Transcript Section 5.5: Multicellular Life

Multicellular Life
Section 5.5
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Objectives
• SWBAT describe the specialization in
multicellular organisms.
• SWBAT identify different types of stem cells.
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Vocabulary
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Tissue
Organ
Organ system
Cell differentiation
Stem cell
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Starter
• Alone or with a partner, come up with as
many different types of cells in your body (or
the body of any multicellular organism) as you
can.
• How did all of those different cells come
about? What do those cells make up?
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Multicellularity
• As near as we can tell, multicellularity has
arisen naturally, throughout evolutionary
history, 20 different times (the last time being
200 million years ago).
• Interestingly, researchers in the United States
have created multicellularity twice in
laboratories.
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Multicellularity
• Multicellularity means that cells communicate
with one another and work together, in
groups, forming increasingly larger and more
complex structures (and more complex
organisms).
• In multicellular organisms we see: cells
forming tissues, tissues forming organs, and
organs forming organ systems.
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Tissues, Organs, Organ Systems
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Tissues, Organs, Organ Systems
• Within multicellular organisms, cells
communicate and work together in groups
that form increasingly larger, more complex
structures.
• Tissues – groups of cells that work together
to perform a similar function.
• Organs – groups of tissues that work together
to perform a specific function or related
functions.
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Tissues, Organs, Organ Systems
The tissues of a
leaf work
together to
form a plant’s
food-producing
organ.
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Tissues, Organs, Organ Systems
• Organ Systems – organs
that carry out similar
functions are grouped
into organ systems.
• Examples of a plant’s
organ systems would be
the plant’s root system
and its shoot system
that includes
reproductive structures
(seeds, fruit, flower,
etc.).
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Tissues, Organs, Organ Systems
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Cell Differentiation
• Cell differentiation – the process by which
unspecialized cells develop into their mature
forms and functions.
– This result is cell specialization.
– Each cell in your body has a full set of your DNA –
but it only utilizes specific genes that correspond
to its function (that of its tissue).
– DNA can be thought of as a cookbook – full of
many different “recipes” (the tissues and how
they are arranged are the result of the “recipes.”)
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Cell Differentiation (Stem Cells)
• Stem Cells – cells that have the ability to:
– divide and renew themselves for long periods of
time;
– remain undifferentiated in form;
– and develop into a variety of specialized cell
types.
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Stem Cells
• Stem cells can divide to form either two stem
cells or one stem cell and one specialized cell.
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Stem Cell Classification
• Classified based on their potential to develop
into differentiated cell types of different
tissues.
– Totipotent stem cells can grow into any other cell type
(example: the fertilized egg – also known as a zygote).
– Pluripotent stem cells can grow into any cell type but a
totipotent cell (example: a blastula – embryonic stem
cells)
– Multipotent stem cells can grow into only of a closely
related cell family (example: adult stem cells).
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Stem Cell Classification
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A blastula (a 5 day old embryo) – a hollow
mass of pluripotent cells)
The cells of this
embryo have not
started to differentiate
yet. Fertilization
clinics use blastulas in
in vitro fertilization.
The embryos can be
frozen at this stage
and “thawed out” for
later use. They are
also of great value to
science.
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Adult Stem Cells
• They are partially undifferentiated cells
located among specialized cells of many
organs and tissues.
– They are found all over the body.
– These stem cells are also found in children and
umbilical cord blood (which leads some to save
the umbilical cord after a child’s birth).
– Advantage – can be taken from a patient,
cultured, and then put back in the patient.
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Adult Stem Cells
– The risk of rejection by a patient’s immune system
is low because it comes from the patient (it should
be a perfect match).
– Disadvantage – The utilization of adult stem cells
has shown promise in the creation of new medical
therapies but few have been truly effective.
– Currently, blood stem cells are the only type of
adult stem cell commonly used – they are
employed in bone marrow transplants.
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Adult Stem Cells
– There has been a great deal of research into using
neural stem cells to treat Parkinson disease and
spinal cord injury, though treatments are only in
the trial phase.
– For more info., visit
http://stemcell.childrenshospital.org/about-stemcells/adult-somatic-stem-cells-101/how-do-adultstem-cells-get-turned-into-treatments/
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Pluripotent Stem Cells
• Pluripotent Stem Cells (embryonic stem cells)
are master cells potentially able to produce any
type of tissue the body needs.
– Embryonic stem cells are procured from unused
embryos created in vitro at fertility clinics (blastulas
are created and frozen – then implanted in the
uterus when needed).
– If reliable techniques can be developed, pluripotent
stem cells could someday allow doctors to create
customized, rejection-proof transplants to patch a
scarred heart, reawaken damaged nerves or reboot
an immune system incapable of fighting infection.
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Pluripotent Stem Cells
• To know more, this is a good place to start:
http://stemcell.childrenshospital.org/aboutstem-cells/pluripotent-stem-cells-101/
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