Your body is made up of trillions of tiny building blocks called cells. Cells need raw materials such as oxygen and food to work with. Your body is organised in a way that makes sure that the cells are supplied with the raw materials they need.In our body there are different levels of organisations.Cells of the same type that carry out the same job in the body are grouped together to form tissues such as muscles and nerves.At the next level of organisation, tissues are grouped to form organs, such as the stomach or brain.An organ is a structure that contains at least two different types of tissue that work together to complete a task.Organs are arranged into organ systems that have two or more different organs that work together.
Respiratory system- takes in oxygenDigestive system- makes food available in a form the body can useCirculatory system- carries the food and oxygen to the cells where it is neededExcretory system- gets rid of wastesSkeletal system- supports the body and enables it to move
Digestion is the process of breaking down food into a usable form and making the nutrients available. Digestion takes place in the digestive system which consists of:-a digestive tract, the pathway that the food takes through a series of organs. The first part of the digestive tract is the mouth.-organs off to the side of the digestive tract that produce chemicals that assist with digestion.
Incisors- four pairs of teeth at the front and their job is to bite off pieces small enough to chew.Premolars and molars- when the food is pushed back, these teeth grind the food into smaller and smaller pieces as you chew.Canine teeth- helps animals hold onto the food as it is torn apart.-Biting and chewing is a form of mechanical digestion but chemical digestion also takes place in the mouth. As the food is being digested mechanically, it is mixed with saliva.
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Saliva is a watery liquid produced by your salivary glands. Saliva contains a chemical that starts to change any starch into glucose.Saliva also moistens the food, making it slippery, slimy and easy to swallow.-The tongue rolls the food into a ball called bolus, which is pushed down into the next part of the system, the oesophagus.-The oesophagus is a long muscular tube that has the mouth at one end and the stomach at the other end.
-The muscles of the oesophagus push the ball of food down the tube by contracting behind the ball. The muscles then relax. This process is called peristalsis. A flap of skin called the piglottis closes the end of the windpipe as you swallow.This makes sure that the food goes into your stomach and not into the lungs via the windpipe.If food does get into the windpipe, you start to choke. You then cough to force the food back up into the mouth so that it could be swallowed correctly.
Swallowing
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The stomach is shaped like a bag. Food is stored in the stomach for 1-6 hours.Once in the stomach, the food really begins to change.The muscular walls of the stomach contract and relax, churning up the food. This digests the food mechanically as well as mixing it with gastric juice.Gastric juices is produces by special cells in the stomach walls. Gastric juice contains:-hydrochloric acid- a strong acid that kills many of the bacteria that may have entered the body with the food.-mucus- creates a layer on the lining of the stomach and prevents the stomach from digesting itself.-digestive juices- contains chemicals that start the digestion of protein, the main nutrient found in meat.
