The basic hierarchy of cellular organisation is:

Cells - Tissue - Organ - Organ system.

All living organisms are composed of cells. Cells of the same type make up a tissue, different tissues make up an organ, and different organs working together make an organ system.

Cells

As animals are multi cellular, their body is composed of many different types of cells. Click here for an image of different cell types.

Tissue

Similar cells make up a single type of tissue. For example muscle cells make up muscle tissue, nerve cells make up nervous tissue and adipose cells make up adipose tissue.

Organs

Various tissues make up a single organ. The stomach can be made up of smooth muscle tissue, epithelial tissue and connective tissue. These tissues work together to complete the function of the organ. A few examples of organs are:

• Heart
• Heart dissection
• Stomach
• Eyes
• Brain
• Lungs

Organ Systems

Different organs working together create an organ systems. These organs work together with a common goal. Some examples of organ system are:

• Digestive system
• Cardiovascular System
• Respiratory System
• Reproductive System
• Nervous system
• Excretory System
• Integumentary system
• Skeletal system
• Endocrine System
• Urinary System
• Lymphatic System

Click here for a assessment on organ systems

Click here for a list of dissections