Chapter 6 - The Muscular System

1. The Muscular System

2. Did you know that ?
- more than 50% of body weight
is muscle !
- And muscle is made up of
proteins and water

4. The Muscular System
• Muscles are responsible for all movement
of the body
• There are three basic types of muscle
– Skeletal
– Cardiac
– Smooth

5. Info About Muscles
• Only body tissue able
to contract
• create movement by
flexing and extending
joints
• Body energy
converters (many
muscle cells contain
many mitochondria)

6. 3 Types of Muscles

7. Three types of muscle
Skeletal Cardiac Smooth

8. Classification of Muscle
Skeletal-
found in limbs
Cardiac-
found in heart
Smooth-
Found in
viscera
Striated, multi-
nucleated
Striated, 1
nucleus
Not striated, 1
nucleus
voluntary involuntary involuntary

9. Characteristics of Muscle
• Skeletal and smooth muscle are elongated
• Muscle cell = muscle fiber
• Contraction of a muscle is due to movement
of microfilaments (protein fibers)
• All muscles share some terminology
– Prefixes myo and mys refer to muscle
– Prefix sarco refers to flesh

10. Shapes of Muscles
• Triangular- shoulder, neck
• Spindle- arms, legs
• Flat- diaphragm, forehead
• Circular- mouth, anus

11. Shapes of Muscles

12. Skeletal Muscle
• Most are attached by tendons to bones
• Cells have more than one nucleus
(multinucleated)
• Striated- have stripes, banding
• Voluntary- subject to conscious control
• Tendons are mostly made of collagen fibers
• Found in the limbs
• Produce movement, maintain posture,
generate heat, stabilize joints

13. Structure of skeletal muscle
• Each cell (fibre) is long and cylindrical
• Muscle fibres are multi-nucleated
• Typically 50-60mm in diameter, and up
to 10cm long
• The contractile elements of
skeletal muscle cells are
myofibrils

14. Skeletal muscle - Summary
• Voluntary movement
of skeletal parts
• Spans joints and
attached to skeleton
• Multi-nucleated,
striated, cylindrical
fibres

15. Smooth Muscle
• No striations
• Spindle shaped
• Single nucleus
• Involuntary- no conscious control
• Found mainly in the walls of hollow organs

16. Smooth muscle
• Lines walls of viscera
• Found in longitudinal or
circular arrangement
• Alternate contraction of
circular & longitudinal
muscle in the intestine
leads to peristalsis

17. Smooth Muscle

18. Structure of smooth muscle
• Spindle shaped uni-nucleated cells
• Striations not observed
• Actin and myosin filaments are present(
protein fibers)

19. Smooth muscle - Summary
• Found in walls of
hollow internal
organs
• Involuntary
movement of
internal organs
• Elongated, spindle
shaped fibre with
single nucleus

20. Cardiac Muscle
• Striations
• Branching cells
• Involuntary
• Found only in the heart
• Usually has a single nucleus, but can have
more than one

21. Cardiac muscle
• Main muscle of heart
• Pumping mass of heart
• Critical in humans
• Heart muscle cells
behave as one unit
• Heart always contracts
to it’s full extent

22. Structure of cardiac muscle
• Cardiac muscle cells (fibres) are
short, branched and
interconnected
• Cells are striated & usually have 1
nucleus
• Adjacent cardiac cells are joined
via electrical synapses (gap
junctions)
• These gap junctions appear as
dark lines and are called

23. Cardiac muscle - Summary
• Found in the heart
• Involuntary rhythmic
contraction
• Branched, striated
fibre with single
nucleus and
intercalated discs

24. Muscle Control
Type of
muscle
Nervous
control
Type of
control
Example
SkeletalSkeletal Controlled
by CNS
Voluntary Lifting a
glass
Cardiac Regulated
by ANS
Involuntary Heart
beating
Smooth Controlled
by ANS
Involuntary Peristalsis

25. Types of Responses
• Twitch-
– A single brief contraction
– Not a normal muscle function
• Tetanus
– One contraction immediately followed by
another
– Muscle never completely returns to a relaxed
state
– Effects are compounded

26. Where Does the Energy Come
From?
• Energy is stored in the muscles in the form
of ATP
• ATP comes from the breakdown of glucose
during Cellular Respiration
• This all happens in the Mitochondria of the
cell
• When a muscle is fatigued (tired) it is
unable to contract because of lack of
Oxygen

27. Fast Twitch and Slow Twitch
Fibers
Fast Twitch vs Slow Twitch

28. Exercise and Muscles
• Isotonic- muscles shorten and movement
occurs ( most normal exercise)
• Isometric- tension in muscles increases, no
movement occurs (pushing one hand
against the other)

29. How are Muscles Attached to
Bone?
• Origin- attachment to immovable bone
• Insertion- attachment to a movable bone
• Muscles are always attached to at least 2
points
• Movement is attained due to a muscle
moving an attached bone

30. Muscle Attachments
Origin
Insertion

31. Muscle Attachments
• The origin is on the clavicle and sternum.
• The insertion is on the skull.
• When the muscle contracts it will shorten
the distance between the origin and
insertion.
• The head will move when this muscle
contracts.

32. Flexion
Types of Musculo-Skeletal Movement

33. Extension

34. Hyperextension

35. Abduction, Adduction &
Circumduction

36. Rotation

37. More Types of Movement……
• Inversion- turn sole of foot medially
• Eversion- turn sole of foot laterally
• Pronation- palm facing down
• Supination- palm facing up
• Opposition- thumb touches tips of fingers
on the same hand

38. The Skeletal Muscles
There are about 650 muscles in the
human body. They enable us to
move, maintain posture and generate
heat. In this section we will only
study a sample of the major muscles.

39. Sternocleidomastoideus
Flexes and Rotates Head

40. Sternocleidomastoideus
• Sometimes called the sternocleitomastoid.
• It is the same neck muscle shown on the previous
slide.
• This muscle has two origins.
– The first origin is on the sternum manubrium.
– The second origin is on the clavicle.
• The insertion is on the mastoid process of the skull.
• Contraction of both sternocleidomastoideus muscles
will flex the head. If just one of the muscles contracts,
the head will rotate.

41. Masseter
Elevate Mandible

42. Masseter
• The masseter is one of major chewing
muscles.
• The origin of the masseter is on the
zygomatic arch.
• The insertion is on the mandible.
• Contraction of the masseter will elevate the
jaw.

43. Temporalis
Elevate & Retract Mandible

44. Temporalis
• The temporalis is another chewing muscle.
– Note how it attaches on the side of skull.
• It also elevates the mandible.
• You do not need to know the insertions and
origins for this muscle

45. Trapezius
Extend Head, Adduct, Elevate or
Depress Scapula

46. Trapezius
• The trapezius is a large muscle in the upper back.
• It attaches to the skull, shoulder and vertebrae of
the back.
• When this muscle contracts it will cause the head
to extend.
• It will also move the scapula.
• The direction the scapula moves depends on
which part of the trapezius contracts.
• The trapezius may elevate or depress the scapula.

47. Latissimus Dorsi
Extend, Adduct & Rotate Arm Medially

48. Latissimus Dorsi
• The latissimus dorsi is a large muscle in the back.
– It is often referred to as a lat.
• It has origins on the vertebrae, ilium ribs and
scapula.
• The insertion is on the humerus.
– When it contracts it moves the humerus.
• It can extend, adduct and rotate the arm medially.
• This is the main muscle used in movement such as
pounding a nail with a hammer.

49. Deltoid
Abduct, Flex & Extend Arm

50. Deltoid
• The deltoid covers the shoulder and has the shape
of a delta.
• It has origins on the scapula and clavicle.
– The deltoid inserts on the deltoid tuberosity of
the humerus.
• Contraction of the deltoid will adduct the arm.
• If only the anterior fibers of the muscle contract it
will flex the arm.
• Contraction of the posterior fibers will extend the
arm.

51. Pectoralis Major
Flexes, adducts & rotates arm medially

52. Pectoralis Major
• The pectoralis major is a large muscle in the
pectoral region of the body.
• It has origins on the clavicle and sternum.
– The insertion is on the greater tubercle of the
humerus.
• Contraction of the pectoralis major will flex the
arm.
• It will also adduct and rotate the arm medially.
• The pectoralis major is used in movements such a
climbing, throwing and doing pushups.

53. Biceps Brachii
Flexes Elbow Joint

54. Biceps Brachii
• The biceps brachii is located on the anterior side of the
upper arm.
• It is often just called the biceps.
– There is a biceps femoris in the leg we will study
shortly.
• The biceps has two origins. One origin is on the
corocoid process and the other on the Glenoid cavity of
the scapula.
• The “bi” in biceps refers to the two origins.
– It inserts on the radial tuberosity.
• Contraction of the biceps will cause flexing at the elbow
joint.

55. Triceps Brachii
Extend Elbow Joint

56. Triceps Brachii
• The triceps is on the back of the upper arm.
• It has three origins.
• Two origins are on the back of the humerus
and one on the scapula.
• The triceps inserts on the olecranon.
• Movement of the triceps will extend the
elbow joint.

57. Rectus Abdominus
Flexes Abdomen

58. Rectus Abdominus
• Rectus abdominus is a long muscle in the
abdomen.
• The muscle originates on the pubis.
• It inserts on the xiphoid process of the
sternum and also on cartilage of the ribs.
• When rectus abdominus contracts it will
flex the abdomen.

59. External Oblique
Compress Abdomen

60. External Oblique
• Another muscle in the abdomen is the
external oblique.
• It has muscle fibers that run in an oblique
direction across the abdomen.
• Contraction of the external oblique will
compress the abdomen.

61. External Intercostals
Elevate ribs

62. External Intercostals
• There are two groups of muscles that run
between the ribs.
• The first are the external intercostals.
• They will elevate the ribs.

63. Internal Intercostals
Depress ribs

64. Internal Intercostals
• The internal intercostals are also located
between the ribs.
• They will depress the ribs.

65. Diaphragm
Inspiration

66. Diaphragm
• This is an inferior view of the diaphragm.
• This muscle separates the abdominal cavity
from the thoracic cavity.
• When it contracts it will cause inspiration.

67. Forearm Muscles

68. Forearm Muscles
• Flexor carpi—Flexes wrist
• Extensor carpi—Extends wrist
• Flexor digitorum—Flexes fingers
• Extensor digitorum—Extends fingers
• Pronator—Pronates
• Supinator—Supinates

69. Gluteus Maximus
Extends & Rotates
Thigh Laterally

70. Gluteus Maximus
• The large muscle on the posterior side of
the body at the top of each leg is the gluteus
maximus.
• The gluteus maximus originates on the
ilium, sacrum and coccyx.
• It inserts on the gluteal tuberosity of the
femur.
• This muscle will extend and rotate the thigh
laterally.

71. Rectus Femoris
Flexes Thigh,
Extends Lower Leg

72. Rectus Femoris
• Rectus femoris is located on the anterior
side of the thigh.
• It originates on the ilium.
• The insertion is on the patella and the tibial
tuberosity.
• When rectus femoris contracts it will flex
the thigh and extend the lower leg.

73. Gracilis
Adducts and Flexes Thigh

74. Gracilis
• The gracilis is on the medial side of the
thigh.
• It adducts and flexes the thigh.

75. Sartorius
Flexes Thigh, &
Rotates Thigh
Laterally

76. Sartorius
• Sartorius is a long, strap like muscle.
• It originates on the anterior superior iliac
spine of the ilium.
• The insertion is on the medial side of the
tibia.
• Contraction of the sartorius flexes the thigh
and rotates the thigh laterally.
• This is the muscle used when crossing the
legs to sit on the floor.

77. Biceps Femoris
Extends Thigh &
Flexes Lower Leg

78. Biceps Femoris
• Biceps femoris is one of the hamstring
muscles.
• The origin is on the ischial tuberosity.
• Biceps femoris inserts on the tibia and
fibula.
• This muscle extends the thigh and flexes the
lower leg.

79. Gastrocnemius
Plantar Flexes Foot
& Flex Lower Leg

80. Gastrocnemius
• Gastrocnemius is commonly called the calf
muscle.
• It originates on the distal end of the femur.
• The insertion is on the calcaneus bone of
the foot.
• It will cause plantar flexion of the foot and
also flex the lower leg.

81. Tibialis Anterior
Dorsiflexes and Inverts Foot

82. Tibialis Anterior
• Tibialis anterior is located on the anterior
side of the tibia.
• It will dorsiflex and invert the foot.