# Science: A Field Of Wonder/Printable version

The current, editable version of this book is available in Wikibooks, the open-content textbooks collection, at
https://en.wikibooks.org/wiki/Science:_A_Field_Of_Wonder

# Preface

Each day is a continuous period of learning for all of us. We attempt to discover more about ourselves, our surroundings, and others.
Science: A Field Of Wonder is based on the competencies prescribed in the K to 12 Science curriculum of the Department of Education. This series is designed to promote interest, foster understanding of scientific knowledge, and develop basic inquiry skills.
This book makes science learning easier with the help of the following features.
* Unit Opener - This provides an overview and an introduction of the topics that will be discussed. It establishes the connections among the unit lessons.
* Chapter Opener - The chapter introduction and encourages continued reading.
* Big Idea - This feature identifies the main idea of the chapter and connects the various lessons within it.
* Learning Targets - Specific objectives are set at the beginning of each lesson.
* Pause and Think - This section poses a question which allows students to activate prior knowledge and motivates them to undertake inductive learning.
* Investigate - Related active-learning experiences are completed by students in class with partners and/or in groups.
* Vocabulary - Definitions of important terms that are crucial to student learning are provided in each lesson.
* Learn More - This feature attempts to clarify existing notions, provides supplementary content, and presents fun facts. It enriches pupils' knowledge and understanding of the concepts in focus.
* Checkpoint - This sections poses a question that reinforces concepts learned.
* Lesson Wrap-up - This section is found at the end of each lesson. It includes Sum It Up and Check Yourself.
** Sum It Up - This provides key scientific principles with visuals that incorporate the lessons in the chapter
** Check Yourself - Students are encouraged to demonstrate their understanding of the concepts learned by recalling important terms and answering critical thinking questions
* Chapter Test - Students are given chapter tests that can check their knowledge of facts and evaluate their understanding and mastery of science concepts. Science, like life is a never-ending journey of wonder and discovery. Let us therefore urge learners to come forward and take the first step.
Science, like life is a never-ending journey of wonder and discovery. Let us therefore urge learners to come forward and take the first step.

# Introduction

What is science? How is science learned? What does "doing science" mean? How is science done? What tools are needed to do science? How are scientific investigations done? By discovering the answers to these questions you will better appreciate what science truly is.
Everyone should realize the contributions of science and scientists to society. The technological advancement that you are enjoying today is the outcome of researches in science and discoveries by scientists. Young people like you should be encouraged to be interested in science or science-related fields in order to build the country's human resources to a level that can change the country toward economic progress. As you go through this introduction, try to see how well you can answer each of ther questions posted earlier. Moreover, see how your answer could influence the way you view the present-day world.

#### Science and Technology

The word science comes from the Latin term scientia, which means "to know". Science refers to an organized body of knowledge, which people have learned and gained through the use of scientific processes. Furthermore, science is often described as any systematic field of study.
The application of scientific knowledge to practical purposes is called technology or applied science. Technology comes from the Latin words techne, meaning "craft or skill" and logia, meaning "study."
The study of science and technology is very important because it deals with the improvement of the quality of life.
An example of this is a modernized tricycle or E-trike which eliminates the effects of noise and air pollution.
Science and technology provide so much impact on our lives. However, their negative effects cannot be ignored.. For instance, soil erosion, waste management, flooding, new diseases, and other health-related problems are the consequences of the processes and products of science and technology. Aside from these threats to individuals and the surroundings, world-related concerns are also present. An example is the hole in the ozone layer of the atmosphere due to the chlorofluorocarbons (CFC) from aerosols and refrigerants. The issue on global warming, the changes in climate patterns, and the rise in sea level around the world are other examples of environmental problems caused by some products and processes of science and technology.
It is now a challenge for humans like you, equipped with scientific knowledge and skills, to be able to decide wisely whether a particular process or product of science and technology can serve as a risk or a support to human lives.

# Limitations of Science: Believe It or Not

What are superstitious beliefs? Why do people believe in superstitions? Why do superstitious beliefs still persist in many societies in many societies in this age of enlightenment and modernization?
Superstitious beliefs are ideas and practices that do not have any scientific basis. Suppose, for example, that a woman who is expecting a baby will eat twin bananas, she will give birth to twins. This is a superstitious belief. By breaking a mirror, one may experience seven years of bad luck is another superstitious belief .
Superstitious beliefs are handed down from generation to generation by word of mouth and through storytelling. Instead of taking these beliefs seriously, investigate and study carefully the issues first so that you can form valid, reliable, and scientific solutions.

# Branches of Science

There are two broad divisions of science, the physical sciences and the biological sciences.

### Physical Science

Physical Sciences deal with the study of nonliving matter. Some of the branches of science that fall under this category are the following:
* Chemistry - It deals with the study of the composition, structure, form, properties, and changes in matter.
* Physics - It deals with the study of matter and energy including light, sound, electricity, magnetism, motion, and radiation.
* Earth Sciences - These deal with the scientific study of Earth, its composition, structure, and other astronomical object, interacting with it. The branches of Earth Science include geology, meteorology, seismology, and astronomy.
** Geology - This branch of science involves the study of the origin, history, structure, and evolution of the crust of Earth. It also involves the examination of soil and rocks.
** Meteorology - This is the study of the atmosphere that focuses on weather processes and forecasting.
** Seismology - This is the study of earthquakes and the movement of waves and artificially produced vibrations of Earth.
** Astronomy - This is the study of celestial bodies, such as stars, planets, comets, and galaxies, and some phenomena which originate outside the atmosphere of Earth.

### Biological Sciences or Life Sciences

Biological Sciences deal with the study of living organisms. The sciences under this category focus on the study of internal body functions and the structure of body cells and tissues. Some of the branches of science under life sciences are the following:
* Biology - This deals with the study of living things. It encompasses all the various aspects like the structure and function of the various organs, morphology, physiology, taxonomy, etc.
* Zoology - This deals with the study of animals — their form and structure.
* Ecology - This deals with the study of the relationship of living organisms among one another and their interaction with their surroundings.
* Botany - This deals with the study of plants.
* Genetics - This deals with the study of heredity — the ways in which characteristics are passed from parent to offspring.

# Characteristics of Scientists and How Do Scientists Think
## Characteristics of Scientists

Scientists must possess certain attitudes or ways of thinking to be successful in making scientific investigations. To think like a scientist, you need to have the following:
* Curiosity or inquisitiveness. Scientists never stop learning. They show interest and pay particular attention to objects of events. They ask questions and seek answers.
* Creativity. Scientists are sensitive to problems and can generate original ideas. They are able to find new and alternative answers to a problem.
* Humility. Scientists are humble. They admit that they are not free from committing errors . They recognize that they may be better ideas and realize that there are individuals whom they may have to consult to consult to arrive at correct observations and conclusions.
* Critical-mindedness. Scientists base suggestions and conclusions on evidence. They prefer accuracy of facts and reliability of sources of information.
* Intellectual honesty. Scientists give a truthful report of observations. They do not withhold important information just to please others.
* Resourcefulness. Scientists think of possible alternative solutions to problems they are working on. They find alternative materials to be used for their experiment.
* Objectivity. Scientists do not allow their feelings and biases to influence recording of observations, interpretation of data, and formulation of conclusions.
* Patience. Scientists spend time or days of work to finish a task and get an accurate result.
* Careful judgement. Scientists do not easily jump to conclusions. Their judgement is based on facts and reliable information.
* Rationality. Scientists believe that in this world, things happen for a reason. They only accept facts and statements that are supported by proofs.

## How Do Scientists Think?

You can do what scientists do. Scientific thinking, also commonly called science inquiry or the scientific method, is a process for both asking and answering questions about the universe. This is used by all kinds of scientists to investigate and answer questions. The scientific method involves the following:
* Using the senses and scientific equipment to make careful observations about the environment.
* Asking specific questions about observations that can be answered, using the tools of science.
* Forming hypotheses that explain what is observed.
* Testing hypotheses through repeated experiments and other tests and through collecting and recording data.
* Analyzing and drawing conclusions from the data
* Asking new questions, making new observations, and forming new hypotheses based on these findings
Science inquiry depends on critical thinking skills. This involves keeping one's mind open to new ideas. Wanting to investigate rather than accepting explanations of others, exemplifies scientific thinking.

#### Science Inquiry Process

Below is a process that most of the scientists follow to answer questions and make new discoveries.

# About The Laboratory
## Basic Laboratory Tools

How do you make scientific investigations? To be reliable and accurate, scientific investigations need data to help prove or disprove a hypotheses. In order to gather appropriate data, the following laboratory equipment and their uses are presented below.
Heating Instruments :
| Laboratory Equipment | Description/Use | Illustration |
| Bunsen burner | A source of heat when nonluminuous flame is needed for experiment work | https://store.schoolspecialty.com/OA_HTML/xxssi_ibeGetWCCImage.jsp?docName=F1635011&Rendition=Large |
| tripod | A stand with three legs used for supporting the wire gauze and container with liquid to be heated | https://cdn11.bigcommerce.com/s-ufhcuzfxw9/images/stencil/original/products/13266/14343/CE-TRIPOD5__70828.1503517910.jpg?c=2&imbypass=on |
| iron stand | This is used to support the setup for the heating process. | https://marslabph.com/wp-content/uploads/2016/12/ironstand.jpg |
| alcohol lamp | It is a source of heat in the laboratory. | https://www.3riversarchery.com/mm5/graphics/00000001/5376_341x500.jpg |
Containers :
| Laboratory Equipment | Description/Use | Illustration |
| beaker | This is a deep, wide-mouthed, cylindrical vessel with a pouring lip. It is used for measuring large quantities of liquid; it also serves as a container of boiling liquid mixture. | https://pim-resources.coleparmer.com/item/l/cole-parmer-3450352-griffin-low-form-beaker-glass-250-ml-12-pk-3450352.jpg |
| Erlenmeyer flask | This is a flat-bottomed flask that has a wide bottom and a narrow mouth or opening. | https://www.labdepotinc.com/admin/uploads/ac070527l_medium.jpg |
| test tube | This is used to contain small amounts of solution for boiling or for storage. | https://5.imimg.com/data5/AU/DY/MY-957949/laboratory-glass-test-tubes-500x500.jpg |
| Florence flask | This is a round-bottomed flask used as a container for boiling liquid solution. | https://cdn11.bigcommerce.com/s-ufhcuzfxw9/images/stencil/original/products/13038/16907/CE-FLOR500__65671.1522703167.jpg?c=2&imbypass=on |
Measuring Device (Mass) :
| Laboratory Equipment | Description/Use | Illustration |
| platform balance | This is used for weighing materials accurately in various containers or vessels. | https://www.mrmprecision.ca/wp-content/uploads/2017/07/Harvard-Trip%C2%AE.jpg |
| top loading balance | This is used for weighing materials electronically | https://www.dataweigh.com/media/11904/entris-top-loader.png |
Measuring Device (Liquid Volume) :
| Laboratory Equipment | Description/Use | Illustration |
| graduated cylinder | This is used for measuring the volume of liquids | https://www.brandtech.com/wp-content/uploads/glass_cylinder_new.jpg |
| pipette | This is used for measuring a small volume of liquid direct from the reagent bottle | https://cdn7.bigcommerce.com/s-ufhcuzfxw9/images/stencil/500x659/products/12140/15341/CE-PIPE05A__25042.1503517926.jpg?c=2 |
| dropper | This is used in transferring and measuring small amount of liquid | https://www.aromatools.com/media/catalog/product/cache/1/image/1800x/6beb0238d6dd6cb8069692f5b293db57/9/1/9157f.jpg |
Measuring Device (Length) :
| Laboratory Equipment | Description/Use | Illustration |
| tape measure | A tape or thin flexible metal, marked at intervals for measuring length | https://s.hswstatic.com/gif/tape-measure-1.jpg |
| meterstick | A one-meter long ruler that is usually marked off in centimeters and milimeters | https://cdn.krafttool.com/images/product/medium/SLM39.JPG |
Measuring Device (Temperature) :
| Laboratory Equipment | Description/Use | Illustration |
| thermometer | This is used for measuring temperature | https://nelsonjameson.com/secure/images/products/1011578.jpg |
Measuring Device (Time) :
| Laboratory Equipment | Description/Use | Illustration |
| stopwatch | This is a special watch with buttons that start and stop. It is used to measure the amount of time to do an activity. | https://sc02.alicdn.com/kf/HTB1rXz8QVXXXXadXpXXq6xXFXXXu/Laboratory-professional-Stopwatch-countdown-Timer.jpg_350x350.jpg |
| Laboratory Equipment | Description/Use | Illustration |
| test tube rack | A framework of wooden or metal bars for supporting the test tubes when not in use or while waiting for the reaction of reagents to take place. | https://cdn11.bigcommerce.com/s-ufhcuzfxw9/images/stencil/original/products/11734/16286/ce-ttrack4__89156.1503517951.jpg?c=2&imbypass=on |
| watch glass | A crystal used for observing a small amount of sample that is undergoing reaction. | http://www.capitolscientific.com/core/media/media.nl?id=59756&c=1250437&h=4ccdc350132ab41e5038 |
| test tube holder | A strong metal wire used to hold test tubes. | https://4.imimg.com/data4/BV/IF/MY-16630388/test-tube-holder-500x500.jpg |
| mortar and pestle | This set is used for pounding and grinding solid substances into powder form. | https://slimages.macysassets.com/is/image/MCY/products/2/optimized/2725842_fpx.tif?op_sharpen=1&wid=500&hei=613&fit=fit,1&$filtersm$ |
| funnel | This is used for pouring liquids or powders into containers with small opening and for holding the filter paper during filtration. | https://pim-resources.coleparmer.com/item/l/pyrex-6140-65-6140-glass-funnel-65-mm-top-dia-62-ml-6-pk-3456051.jpg |
| wire gauze | This is used to regulate the heat of the glame when used in heating. | https://cdn11.bigcommerce.com/s-ufhcuzfxw9/images/stencil/500x659/products/13125/14331/CE-GAUZE4__94252.1503517909.jpg?c=2 |
| clay triangle | This is used to support the crucible for direct heating. | https://cdn11.bigcommerce.com/s-ufhcuzfxw9/images/stencil/original/products/11320/13772/CE-TRIAN25__84696.1503517900.jpg?c=2&imbypass=on |
| evaporating dish | A porcelain dish in which a solution may be evaporated to leave the dissolved substance as a residue | https://cdn11.bigcommerce.com/s-ufhcuzfxw9/images/stencil/original/products/12072/14358/CE-EVAPDSH__23331.1503517910.jpg?c=2&imbypass=on |

## Safety Devices

Safety devices are used to protect yourself when working inside the laboratoryroom. Common examples of safety devices are as follows:

### Laboratory Gown or Apron

A laboratory gown is worn to protect the skin and clothing from spills.

### Safety Goggles

These are worn in the laboratory to protect the eyes from harmful and toxic substances.

### Gloves

These are used to protect the hands from contact with harmful substances, broken glass, and hot objects.

## Safety Symbols

The following safety symbols will appear in the laboratory experiments to emphasize additional important areas of caution. Learn what they represent so you can take the appropriate precautionary measures.

### Electric Shock

This indicates that electrical outlets should not be touched when hands are wet.

### Disposal

This means that used chemicals must be properly disposed of in specific containers.

### Poison

This means that the substance is harmful, deadly, and should not be touched, tasted, or inhaled.

## Common Laboratory techniques
### Heating a Substance in a Test Tube

When you are heating a test tube
* always use a test tube holder.
* always hold the test tube at an angle like in figure shown below
* never point a test tube of liquid being heated to yourself or to your classmates.
* distribute the heat at the bottom of the test tube by passing the sides of the test tube up and down along the flame.

### Measuring Volume

The volume of a liquid is measured by using a graduated cylinder. A graduated cylinder is marked in milliliters (mL). It measures small amounts like 10mL or large amounts like 100mL.
In reading the volume of liquid in a graduated cylinder, place the setup on a flat surface. At eye level, read the lower meniscus.

## Laboratory Safety Measures

Safety and environmental consciousness is vital in doing laboratory activities. Always consider your own, your co-workers, and the environment's safety.
* Read the laboratory instructions of the experiment carefully before you start working on the experiment. Listen for further instructions from the teacher.
* Regard all waste disposals as a potential safety and environmental risk. Dispose of solid and liquid wastes properly. Ask your teacher how.
* Wear appropriate protective apparel such as gloves, laboratory gowns or aprons, and safety goggles.
* Take care of all equipment and apparatus. Clean them after use.
* Know all emergency and fire procedures. Become familiar with safety signs and symbols.
* Never taste a chemical or solution unless told to do so.
* Do not eat or drink in the laboratory.
* Report immediately any breakage of glassware or equipment to the teacher or laboratory assistant for proper disposal.
* Do not touch electrical outlets and gas cocks if not needed in the experiment.
* Never work inside the laboratory room unless supervised by the teacher or the laboratory staff.

# First Unit Opener

Look around you and observe the things that surround you - the animals and the plants, the concrete buildings, the vehicles, the glass doors and windows, the wooden tables, the clothes you wear, your rubber shoes, books, pen, pad paper, the food you eat, the water you drink, the people around you, and everything in the sky above you. These are forms of matter.
In Unit I, you will learn the types, characteristics, and the ways on how to separate mixtures.

# Homogeneous and Heterogeneous Mixtures

   When you slice apples, strawberries, kiwis, pineapples, and grapes, and you mix them all together in a bowl, you have just made a salad that tastes good and healthy. Like salad, many useful things are made by mixing two or more kinds of matter. These are called mixtures.

## Pure Substances and Mixtures

You have learned that a fruit, cheese, spoon, plate, and bowl are matter. Some things are made of only one kind of matter. Sugar is one example. Sugar is made only of sugar. It does not contain any other kind of matter. Sugar is a pure substance. A pure substance is made of a single kind of matter with certain properties. Every part of a substance is the same throughout.
Most of the things around us are mixtures, such as the air, the ocean, the soil, and even food! A box of mixed nuts and assorted marshmallows, pile of leaves and twigs under a tress, and a gallon of ice cream are all mixtures.
A mixture is a physical combination of two or more substances. The substances in a mixture are not chemically combined as they are in a compound. Hence, a mixture is not a pure substance. One important property of mixtures is that proportions of its parts can change. Mixtures have two kinds: homogeneous mixtures and heterogeneous mixtures.
Making a mixtures is a physical change. Mixing together two or more substances often changes the form, color, size, or texture of those substances, but the properties of each substance in the mixture do not change. When you look at the salad, how do you know it is made with different kinds of vegetables? You can pick the onions out of the vegetable salad, and they are still onions.

### Homogeneous Mixture
#### Solution

You have read that when you mix sugar in water, the sugar particles dissolves and thus, you do not see them in water. Sugar-water mixture is a solution. A solution is a homogeneous mixture in which two or more substances are so evenly mixed that the separate parts cannot be seen. The properties of the substances that make up the mixture are the same as they were before they mixed together. That is why you can taste the sugar in the water.
In a sugar-water solution, the sugar has dissolved in water. To dissolve means to mix completely with another substance to form a solution. In a solution of water and sugar, water is the solvent and sugar is the solute.
Water is called as the "universal solvent" because it is capable of dissolving more substances than any other liquid.
Particles in a solution spread evenly throughout the solution. There are solutions, such as lemonade and saltwater, that have a liquid solvent and a solid solute. However, solutions can have other combinations . Soda water is a solution made of carbon dioxide dissolve in water. Air is a solution of several different gases.
Since not all solutions are made by mixing a solid substance with water, many solutions are mixtures of matter in other states.
Some Types of Solutions :
| Types | Examples | Parts |
| gas dissolved in gas | air | oxygen, nitrogen, other gases |
| solid dissolved in solid | steel | iron, nickel, chromium |
| solid dissolved in liquid | ocean water | salt, minerals, water |
| gas dissolved in liquid | soda water | carbon dioxide, water |
Recall that the substances in a solution are evenly mixed that the specific parts cannot be seen. This means that the molecules of the two substances become evenly mixed.

### Heterogeneous Mixture

Another type of mixture is the heterogeneous mixture. Mixing salt in water forms a solution, but mixing soul with water forms another kind of mixture called suspension.
A suspension is a heterogeneous mixture that contains particles huge enough to be seen by your naked eye. These are mixtures from which some of the particles settle slowly when set aside. Examine some liquid food and medicines, if you see Shake before using on the label, it means it is a suspension. Another example of this is soil shaken with water. The soil particles start to settle when the shaking tops.
Take a glass of water and place a handful of sand or dirt. Stir it well. Have you made a solution? Sand and dirt do not dissolve in water. Although it may look homogeneous for a few moments, the sand or dirt gradually sinks to the bottom of the glass. Therefore, it is an example of a suspension.

#### Colloid

Another type of heterogeneous mixture is colloid. A colloid is a mixture that contains particles that are too small to be seen. its particles are intermediate in size between those found in solutions and suspensions and can be mixed such that they remain evenly distributed without settling out.
A colloid is exactly like a suspension, but because the particles are so small, they never settle to the bottom. Milk is a colloid because it scatters a beam of light passing through it; therefore, it shows the Tyndall effect.
Emulsion is a kind of colloid. An emulsion is a mixture of two liquids that do not dissolve. For example, mayonnaise is an emulsion of vegetable oil, egg yolks, and vinegar or lemon juice.
What you see in the picture below is a colloid of water droplets suspended in air. Fog is a mixture of water droplets and air. Even though fog appears to be gas, it is still a heterogeneous mixture because it contains water droplets.
Have you see smoke rising from a barbeque grill? Is smoke a mixture? Smoke is a mixture made up of air, other gases, and tiny solid particles of ash. Dust is another solid that mixes with air.

# Integumentary System

In studying the structures of the body, it is appropriate to begin with the integument. Like wrapping around a gift, it is the first thing that you see. It is a compound organ because it is structurally double, being made up of the epidermis and dermis. It is also a versatile organ because it performs a wide range of functions, that is why it is also termed as "Jack/Jane of all trades."

## Functions of the Integumentary System

The integumentary system forms a shield between the external environment and the inner tissues of the body. The organs of the integumentary system work together to provide and regulate heat, and help in removing waste from the body.
The skin, which is the largest organ of the body is also the principal organ of the integumentary system. It provides protection to the inner tissues. Besides the protection to the organs, the integumentary system has other functions as well. In the deeper layers of the skin, reserved energy in the form of fat is stored to be used in times of need.
The skin has a large number of nerve openings that help us in perceiving the sense of touch, pressure, pain, and changes in temperature.
Beneath the skin are layers that secrete an oily substance which also regulates hear and gives moisture to the skin.
   Melanin is a primary determinant of skin color.

## The Layers of the Skin and Their Functions

The skin is composed of three layers: the epidermis, dermis, and hypodermis.
The epidermis is the outermost layer of the skin. It consists of epithelial tissues in which the cells are tightly packed together, providing a barrier from the outside of the body.
The dermis is the layer of connective tissues located below the epidermis. It provides support for the skin and it also contains nerve tissues that provide feeling the skin. It also contains muscle tissues that is responsible for giving you goose bumps when you get cold or frightened.
The subcutaneous layer or hypodermis is found beneath the dermis and consists mainly of connective tissues called adipose tissue or fats. It attaches the skin to underlying bones and muscles and also supplies it with blood vessels and nerves.
   The skin is the largest organ in the body. In adults, the skin covers an area of approximately 2 square meters and accounts for nearly 20% of one's body weight. Its thickness varies from 0.3 - 4.0 mm depending on the location on the body.

## Common Skin Diseases

The proper functioning of the integumentary system is important for a healthy body. However, due to external factors and improper hygiene, some diseases affect the skin.
Some of the common skin diseases are as follows:
* Athletes foot is a fungal infection that causes scaling, flaking, and itching of various areas of the skin. This condition is transmitted mostly in moist areas where people walk barefoot.
* Eczema is an inflammatory skin disorder that manifests as rashes, severe itching, hives, and in acute cases, blisters and crusts.
* Psoriasis is a chronic, noncontagious, autoimmune disease. Red and scaly patches or lesions can be observed on the skin.
* Warts are characterized by tiny, round, rough, tumors found typically on hands and feet. Warts could be contagious, spreading from one person to another via physical contact.
* Acne is a common human skin disease affecting the skin of the face, upper parts of the chest, and back.
   We lose 30 000 to 40 000 dead skin cells every minute!

## Ways to Take Care of the Skin

Taking care of your skin will benefit your overall health and help you look young.
* Bathe every day
* Wash your hands regularly.
* Keep your nails and skin clean to prevent infections.
* Eat a healthy, well-balanced diet.
* Examine your entire body regularly if there are changes or an abnormal growth that looks different on your skin.

# Musculo-Skeletal System

The musculo-skeletal system constitutes bones, muscles, joints, and connective tissues. Together, these body parts provide the framework for your body, generate your movements, and dictate your grade of flexibility. They comprise roughly sixty percent of your body mass and use up most of your energy. What will happen to humans without the musculo-skeletal system?

## Functions of the Musculo-Skeletal System

The human skeletal system is comprised of individual bones and cartilage that receive a supply of blood and are held together by fibrous connective tissues. Its three main functions are protection, motion, and support. The system protects the body by enclosing the vital organs. It permits movement by responding at certain joints to the activities of skeletal muscles. It supports the body by serving as a framework to which tendons and fascia are attached.
Movements such as walking and running are caused by the coordinated work of joints, bones, and skeletal muscles. Skeletal muscles are also responsible for various facial expressions, eye movements, and respiration. Nearly all movements in the body are the results of muscle contraction.
The bones are the main structures of support and movement. They are made up of hard material to which the skeletal muscles attach. They consist of living cells incorporated within a dense layer of protein and minerals. The main function of the bones is to support the weight of the body. Together with the muscles, the bones maintain good posture and control the movements of the body. Without the skeleton , contracting muscle fibers could not make you stand, sit, walk, or run.
Every bone in the skeleton contains two form of tisses. The compact (firm) bone is somewhat solid and is found on the external surface. The spongy (cancellous) bone is located inside the bone. Bones are made up of sodium, phosphorus, calcium, and other minerals, as well as the protein collagen. Bones originate as cartilage which slowly transforms to bones through a process called ossification.
The bones also store fats, minerals, and lipids in are areas filled with yellow marrow. Red blood cells, white blood cells, and other blood components are produced in the red marrow found in the bones,
The bones protect the different organs of the body. Below are the most important bones in the body and functions:
* The skull protects the brain and forms the shape of our face.
* The ribs shelter the heart, lungs, liver, and spleen.
* The spinal cord which is the passageway for messages between the brain and the body, is protected by the backbone or spinal column.
* The pelvis protects the urinary bladder, intestines, and reproductive organs.

### Muscles and Joints

The human body has more than 600 muscles. Muscles make up 50 percent of a person's body weight. Each muscle is attached by a connective tissue to two or more bones and they tend to function in group or pairs. When an individual muscle contracts, the opposing muscle usually relaxes,
Humans have three different kinds of muscles.
* Cardiac muscles are found in the walls of the heart's chambers. They are involuntary muscles. Their regular, powerful contractions force blood out of the heart as it beats.
* Smooth or involuntary muscles are also made of fibers. These muscles look smooth and are controlled by the nervous system. Examples of smooth muscles are the walls of the stomach and intestines, which helps break up food and move it through the digestive system.
* Skeletal muscles, also know as voluntary muscles, are attached to the bone, mostly in the arms. They are also called striated because they are made up of fibers. These muscles clutch the skeleton together, provide the body shape, and help with everyday movements.
Joints make the skeleton flexible; they occur when two bones meet. Muscles pull on the joints, allowing us to move.
Joints are classified based on the movements they produce.
* Immovable or fibrous joints do not move. For example, the skull is made of bony plates which mush be steady to protect the brain. Between the boundaries of these plates are joints of fibrous tissues. Fibrous joints also grip the teeth in the jawbone.
* Partially movable or cartilaginous joints move a little. The bones in the spinal column are connected by a cartilage. Each of the bones in the spine moves in relation to one another and together, these movements give the its flexibility.
* Freely movable joints are the main joints of the body usually found at the shoulders, elbows, wrists, hips, knees, and ankles. They move in different directions. They are filled with synovial fluid, a lubricant that helps the joints move freely.
There are three kinds of freely movable joints that play a big part in voluntary movement.
* Hinge joints permit movement in one direction, like the knees and elbows.
* Ball-and-socket joints allow free movement, like the hips and shoulders.
* Pivot joints allow a rotating motion, like that of the head moving from side to side.
* Gliding joints allow the bones to glide pass one another in any direction along the plane of the joint, like the wrist and bones of the ankle.
* Saddle joints allow movement in two directions, like the thumb.

### How Joints and Muscles Work

Even when you are not moving, muscles throughout your body are still regularly working. Muscles allow your chest to expand and contract as you breathe. They also enable your heart to beat and your blood vessels to control the pressure and flow of blood through your body.
When you sit, walk, run, laugh, talk, and exercise, your muscles are working to help you do all these activities. The movements your muscles make are controlled and guided by the nervous system. If you want to move any part of your body, your brain sends messages to the muscles. When you run, many muscles have to work in rhythm. Your muscles can pull bones, but they cannot push them back to the original position.

### Connective Tissues

Generally, skeletal muscles are attached to two bones through tendons. Tendons are strong bands of dense regular connective tissues which firmly attach muscles to to bones. When you wiggle your fingers, you can see the tendons move at the back of your hand as they do their job. To produce, motion, they transmit tension from the muscle to the bone.
The fascia is a soft, thin, jelly-like membrane that is merged with the bones, muscles, tendons, nerves, blood vessels, and organs throughout the body. It supports and connects the different body parts.
Bones are fixed firmly to other bones by long, fibrous straps called ligaments. Ligaments make the bones stable and support the joints by holding them in place

## Diseases and Disorders of the Musculo-Skeletal System

Even though bones are strong, they can also break. Muscles can weaken and joints (as well as tendons, ligaments, fascia, and cartilages) can be damaged by injury or disease. Here are some conditions that can affect the muscles, bones, and tendons.
* Arthritis is the inflammation of the joints. People who have it experience swelling and pain in the affected areas, and they often have difficulty in moving.
* Fracture occurs when a bone breaks due to a forceful impact. After a bone fracture, fresh bone cells fill the gap and repair the break.
* Osteoporosis is experienced when the bone tissue becomes breakable, slender, and malleable. The bones break easily and the spine begins to disintegrate and collapse. Exercising regularly and getting plenty of calcium can help avoid getting osteoporosis later in life.
* Scoliosis is a condition which causes the spine to cure abnormally. Every person's spine allows a certain amount of curvature which is necessary for movement and other activities.
* Sprains and strains are caused by the overstretching or the partial tearing of the ligaments. Strains frequently happen when a person takes part in a strenuous activity without preparing the muscles through warm-up exercises. Sprains, on the other hand, are usually the result of an injury, such as the twisting of the ankle or knee.
* Tendinitis is a common sports injury that happens after overusing a muscle. The tendons become swollen, which can be painful.

## Taking care of the Musculo-Skeletal System

* Regular exercise can keep the bones and muscles strong. Walking, jkogging