Download Chapter 20 Support and Movement

Key words
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Flexor
Extensor
Smooth muscle
Skeletal muscle
Cardiac muscle
Chapter 20 Support and Movement
Formation of Bones
• As a developing baby,
your skeleton was made
mostly of cartilage.
– During the 2nd and 3rd
months of development
bones begin to form.
– Bone cells replace cartilage
and calcium compounds
were deposited
Formation of Bones cont.
• Growth in height from infancy to adulthood takes
place because new bone tissue was produced in
the round ends of your bones.
– Bone growth continues until the cartilage is replaced
by bone.
– The replacement of cartilage into bone is a long
process that will not be completed until you are about
20 years old.
Skeletal problems
• Have you ever fractured a
bone?
• A fracture is a break in a
bone, which may be partial
or complete.
• Some skeletal problems
arise from injury while
others can arise from birth,
disease, or unknown
sources.
– Ex: Arthritis, scoliosis,
osteoporosis
The Muscular System
• Your body contains more than 600 muscles.
Types of Muscles
• Skeletal muscles (voluntary muscles)
• Smooth muscles (involuntary muscles)
• Cardiac muscles
Skeletal muscles (voluntary muscles)
• This type of muscle is attached to bones, and
make movement possible.
• You can make skeletal muscles move whenever
you want, therefore they can also be called
voluntary muscles.
• Skeletal muscles are attached to bones by
tendons, which are tough elastic bands of tissue.
Smooth muscles (involuntary muscles)
• This type of muscle is found in the walls of
blood vessels, the stomach, and other organs.
• Involuntary muscles are muscles that you can
not control.
Cardiac muscles
• This type of muscle makes up the heart.
• It pumps blood through the heart and the rest
of the body.
• Is the cardiac muscle voluntary or involuntary
muscle? How do you know?
Muscle actions
• Muscle cells can change their length.
– When a muscle does its job, the cells in the muscle
contract, or shorten.
– When a skeletal muscle contracts, the muscle pulls on
the bone to which it is attached causing that body
part to move.
– Skeletal muscles always work in pairs.
• Ex: biceps and triceps
Muscle actions cont.
• A muscle that bends a joint is called a flexor.
• A muscle that straightens a joint is called an
extensor.
Muscle problems
• Have you ever had a muscle cramp?
• Do your muscles get sore after you exercise?
• Cramps occur when muscles spasm by
contracting suddenly and strongly.
• Sore muscles are caused by overuse or small
tears in muscle.
• A muscle strain is caused by a large tear that
requires rest and time to heal.
• What are some other muscle problems?
Skin
• Skin is the largest organ
of the human body.
• Dead skin cells form
much of the outer layer
of skin, which is called
the epidermis.
• The main function for
skin is to support and
protect the body.
Careers in Biology
• X-Ray Technician
• Physical Therapist
• Chiropractor
X-Ray Technician
• They make x-ray films of parts of the human
body for in use of diagnosing medical
problems. They work in hospitals, clinics,
medical laboratories, nursing homes, and in
private practice.
Physical Therapist
• They plan and treat people who have suffered
disabling accidents or who have permanent
physical disabilities. They work in hospitals,
doctors’ offices, and rehabilitation centers.
Chiropractor
• They treat based on the principle that a
person’s health is determined largely by the
nervous system.