Learning how the body works

HEALTH

In this new series of articles every Friday I will explain your body to you, and how you can use this understanding to improve your health, and hopefully live a longer and more enjoyable life. You will learn how your body works, and how you can avoid damaging it. You will also learn how we doctors examine you and treat illnesses. And most importantly, you will learn how you can change your lifestyle to stay healthy.
I am Dr Roland Fasol, the new Medical Director and Chief Cardiac Surgeon at the Pacific International Hospital here in Port Moresby. I am an academic surgeon from the University of Vienna in Austria, and I have worked, built and managed hospitals in Europa, Africa and China operating and treating thousands of patients. This new series of articles will help you to know more about your body, about health and disease. PIH doctors will answer your questions in a column every Wednesday. You can email questions to  [email protected]

Our body – organs and facts
We use our eyes to see, our ears to hear and our muscles to do the heavy lifting. Well, sort of. In fact, most body parts are far more complicated than that, while some body parts at first sight have no obvious function. In this series of articles we will explain how our body works.
Our bodies consist of a number of biological systems that carry out specific functions necessary for everyday living.

Vital organs
Humans have five vital organs that are essential for survival. These are the brain, heart, kidneys, liver and lungs.
The human brain is the body’s control center, receiving and sending signals to other organs through the nervous system and through secreted hormones. It is responsible for our thoughts, feelings, memory storage and general perception of the world.
The human heart pumps blood throughout our body.
Kidneys remove waste and extra fluid from the blood. The kidneys take urea out of the blood and combine it with water and other substances to make urine.

The liver has many functions, including detoxifying of harmful chemicals, breakdown of drugs, filtering of blood, secretion of gall (or bile) and production of blood-clotting proteins.
Our lungs are responsible for taking oxygen from the air we breathe and transferring it to our blood where it can be sent to our cells, where the oxygen is used for energy generation to run our body. The lungs also remove the resulting carbon dioxide, which we exhale.
We call them ‘vital organs’, but all the other organs are also equaly vital for us: for example the circulatory system.
The circulatory system moves blood, nutrients, oxygen, carbon dioxide and hormones around the body. It consists of the heart, blood, blood vessels, arteries and veins.
Your digestive system consists of a series of connected organs that together allow the body to break down and absorb food and remove waste. It includes the mouth, esophagus, stomach, small intestine, large intestine, rectum and anus. The liver and pancreas also play a role in the digestive system because they produce digestive juices.
The endocrine system has a complicated structure and consists of eight major glands that secrete hormones into the blood. These hormones, in turn, travel to different tissues and regulate various bodily functions, such as metabolism, growth and sexual function.
The immune system is the body’s defense against bacteria, viruses and other pathogens that may be harmful. It includes lymph nodes, the spleen, bone marrow, lymphocytes (including B-cells and T-cells), the thymus and leukocytes, which are white blood cells.
The lymphatic system includes lymph nodes, lymph ducts and lymph vessels, and also plays a role in the body’s defenses. Its main job is to make and move lymph, a clear fluid that contains white blood cells, which help the body fight infection. The lymphatic system also removes excess lymph fluid from bodily tissues, and returns it to the blood.
The nervous system controls both voluntary action (like conscious movement) and involuntary actions (like breathing), and sends signals to different parts of the body. The central nervous system includes the brain and spinal cord. The peripheral nervous system consists of nerves that connect every other part of the body to the central nervous system.
The body’s muscular system consists of about 650 muscles that aid in movement, blood flow and other bodily functions. There are three types of muscle: skeletal muscle which is connected to bone and helps with voluntary movement, smooth muscle which is found inside organs and helps to move substances through organs, and cardiac muscle which is found in the heart and helps pump blood.

The reproductive system allows humans to reproduce. The male reproductive system includes the penis and the testes, which produce sperm. The female reproductive system consists of the vagina, the uterus and the ovaries, which produce eggs. During conception, a sperm cell fuses with an egg cell, which creates a fertilized egg that implants and grows in the uterus.
Our bodies are supported by the skeletal system, which consists of 206 bones that are connected by tendons, ligaments and cartilage. The skeleton not only helps us move, but it’s also involved in the production of blood cells and the storage of calcium. The teeth are also part of the skeletal system, but they aren’t considered bones.
The respiratory system allows us to take in vital oxygen and expel carbon dioxide in a process we call breathing. It consists mainly of the trachea, the diaphragm and the lungs.
The urinary system helps eliminate a waste product called urea from the body, which is produced when certain foods are broken down. The whole system includes two kidneys, two ureters, the bladder, two sphincter muscles and the urethra. Urine produced by the kidneys travels down t he ureters to the bladder, and exits the body through the urethra.
The skin, or integumentary system, is the body’s largest organ. It protects us from the outside world, and is our first defense against bacteria, viruses and other pathogens. Our skin also helps regulate body temperature and eliminate waste through perspiration. In addition to skin, the integumentary system includes hair and nails.

• Next week: Our Immune System – how our body is protecting us