Chapter 15
Body Organization and Structure
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Section 1 Body Organization
Section 2 The Skeletal System
Section 3 The Muscular System
Concept Map
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Chapter 15
Section 1 Body Organization
Bellringer
In your Science Journal, match each organ system
with its correct function.
Organ systems: respiratory system, muscular system,
digestive system, cardiovascular system
Functions: to pump blood, to enable movement, to send
out chemical messages, to absorb oxygen, to break
down food.
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Chapter 15
Section 1 Body Organization
What You Will Learn
• The levels of organization in the human body include
cells, tissues, organs, organ systems, and the
organism.
• Human cells are differentiated to perform specific
jobs in the body.
• There are 11 human organ systems.
• Organ systems work together to maintain
homeostasis. The failure of one organ system
affects the entire body.
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Chapter 15
Section 1 Body Organization
A Stable Environment
• Cells, tissues, and organs work together to maintain
a stable environment inside the body.
• The maintenance of a stable environment inside the
body is called homeostasis.
• When homeostasis is not maintained, cells may not
function properly or die.
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Chapter 15
Section 1 Body Organization
Cells, Tissues, and Organs
• Most cells in your body are differentiated.
Differentiated cells are specialized to perform specific
functions for the body.
• The structure of each cell is related to its function.
• Similar cells are organized into groups. A group of
similar cells working together to perform a common
function forms a tissue.
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Chapter 15
Section 1 Body Organization
Cells, Tissues, and Organs, continued
• Your body has four main kinds of tissue: epithelial
tissue, nervous tissue, muscle tissue, and connective
tissue.
• Epithelial tissue covers and protects underlying
tissue. Your skin is primarily epithelial tissue.
• Nervous tissue sends electrical signals through the
body. It is found in the brain, nerves, and sense
organs.
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Chapter 15
Section 1 Body Organization
Cells, Tissues, and Organs, continued
• Muscle tissue is made of cells that contract and relax
to produce movement.
• Connective tissue supports and protects the organs
of the body. Connective tissue holds everything in its
proper place.
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Chapter 15
Body Organization and Structure
Body Tissues
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Visual Concept
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Chapter 15
Section 1 Body Organization
Cells, Tissues, and Organs, continued
• Two or more types of tissues working together to
carry out a function form an organ.
• The heart is an organ made of muscle, connective,
and epithelial tissues. None of these tissues alone
could carry out the function of the heart.
• The stomach is another organ made up of four
different tissues.
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Chapter 15
Section 1 Body Organization
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Chapter 15
Section 1 Body Organization
Cells, Tissues, and Organs, continued
• Two or more organs working together to carry out a
function form an organ system.
• Organ systems perform jobs that organs cannot
perform by themselves.
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Chapter 15
Section 1 Body Organization
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Chapter 15
Section 1 Body Organization
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Chapter 15
Section 1 Body Organization
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Chapter 15
Section 1 Body Organization
Organ Systems Working Together
• Your body’s organ systems work together to maintain
homeostasis.
• For example, the cardiovascular system and
respiratory system work together to provide oxygen
to all cells of the body.
• Some organs are part of more than one organ
system.
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Chapter 15
Section 2 The Skeletal System
Bellringer
In your Science Journal, brainstorm problems you
would have if you did not have bones.
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Chapter 15
Section 2 The Skeletal System
What You Will Learn
• The skeletal system includes bones, cartilage, and
connective tissue.
• Bones have four important functions in the body.
Bones are structured to perform these functions.
• Three human body joints are gliding, ball-andsocket, and hinge.
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Chapter 15
Section 2 The Skeletal System
Bones, continued
• The skeletal system is made up of your bones,
cartilage, and the connective tissue holding your
bones together.
• The functions of the skeletal system include support,
protection, movement, and the production of blood
cells.
• Bones help maintain homeostasis by storing minerals
and fat that can be used in the body.
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Chapter 15
Section 2 The Skeletal System
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Chapter 15
Section 2 The Skeletal System
Bones, continued
• Bones are made of two types of bone tissue.
Compact bone is dense and rigid. Spongy bone
contains open spaces, but is actually responsible for
most of the bone’s strength.
• Blood cells are produced in larger bones that contain
marrow. Red marrow makes red and white blood
cells. Yellow marrow stores fat.
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Chapter 15
Section 2 The Skeletal System
Bones, continued
• Bone Growth Most bones start as a flexible tissue
called cartilage. As you age, most of the cartilage is
replaced by bone.
• Bones grow at sites called growth plates, which
consist of cartilage. Children loose their growth plates
as they reach adult size.
• Your ears and the tip of your nose are sites that never
lose their cartilage.
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Chapter 15
Body Organization and Structure
Human Bone Growth
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Visual Concept
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Chapter 15
Section 2 The Skeletal System
Joints
• A place where two or more bones meet is called a
joint.
• Fixed joints allow little or no movement. The bones in
your skull are fixed joints.
• Ball-and-socket joints allow the widest range of
movement. Hinge joints allow one-way movement,
and gliding joints allow bones to slide over one
another.
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Chapter 15
Section 2 The Skeletal System
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Chapter 15
Section 2 The Skeletal System
Joints, continued
• Joints are able to withstand the stresses of
movement because of their structure.
• Joints are held together by ligaments. Ligaments are
strong, elastic bands of connective tissue.
• Cartilage also helps reduce wear and tear on joints
by cushioning the areas where bones meet.
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Chapter 15
Section 2 The Skeletal System
Skeletal System Injuries and Diseases
• Despite their strength and flexibility, bones can
break, or fracture.
• Joints can become dislocated when bones move out
of their proper positions.
• A sprain occurs when the ligaments of a joint have
been stretched too far or have torn.
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Chapter 15
Section 2 The Skeletal System
Skeletal System Injuries and Diseases,
continued
• Osteoporosis is a disease of the skeletal system. In
osteoporosis, bones become less dense, which
makes them break more easily.
• Arthritis is a painful disease that affects joints. In
arthritis, joints become swollen and stiff.
• As people age, they are more likely to have
osteoporosis or arthritis.
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Chapter 15
Section 3 The Muscular System
Bellringer
List at least five parts of your body that you use to drink
water.
Record your answers in your Science Journal.
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Chapter 15
Section 3 The Muscular System
What You Will Learn
• There are three kinds of muscle tissue: cardiac,
smooth, and skeletal.
• Bones and muscles work together to form levers,
which increase the mechanical advantage of most
movements.
• The two kinds of exercise include resistance exercise
and aerobic exercise.
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Chapter 15
Section 3 The Muscular System
Kinds of Muscle
• The muscular system is made up of the muscles
that let you move. Muscles also let you breathe and
hold you upright.
• The muscular and skeletal systems work together to
provide a structural framework for movement.
• The combined organ systems are sometimes called
the musculoskeletal system.
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Chapter 15
Section 3 The Muscular System
Kinds of Muscle, continued
• Muscle actions can be voluntary or involuntary.
Voluntary actions are under your control. Involuntary
actions happen without your control.
• Smooth muscle is found in the digestive tract and
blood vessel walls. Their actions are involuntary.
• Cardiac muscle is found only in the heart. Its action is
involuntary.
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Chapter 15
Section 3 The Muscular System
Kinds of Muscle, continued
• Skeletal muscle is attached to bones and allows you
to move. Their actions can be voluntary or
involuntary.
• An example of an involuntary skeletal muscle action
is an eye blink that happens without your awareness.
• You can also blink your eyes voluntarily.
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Chapter 15
Section 3 The Muscular System
Movement
• When you want to move, signals travel from your
brain to your skeletal muscle cells.
• The muscle cells then contract, or get shorter.
• Tendons connect the muscles to the bones. As
muscles contract, they pull on the tendons which
move the bones.
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Chapter 15
Section 3 The Muscular System
Movement, continued
• Skeletal muscles often work in pairs, as the biceps
and triceps of the arm.
• Usually, one muscle in the pair bends a part of the
body. The other muscle in the pair straightens the
part of the body.
• Bending muscles are called flexors. Extending
muscles are called extensors.
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Chapter 15
Section 3 The Muscular System
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Chapter 15
Body Organization and Structure
Muscular Movement and Bones
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Visual Concept
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Chapter 15
Section 3 The Muscular System
Levers in the Human Body
• The action of a muscle pulling on a bone can work
like a lever.
• A lever is a rigid bar that pivots at a fixed point known
as a fulcrum. A lever is a type of simple machine.
• Levers increase the amount of work that can be
done. This increase in work is called mechanical
advantage.
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Chapter 15
Section 3 The Muscular System
Levers in the Human Body, continued
• In your body, the rigid bar, or lever, is the bone. The
fulcrum, or pivot point, is the joint.
• Any force applied to a lever is called the effort force.
Any force that resists the motion of the lever is called
the load.
• In your body, the effort force is supplied by muscles.
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Chapter 15
Section 3 The Muscular System
Levers in the Human Body, continued
• There are three classes of levers. First and second
class levers increase the amount of force applied to
the load.
• Third class levers increase the speed of the motion.
Most of the moving joints in the body are third class
levers.
• The class of a lever is determined by the location of
the fulcrum, load, and effort force.
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Chapter 15
Section 3 The Muscular System
Levers in the Human Body, continued
• The joint at your neck acts as the fulcrum in a first
class lever.
• The action of raising up onto your toes is due to a
second class lever.
• Lifting a textbook uses a third class lever. Your elbow
is the fulcrum, the book is the load, and the biceps
muscle provides the effort force.
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Chapter 15
Section 3 The Muscular System
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Chapter 15
Section 3 The Muscular System
Use It or Lose It
• When skeletal muscles are not used, they become
smaller and weaker. Exercised muscles are larger
and stronger.
• Resistance exercise uses resistance, or weight, to
strengthen muscles.
• Aerobic exercise strengthens the heart and increases
endurance. Endurance allows muscles to work longer
without getting tired.
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Chapter 15
Section 3 The Muscular System
Muscle Injury
• A strain occurs when a muscle or tendon is
overstretched or torn. Stretching and warming-up can
help prevent strains.
• Tendonitis occurs when a damaged tendon becomes
swollen and painful.
• Use of anabolic steroids to strengthen muscles can
cause long-term damage to the heart, liver, kidneys,
and bones.
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Chapter 15
Body Organization and Structure
Concept Map
Use the terms below to complete the concept map
on the next slide.
connective
nervous
homeostasis
organs
epithelial
epithelial
tissues
organ systems
cells
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Chapter 15
Body Organization and Structure
Concept Map
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Chapter 15
Body Organization and Structure
Concept Map
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