1. CHAPTER 19
Musculoskeletal System

2. 1. THE SKELETAL SYSTEM
• A skeleton has many functions:
– Supports body
– Protects soft body parts
– Produces blood cells
– Stores mineral and fat
– Along with muscles, permits flexible body
movement
• The human endoskeleton is composed of
cartilage and bones

3. – The axial skeleton
• Supports the axis of the body and
includes the skull, vertebral column,
and rib cage.
– The appendicular skeleton
• Is made up of the bones of the limbs,
shoulders, and pelvis.

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Axial skeleton Skull:
Appendicular skeleton cranium
mandible clavicle
Thoracic cage: scapula
sternum
ribs humerus
Costal cartilages
Vertebral column
ulna
Pelvic girdle radius
sacrum carpals
coccyx metacarpals
phalanges
femur
patella
fibula
tibia
tarsals
metatarsals
phalanges

5. The Vertebral Column
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7 cervical vertebrae in Neck region
12 thoracic vertebrae
Ribs attach here.
5 lumbar vertebrae in small of back
Sacrum: 5 fused vertebrae
Coccyx: usually 3–5 fused vertebrae "tailbone".

6. JOINTS
There are 3 types of joints:
1. FIBROUS– immovable
– Sutures between bones of skull
2. CARTILOGENOUS– slightly movable
– Connected by hyaline cartilage
– Ribs / sternum
– Connected by fibrocartilage
– Intervertebral discs
3. SYNOVIAL – freely movable

7. TYPES OF SYNOVIAL JOINTS
Synovial which means they are freely movable
– Bones are separated by a cavity
– Tendons help to stabilize the joint
– Synovial membrane produces synovial fluid
3 types:
permit movement in permit movement in permit only
all planes one direction only rotational
Ex: shoulder joint Ex: elbow movement

8. Bone Structure
Bones are complex organs consisting of several kinds of
tissues.
Bones
– Are covered with a connective tissue
membrane.
– Have cartilage at the ends that cushions the
joints.
– Are served by blood vessels and nerves.

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cartilage
spongy bone
epiphysis
(contains red bone marrow)
compact bone
Central cavity
(contains yellow bone marrow)
diaphysis
Fibrous connective tissue
blood vessel
epiphysis

10. – The central cavity of a long bone (or
diaphysis)
• Contains yellow bone marrow, which
is mostly stored fat.
– The end of a long bone (or epiphysis)
• Contains red bone marrow, a
specialized tissue that produces blood
cells.

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central canal
osteon
compact
bone
spongy bone Blood vessels

12. Compact Vs Spongy Bones
• COMPACT BONE
– HARD MATERIAL of the bone
– Highly organized
• SPONGY BONE
– Unorganized appearance (but plates follow
lines of stress so spongy bone is strong)
– Spaces filled with red bone marrow

13. Skeletal Diseases and Injuries
The human skeleton is quite strong and
provides reliable support, but it is susceptible to
disease and injury, such as:
A. Fracture
B. Osteoporosis
C. Arthritis

14. A. Fracture
• If a force applied to a bone exceeds its capacity to
bend, the result is a broken bone or fracture.
• The treatment of a fracture involves 2 steps:
1. Putting the bone back into its natural shape
2. Immobilizing it until the body can repair the fracture
– In severe cases, a fracture can be repaired surgically by
inserting plates, rods, and/or screws to hold the broken
pieces together.

15. SOME TYPICAL BONE FRACTURES
LINEAR SPIRAL COMMINUTED TRANSVERSE COMPOUND
The fracture is At least one The bone has The fractured is or OPEN
parallel to the part of the fractured into a at a right angle The skin is
bone long axis bone is twisted number of pieces with the bone broken, the
axis bone sticks out

17. B. Osteoporosis
• Bones lose mass and mineral content
• Leads to an increase risk of fractures

18. C. Arthritis
• Osteoarthritis
– Degenerative joint disease
(cartilage)
• Rheumatoid arthritis
– Autoimmune disease
– Joints and other tissues
are attacked

19. 2. THE MUSCULAR SYSTEM

20. 2. THE MUSCULAR SYSTEM
• Pull on bones to produce movements
• Skeletal muscles = voluntary
movements
• Attached to the bone by tendons
• 650 human skeletal muscles

21. Antagonistic pairs of muscles bring about
movement in opposite directions

22. a. Anterior view
frontalis
trapezius
deltoid
pectoralis major
biceps brachii
rectus abdominis
external oblique
adductor longus sartorius
quadriceps femoris group
peroneus longus gastrocnemius
tibialis anterior
extensor digitorum longus
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23. b. Posterior view
occipitalis
trapezius
deltoid
Latissimus dorsi triceps brachii
External oblique Gluteus medius
Extensor digitorum
Gluteus maximus Hamstring group
gastrocnemius
Peroneus longus
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24. Muscle structure
• The skeletal muscle consists of
bundles of parallel muscle fibers
• One muscle fiber is a muscle cell
bundle of
muscle fibers
One muscle
fiber/cell
myofibrils
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25. MUSCLE FIBER
• One muscle fiber has many myofibrils
• Is called striated, because the myofibrils
exhibit alternating light and dark bands
when viewed with a light microscope.
• A sarcomere is the region between two dark,
narrow lines called Z lines. It is the unit of
contraction

27. How does a muscle contract?
• A myofibril is composed of 2 kinds of filaments:
– Thin filaments, made mostly of the protein actin
– Thick filaments, made mostly of the protein myosin
• A sarcomere contracts
– When its thin filaments slide across its thick
filaments.

28. Figure 27.33

29. The sliding-filament model
Myosin heads in the thick filaments binds to specific
sites on actin molecules in the thin filaments.

30. Muscle contractrion videos
• http://www.youtube.com/watch?
v=CepeYFvqmk4
• http://www.youtube.com/watch?
v=v71ZP8_RoOU&feature=related
• http://www.youtube.com/watch?
v=0kFmbrRJq4w&NR=1

31. Control of muscle contraction
Motor neurons
• Stimulate muscles to contract.
• Can branch to a number of muscle
fibers.
A motor unit consists of a neuron and all
the muscle fibers it controls.

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Skeletal muscle fiber
Axon branch
Axon terminal
myofibril
neuromuscular
junction
a. One motor axon causes
several muscle fibers to
contract.

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© Victor B. Eichler, Ph.D.

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synaptic
vesicle
synaptic
cleft
acetyl choline
(ACh)
Na+
folded
sarcolemma
ACh receptor
The release of a neurotransmitter (ACh) causes
receptors to open and Na+ to enter a muscle fiber.

35. Whole Muscle Contraction
• In the Body
– A motor unit is a nerve fiber together with
all the muscle fibers it innervates
– As the intensity of nervous stimulation
increases, more motor units are activated
– Some muscle fibers are contracting while
others are relaxing
– Even when muscles appear to be at rest,
some fibers are always contracting (muscle
tone)

36. Athletics and Muscle Contraction
• Exercise and Size of Muscles
– Muscles that are not used decrease in size
(atrophy)
– If stimulation is not restored, muscle fibers are
gradually replaced by fat and fibrous tissue
– Forceful activity over prolonged period causes
muscle to increase in size
• Hypertrophy occurs only if muscle contracts to at least
75% of maximum tension
• Increase in number of myofibrils within fibers causes
hypertrophy

37. Are all your muscle fibers the same?
• What types of exercises can you do?
• Aerobic such as running
• Anaerobic such as lifting weight
• Are their requirements in oxygen the same? NO
• Aerobic such as running needs lots of oxygen
• Anaerobic doesn’t
• They will need different amount of :
– mitochondria (remember turns oxygen into
energy)
– myoglobin (protein that binds oxygen and iron)

38. Different fibers for different types of exercises:
Slow-Twitch and Fast-Twitch Muscle Fibers
slow-twitch fast-twitch
fibers fibers
Slow-twitch muscle fiber: Fast-twitch muscle fiber:
• Is dark in appearance • Is light in appearance
(Contains lots of mitochondria • is anaerobic
and myoglobin) has explosive power
• is aerobic • Fatigues easily
has steady power
• has endurance
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