Muscular and Skeletal Systems Review
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Name ____________________________________________________
The human body is truly amazing! Have you ever thought about how your body works? What happened to the food you ate for dinner last night? How does your body use the oxygen that you inhale? There are pathogens everywhere! Why don’t you get sick more often? How does your body know how and when to grow?
Each body system does a specific job and many of those systems work closely together as a team to keep the human body healthy and functioning. The human body is a system because many separate systems work together to keep the body alive, similar to the way the parts of a bicycle work together to make a bike work.
What’s so amazing is that each of these separate systems is made of parts called organs. Each organ is made of its own special material called tissue, and tissues are made of the smallest players on the team – cells. All organisms are made of cells. A cell is the smallest living part of an organism. Some kinds of organisms, such as bacteria, are made of only one cell. That single cell is the organism’s entire body! Many other kinds of organisms, including elephants, trees, and people, are made of trillions of cells.
The human body is a complex organism. All the body systems must constantly work together so you can survive, grow, and stay healthy!
All Systems Go!
Marvels of Design
Cells
A living thing is an organism. Many kinds of organisms have a body with different parts called structures, and each structure has a “job” or function. All organisms are made of cells. A cell is the smallest living part or structure of an organism. An average cell is about 1/1,000 of inch across. Can you imagine anything as small as that?
Human bodies are marvels of design; they are made of different kinds of cells. Some of these cells are: bone cells, nerve cells, muscle cells, skin cells, sex cells, fat cells, and blood cells. Each kind of cell in an organism performs a different function. For example, nerve cells carry messages to and from your brain. Muscle cells make part of your body move. Red blood cells carry oxygen and nutrients to all your other cells. And each kind of cell has a different shape. No cell works alone; cells work together tirelessly day and night to keep your body working!
The human body is made of trillions of cells. Every second, millions of old cells die and millions of new cells replace them. Cells are grouped together to form tissues. Tissues form organs. And organs form organ systems. Systems work together to keep you alive and healthy.
Blood Cell Nerve Cell Muscle Cells Sperm Cells
Write True or False for each statement below.
1. _______ The smallest structure in the human body is the cell.
2. _______ Some cells are nerve cells.
3. _______ There is only one kind of cell in the human body.
4. _______ Each kind of cell has a different function (job).
5. _______ Every second, millions of old cells die and new cells replace them.
6. _______ All cells have the same shape.
All About Cells and Body Systems (video)
1. The body’s smallest living structures are called ______________________________.
2. Cells work together to form ___________________________________.
3. Tissue forms __________________________, and organs form ___________________________.
4. ____________________________ of different kinds of cells make up the human body.
5. Standing, dancing, throwing a ball is possible because of __________________________
and _____________________________ working together.
6. The human adult skeleton has ________________________ bones.
7. The function of the skeleton is to ________________________________ vital organs.
8. The skull protects the __________________. The ribs protect the ___________________.
9. The function of muscles is to help animals ___________________________.
10. The ________________________ system breaks down food into nutrients, which are then delivered by red blood cells to all the cells in your body.
11. ________________________________ pass through the wall of the small intestine into the bloodstream. This is where the red blood cells pick up the nutrients that all your cells need.
12. Every cell in the human body needs ______________________ & ______________________ .
13. The three main organs of the nervous system are: _______________________________,
______________________________________, and ______________________________________
14. What type of cells do skeletal bones make? They are the cells that carry oxygen and nutrients to all the other cells in your body, and they pick up waste like carbon dioxide to be removed from the body. These cells are called ________________________________ .
15. This system moves the blood around the body: ____________________________________system.
16. This organ pumps the blood around the body: _______________________________
17. The endocrine system produces chemical messengers called ____________________________, which tell your body when it’s thirsty or your bladder is full, when to grow or when to sweat.
18. What system removes wastes (carbon dioxide, liquid and solid wastes, salts) from the body?
_______________________________________________
Your heart, your brain, and your stomach are all organs in your body. An organ is a part of the body that does a specific job. Can you name the largest organ in the body? That’s right. It’s the skin.
Super Skin
What would you be like without skin? The answer is, quite simply, a big squishy mess! Your skin is like a very large container. It performs five important jobs:
1. Skin is a strong, waterproof, and self-repairing protective wrapping. It protects you from germs, dust, water, and the sun’s ultraviolet rays.
2. It helps you maintain a constant body temperature of 98.6(F by keeping your body cool and comfortable through sweating. The evaporation of perspiration (water and salt) helps keep your body from overheating.
3. In the presence of sunlight, the skin produces vitamin D.
4. It gives you the sense of touch, including pain, pressure, and temperature sensations.
5. It burns and stores fat. Fat insulates you against all kinds of bumps, bangs & wear and tear.
Skin is alive. Every square inch of skin contains layers of fat, dozens of hairs, cells in which you’ll find nerves, sweat glands, sensory receptors, and blood vessels. Skin also teems with life on its surface. No matter how hard you wash, there are millions of bacteria on each square inch of skin. Some cause illness. In fact, skin is our first line of defense against the diseases that some bacteria cause.
Skin can identify heat, cold, pain, and pressure. Just one square inch of skin on the back of your hand contains around 30 hairs and 9,000 nerve endings. They automatically inform your brain of the conditions around you. But the skin on your lips is much more sensitive than the skin on your elbows. That is because lips have more nerves that are packed closely together.
Microscopic cells are the body’s building blocks. It takes about 100 trillion of them to make up one adult. Like all other cells, skin cells are constantly being replaced. Roughly 30,000 to 40,000 dead skin cells flake off invisibly every minute. They pop off like tiles blown from a roof in a strong wind. They have to make way for an equal number of fresh ones the body is producing. In fact, about 28 days from now, you will have a completely new skin! But when these dead layers pile up and don’t shed, they create calluses, warts, and thick white skin flakes of psoriasis.
Factoid:
• As an adult, you may have more than 20 square feet of skin – about the size of a blanket
• You are likely to shed some 40 pounds of skin in a lifetime
• Right now, there are over a million dust mites, microscopic critters invisible to the naked eye, on your mattress and pillow, chomping on the dead skin cells that fell off you last night!
Skin’s Three Main Layers
Epidermis or growth layer – Although this outer layer of skin is about as thick as a piece of paper, it still has four layers. This is where new skin cells are continuously made and dead cells are pushed outward.
Dermis or true skin – The dermis contains blood vessels, nerve endings, sweat glands, oil glands, hair follicles, muscles, and fatty tissue. It is made of tough but bendable fibers called collagen and elastin. They allow the skin to keep its shape even after it’s been pinched. Most of the blood flow and nerves can be found in the dermis.
Subcutaneous Fat – This layer of fat is made mainly of blood vessels and cells that store fat. The fat helps insulate the body and protects it against blows. The body can burn this fat when it is short on food and needs energy.
Fight Fat!
Fat is the body’s best way to store energy. Most of it is part of the subcutaneous fat layer, although fat is found in organs and other tissues as well. Our ancient ancestors often got fat when food was plentiful. During lean times, that fat gave them energy to survive. But most Americans have no shortage of food. Many people eat and eat without burning off the extra fat. They also eat fattening junk food and get little exercise. The result? One out of three Americans is obese (severely overweight). 15% of children and teens are obese, up from 5% in 1980. Many believe that obesity will soon surpass smoking as the Number 1 cause of preventable death. Diseases caused by too much fat occur most often in adults. Exercising and eating a healthy diet today can help prevent diseases later in life.
Skin Gone Wrong
The world’s most common skin ailment is acne vulgaris – clogged pores, pimples, and deeper lumps that occur on the face, neck, chest, and other parts of the body. Many people believe that chocolate or greasy foods cause it. Others say not washing thoroughly enough is the problem. Both are myths, although a nutritious diet and good hygiene are still crucial to being and staying healthy. Rising hormone levels causes teenage acne. Hormones are the body’s internal chemical messengers. They carry information that controls the function of almost all of the body’s cells and tissues. Hormones greatly increase the production of oil and then the hair follicles can become clogged by dead skin cells. This leads to whiteheads, blackheads, and angry red lumps. The good news about acne is that it’s treatable. Stores sell creams and medicines that can get rid of mild-to-moderate acne.
Skin cancer is the most common type of cancer. The tanning craze has also made skin cancer the fastest growing type of cancer in the U.S. Fair-skinned people are especially vulnerable. Many people don’t realize that a sunburn or tan is the body’s way of signaling sun damage or radiation poisoning. When in the sun, always put on a sun block or a sunscreen and reapply it often.
Move Your Body!
Your body has two organ systems that work together to help you move. They are the skeletal system and the muscular system. The skeletal system is made of bones and cartilage. Cartilage is a strong tissue that is more flexible than bone. Bones and cartilage make up the framework of your body.
Skeletal System
Without your system of bones, you’d be floppy like a beanbag. Could you stand up? Forget it. Could you walk? No way! Without bones, you’d be just a puddle of skin and guts on the floor.
The skeletal system…
• Creates a frame of 206 bones, which supports your body
• Makes red blood cells that carry oxygen and white blood cells to fight disease
• Provides places for muscles to hold on to so that you can move
• Protects important body organs from injury (ribs protect heart & lungs, skull protects brain)
• Stores an important mineral – calcium – to keep bones hard and strong
Together with the skeletal system, the muscular system and its 650 muscles help us to walk, run, play and even show facial expressions. Many muscles are attached to bones and when muscles tighten up, or contract, they move the bones, which in turn move the body!
Bones are alive! Bones are made of living cells, which help them grow and repair themselves. Like other cells in your body, the bone cells rely on blood to keep them alive. Blood brings nutrients and oxygen to all of your cells and takes away waste. If bones weren’t made of living cells, things like broken toes or arms would never mend, but don’t worry, they do!
Bones store an important nutrient called calcium, which gives bones their hardness and strength. We get calcium from drinking milk and eating foods like cheese. Without enough calcium, bones become softer and can break more easily. But bones do not start out being hard and strong.
Babies are born with about 350 bones, many of which are soft and bendable and made of cartilage. Over time, softer cartilage is replaced by hard bone and some of the bones join together to form one bone. By the time you become an adult, you will only have about 206 bones in your body.
1. List 3 functions of the skeletal system.
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
2. Bones are alive! What are they made of? ___________________________________________
3. What nutrient keeps bones strong and hard? ________________________________________
4. Blood brings ______________________________ and _____________________________ to keep all your cells healthy.
Inside a Bone
Bones are made of hard, strong tissue. Bone tissue is made of cells, microscopic living structures. All living things are made of cells. Bones make up the skeletal system. An important job or function of the skeletal system is to make red blood cells that carry oxygen and white blood cells that fight germs.
Bone marrow is found in the center of many bones.
Bone marrow makes new red and white blood cells.
Red blood cells deliver oxygen and nutrients to all
parts of your body.
Moving Your Bones
Our bones don’t simply work by themselves. Two or more bones join together at a joint. Different kinds of joints allow different kinds of movement. For example, your shoulder joint lets you move your arm in a large circle. Your elbow joint lets you move your lower arm toward and away from your upper arm. The bones of some joints are not moveable. For example, the bones that make up your skull are joined tightly together and do not move.
A tough, smooth shiny tissue called cartilage covers the end of each bone, this keeps your bones from scratching and bumping against each other when you move. Strong stretchy bands called ligaments hold our bones together. Ligaments are tough, flexible cables that attach bones to other bones to help keep them in place.
How do your bones move? You need muscles to pull on bones so that you can move. Your muscles are attached to bones with tendons. Tendons are strong cords that attach skeletal muscles to bones. When muscles contract, the bones to which they are attached act as levers and cause various body parts to move.
Muscular System
Muscular System
Your muscular system is made of muscles that cause parts of your body to move. Muscles move your bones. They make your heart beat. They make you breathe. They even make the pupils of your eyes become larger or smaller. There are about 650 muscles in your body.
So, what do muscles do? Muscles move cows, snakes, worms and humans. Muscles move you! Without muscles you couldn’t open your mouth, speak, shake hands, walk, talk, or move food through your digestive system. There would be no smiling, blinking, or breathing.
There are three kinds of muscles in your body and each kind has a special function.
Skeletal muscles move bones. For example, when you hold a pencil, skeletal muscles pull on your finger bones. When skeletal muscles contract, or shorten, they pull the bones to which they are attached. That’s how the body moves and bends. Many skeletal muscles work in pairs; when one muscle in the pair contracts, the other muscle relaxes. When your biceps muscles contract, your triceps muscles relax. Your lower arm is pulled toward your upper arm. You can control your skeletal muscles; skeletal muscles are voluntary muscles.
Cardiac muscles make your heart beat and pump blood through your body. You cannot control your heart muscles. Your heart beats automatically without thinking about it…it is an involuntary muscle movement.
Smooth Muscles are found in many of your organs. For example, smooth muscles move food through your digestive system. They also let you breathe, cough, and sneeze. Smooth muscles work automatically, but you can control some of them. For example, you can blink your eyes on purpose if you want to.
Did You Know?
• You have over 30 facial muscles, which create looks like surprise, happiness, sadness, and frowning.
• Eye muscles are the busiest muscles in the body. Scientists estimate they may move more than 100,000 times a day!
• The largest muscle in the body is the gluteus maximus muscle in the buttocks.
• The longest bone in your body is your thigh bone, the femur. It is about ¼ of your height.
• Humans and giraffes have the same number of bones in their necks.
• Your ears can bend because they have cartilage inside them, not bones.
• Animals with a backbone are called vertebrates. Worms, flies, and crayfish do not have backbones; they are called invertebrates.
Muscular and Skeletal Systems Review
1. Together our skeletal and muscular systems give our body shape and allow us to move. An important job of your skeleton is _______ the internal organs, like the heart, lungs, and brain.
a. to protect b. to shape c. to restrict d. to grow
2. We must have a balanced diet for our bones and muscles to develop. Vitamins and minerals such as ____ help bones to grow and become strong. Foods such as milk and dairy products are rich in these minerals.
a. niacin b. calcium c. iron d. zinc
3. There are different tissues that make up the bones in the human body. One tissue is called _____, it has a very important job…it makes blood cells for your body!
a. cartilage b. spongy bone c. compact bone d. marrow
4. Specific bones have a special job in protecting the internal organs within our bodies. The brain is protected by the ____. It’s actually 28 bones and covers the brain like a helmet.
a. ribs b. spinal column c. skull d. sternum (breast bone)
5. Another series of bones protects the spinal cord, the nerve center of the human body. The ___ is made up of vertebrae, which encase the spinal cord like beads on a string. (The string is the spinal cord, the beads are the vertebrae).
a. skull b. spinal column c. ribs d. sternum
6. Our circulatory system moves oxygen and nutrient rich blood to all the cells in the body. The red blood cells, which carry the oxygen, are produced in the _____ of the bones. This is a very important function of the bones since red blood cells are used up and must be constantly replaced.
a. ligament b. marrow c. spongy bone d. cartilage
7. The muscular system enables the bones to move in various ways. Those specific muscles that are attached to bones are called _____ muscles. They are found throughout all parts of our body.
a. skeletal b. cardiac c. smooth d. voluntary
8. A series of bones which looks like a cage protects other body parts. The ____ guard the lungs and heart against injury.
a. skull b. ribs c. spinal column d. femur
9. Another set of muscles assist the heart. The ____ muscles keep the heart beating throughout our lives. They consist of strong bands of muscles that wrap around the heart.
a. skeletal b. cardiac c. smooth d. voluntary
10. A third kind of muscle is found inside of various internal organs. The ____ type of muscle tissue is found inside of our stomachs and blood vessels. They are strong and assist the movement of liquids through these organs; they are involuntary muscles which means they work automatically without you thinking about them.
a. smooth b. cardiac c. skeletal d. skull
11. Some animals, like spiders and insects, have skeletons on the outside of their bodies. This kind of skeleton is called an _____.
a. internal skeleton b. endoskeleton c. exoskeleton
The story we’re about to read is of stormy seas,
acid rains, and dry, desert-like conditions. It’s an
arduous journey that traverses long distances
and can take several days. It’s one in which nothing
comes through unchanged. It’s the story of your
digestive system whose purpose is to turn the food
you eat into something useful for your body!
Down the Hatch…so there you are, sitting at lunch,
enjoying the delicious aromas of hot, freshly baked
pizza, just out of the oven. Your teeth tear off a big
piece of crust. Your saliva glands start spewing out
spit like fountains. Your molars grind your pizza crust,
pepperoni, and cheese into a big wet ball. Chemicals in
your saliva start chemical reactions. Seemingly like
magic, starch in your pizza crust begins to turn to
sugar! A couple of more chews and, then, your tongue
pushes the ball of chewed food to the back of your
throat. But be careful, don’t swallow too fast, your
windpipe is also at the back of your throat. A special
flap called the epiglottis will automatically, involuntarily,
flop down over the opening of your windpipe to make
sure the food enters the esophagus and not the
windpipe (You don’t want your pizza to
“go down the wrong way”). A trap door opens,
and there it goes, down your gullet!
Next, your muscles squeeze the wet mass of food
down, down, down a tube, or esophagus, the way you
would squeeze a tube of toothpaste. It’s not
something you tell your muscles to do…they just do
it involuntarily…in a muscle action called peristalsis.
Then, the valve to the stomach opens and pizza mush
lands in your stomach!
Inside your stomach…Imagine being inside a big pink
muscular bag, sloshing back and forth in a sea of
half-digested mush and being mixed with digestive
chemicals. Acid rains down from the pink walls, which
drip with mucus to keep them from being eroded.
Sound a little like an amusement ride gone crazy?
Every time you think you’ve got your equilibrium back,
the walls of stomach contract and fold in on themselves.
Over and over again, you get crushed under another wave of slop. Every wave mixes and churns the food and chemicals together more, breaking the food into even smaller and smaller bits. Then another valve opens. Is the end in sight you ask, as the slop gets pushed into the small intestine?
Inside the small intestine, chemicals and liquids break down the food mixture even more so your body can absorb all the vitamins, minerals, proteins, carbohydrates, and fats. These nutrients will be extracted with a little help from three friends: the pancreas, liver, and gallbladder. Your pancreas is like a giant salivary gland. Each day it pours one to two pints of digestive juices into the digestive system.
The small intestine looks like a strange underwater world filled with things that resemble small finger-like cactuses. But they’re not cactuses, they’re villi. Like sponges, they’re able to absorb tremendous amounts of nutrients from the food you eat. From the villi, the nutrients will flow into your bloodstream.
Next stop for the nutrients…the liver! The nutrient-rich blood comes directly to the liver for processing. Your liver will store these nutrients and release them to your red blood cells, as your body needs them.
But hold on! The story’s still not over yet…the leftovers that your body can’t use still have more traveling to do! Next, they’re pushed into the large intestine. It’s much wider and much drier. You find that the leftovers are getting smaller, harder and drier as they’re pushed through the tube. After all, this is the place where water is extracted and recycled back into your body. In fact, the leftovers that leave your body are about 1/3 the size of what first arrived in your intestines!
Where food turns into poop…finally, the end of the large intestine is in sight! Now the drier leftovers are various handsome shades of brown. They sit, at the end of their journey, waiting for you to expel them out your anus. Of course, you know the rest! A glorious, if slightly stinky, journey, don’t you think?
Foods high in calories give you lots of energy. The more active you are, the more energy you need, and the more Calories you burn. The nutrients that contain the most Calories are fats.
Butter, margarine, and oils are fats. Snack foods like chips, cookies, cakes, and candy usually contain a lot of fat. Foods such as meats, nuts, and milk products also contain fat. However, they also have many other important nutrients.
When you take in more Calories than you need, your body changes the excess to fat. Fats give your body energy, and they can be stored in your body for later use.
Digestion Factoids
*Chewing food takes from 5-30 seconds *Swallowing takes about 10 seconds
*Food sloshing in the stomach can last 3-4 hours *Food drying up & hanging out in the large
*Americans eat about 700 million pounds of peanut butter intestine can last 18 hours to 2 days!
*An adult’s intestines are at least 25 feet long * Horses intestines are 89 feet!
How the Digestive System Works Name ________________________________
Due Date: ______________
Use your science packet and other resources to help you write your essay.
Words you can include in your essay:
mouth saliva stomach pancreas
teeth epiglottis digestive chemicals gall bladder
salivary glands esophagus small intestine large intestine
saliva peristalsis liver anus
Title (a captivating name) ________________________________________________
Paragraph 1
Hook the reader! Begin with an anecdote (a short story) about eating.
o A mother feeding her baby, “here comes the airplane…”
o Describe your favorite meal
o Tell about what you ate for breakfast or dinner
• State the function of the digestive system. Why do we need to eat food? How does your body use the nutrients in food?
Paragraph 2
• Explain how the digestive system works
o The journey of food…from beginning to end
Paragraph 3
• Closing…retell why the digestive system is fascinating and important
o What do our bodies get from the food that we eat?
o How can we keep the digestive system healthy?
Planning Your Essay
Make an outline to plan out your essay.
Final - Perfect Copy
Check it out! Make sure your writing reads smoothly and is free of errors.
Have an adult read your essay and make the necessary changes.
You will receive a language arts and a science grade for this assignment.
They’re squishy like sponges and stretchy like balloons. You use them every day, all day…and night too…no matter what you’re doing. And, most likely, you never even think about them.
They’re your lungs, those elastic bags with millions of tiny air pouches inside. All day long, those sacs in your chest fill and empty with the breath that feeds your body the oxygen it needs to stay alive. But, breathing isn’t the only way these two pouches help you be you.
Your lungs work to keep dust, viruses, pollutants, and other particles in the air from invading your body. They also filter the blood that passes through them, eliminating tiny clots and fat globules. And don’t forget about their role in speech, without the air your lungs exhale, you’d be silent.
Why do you need to breathe? All the cells in your body require oxygen. Without it, they couldn’t move, build, reproduce, and turn food into energy. In fact, without oxygen, they and you would die! How do you get oxygen? From breathing in air, which your blood circulates to all parts of the body.
How do you breathe? You breathe with the help of your diaphragm and other muscles in your chest and abdomen. These muscles literally change the space and pressure inside your body to accommodate breathing. When your diaphragm pulls down, it leaves more space for the lungs to expand. Your lungs now have enough space to take in the air you inhale. The air then expands your lungs like a pair of balloons. When your diaphragm relaxes, the cavity inside your body gets smaller again. Your muscles squeeze your rib cage and your lungs begin to collapse as the air is pushed up and out your body in an exhale.
It all starts at the nose. About 20 times a minute, you breathe in. Respiration is the act of breathing. When you do, you inhale air and pass it through your nasal passages where the air is filtered, heated, moistened and enters the back of the throat. Interestingly enough, it’s the esophagus or food pipe, which is located at the back of the throat and the windpipe for air, which is located at the front. When we eat, a flap, the epiglottis, flops down to cover the windpipe so that food doesn’t go down the windpipe.
So, back to breathing, the air has a long journey to get to your lungs. It flows down through the windpipe, past the voice box or vocal cords, to where the lowermost ribs meet the center of your chest. There, your windpipe divides into two tubes, which lead to the two lungs, which fill most of your ribcage. Inside each of your sponge-like lungs, tubes, called bronchi, branch into even smaller tubes much like the branches of a tree. At the end of these tubes are millions of tiny air sacs called alveoli. Spread out flat, all the alveoli in the lungs of an adult would cover an area about the third of a tennis court.
What do the alveoli, air sacs, do? They help perform an incredible magic act. Your air sacs bring new oxygen from air you’ve breathed to your bloodstream. They exchange it for waste products, like carbon dioxide, which the cells in your body have made and can’t use.
How does this exchange work? With the help of the red blood cells in your bloodstream. Your red blood cells are like box cars on train tracks. They show up at the sacs at just the right time, ready to trade in old carbon dioxide that your body’s cells have made for some new oxygen you’ve just inhaled. In the process, these red blood cells turn from purple to that beautiful red color as they start carrying the oxygen to all the cells in your body.
But what happens to the carbon dioxide? It goes through the lungs, back up your windpipe and out with every exhale. It’s a remarkable feat, this chemical exchange and breathing in and out. You don’t have to tell your lungs to keep working. Your brain does it automatically for you.
Factoids
• Your lungs contain almost 1,500 miles of airways and over 300 million alveoli.
• Every minute you breathe in 13 pints of air.
• Plants are our partners in breathing; we breathe in air, use the oxygen in it, and release carbon dioxide. Plants take in carbon dioxide and release oxygen. Thank goodness!
• People tend to get more colds in the winter because we’re indoors more often and in close proximity to other people. When people sneeze, cough and even breathe…germs go flying!
• Love your lungs! Don’t smoke. Smoking isn’t good for any part of your body, and your lungs especially hate it.
ALL THAT BREATHING GOING ON
We humans aren’t the only creatures with lungs. All mammals have them, from the tiny bumblebee bat, the world’s smallest mammal, to the great blue whale, the world’s largest. So do spiders, lizards, frogs, and many other creatures. But no critter’s lungs can compare to those of birds for efficiency and flow.
Unlike human lungs, which fill and empty like balloons, birds’ lungs are part of a circuit that supplies them with a constant flow of air. It’s no wonder they can soar to the top of Mount Everest, where the air is thin, while most humans need tanks of oxygen to hike there.
Yawning…Tired? Bored? Perhaps so.
But that doesn’t explain why you yawn.
The fact is, scientists don’t know why
people and many animals yawn. But
they do know that most people will
yawn soon after they see someone
else yawn…tired or not.
"A yawn is quite catching you see.
Like a cough, it just takes one yawn to
start other yawns off."
--- Dr. Seuss
The Nervous System
Tasting, smelling, seeing, hearing, thinking, dreaming, breathing, heart beating, moving, running, sleeping, laughing, singing, remembering, feeling pain or pleasure, painting, writing…you couldn’t do any of these things without your nervous system!
What is the nervous system? Made up of your brain, your spinal cord, and an enormous network of nerves that thread throughout your body, it’s the control center for your entire body. Your brain uses information it receives from your nerves to coordinate all of your actions and reactions. Without it, you couldn’t exist!
What are nerves? They’re the thin threads of nerve cells, called neurons that run throughout your body. Bundled together, they carry messages back and forth just the way that telephone wires do. Sensory nerves send messages to the brain and generally connect to the brain through the spinal cord inside your backbone. Motor nerves carry messages back from the brain to all the muscles and glands in your body.
So how do they pass along messages? Through the marvels of chemistry and a kind of electricity! Neurons are thin. Some are very small, and some can be three feet long! All are shaped somewhat like flat stars, which have, to varying degrees, been pulled at each end so that they have long fingers. The fingers of one neuron almost reach to the next neuron.
When heat, cold, touch, sound vibrations or some other message stimulates a neuron, it begins to actually generate a tiny electrical pulse. This electricity and chemical change travels the full length of the neuron. But when it gets to the end of finger-like points at the end of the neuron, it needs help getting across to the next extended finger. That’s where chemicals come in. The electrical pulse in the cells triggers the release of chemicals that carry the pulse to the next cell…and so on and so on; like a relay of dominoes!
The Human Brain
The human brain is large and in charge. It controls everything you do…breathing, eating, reading this sentence. Everything. Be glad you’re a human. Because human brains are more complex than the brains of any other animal on Earth! Why? It’s not that they’re the biggest. But human brains are larger and heavier (about 3 pounds) in comparison to the human body, then any other animal. Humans have the largest brain for their body size in the animal world. Our closest relatives, chimpanzees, cannot perform tasks beyond those of an average toddler. What makes us so smart?
It’s not in the brain stem. This part controls sleeping, heartbeat, and other life-or-death activities. Our brain stem is a lot like the brain stems of reptiles, birds, and other mammals. That makes sense. We all need to perform the same life-or-death activities.
It’s not in the cerebellum. This part controls movement. Reptiles, birds, and mammals (including us) all move. So our cerebellums are similar. But other animals use much of their brainpower for moving, sensing, and surviving. They have relatively little left for thinking.
It’s in the cerebrum. This wrinkled, squishy mass makes up 85 percent of the human brain’s weight. It thinks, reasons, composes a language, directs how we play an instrument, designs a bridge…all the unique abilities that make us human.
Humans take longer to grow up than almost all other animals because the human brain is so complex. It takes about 12 years to develop.
Train Your Brain – The day you were born, you had a full set of neurons –just as you do now! So why couldn’t you play the piano? Or even walk and talk? Brain cells are like a railway system. Each station, or cell, is useless unless connected to the rest of the system by a track. You start our life with few “tracks,” or paths. That’s why babies are helpless. But as you learn and remember, your brain creates new paths –shortcuts to help you think faster and better.
Suppose you’re learning to play the piano. The first time, your fingers feel clumsy. You play slowly and make mistakes. Your brain has to think about moving each finger, reading music, and not falling off the bench. As you practice, sets of neurons are connected together to create shortcuts. Your soon play almost without thinking. The “piano path” is now wired into your brain.
When you’re young, you can forge new paths easier and faster. Now is the best time to train your brain. You can even choose what kind of brain you want! If you love reading, your brain will hardwire paths in the language area. If you play sports, the motor-control section will grow thick with connections. In short, you are what you think!
The Circulatory System
It’s a big name for one of the most important systems in the body. Made up of the heart, blood and blood vessels, the circulatory system is your body’s delivery system. Blood moving from the heart, delivers oxygen and nutrients to every part of the body. On the return trip, the blood picks up waste products so that your body can get rid of them.
You Gotta Have Heart! As you read this, your heart is pumping about five quarts of blood throughout your body. The blood is traveling through more than 60,000 miles of blood vessels (arteries, veins, capillaries). That’s enough to circle the equator 2 ½ times! The tubes that carry blood away from your heart are called arteries. They’re hoses that carry blood pumped under high pressure to smaller and smaller branched tubes called capillaries. The tubes that more gently drain back to the heart are called veins.
A heart works tirelessly over a lifetime. During an average life span, the heart beats three billion times without a single break. Not bad for a muscle the size of a fist and lighter than a couple of baseballs. It contracts and relaxes some 70 or so times a minute at rest and more if you are exercising, squeezing and pumping blood through its chambers to all parts of your body. What’s the point of all this hard labor? The biggest point of all: life itself.
Lungs Heart
Lifeblood...The main purpose of your heart is to pump blood around your body all the time. How does blood keep you alive? Every second of every day, blood delivers vital nutrients, oxygen, and other chemicals to all of the cells in your body. Remember…cells are alive! A cell is the smallest living part or structure of an organism.
Blood also carts away your body’s waste. In addition, flowing blood can cool you off or warm you up, when necessary. Blood is also your best weapon against germs and other invaders. If a virus invades your body, blood carries an army of disease-fighting white blood cells to the site of attack.
Cells, tissues, and organs, especially the brain, need a steady supply of oxygen to live. Red blood cells carry oxygen. Without it, brain tissue begins to die off in a few minutes. Treat your heart right, and this tireless machine will keep going and going and going.
What’s in a speck of blood? Most of your blood is made up of plasma - a yellowish liquid “river” in which blood cells flow. 5,000,000 Red blood cells in your body make the blood look red. They pick up oxygen from the lungs, deliver it to other cells in your body and carry back waste gases, like carbon dioxide back to your heart which pumps it back to the lungs. The carbon dioxide gas is removed from your body every time you exhale.
Your body has 5,000 to 10,000 white blood cells: There are several types of white blood cells that fight infection all over the body. They kill germs and carry off dead blood cells. Some attack and kill germs by gobbling them up, others by manufacturing chemical warfare agents that attack the infection. Platelets are brownish-yellow bits of cells that help blood to form clots. They help your body repair itself after injury.
So, what’s the endocrine system? It’s a little known system made up of a whole collection of glands and it does very BIG things. It regulates, coordinates and controls an extraordinary number of your body’s functions. How? While your nervous system uses electricity to orchestrate all sorts of things in your body, your endocrine system does even more through the wonder of chemicals.
Where do these chemicals come from? They come from glands and a few organs, like the stomach, pancreas, and kidneys that produce them and ooze them. While the chemicals that your organs manufacture are used close to home, endocrine glands throughout your body make chemicals called hormones that travel much further. Endocrine glands spew their hormones directly into your bloodstream! You’re not likely to be aware that all these chemicals are traveling to all parts of your body. But they are, and they’re acting as chemical messengers.
What are hormones? “Hormone” means to excite or spur on and that’s exactly what hormones do. They cause other things to start happening. You’ve got over 30 of these amazing hormones busily orchestrating and regulating such things as: when you feel hungry or full; how you sleep; your body temperature; how you break down and utilize the food you eat and whether you are fat or thin; when you start puberty and how long it takes; how you handle stress; how much adrenaline you have in an emergency situation…and how and when you grow. Phew!
Now you might say that you thought it was genes that determined things like how tall you’re going to eventually grow. But when, and if, you grow as tall as the instructions from your genes would suggest depends on hormones…in this case growth hormones.
What is puberty? These hormones also control the time when your body begins its final journey to become adult. It’s called puberty and it involves all sorts of big and small changes to your body…and your brain!
During puberty, your body’s shape begins to change…girls develop breast and hips; boys, taller and broader bodies and more muscle. Hair begins to develop in varying degrees on boys and girls: pubic hair, underarm hair, leg hair, and, on boys, facial and body hair. By the time you’ve finished puberty, you will have reached your adult size. For girls, puberty generally begins sometime between ages 9 - 13 and for boys, ages 10 - 15. Puberty is a time in which you may find yourself feeling confused. One minute you may find yourself giggling, and then next find yourself feeling sad or cranky. Just understand that you haven’t changed into a different person & your body is just adjusting to all those molecules of hormones racing around inside your body. And, don’t worry! By the end of puberty, your body will have adjusted the hormone levels so that you will feel on a much more even keel. You may find it surprisingly helpful to talk with your parents, teachers or mentors about all of this. After all, whether you believe it or not, the adults around you have actually experienced this confusing time, too!
Reproductive System
All living things must reproduce, or make more living things like themselves. If a species did not reproduce, all living things of its kind would die out. The reproductive system of humans allows people to make more humans, or to have children.
Do you look like your mom or dad? Maybe you have your mom’s brown eyes or your dad’s curly hair. Perhaps your personality is just like one of them. These special features that make us like our parents and different from other people are called inherited traits and the transmission of these traits from generation to generation is called heredity. There will be certain things you do that will remind people of your mother or father, or even some other relative. All these things are inherited. Other things, such as likes and dislikes and personal fitness, are not inherited. These are the result of the person’s lifestyle and environment.
No baby is an exact copy of one parent, but receives a mix of traits from both parents. The key to inherited traits is found in the nucleus of every cell in the body, on structures called chromosomes. The nucleus of a cell contains chromosomes. The nuclei of most human cells contain 23 pairs of chromosomes for a total of 46, but specialized reproductive cells (the sperm and egg cells) contain half as much genetic information. When a female egg cell (with 23 chromosomes) is fertilized by a male sperm cell (with 23 chromosomes), their nuclei join and the fertilized egg can then develop into an embryo with 46 chromosomes, half from each parent.
On the chromosomes are genes. Genes determine how offspring will look and act. Each child receives genes from both parents, but some genes are stronger than other are these genes are called dominant. The weaker genes are called recessive. The gene for brown hair is a dominant trait. Blond hair is a recessive trait. If both parents have brown hair, their children will probably have brown hair. If one parent has brown hair, and the other parent has blond hair, the children will still likely have brown hair, but it is possible for a child to have blond hair. If both parents are blond, then the children will probably be blond.
Excretory System
The word excretion means the removal of waste substances from the body. Several organs are involved with the excretory system, including the kidneys, sweat glands, lungs, and large intestine.
Your cells produce a waste called urea. The cells of your body excrete this urea into your blood. As your blood travels along within your body, it becomes more and more polluted with urea and other wastes. Eventually the blood enters a special filter, an organ known as your kidneys. As the blood enters your kidneys, it is cleansed. Your kidneys remove the urea from the blood, sending it to your bladder for storage, in the form of urine, commonly known as pee. It takes about 45 minutes for your kidneys to completely filter all of the blood in your body.
The kidneys work as they do because they contain millions of extremely small filters. Hundreds of times a day the blood in your body gets filtered and the liquid and wastes are removed. The wastes trickle down and collect in the center of your kidneys. Your kidneys are always working and the pee is always drip…drip…dripping down through tubes called the ureters into a stretchy pouch called the bladder. When your bladder becomes too full, hormones send a message to your brain. You feel the need to pee and start looking for a place to do it. The kidneys, the bladder, and their tubes are called the urinary system.
• The kidneys: filters that take the waste out of the blood and make urine
• The ureters: tubes that carry the urine to the bladder
• The bladder: a bag that collects the urine
• The urethra: a tube that carries the urine out of the body
You might notice that sometimes your urine is darker in color than other times. Remember, urine is made up of water plus the waste that is filtered out of the blood. If you don’t take in a lot of fluids or if you’re exercising and sweating a lot, your urine has less water in it and it appears darker. If you’re drinking lots of fluids, the extra fluid comes out in your urine, and it will be lighter.
Excretion is vital to the health of the body because the wastes are poisonous. If the wastes build up and are not eliminated, they can cause serious problems. As you know, the lungs remove carbon dioxide and water vapor, the kidneys remove urea from the blood, and the large intestine stores solid waste from the food you eat.
Now you know what the kidneys do and how important they are. Maybe next Valentine’s Day, instead of the same old heart, you can give your teacher a special card featuring the kidneys!
Endocrine/Excretory/Reproductive Review
1. This system removes liquid waste and waste gases from the body. ________________________
2. Chemical messengers released from the body’s glands. _______________________
3. This is one way your body regulates its temperature. ______________________
4. A fluid that carries oxygen and nutrients to your cells. _______________________
5. This is a system of glands, which produces chemical messengers. ___________________
6. This hormone gives your body a boost of energy. _____________________
7. The body’s liquid waste is called _____________________
8. Most cells contain _______ chromosomes.
9. ____________________ occurs when the egg cell is united with sperm cell.
10. The name of the male sex cell is __________________
11. This organ releases wastes through perspiration. ____________________
12. The number of chromosomes in a sperm cell or an egg cell is _________________
13. These organs remove carbon dioxide and water vapor from your body. _______________
14. This organ cleans waste particles from the blood. __________________
15. This body system recreates more humans. __________________________
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Hiccupping …If your diaphragm gets irritated, it might spasm, or move in a jerky way, as you exhale. The bursts of breath are the hiccups. Hiccups have a variety of causes. For example, eating too fast may cause you to swallow air with your food and irritate your diaphragm. Overeating may make your stomach full enough to irritate your diaphragm.
10 Steps to a Better Brain
1. Go to sleep and get up at about the same time each day.
2. Get the right amount of sleep –not too much or too little.
3. Exercise your brain: do puzzles, solve problems, make things.
4. Exercise your heart, which supplies oxygen to the brain.
5. Eat protein–rich foods (lean meat, skim milk, seafood) to activate your brain.
6. Eat foods with calcium (dairy products), lettuce, spinach) to clean your brain.
7. Don’t skip breakfast. Students who eat breakfast do better in school.
8. Don’t drink caffeine. It throws off your brain’s clock.
9. Don’t take drugs or drink alcohol. They kill brain cells, and can destroy your memory.
10. Wear a helmet when skateboarding, biking, or other risky sports.
Babies have a full set of brain cells, about 100 billion. Brain cells are called neurons. But the cells aren’t well connected. A baby’s skull is partially open so the brain has room to expand.
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By age 5, the brain is almost completely formed. It doesn’t get any more brain cells, but it does get more connections between cells.
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Up to age 8, humans can recover from severe brain injury. Healthy nerve cells take over for lost or damaged ones.
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At age 12, the brain stops growing and the skull fuses, or unites, into a solid case. Though it has stopped growing, the brain keeps learning. It makes new connections between cells throughout life.
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When humans reach their early 20s, the brain begins to shrink. Each day, an adult loses thousands of brain cells. Starting in their late 50s and 60s, people lose brain cells at a faster rate. Their brains make new connections at a slower rate.
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Your digestive system processes or breaks down food into nutrients, which provides your body with the energy it needs for maintenance and repair.
Did you know? Not all blood is red. Crabs, for instance, have blue blood. It contains copper instead of iron, which makes blood red. Earthworms and leeches have green blood, and many invertebrates, such as starfish, have clear or yellowish blood.
How does your blood get oxygen? When you inhale, you breathe in air and send it down to your lungs. Blood is pumped from the heart to your lungs, where oxygen from the air you’ve breathed in gets mixed with it. That oxygen-rich blood then travels back to the heart where it is pumped through arteries and capillaries to the whole body, delivering oxygen to all cells in the body…including bones, skin and other organs. Veins then carry the oxygen-depleted blood back to the heart for another ride.
Factoids:
• The body of an adult contains over 60,000 miles of blood vessels! (arteries, veins, capillaries)
• An adult’s heart pumps nearly 4,000 gallons of blood each day!
• Your heart beats some 30,000,000 times a year!
• You have about 9 pints of blood in your body.
• A “heartbeat” is really the sound of the valves in the heart closing as they push blood through it s chambers.
Germs such as viruses and bacteria can get into the bloodstream. Defenders, called antibodies, can latch onto the germs so white blood cells can kill the germs.
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Blood pressure is a measure of how hard blood is pressing against blood vessels. High blood pressure would be like a flood in Venice. The waterways would swell and crash against the walls. Low blood pressure would be like a drought – not enough current (flowing liquid) to carry boats (or blood) around.
What happens when blood doesn’t flow well?
• If fatty buildup blocks the flow of blood in your arteries, you have a heart attack.
• If your blood freezes, frostbite occurs. It can “kill” a finger, toe, nose tip, or outer ear.
• If the flow of blood stops or slows in your foot, your foot falls asleep.
• To keep blood circulating, stay active. Move your muscles! Get up and walk around!
What body parts make blood? Your bone marrow, for one. In the center of your bones is a factory that makes red blood cells, some white blood cells, and platelets. Your spleen and lymph system (glands) supply other white blood cells. When you have an infection, your lymph glands work overtime and swell. You can feel the swollen bumps in your neck or armpits.
We eat food to give our cells the energy they need to grow, repair, and maintain our bodies. The amount of energy released by food is measured in units called Calories.
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