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The Skeletal System- Reinforcement
Grade Seven Science Content Standard. 5.c. Students know how bones and muscles work together to provide a structural framework for movement.
Before You Read
-!). )DEA
Imagine a builder that only builds the outside walls of a
house. Although the house would be protected from the
elements, it wouldn’t be a home until the inside was finished.
On the lines below, write about what would be needed to
complete the house. In this lesson, you will read about parts
of the body that work together so that you can move.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Read to Learn
Muscles, tendons, ligaments,
and bones work together to
produce movement.
What You’ll Learn
the main characteristics of the
skeletal system
■ how muscles contract and relax
■
3TUDY #OACH
The Skeletal System
Write Questions As
The hard structures within your body are part of your
skeletal system (SKE luh tuhl • SIS tum), which provides
support, protection, and movement. The human body has
over 200 bones that make up the skeletal system. A bone is
a hard tissue made mostly of cells, collagen, and calcium.
Collagen is a protein that forms strong fibers. Calcium is a
mineral that adds strength to the collagen fibers.
Bones have different shapes and sizes. Blood vessels and
nerves enter and leave bones. Bones have many small, open
spaces. The spaces make bones lighter.
One function of bone is protection. The bones in your
skull, for example, protect your brain from injury. The
vertebrae in your back protect the spinal cord. Without
support from the skeletal system, you would be a soft
mass without definite shape. Your muscles attach to bones
and allow you to move. The middle of some bones, called
marrow, is the place where blood cells are formed.
A Define Make a fourtab Foldable and label the
front tabs as illustrated. Define
and record what you learn
about bones, ligaments,
tendons, and cartilage under
the tabs.
Reading Essentials
you read this lesson, write a
question for each paragraph.
After you’re done reading,
answer your questions.
Chapter 9 The Musculoskeletal System and Levers
107
How do bones connect at joints?
Academic
Vocabulary
similar (SIH muh lur)
(adj.) alike; much the same
as
Bones are hard and cannot bend. Yet, your body is
flexible. You can bend, twist, and rotate because your
bones connect at joints, such as those in the figure below.
The softer tissues of the skeletal system help hold bones
together at joints. Ligaments connect bones. Ligaments are
similar to strong rubber bands that stretch when you move.
Cartilage is a strong, elastic tissue that reduces friction and
increases flexibility. Read the descriptions and label the type of
joint each picture represents. (write your response below the
pictures)
skull
arm
shoulder
knee
vertebrae
Picture This
1. Identify the type of
joint used in each of the
following activities.
raise your arm:
kneel:
The structure of a joint determines how the bones that
connect at the joint can move. For example, you can twist
your lower arm to the right or left without moving your
upper arm. Your elbow joint allows this movement.
Hinge Joint The joints in your fingers, elbow, and knee
are hinge joints. Hinge joints only allow bones to move
back and forth, like the hinges of a door.
Saddle Joint Your thumb has a saddle joint. In a saddle
joint, the bones at both ends are shaped liked saddles.
Compare the movement of your thumb to the other fingers
in your hand. The thumb has a wider range of motion.
The only saddle joint in your body is your thumb joint.
2. Locate Where
is the saddle joint
in the human
body?
108
Ball-and-Socket Joint Your hip and shoulder joints
are ball-and-socket joints. They can move in nearly every
direction. One bone in a ball-and-socket joint is round. It
fits into a cuplike depression of the joint’s other bone. An
ellipsoid joint is like a ball-and-socket joint, except the end
of the bone is shaped like an ellipse instead of being round.
The knuckles of your hands are examples of ellipsoid joints.
Chapter 9 The Musculoskeletal System and Levers
Reading Essentials
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What are the different types of joints?
Pivot Joint You can turn your head from side to side
because of a pivot joint between the first two vertebrae
in your neck. In a pivot joint, the cylindrical region of one
bone fits into a ring-shaped structure of another bone. Pivot
joints only allow bones to rotate.
Academic Vocabulary
region (RIH juhn) (noun) an
area
Gliding Joint Two bones that connect at flat surfaces form
a gliding joint. The bones in a gliding joint can only move
from side to side or front to back. Your ankles and wrists
have gliding joints.
Immovable Joint Two bones held firmly together form
an immovable joint. An immovable joint allows very little
or no movement. Your skull contains immovable joints.
When you were born, there were spaces between some of
the bones of your skull. These spaces allowed your brain to
grow. As you grew, the immovable joints fused the bones in
your skull together.
Define What is an
immovable or fused joint?