What are the organ systems?

Plants and animals consist of cells that work together. A cell is the basic building block of all living organisms. They are very small and are only seen using a microscope. Some organisms are unicellular – this means they have only one cell, for example, bacteria, protists, and yeast. Some organisms are multicellular – this means that they have many cells, for example animals and plants.

Level of organisation: 

  • Similar cells form a tissue. 
  • Similar tissues form an organ.
  • Different organs interact to form systems. 
  • Different systems interact to form an organism.  

There are 12 important organ systems in the human body. Each organ system plays an important role in the body’s function.

The 12 important organ systems are:

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

Integumentary system 

The integumentary system forms the outermost layer of an organism. It consists of the skin, nails, hair, and some glands. This system forms the physical barrier between the external and internal environment. It helps to protect and maintain what comes in and what goes out of the body. The integumentary system protects the body from harmful microbes and materials. It also maintains body temperature and body fluids, alongside assisting in eliminating waste products.

Skeletal system

The skeletal system consists of the bones and joints that help to support the body and protects the organs inside the body. The bones making up the skeletal system also produce blood cells in the bone marrow.

Muscular system 

The muscular system consists of muscles that help the body to move around – they do this by contracting and relaxing. There are three types of muscles in the body: skeletal muscles, cardiac muscles, and smooth muscles. This system is also referred to as the musculoskeletal system. Some muscles are attached to bones, and they help to hold the bones in place. Muscles also help to move blood around the body.

Nervous system

The nervous system consists of the brain, spinal cord, and nerves. These components make up the central nervous system and the peripheral nervous system. This system works by sending electrical impulses around the body enabling them to move.

Circulatory system

The circulatory system is commonly referred to as the cardiovascular system. This system consists of the heart and blood vessels. There are three types of blood vessels in the body: arteries, veins, and capillaries. The heart pumps blood around the body via blood vessels and removes any waste products.

Respiratory system

The respiratory system works to provide oxygen into the bloodstream from the air we inhale and releases carbon dioxide when we exhale. This occurs automatically without you even thinking about it as it’s part of the autonomic nervous system. This system is made up of the nose, pharynx, larynx, trachea, and lungs.

Digestive system

The digestive system works to process the food that is eaten into substances so that the body can use it as energy. In order to do this, the food that is eaten passes through the digestive system. There are many body parts and organs that have different roles, including the mouth, tongue, teeth, oesophagus, stomach, pancreas, liver, gallbladder, small intestine, and large intestine. Once the food is digested and nutrients are absorbed into the body, the solid waste products pass through the large intestine and are removed from the body via the process of excretion. This occurs in the excretory system.

Excretory system

The excretory system carries out the process of excretion. After food is digested and nutrients are absorbed into the body, solid waste products pass through the large intestine and are removed from the body via the process of excretion.

Urinary system 

The urinary system is also known as the renal system. This system consists of the kidneys, ureters, bladder, and urethra. The kidneys receive unfiltered blood from the renal artery. The kidneys then work to filter the blood by identifying useful and waste products in the blood. The waste products and excess fluid in the blood are removed and released as urine. The urine produced travels down the ureters from each kidney into the bladder. The bladder stretches to store the urine and then contracts when releasing urine via the urethra.

Reproductive system 

The reproductive system consists of the tissues, glands, and organs involved in reproduction. Reproduction is the process in which organisms make more organisms using the male and female reproductive systems. The reproductive system differs in males and females. It is where the process of fertilisation occurs. The process of human reproduction consists of the fusion of gametes (sex cells) – the male gamete is the sperm, and the female gamete is the egg. The sperm fertilizes an egg – this fertilized egg is called a zygote. Following this, the zygote becomes an embryo and then develops into a fetus.

Endocrine system

The endocrine system consists of glands that help to regulate the processes in the body. The glands in the body are able to detect and distribute hormones around the body.

Immune system

The immune system is also known as the lymphatic system. This system works to protect the body against foreign bodies. It helps to detect foreign cells and sends white blood cells to fight infections. The immune system is a very important part of the human body.

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