Explained | Organ and Organ System

Many living things have Organs.

Your Heart, Brain, Lungs, Liver, and Kidneys are organs.

Organs are made of two or more tissues.

Organs each have something that they do. The heart pumps blood. The lungs give you air.

Organs work together in groups called Organ systems.

Organ systems

Two or more organs that work together make an organ system.

Organ systems are found in all different kinds of living things.

Some of the organ systems found in humans include:

• Circulatory System
• Respiratory System
• Digestive System
• Endocrine System
• Reproductive System
• Urinary System
• Immune System
• Muscular System
• Skeletal System
• Integumentary System
• Nervous System

The Circulatory System

The Circulatory System moves blood around your body. This blood carries food and oxygen around to all of the cells of the body. It also carries signals called hormones that help the body work together

The major organ of the circulatory system is the heart, which pumps the blood. Blood goes away from the heart in tubes called arteries and comes back to the heart in tubes called veins. The smallest tubes are called capillaries.

The Respiratory System

The Respiratory System is how air gets into our bodies. We breathe in and out with our lungs. The air we breathe in has something called oxygen that our cells need. Cells make carbon dioxide which can poison our bodies. Our lungs push this out of our bodies.

The respiratory system works together with the circulatory system to make sure that air gets to each cell of the body.

Parts of the respiratory system are the nose, pharynx, larynx, trachea, bronchi, bronchioles, and alveoli.

The process of breathing

• Air comes in through the nose and mouth.
• Dust is removed by the hair in the nose.
• Air goes through the pharynx (in the back of the mouth), the larynx or the voice box, and down the trachea (windpipe).
• The trachea splits into two major bronchi, one for each lung.
• This further splits into smaller bronchi, then into smaller tubes called bronchioles which lead into the air sacs called alveoli.
• This is where the oxygen goes into the blood and carbon dioxide comes out.

The Digestive System

The digestive system is what a human uses to eat. Food comes in through our mouth is broken down in our stomach and our body takes the food in through the intestines. Then the waste goes out through the anus.

The digestive system is made of many organs. Here are some of the organs and their functions

Oesophagus

Pushes food down into the stomach.

Stomach

Breaks down complex sugar by acid.

Liver

Makes a thing called bile that breaks down fat.

Gall bladder

Stores the bile and adds it when it is needed.

Pancreas

Makes chemicals that break down food.

Small intestine

Absorbs food for body.

Large intestine

Absorbs water and salt.

Rectum

Stores waste.

Appendix

Vestigial organ(has no function in human body).

The Endocrine System

The human body is made of many, many cells. To make the cells work together, the body sends signals through the blood called hormones that tell the cells in the body what to do.

The Endocrine System is the organ system made of the organs that make hormones.

The endocrine system organs:

• Pineal gland
• Pituitary gland
• Thyroid gland
• Thymus
• Adrenal gland
• Pancreas
• Ovary
• Testis

How are babies made?

In humans there are two sexes: Men and Women. Babies are made when cells23 called sperm (produced by men) get together with cells called eggs (produced by women) in a process called fertilization. When the cells combine, they form a new cell, called a zygote which has all it needs to make a new man or woman. The zygote will make a baby like his mother and father.

Where do babies come from?

Babies come from their mother. To make a baby, the father must put his sperm into the mother's body. This is called having sex. The man puts his penis into the woman's vagina and the sperm cells swim into the mother's body. Fertilization happens in the mother. The new zygote grows into a ball which will stick to the mother's womb. This ball grows into a baby.

Nine months later (266 days after fertilization) a new baby will come out of the mother's vagina in a process called birth.

Reproduction | Glossary

cell

Things that are alive are made of little boxes called cells.

womb

The place in a body where a baby grows.

zygote

The one cell made from a sperm cell and an egg cell that will grow into a person.

sperm

A sex cell made by a man.

egg

A sex cell made by a woman.

fertilization

When sperm and egg get together and make a zygote.

The Urinary System

The Urinary system takes bad things out of the blood and washes it out of the body. This liquid waste is called urine. Without the urinary system, poisons would fill up the blood and kill a person. The kidneys are organs24 that filter the blood and remove poison. Urine is stored in a bag called the bladder and it leaves the body through a tube called the urethra.

Immune System

The immune system protects our bodies from disease. Cells called white blood cells found in our blood are able to kill bad things such as bacteria and viruses .

There are many different types of white blood cells. Some of them make things called antibodies that stick to things that enter our bodies making them easy to find. Other white blood cells get rid of bacteria and stop viruses like the flu.

When our immune system does not work well, we are vulnerable to disease caused by bacteria and viruses. Problems with the immune system include allergies; in allergies, white blood cells attack things that are not bad, like pollen in our eyes or cat dander. AIDS (Acquired Immunodeficiency Syndrome) is a disease caused by a virus that kills some white blood cells, leaving our bodies vulnerable to bacteria or viruses.

Muscular system

The muscles of the body are what make the body move. They are made of muscle tissues

All of the muscles of the body together make up the muscular system.

Signals from the nervous system tell the muscles when to move. The muscles are attached to the skeleton which holds them up.

The Skeletal System

The Skeletal System is made of all of the bones in the body. It protects the reproductive organs and is a place for muscles33 to attach. Bones are a very important part of the human body. Without them, we would simply collapse, and be very unstable. They support all of our tissue and muscles, and they are very difficult to break.

The inside of the bones is called the bone marrow. This is where most blood cells are made.

The Integumentary System

The Integumentary System is the system of the body made up of the skin, the nails, and the hair.

Skin keeps you cool by sweating. It also protects you by keeping things out of your body. The hair on your body keeps you warm. Skin also holds nerves35 that we use to touch and hold and kiss. Your nails help you pick up things. The skin is the largest organ of the human body.

The Nervous System

The nervous system helps you sense the world around you. It includes the brain and the nerves as well as the senses.

The nervous system helps you sense the world around you. It includes the brain and the nerves as well as the senses. electric currents, are conveyed to the appropriate organs such as muscles or glands, at a great speed.

The Senses

Your five senses are: smell (with your nose), taste (with your tongue), touch (with your fingers, and so on), sight (with your eyes), and hearing (with your ears).

If human beings couldn't smell, they wouldn't know if their food had a bad odor. If they couldn't taste either, they might like to eat everything, or, also bad in a different way, they might not like to eat anything. If they couldn't see, it would be harder for them to find their way around and avoid danger. And if they couldn't hear, they could not communicate with each other as easily.