Do you know what you are made of?

In this ebook & post, we are going to learn about cells, tissues, organs and systems that make up our body.

You will be amazed to discover how complex your body is and how intricately you have been made. There are so many processes that  are going on in our bodies to keep us healthy, comfortable and alive. Yet, we are not even aware of all these working processes that are taking place within us.


Do you know that human beings are made up of cells? Scientists estimate that a human being has around 37 to 100 trillion cells, depending on age, size and overall health. Not all cells are the same. There are more than 200 types of cells in a human. Each type of cell has a different shape and size to perform specific function.

A cell is the basic unit of life that forms all living things on Earth. Any living thing that can live on its own is called an organism. Micro-organisms such as bacteria and yeasts are made up of only one cell. Animals and plants have thousands to trillions of cells, depending on species, sizes and developmental stage.


Red blood cell is a type of blood cell that is made in the bone marrow and found in the blood. Red blood cells contain a protein called hemoglobin, which carries oxygen from the lungs to all parts of the body. Our body also have white blood cells which help our body fight infection and other diseases. 


Red Blood Cells

Image by Aseedtolife, CC BY-SA 4.0 <>, via Wikimedia Commons

In addition, we have stem cells that serve as a repair system for our body. They are unspecialized, but have the potential to become specialized cells, such as muscle cells, blood cells, and brain cells.


Stem Cells

Image by UCSanDiegoStemCellProgram, CC BY-SA 3.0 <>, via Wikimedia Commons

Above image by Haileyfournier, CC BY-SA 4.0 <>, via Wikimedia Commons

There are 2 types of Stem Cells. They are embryonic stem cells and adult stem cells. The embryonic stem cells used in research today come from unused embryos. They can turn into more than one type of cell. Adult stem cell comes from fully developed tissues, such as the brain, skin, and bone marrow. They are more likely to generate only certain types of cells. For example, a stem cell that comes from the liver will only make more liver cells. Read more in this article.



Cells unite to form tissues. Our muscles and nerves are examples of tissues.


Cross section of skeletal muscle fibers at 200x magnification

Image by Berkshire Community College Bioscience, CC0, via Wikimedia Commons



Several types of tissues group to make an organ for specific function. Our lung, stomach, brain, heart are examples of organs.


Examples of Organs

Above images of Lung and Brain available at Wikipedia Commons.



When several organs work together to perform a special purpose, we call it an organ system. Humans have 12 major systems. Let’s look at the 12 systems:

1. The Digestive System

Image by LadyofHats, Public domain, via Wikimedia Commons


In order for us to consume food to give us energy, nourish us and keep us alive, we have the digestive system that is made up of many organs. From our mouth to stomach, intestines, all the way to our anus. The bowel is part of the digestive system  and it works to digest the food we eat, absorb the goodness and nutrients into our blood stream, then process and expel the waste that the body cannot use.


2. The Excretion & Urinary System

Image by Jordi March i Nogué [1], CC BY-SA 3.0 <>, via Wikimedia Commons

The urinary system (also known as the urinary tract) is a major part of the excretory system. It filters wastes and water from the blood, and eliminates them from the body.  The 4 major organs, namely the kidneys, the ureters, the bladder and the urethra work together to eliminate wastes from our body. Each of our kidneys is made up of about a million filtering units called nephrons. Each nephron includes a filter which filters your blood, returns needed substances to your blood and removes wastes. A waste product called urine is produced and then transported from the kidneys through the ureters and into the bladder. It remains stored in the bladder until it is released through the urethra.



The urinary system maintains an appropriate amount of fluid in your body, regulate the concentrations of electrolytes, maintain a normal pH of your blood, controls red blood cell production and maintain a normal blood pressure.

1.Urinary system (consists of item 2 to 6)


3.Renal pelvis


5.Urinary bladder

6.Urethra (Left side with frontal section)

7.Adrenal gland

8.Renal artery and vein

9.Inferior vena cava

10.Abdominal aorta

11.Common iliac artery and vein


13.Large intestine


The excretory system removes metabolic wastes from the body. The urinary system is one part of the excretory system. There are several other organs that are also involved in excretion, including:

  • the skin, which rids the body of wastes through the sweat glands
  • the lungs, which exhale carbon dioxide, and
  • the liver, which breaks down toxic substances in the blood and convert nitrogenous waste into urea

The major task of excretion still belongs to the urinary system. If it fails the other organs cannot take over and compensate adequately.


3. The Circulatory System

Image by LadyofHats, Public domain, via Wikimedia Commons


There is a circulatory system in our body that carries digested food and oxygen to all parts of our body. It also carries waste materials away from all parts of our body to be excreted.


4. The Respiratory System

Image by LadyofHats, Public domain, via Wikimedia Commons


The respiratory system consists of the nose, the airways, the lungs, and the respiratory muscles that mediate the movement of air into and out of the body. It takes oxygen into the body and removes carbon dioxide from the body.


5. The Skeletal System

Image by LadyofHats, Public domain, via Wikimedia Commons



The Skeletal system supports our body. It gives us the body shape and protects the delicate organs in our body. It works with the muscular system to help us move.


5. The Muscular System

Derivative of original by Bibliographisches Institut (copyright extinct), Public domain, via Wikimedia Commons



The Muscular system is made up of muscle fibers and helps the body to move. It provides the body with strength and stability. This system is controlled by the nervous system.


All Systems work together

Our body has 78 organs and 12 major systems:

1.Digestive System

2.Excretion/ Urinary System

3.Circulatory System

4.Respiratory System

5.Skeletal System

6.Muscular System

7.Endocrine System

8.Immune/ Lymphatic System

9.Reproductive System

10.Integumentary System

11.Nervous System

12.Endocannabinoid System

In this post, we have covered the first 6 systems. We will learn more about the next 6 systems in part II of Our Amazing Body.

All the systems in our bodies work together to enable our bodies to function properly. If one part of a body system does not work properly, it will affect other systems and our entire body will feel it.

Give it a thought

So far, we have only look at an overview of 6 of the major systems in our body. Each system has specific purpose to keep us alive and healthy – digesting the food we eat, removing the wastes from our body, enabling us to move…. Yet, we do not even know that there are so many processes happening within our body! Certainly there is a God, our Creator, who loves us so much and has so intricately make us and is always lovingly watching over us to keep us safe and comfortable!