Grade 3 Science(NSO) : Human body part 2

We have already covered Skeletal, immune, cardiovascular, muscular and integumentary system in part 1.

Grade 3 Science (NSO) : Human body part 1

Lymphatic system :

It is responsible for the removal of interstitial fluid from tissues. It absorbs and transports fatty acids and fats as chyle from the digestive system. It transports white blood cells to and from the lymph nodes into the bones.

-picks up fluids leaked from the capillaries
-supports immune systems: houses white blood cells

Lymphatic system includes:
-bone marrow: makes lymphocytes
-thymus: matures T cells
spleen: destroys old blood cells
lymph nodes: filter lymphs
lymphatic ducts: transport lymphs through out the body

 Excretory system

The system through which our body waste is removed regulary is called the excretory system.

  • It consists of a pair of kidneys, skin and a pair of lungs
  • The kidneys remove urine. The kidneys make urine by filtering wastes and extra water from blood. Urine travels from the kidneys through two thin tubes called ureters and fills the bladder. When the bladder is full, a person urinates through the urethra to eliminate the waste.
  • The lungs exhale carbon diaoxide through the nose.
  • Skin removes sweat. Sweat glands in the dermis can remove salts and some excess water.

Digestive system

The human digestive system is a series of organs  (the tongue, salivary glands, pancreas, liver, and gallbladder) that converts food into essential nutrients that are absorbed into the body and eliminates unused waste material.

  • Digestion starts in our mouth as soon as we begin to chew our food.
  • The food goes into the stomach through the food pipe.
  • In the stomach, the food mixes with digestive juices and is partly digested there.
  • From stomach, food goes into the small intestine where food is completely digested to simpler forms. It is absorbed and then passed into blood.
  • The undigested food goes to the large intestine.
  • It stays there for some time and is released out of the body through anus as faeces.



Respiratory system

  • The human respiratory system is a series of organs responsible for taking in oxygen and expelling carbon dioxide. The primary organs of the respiratory system are lungs, which carry out this exchange of gases as we breathe.
  • Hidden under your skin and beneath your rib cage is a very complex organ that causes the constant rise and fall of your chest: your lungs. Your lungs are one of the largest organs in your body. The outside of your lungs look pink and rubbery. The inside of your lungs look a lot like sponges.
  • A breath of air travels in through your nose or mouth. Then it makes its way down your trachea or windpipe. Finally it arrives in your lungs. The air then fills up millions of air sacs. Six hundred million, to be exact! These sacs, or alveoli, let the oxygen from the air pass into your bloodstream. The newly oxygenated blood travels all the way to your heart. Your heart then pumps that blood all through your body!
  • The air that we breathe is often filled with many things. Dust, pollen, dirt, and many other things can be floating in the air. Cilia, tiny hairs in the nose and other parts of the respiratory system, help to clean the air that you breathe before it reaches your lungs. The cilia keep debris out of the lungs by pushing it in another direction. Some are pushed up into the throat or nose where they can be blown out with a cough or a sneeze
  • Oxygen burns up the food that we eat and releases energy and carbon dioxide. carbon dioxide is carried by the blood to the lungs and is breathed out through the nose. In this way breathing purifies the blood.
There are 3 major parts of the respiratory system: the airway, the lungs, and the muscles of respiration. The airway, which includes the nosemouth,pharynxlarynxtracheabronchi, and bronchioles, carries air between the lungs and the body’s exterior.