Biology - Tissues, Organs and Organ Systems

• Large Multicellular Organsims are made up of Organ Systems
• Similar Cells are Organised into Tissues
• Tissues are Organsied into Organs
• Organs are Organised into Organ Systems

Large Multicellular Organisms are made up of Organ Systems

• Specialised cells carry out a particular function
• The process oby which cells become specialised for a particular job is DIFFERENTIATION
• Differentiation occurs during the development of an organism
• These specialised cells form tissues, which form organs, which form organ systems
• Large organisms have different systems inside them for transporting and exchanging materials

Similar Cells are Organised into Tissues

A tissue is a group of similar cells that work together to carry out a function. It can include more than 1 type of cell. In mammals examples of tissues are...

• Muscular Tissue - Contracts(Shortens) to move whatever it's attached to
• Glandular Tissue - Makes and Secretes chemicals like hormones and enzymes
• Epithelial Tissue - Covers some parts of the body like the inside of the gut

Tissues are Organised into Organs

An organ is a group of different tissues that work together to preform a function. Example the stomach is an organ made of the following tissues...

• Muscular Tissue - Moves stomach wall to churn food
• Glandular Tissue - makes digestive juices to digest food
• Epithelial Tissue - covers the outside and inside of stomach

Organs are Organised into Organ Systems

An organ system is a group of organs working together to carry out a function. Example the digestive system breaks down food and is made up of the organs...

• Stomach and small intestine -  digest the food
• Liver - produces bile
• Pancreas and salivary gland - produce digestive juices
• Small Intestine - absorbs soluble foods
• Large Intestine - absorbs water form undigested food leaving faeces

The digestive system exchanges materials with the environment by taking in nutrients and releasing substances such as bile.