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THE SKELETAL AND MUSCULAR SYSTEM
Chapter 15.1
Bones and Joints
OBJECTIVES
Describe the structure and function of bones
 Explain the roles of joints and muscles in
movement
 Contrast skeletal, cardiac and smooth muscles
 Describe some disorders of bones, joints, and
muscles

KEY TERMS
Joint
 Ligament
 Tendon
 Flexor
 Extensor
 Osteoporosis
 Arthritis

THE SKELETON IS MADE OF BONES
There are 206 bones in the adult body
 Calcium Phosphate is the mineral that
makes bones hard
 The toughness of bone gives the body strength
 Bones are not rigidly connected to each
other


Exception: the bones of your skull
BONES ARE MADE OF LIVING CELLS
Bones contain blood vessels and nerves
 The blood carries nutrients to and wastes away from
the bone cells
 Many bones have a spongy interior called marrow
which produces blood cells
 The main function of bones are to:

Allow movement, support the body, and protect internal
organs
 The picture shows an osteocyte

JOINTS CONNECT DIFFERENT BONES
•
•
A place where two or more bones are connected is
a joint
There are several types of joint:
–
–
–
–
–
–
Fixed joints connecting the skull plates
Pivot joints like your elbow
Hinge joints like your knee
Ball and socket joints like you shoulder
Gliding joints like your fingers or toes
Saddle joint like your thumb
LIGAMENTS
Moveable joints do not
hold bones tightly
together
 Flexible but strong
straps of tissue hold
the bones tightly
together


Ligaments
connect bone to
bone
MUSCLES
•
There are three types
of muscle:
–
Cardiac
•
–
Skeletal, (move in
pairs)
•
–
Found only in the heart
Attach to two or more
bones
– Flexor
– Extensor
Smooth
•
Found in the bladder
and digestive system
MUSCLES AND FORCE
Bones need muscles to allow them to
move
 Tendons are the attachment point
for muscles to bones
 Muscles must be anchored to more
than one bone to allow for
movement
 Muscles work in pairs to flex and
extend the bone through the range
of motion of the joint

MUSCLES AND NERVE SIGNALS
Muscles contract due
to nerve signals
 Muscles relax after
the signal has passed
 Sometimes muscles
contract without YOU
having to think about
it

Breathing
 Blinking

DISORDERS OF THE BONES, JOINTS,
AND MUSCLES
Osteoporosis is a bone
disorder
 Bones can “break” when
under stress

Osteocytes or “bone cells”
can heal a broken bone
given time
 A fracture or break causes
bone cells to fill in the gap

JOINT DISEASE
Arthritis causes pain
by the ends of bone
rubbing together at
the joint
 The smooth covering
is worn away and the
bones begin to show
signs of damage

SPRAINS AND STRAINS OF LIGAMENTS
The picture is of a
sprained elbow, notice
the joint is displaced
 Ligaments, tendons,
and muscles may all
become damaged by
the displacement
 Muscles repair first,
then tendons, then
ligaments, (if at all)

SUMMARY
Bones are living tissue.
 They produce blood cells, allow movement,
support the body, and protect internal organs
 Bones move when skeletal muscles contract in
response to chemical signals from the brain and
spinal cord
 Dietary calcium and certain types of exercise can
strengthen bones

DEFINITIONS
A joint is a place where two or more bones meet
 A ligament is a strong strap of body tissue that
holds the bones of a joint in place
 A tendon is a strong cord of body tissue that
connects skeletal muscle to bone

DEFINITIONS
A flexor muscle is a muscle that decreases the
angle between two bones
 An extensor is a muscle that increases the angle
between two bones
 Osteoporosis is a bone disorder in which the bone
becomes less dense and more fragile
 Arthritis is a condition in which the joints
become swollen and painful
