Human Body Systems Study Guide
Cells:
A cell is the smallest structural and functional unit of an organism. It is the basic unit of
all living things.
All living organisms have a cell or cells.
Unicelluar (or single-celled)
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an organism that is only ONE cell. That one cell is able to carry out all its life
processes.
have all of their needs met within that one cell.
small
viewed through a microscope
a simple cell, not specialized
purpose is to survive, injury to the cell can cause death to the organism.
Examples:
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Bacteria
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Algae
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Amoeba
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Fungi (some)
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Yeast (some)
Multicellular
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organism is composed of many cells
each cell is specialized to perform a different function
complex
larger
an injury or death of some cells doesn't affect the organism as it can be replaced
by a new one
Examples:
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humans
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animals
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plants
Both Unicellular and Multicellular
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are living things
obtain energy from nutrients to maintain life and growth
need food for energy in order to grow
have a way to get rid of waste
can reproduce
Skeletal System:
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Supports our body and protects our organs
Gives us shape
Stores calcium
Our tendons connect bones and muscles
Makes red blood cells in the bone marrow
Muscular System:
 Two types: voluntary and involuntary
 They help us move our bones
 Our reflexes are controlled by voluntary muscles
 We have no control over involuntary muscles
 Helps us stand up straight (posture)
Circulatory System:
 Transports oxygen-rich blood throughout the body
 Transports cells where they need to go
 Transports gases throughout the body
 Transports waste material
 Delivers blood to our tissues
 Works with the digestive system to deliver nutrients from food throughout the
body
 Works with the digestive system to deliver oxygen to cells.
 The heart is a muscle and expands and contracts like other muscles
 Works with the muscular system to help deliver oxygen to the muscles
 Heart, blood, veins, arteries
Respiratory System
 Supplies oxygen to our cells
 Helps people breathe in oxygen and breathe out carbon dioxide
 Controls breathing and gas exchange in the body
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Works with circulatory system to get oxygen to cells
Controlled by involuntary muscle movement in the diaphragm
Nervous System:
 Major organs include the brain and spinal cord
 Carries signals to and from the brain
 The signals to our brain cause us to react
 Brain, spinal cord, nerves
Digestive System:
 Breaks down food to release nutrients needed to produce energy
 Important because it provides nutrients that cells need to produce energy
 Works with our circulatory system to deliver nutrients to cells
 Mouth, esophagus, stomach, small intestine, large intestine