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CELL ORGANISATION - an introduction
specialised cells ==> specific
tissues ==> organs ==> organ systems ==> complete multicellular
animal or plant organism
Introduction to cell organisation of plants and animals explaining from
cells to tissues to organs to organ systems to whole organism
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Doc Brown's school biology revision notes
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1. Introduction
and reminders about cells
Many organisms consist of a huge number
of cells. (cell
structure)
Most cells can be thought of as a unit of life
surrounded and enclosed by an outer membrane of some sort.
But, how are they organised to form
e.g. a fully functioning animal?
Cells are the building blocks of
multicellular organisms.
In the process called
differentiation, cells become specialised to carry out a particular
function e.g.
The derived specialised cells include:
Bone cells in skeletal systems.
Blood cells in the circulatory transport system.
Nerve cells in the nervous system.
Sperm cells and egg cells in the reproductive systems.
Differentiation happens during the growth and
development of a multicellular organism.
Specialised cells form tissues, which
can connect to form organs and these connect together to form organ
systems.
Large multicellular organisms like animals
have different organ systems for exchanging and transporting substances.
2. Tissues
A tissue is a group of similar specialised cells that work
together to carry out a particular function.
Obviously the cells must be connected in someway
AND there may be different types of cell cooperating with each other.
Examples of tissues
(a) Epithelial tissue
Layers of epithelial cells make up
epithelial tissue which covers a lot of the body, including the
inside of the gut, including the stomach.
(b) Muscle tissue
muscle tissue
Muscular tissue must have the ability to
contract (and relax) to move whatever the tissue is attached to
e.g. bones.
(c) Glandular tissue
Glandular tissues are production sites for
enzymes and hormones - important secretions for the efficient functioning
of organs.
3. Organs and
glands
An organ is a group of different specialised
tissues that work together to perform specific functions.
Examples of organs
The stomach - part of the digestion
system
The stomach is an organ that uses all of
the three tissues mentioned above.
The inside and outside lining of the stomach is made from
epithelial tissue - it holds the stomach together and contains
food starting to be digested.
The wall of the stomach has attached muscle tissue
to enable it to churn up food prior to digestion.
Glandular tissue makes digestive
juices to breakdown the food at the start of the digestion
process.
(Other examples of glandular tissue
structures include the pituitary gland, the adrenal gland
and the thyroid gland.)
 4. Organ
systems
An organ system is a group of organs that work
together to perform overall a more complex function - each organ
performs its own function as part of the overall process
Examples
of organ systems
The digestive system of mammals is an excellent
example of an organ system - this organ system breaks down food and
absorbs the molecules and ions.
It consists of a whole series of organs and glands
working together.
(1) The pancreas and salivary glands produce
digestive juices containing enzymes to break down food.
(2) The stomach and small intestine digest the
food - nutrients pass from the small intestine to the blood stream -
absorption of soluble food molecules.
(3) The liver produces bile that helps digestion
in the small intestine.
(4) The large intestine absorbs water from
undigested food to leave the waste as faeces.
See
Enzymes - including structure and function of
digestion system
Other organ systems in the human body
(with links to detailed notes)
The human body contains 11 important organ
systems, including:
circulatory transport system - blood
vessels and heart (cardiovascular system),
respiratory system - from mouth to lungs
digestive
(described above) - oesophagus, stomach, small intestine, large
intestine and anus
excretory system - kidney, urinary
bladder, ureter, urethra
nervous - central nervous system and
brain (and
specific brain notes)
endocrine systems - complex system of
glands and small organs
skeletal and muscle systems
reproductive systems
A summary of human sense organs
All these systems work closely together to
maintain a fully functioning healthy human body.
The failure of any of the organ systems can
lead to a serious, and potential fatal, medical condition.
5. More summary examples as part of whole organism
e.g. part of an animal organism
epithelial cell ==> epithelial tissue ==> stomach
organ lining ==> upper
part of digestive organ system ==> full digestion system from mouth to
anus
e.g part of a plant organism
palisade cell => palisade tissue => plus other tissues makes
up a leaf => plus more leaves and other organs gives a plant
BUT remember, relatively large multicellular systems consist of
multiple organ systems.
Some learning objectives for this page
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Know that the cells of multicellular organisms may differentiate and become adapted for
specific functions - specialised cells.
-
Know that tissues are
aggregations of similar cells and organs are aggregations of tissues performing
specific physiological functions eg heart and liver.
-
Know that organs are organised into organ systems, which work together to form organisms.
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Know that large multicellular organisms develop systems
for exchanging materials.
-
Know that during the development
of a multicellular organism, cells differentiate so that they can perform
different functions.
-
The specialised cells form
tissues, one or more types of tissue are structured to form organs and two
or more organs can work together in an organ system.
-
Bigger multicellular systems
e.g. animals like mammals have several different organ systems for absorbing
(e.g. gut), transporting (e.g. blood system) and exchanging materials (e.g.
lungs).
-
You should develop an
understanding of size and scale in relation to cells, tissues, organs and
organ systems.
-
Know that a tissue is a group of
specialised cells with similar structure and carry out a particular function.
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General HUMAN BIOLOGY revision notes
See also cell biology section
Introduction to the organisation of cells =>
tissues => organs => organ systems (e.g. in humans)
Homeostasis - introduction to how it functions (negative
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Homeostasis - osmoregulation, ADH, water control, urea and ion
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Homeostasis - thermoregulation, control of temperature
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The brain - what the different parts do and the dangers
if damaged gcse biology revision notes
An introduction
to the nervous system including the reflex arc
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Hormone Systems - menstrual cycle
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Respiration - aerobic and anaerobic in plants and animals. gcse
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Keeping Healthy - Diet and Exercise
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Keeping Healthy - How do our bodies defend themselves against infectious diseases?
gcse biology revision notes
See also
Enzymes - section on digestion and synthesis gcse
biology revision notes
Examples of surfaces for the exchange of substances in
animal organisms gcse biology revision notes
Optics - lens types (convex, concave, uses),
experiments, ray
diagrams, correction of eye defects (gcse physics)
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