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Lesson 2 Summary
Use with pp. 42–45
Lesson 2: How do cells work together?
Vocabulary
tissue a group of the same kind of cells working together doing the
same job
There are about 200 different kinds of
cells in your body. Cells have different jobs.
A cell’s shape helps the cell do its job.
tissues do the same job. Muscle tissue is made
of muscle cells grouped together. Bone cells
grouped together make up bone tissue. Nerve
cells grouped together make up nerve tissue.
Branching Cells
Tissues Form Organs
Types of Cells and Their Work
Flat cells join together to cover a surface.
Your skin has many layers of flat cells. This
makes your skin strong. Flat cells are also
on the inside of your mouth and stomach.
Tissues join together to make organs. Your
heart, eyes, ears, and stomach are organs.
Your body’s largest organ is your skin.
Organs have jobs. Hair is a tissue in the
organ of your skin. It protects your skin. It
holds warm air next to your body. Sweat
glands are tissues in your skin. They make
sweat. Sweat helps cool your skin. Sweat also
carries waste products from the cells.
Plants have organs too. Stems, roots, leaves,
and flowers are all plant organs.
Round Cells
Skin Cell Tissue
Red blood cells move through blood
vessels easily because they are smooth. Red
blood cells look like small discs. Their shape
helps them pick up oxygen and carry it to
all the cells in your body.
Skin cells form in many layers. New cells
are made in the bottom layers. They push
older cells away from any blood supply.
Older cells are dead when they reach the
outside surface of the skin. The dead cells
fall off your body.
Nerves cells carry signals between the brain
and the rest of the body. Nerve cells look
like tree branches. These branching shapes
connect many parts of the body. This helps
signals reach the brain quickly.
Flat Cells
Special Cell Structure
Cells have different structures. For example,
muscle cells have long thread-like fibers. Cells
in your ears and lungs have structures like
hair. In the lungs, these structures are called
cilia. They sweep dirt and germs out of your
airways.
Cells Form Tissues
Cells usually don’t work by themselves.
They often work in tissues. Tissues are like
teams of cells that work together. Cells in
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Chapter 2, Lesson 2 Summary
Other Tissues in the Skin
Skin has many tissues. They work
together to do many jobs. Skin protects your
insides. Skin keeps out germs. Skin doesn’t
let too much water leave your body. Nerve
tissue in your skin helps you sense touch
and temperature. Blood vessels carry food
and oxygen to cells. Oil glands keep your
skin soft. When you are cold, muscle tissue
makes the hair on your skin stand up. The
hairs trap warm air next to the skin and
keeps the skin warm.
Quick Study
© Pearson Education, Inc. 5
organ a grouping of different tissues combined together into one
structure to perform a main job in the body
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Lesson 2 Checkpoint
Use with pp. 42–45
Lesson 2 Checkpoint
1. What are cilia and what do they do?
2. How does a nerve cell’s shape and structure help it do its job?
3. How is a tissue like a team?
Draw Conclusions Why is it an advantage to have dead cells
on the surface of the skin?
© Pearson Education, Inc. 5
4.
Quick Study
Chapter 2, Lesson 2 Checkpoint
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