What are tissues?
Millions of cells that do the same job are grouped together into tissues, so they can be put to work by the body. There are many different types of tissue, for example muscle tissue. Muscle is built up from millions of thread-like muscle cells.
What do cells need to survive?
Cells need food, oxygen and a watery environment in order to survive. Food and water are supplied by the blood and other body fluids, which also carry away wastes. Blood also contains all of the food substances and chemicals needed by the cell.
What are organs?
Organs are made up from different types of tissue that are grouped together to carry out a particular body function.
The heart, for example, is a collection of muscle tissue, connective tissue and nervous tissue. These tissues work together to pump blood around the body.
Different types of organs are in turning grouped together to form systems, such as the circulatory system. It includes the heart and all the body’s blood vessels. The digestive system includes the mouth, gullet, stomach and intestines, while the nervous system includes the brain, spinal cord and nerves extending throughout the body. The human body also has a skeletal system, a muscular system, an endocrine system (glands), a respiratory system, a urinary system and a reproductive system.
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