Body Systems
A Brief Overview
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Levels of Organization in
Cell
Living Things
– Red blood cell
– Epithelial cell
– Neuron
Tissue
– Epithelial tissue
– Connective tissue
– Nervous tissue
– Muscle tissue
Organ
– Skin
– Brain
– Heart
Organ System
– Nervous
– Integumentary
– Lymphatic
Organism
Nervous System
Major Functions
• Controls and
coordinates the
functions throughout
the body by
transmitting electrical
signals or impulses via
neurons
• Responds to internal
and external stimuli in
order to maintain
homeostasis
Examples of Nervous
Systems in Animals
• Nerve Net (individual nerve
cells) - Cnidarians
• Ganglia (more centralized
nerve cells) – worms,
mollusks & arthropods
• Neurons
• Cephalization
(concentration of nerves at
the head or anterior end of
organism leading to the
development of a true
brain)
Skeletal System
Major Functions
• Supports the body
• Protects the
internal organs
• Serves as muscle
attachment for
movement
Examples of Skeletal
Systems in Animals
• Hydrostatic Skeleton: fluid
filled body cavity that
supports the muscles
found in some worms &
cnidarians
• Exoskeleton: external
skeleton made of chitin
found in arthropods
• Endoskeleton: internal
skeleton made of calcium
found in echinoderms &
vertebrates
Muscular System
Major Functions
• Works with the
skeletal system to
provide voluntary
movement
• Provides
involuntary
movement such as
pumping and
circulating blood
& moving food
through the
digestive system
Integumentary System
Major Functions
• Serves as a barrier
against infection
and injury
• Regulates body
temperature in
order to maintain
homeostasis
Examples of Integumentary
Systems in Animals
• Skin
• Hair & Fur
• Nails
• sweat & oil
glands
• Feathers
• Scales
Circulatory System
Major Functions
• Transports oxygen,
nutrients & hormones
to all the cells
throughout the body
• Fights infection
• Removes metabolic
wastes
• Regulates body
temperature in order
to maintain
homeostasis
Examples of Circulatory
Systems in Animals
• Open Circulatory System:
Blood is not completely
contained in vessels
(blood found in sinuses or
open cavities) –Most
Mollusks & Arthropods
• Closed Circulatory
System: Blood is
contained in vessels some worms & mollusks
and vertebrates
• More complex systems &
hearts develop as
organisms move up the
evolutionary ladder
Respiratory System
Major Functions
• Provides oxygen
for cellular
respiration
• Removes excess
carbon dioxide
from the body
Examples of Respiratory
Systems in Animals
• Must have large
surfaces for
diffusion
• Must be moist
• Skin – worms &
mollusks
• Gills – aquatic
animals
• Lungs – terrestrial
animals
Digestive System
Major Functions
• Breaks down large
molecules of food
into simpler, smaller
molecules to be used
by the cells of the
body
– glucose for cellular
respiration
• Absorbs nutrients
• Eliminates wastes
• Food moves through
the digestive system
thru a muscle action
called peristalsis
Examples of Digestive
Systems in Animals
Intracellular vs. Extracellular Digestion:
Food digested within cells as opposed to food digested outside of the cells in a
digestive cavity or a digestive tract (more complex animals)
Excretory System
Major Functions
• Eliminates
metabolic wastes
from the body in
order to maintain
homeostasis
• Regulates water
also to maintain
homeostasis
Examples of Excretory
Systems in Animals
• Flame cells (eliminates
excess water from
flatworms)
• Skin & Gills (aquatic
organisms)
• Nephridia (annelids &
mollusks
• Malpighian Tubules
(arthropods such as insects
& arachnids)
• Kidneys (vertebrates)
Reproductive System:
General
• Most invertebrates reproduce SEXUALLY during at least
part of their life cycle.
• Depending on environmental conditions, many
invertebrates may also reproduce ASEXUALLY
REMEMBER…
THERE ARE ADVANTAGES & DISADVANTAGES TO BOTH
External vs. Internal Fertilization
Eggs are fertilized OUTSIDE of the FEMALE’S BODY as opposed
to INSIDE the FEMALE’S BODY
Reproductive System
Major Functions - Female
• Produces
reproductive cells
called eggs or ova
in the ovaries
• Nurtures and
protects
developing
embryo
Reproductive System
Major Functions - Male
• Produces
reproductive cells
called sperm in
the testes