Hierarchy of Structures in Animals. The Hierarchy of Structure Least complex Most complex Cells Tissues Organs Organ Systems Organism.

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