from thigh to knee- tailors muscle –helps effect cross-legged position

57. Muscles of the Calf: Posterior/Anterior
Muscles That Produce Extension (Plantar Flexion) at the Ankle
Gastrocnemius -flexes knee and ankle
Soleus - flex ankle
The Achilles Tendon - calcaneal tendon
Shared by the gastrocnemius and soleus
Muscles That Produce Flexion (Dorsiflexion) at the Ankle
Tibialis anterior
Opposes the gastrocnemius

59. Muscles that move the tarsals, metatarsals, and phalanges and originate and insert only on those bones

60. gluteus medius – never the maximus; risk of damaging the sciatic nerve
Injections
Subcutaneous
Intramuscular: Most common sites:
deltoid
gluteus medius – never the maximus; risk of damaging the sciatic nerve
vastus lateralis
Intravenous