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Skeletal System
Two Kinds of Skeletons
Exoskeletons are formed on the outside of the organisms. They are tough and hard to provide the organism with protection. Lobster
and crabs are some animals that have an exoskeleton.
Endoskeletons are formed on the inside of the organism. This type of skeleton can be found in humans, dogs, cats and most of the
animals we can think of today.
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Give two other examples of organisms with a exoskeleton ____________________________________________
Give two other examples of organisms with a endoskeleton___________________________________________
Your Skeleton
How important is your skeleton? Can you imagine your body without it? You would be a wobbly pile of muscle and internal organs,
and you would not be able to move.
The adult human skeleton has 206 bones, however you are born with 300 some of which fuse together over time. Bones are made up
of living tissue. They contain many different types of tissues. Cartilage, a dense connective tissue, is found at the end of bones and is
made of tough protein fibers. Cartilage creates smooth surfaces for the movement of bones that are next to each other, like the bones
of the knee.
Ligaments are made of tough protein fibers and connect bones to each other. Your bones, cartilage, and ligaments make up your
skeletal system.
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6.
How many bones does an adult human contain? __________________________________________
Name two bones in the human skeletal system____________________________________________
What is cartilages job and location _____________________________________________________
What is the function of ligaments_______________________________________________________
Functions of Bones
Your skeletal system gives shape and form to your body, but it also plays other important roles. The main functions of the skeletal
system include:
Support. The skeleton supports the body against the pull of gravity, meaning you don't fall over when you stand up. The large bones
of the lower limbs support the rest of the body when standing. The spine is your main support. It is made up of bones called vertebras
that stack up but have cartridge in between
Protection. The skeleton supports and protects the soft organs of the body. For example, the skull surrounds the brain to protect it
from injury. The bones of the rib cage help protect the heart and lungs. This is a connection to the nervous system, digestive system,
respiratory system, circulatory system and any system that has organs.
Movement. Bones work together with muscles to move the body.
Making blood cells. Blood cells are mostly made inside certain types of bones. This is a connection to the circulatory system which
requires blood to transport oxygen and carbon dioxide.
Storage. Bones store calcium. They contain more calcium than any other organ. Calcium is released by the bones when blood levels
of calcium drop too low. The mineral, phosphorus is also stored in bones. This a connection to the nervous system which will
communicate the body’s need for the minerals.
Maintaining mineral homeostasis is a very important function of the skeleton, because just the right levels of calcium and other
minerals are needed in the blood for normal functioning of the body. When mineral levels in the blood are too high, bones absorb
some of the minerals and store them as mineral salts, which is why bones are so hard. When blood levels of minerals are too low,
bones release some of the minerals back into the blood, thus restoring homeostasis.
7.
Your skeletal system has 5 functions explain what might happen to your body if one of these functions stopped working.
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Structure of Bones
Bones come in many different shapes and sizes, but they are all made of the same materials. Bones are organs, and recall that organs
are made up of two or more types of tissues.
Are bones living?
It's common to think of bones as not living. But bones are very much living. In fact, you are constantly making new bone tissue. That
means that you are also constantly getting rid of bone. Bone is full of blood and nerves and all sorts of cells and proteins, making it an
extremely complex living tissue.
Many people think of bones as being dead, dry, and brittle. These adjectives correctly describe the bones of a preserved skeleton, but
the bones in a living human being are very much alive. As shown in Figure below, the basic structure of bones is bone matrix, which
makes up the underlying rigid framework of bones, composed of both compact bone and spongy bone. The bone matrix consists of
tough protein fibers, mainly collagen, that become hard and rigid due to mineralization with calcium crystals. Bone matrix is
crisscrossed by blood vessels and nerves and also contains specialized bone cells that are actively involved in metabolic processes.
8.
Describe the bone matrix
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Bone matrix provides bones with their basic structure. Notice the spongy bone in the middle, and the compact bone towards the outer
region. The osteon is the functional unit of compact bone.
Bone Cells
There are three types of specialized cells in human bones: osteoblasts, osteocytes, and
osteoclasts. These cells are responsible for bone growth and mineral homeostasis.
 Osteoblasts make new bone cells and secrete collagen that mineralizes to become bone
matrix. They are responsible for bone growth and the uptake of minerals from the blood.
 Osteocytes regulate mineral homeostasis. They direct the uptake of minerals from the
blood and the release of minerals back into the blood as needed.
 Osteoclasts dissolve minerals in bone matrix and release them back into the blood.
9.
Which of the bone cells do you consider the most important and why
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Bones are far from static, or unchanging. Instead, they are dynamic, living tissues that are constantly being reshaped. Under the
direction of osteocytes, osteoblasts continuously build up bone, while osteoclasts continuously break it down.
Bone Tissues
Bones consist of different types of tissue, including compact bone, spongy bone, bone
marrow, and periosteum. All of these tissue types are shown in Figure
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Compact bone makes up the dense outer layer of bone. Its functional unit is the
osteon. Compact bone is very hard and strong.
Spongy bone is found inside bones and is lighter and less dense than compact bone.
This is because spongy bone is porous.
Bone marrow is a soft connective tissue that produces blood cells. It is found
inside the pores of spongy bone. Red produces blood cells and yellow stores fat.
Periosteum is a tough, fibrous membrane that covers and protects the outer
surfaces of bone.
10. Explain how all these types of bone tissue work together to make our bones function
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Why does your knee hurt?
As you age, you might start noticing pain in your knees or elbows. These are examples of joints. Joints are the part of the skeletal
system that connect your bones. Joint pain is a common problem as people age.
Joints and How They Move
A joint is a point at which two or more bones meet. There are three main types of joints in the body:
1.
Fixed joints do not allow any bone movement. Many of the joints in your skull are
There are eight bones that fuse together to form the cranium. The joints between
bones do not allow movement, which helps protect the brain.
The skull has fixed joints. Fixed joints do not allow any movement of the bones, which
the brain from injury.
2.
fixed
these
protects
Partly movable joints allow only a little movement. Your backbone has partly movable joints between the vertebrae
The joints between your vertebrae are partially movable.
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Movable joints allow the most movement.
Movable joints are also the most common type of joint in your body. Your fingers, toes, hips, elbows, and knees all provide examples
of movable joints. The surfaces of bones at movable joints are covered with a smooth layer of cartilage. The cartilage reduces friction
between the bones. Ligaments often cross a joint, holding two bones together. For example, there are numerous ligaments connecting
the leg bones across the knee joint.
11. What will reduce friction between bones _____________________________________________________
Types of Movable Joints
Four types of movable joints are discussed here.
1. In a ball-and-socket joint, the ball-shaped surface of one bone fits into the cuplike shape of another. Examples of a ball-and-socket joint include the hip and the
shoulder.
Your hip joint is a ball-and-socket joint. The “ball” end of one bone fits into the “socket”
of another bone. These joints can move in many different directions.
2.
In a hinge joint, the ends of the bones are shaped in a way that allows motion in two directions, forward and backward.
Examples of hinge joints are the knees and elbows.
Hinge Joint. The knee joint is a hinge joint. Like a door hinge, a hinge joint allows backward and
forward movement.
3.
The pivot joint only allows rotating movement. An example of a pivot joint is the joint
between the radius and ulna that allows you to turn the palm of your hand up and down.
Pivot Joint. The joint at which the radius and ulna meet is a pivot joint. Movement at this
joint allows you to flip your palm over without moving your elbow joint.
4. A gliding joint is a joint which allows only gliding movement. The gliding joint
allows one bone to slide over the other. The gliding joint in your wrist allows you to flex
your wrist. It also allows you to make very small side-to-side motions. There are also
gliding joints in your ankles.
12. Of the 4 joints which one do you think would affect your movement the most if all in your body were damaged beyond repair
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Keeping Bones and Joints Healthy
You can help keep your bones and skeletal system healthy by eating well and getting enough exercise. Weight-bearing exercises help
keep bones strong. Weight-bearing exercises and activities work against gravity. Such activities include basketball, tennis, gymnastics,
karate, running, and walking. When the body is exercised regularly by performing weight-bearing activity, bones respond by adding
more bone cells to increase their bone density.
Eating Well
Did you know that what you eat as a teenager can affect how healthy your skeletal system will be in 30, 40, and even 50 years?
Calcium and vitamin D are two of the most important nutrients for a healthy skeletal system. Your bones need calcium to grow
properly. If you do not get enough calcium in your diet as a teenager, your bones may become weak and break easily later in life.
Osteoporosis is a disease in which bones lose mass and become more fragile than they should be. Osteoporosis also makes bones
more likely to break. Two of the easiest ways to prevent osteoporosis are eating a healthy diet that has the right amount of calcium and
vitamin D and to do some sort of weight-bearing exercise every day. Foods that are a good source of calcium include milk, yogurt, and
cheese. Non-dairy sources of calcium include Chinese cabbage, kale, and broccoli. Many fruit juices, fruit drinks, tofu, and cereals
have calcium added to them. It is recommended that teenagers get 1300 mg of calcium every day. For example, one cup (8 fl. oz.) of
milk provides about 300 mg of calcium, or about 30% of the daily requirement. Other sources of calcium are pictured
13. What is the problem happening in Osteoporosis? _________________________________________________________
There are many different sources of calcium. Getting enough calcium in your daily diet is important for good bone health. Vitamin D
is unusual since you don't have to rely on your diet alone to get enough of this vitamin. Your skin makes vitamin D when exposed to
sunlight. Pigments in the skin act like a filter that can prevent the skin from making vitamin D. As a result, people with darker skin
need more time in the sun than people with lighter skin to make the same amount of vitamin D.
You can also get vitamin D from foods. Fish is naturally rich in vitamin D. In the United States, vitamin D is added to other foods,
including milk, soy milk, and breakfast cereals. Teenagers are recommended to get 5 micrograms (200 IU) of vitamin D every day. A
3½-ounce portion of cooked salmon provides 360 IU of vitamin D. A 8-ounce glass of milk is fortified with about 100 IU of vitamin
D.
14. What are 3 good sources of calcium _____________________________________________________________________
Bone Fractures
Even though they are very strong, bones can fracture, or break. Fractures can happen at different places on a bone. They are usually
caused by excess bending stress on the bone. Bending stress is what causes a pencil to break if you bend it too far. A cast is usually
used to keep the movement restricted in the bone.
Soon after a fracture, the body begins to repair the break. The area becomes swollen and sore. Within a
few days, bone cells travel to the break site and begin to rebuild the bone. It takes about two to three
months before compact and spongy bone form at the break site. Sometimes the body needs extra help
in repairing a broken bone. In such a case, a surgeon will piece a broken bone together with metal pins.
Moving the broken pieces together will help keep the bone from moving and give the body a chance to
repair the break. Below, a broken ulna has been repaired with pins
The upper part of the ulna, just above the elbow joint, is broken, as you can see in the X-ray to the left. The x-ray to the right was
taken after a surgeon inserted a system of pins and wires across the fracture to bring the two pieces of the ulna into close proximity.
15. What is used to diagnose a fracture ________________________________________________________________
Cartilage Injuries
Osteoarthritis occurs when the cartilage at the ends of the bones breaks down. The break down of the cartilage leads to pain and
stiffness in the joint. Decreased movement of the joint because of the pain may lead to weakening of the muscles that normally move
the joint, and the ligaments surrounding the joint may become loose. Osteoarthritis is the most common form of arthritis. It has many
contributing factors, including aging, sport injuries, fractures, and obesity. The other type is Rheumatoid which is where the body’s
immune system attacks and kills tissue.
16. How does osteoarthritis affect your body
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Ligament Injuries
Recall that a ligament is a short band of tough connective tissue that connects bones together to form a joint. Ligaments can get
injured when a joint gets twisted or bends too far. The protein fibers that make up a ligament can get strained or torn, causing swelling
and pain. Injuries to ligaments are called sprains. Ankle sprains are a common type of sprain.
17. Have you ever had a sprain if so how did you feel
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Cancer
Although it is rare, cancer can occur in any part of any bone. Cancer begins when healthy cells in the bone change and grow out of
control, forming a mass called a tumor. A bone tumor can be cancerous or benign.
A cancerous tumor is malignant, meaning it can grow and spread to other parts of the body. A malignant tumor can destroy the cortex
and spread to nearby tissue. If bone tumor cells get into the bloodstream, they can spread to other parts of the body, especially the
lungs, through a process called metastasis.
A benign tumor means the tumor can grow, but it will not spread to other parts of the body. Even though a benign tumor does not
spread outside the bone, it can grow large enough to press on surrounding tissue, weaken the bone, and cause the bone to fracture.
Bone cancer is divided into primary and secondary bone cancer: primary bone cancer first forms in the cells of the bone and secondary
bone cancer starts elsewhere in the body, eventually spreading to bones.
People with bone cancer may experience the following symptoms or signs. Sometimes, people with bone cancer
do not have any of these changes. Or, the cause of a symptom may be another medical condition that is not
cancer.
When a bone tumor grows, it presses on healthy bone tissue and can destroy it, which causes the following symptoms:
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Pain. The earliest symptoms of bone cancer are pain and swelling where the tumor is located. The pain may come and go at
first. Then it can become more severe and steady later. The pain may get worse with movement, and there may be swelling in
nearby soft tissue.
Joint swelling and stiffness. A tumor that occurs near or in joints may cause the joint to swell and become tender or stiff. This
means a person may have a limited and painful range of movement.
Limping. If a bone with a tumor breaks, or fractures, in a leg, it can lead to a pronounced limp. Limping is usually a symptom
of later-stage bone cancer.
Other less common symptoms. Rarely, people with bone cancer may have symptoms such as fever, generally feeling unwell,
weight loss, and anemia, which is a low red blood cell level.
18. Can bone cancer spread if so explain why this might happen
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Preventing Injuries
Preventing injuries to your bones and ligaments is easier and much less painful than treating an injury. Wearing the correct safety
equipment when performing activities that require such equipment can help prevent many common injuries. For example, wearing a
bicycle helmet can help prevent a skull injury if you fall. Warming up and cooling down properly can help prevent ligament and
muscle injuries. Stretching before and after activity also helps prevent injuries.
19. What can prevent a head injury _______________________________________________________________________