Tissues and OrgansWhat are they and why does it matter?

Introduction

• Animals and plants are made up of cells but a big lump of cells isn’t going to be able to organise itself to do all of the things a living creature needs to do

• Cells are therefore arranged into tissues, organs and ultimately organ systems to make sure these things can happen

Outline

• What is a tissue?• What is an organ?• What is an organ system?• Why does it matter?

What is a tissue?

• A collection of cells gathered for a particular function, e.g.– Heart muscle– Fat cells– Nerve cells in the surface

of the brain

What is a tissue?

• Often made up of only a few cell types (even just one) that are grouped together in order to perform this one function

What is a tissue?

• Rather than taking oxygen and nutrients to individual cells, the blood transports these things to groups of cells around the body

• This is why you will hear that blood takes them to the tissues. This is referring to all the groups of cells around the body

What is an organ?

• An organ is a group of tissues gathered together for a particular task, e.g.– The heart is made up of

muscle, valves, coverings and chords. Each bit has a different function, and they work together to perform the task of pumping blood around the body

What is an organ?

• An organ is a group of tissues gathered together for a particular task, e.g.– The brain is made up of

nerve cells in the brain, special immune cells, and other helper cells so that the brain can control the activity of nerves in the body

What is an organ system?

• When lots of organs are linked together to perform one bigger purpose, it is called an organ system, e.g.– The heart and blood vessels (and lungs) are linked

together to form the circulatory system– The brain, the spinal cord, their coverings and the

fluid around them are linked together to form the central nervous system

So what?

• If everything were a big, disordered mess, the body wouldn’t achieve anything

• Instead, everything is specially designed to work together– Each cell performs a job– Cells together form a tissue to perform a function– Tissues together form an organ to perform a task– Organs together form an organ system to make

sure a particular purpose is fulfilled

So what?

• And all the organ systems together form a body, so that you can live, breathe, create…

• But without all this clever organisation, you’d just be a messy lump of cells.

• So it’s rather useful, hey?

Any questions?Further reading:•Alberts B, Bray D, Hopkin K, Johnson A, Raff M, Roberts K, Walter P (2009) Essential Cell Biology. 3rd Ed. New York: Garland Publishing

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