Hierarchy of Structures in Animals
The Hierarchy of Structure
Least complex
Most complex
Cells
Tissues
Organs
Organ Systems
Organism
•
• Organ systems : groups of organs that work together to perform a single function in the organism
• eg. Digestive system
A complex organism such as an animal is made up of various organ systems
Most Organs are composed of several different types of tissue
stomach
The Four Types of Animal Tissue
1. Epithelial
2. Connective
3. Muscle
4. Nerve
• Remember: tissue is made up of multiple cells
Epithelial Tissue-structure
• Thin sheets of tightly packed cells
• Covers surfaces and lines internal organs
Epithelial Tissue-function
• Protects from dehydration
• Creates low-friction surfaces
• Ex: skin, lining of digestive system
Connective Tissue-structure
• Various cells and fibres held together by a matrix of solids and liquids
Connective Tissue-function
• Provides support and insulation
• Ex. Bone, tendons, blood, connection between skin and muscle
Muscle Tissue-structure
• Bundles of long parallel cells
• Contain specialized proteins that allows fibres to contract or shorten
Muscle Tissue-function
• Allows movement of tissue and organs
• Ex. Skeletal muscle (biceps, quads)
• Cardiac muscle
• Digestive muscles
Nerve Tissue-structure
• Long, thin cells
• Have fine branches at ends to conduct electrical impulses
Nerve Tissue-function
• Used to sense environment and communicate with the rest of the body
• Ex. Brain, spinal cord, optical nerves
Stem Cells and Cellular Differentiation
Multicellular organisms develop from a single cell, which is called a zygote.
The zygote divides continuously
to form an embryo
Cellular differentiation: occurs when the cells of the embryo divide and begin to differ in
shape, size, contents and function.
What do we call plants’ stem cells?
• Meristems or meristematic cells
• Located at root tips, terminal and lateral buds of plants
Stem CellsA Stem cell is a cell that can differentiate into
many different types of specialized cells.
There are 2 types of stem cells in animals:
1) Embryonic Stem Cells:
• taken from the embryonic stage
• can differentiate into any type of cell.
2) Tissue or Adult Stem Cells:
• found in certain specialized tissue
• Can differentiate into ONLY certain types of cells.
Ex. Bone marrow tissue stem cells can differentiate into white or red blood cells, platelets and many other types of cells.
Stem Cell Applications- To study development
- Aids our understanding of how normal development and abnormal development occurs.
- May lead to therapies for diseases and birth defects
eg Cleft palate
Stem Cell Application- To replace damaged
cells and treat diseases- Treat burns - To replace blood in leukemia
patients- Possible future application:
replaced damaged tissues for Parkinson's disease, stroke, heart disease and diabetes.
Stem Cell Application
- To study disease- Stem cells, engineered to contain the diseased gene
are used to model & understand the disease process
Stem Cell Application
- Could provide a resource for testing new medical treatments- New medications could be
tested for safety on specialized cells generated in large numbers from stem cell lines – reducing the need for animal testing.
Stem cell research is controversial and involves moral and ethical dilemmas for many
people
What are the ethical issues around stem cell
usage?
Watch: The role of stem cells(12 mins)
• Go to http://www.learn360.com/
• Username: calctor
• Password: calctor
• Put in keyword: “Clone the role of stem cells”
• Click and watch; make sure speakers are on
The End
