2.1 – Levels of Organization
Learning Objectives
- Connect medical language learning to the context of anatomy and physiology
- Introduce the basic architecture and levels of organization of the human body
- Evaluate the anatomical position, regional terms, directional terms, body planes, and body quadrants for anatomical positioning
- Describe body cavities and the functions of associated membranes
As you memorize the language components of medical terminology, it is important to support that learning within the context of anatomy and physiology. Proceeding through the body system chapters, you will learn word parts, whole medical terms, and common abbreviations. It is important to put into context where in the body the medical term is referencing, and then consider how it works within the body.
Anatomy focuses on structure and physiology focuses on function. Much of the study of physiology centers on the body’s tendency toward homeostasis.
Consider the structures of the body in terms of fundamental levels of organization that increase in complexity: subatomic particles, atoms, molecules, organelles, cells, tissues, organs, organ systems, organisms, and biosphere (Figure 2.1).
The Levels of Organization
All matter in the universe is composed of one or more unique pure substances called elements; familiar examples are hydrogen, oxygen, carbon, nitrogen, calcium, and iron.
- The smallest unit of any of these pure substances (elements) is an atom.
- Atoms are made up of subatomic particles such as the proton, electron, and neutron.
- Two or more atoms combine to form a molecule, such as the water molecules, proteins, and sugars found in living things.
- Molecules are the chemical building blocks of all body structures.
- A cell is the smallest independently functioning unit of a living organism.
- Even bacteria, which are extremely small, independently-living organisms, have a cellular structure. Each bacterium is a single cell. All living structures of human anatomy contain cells, and almost all functions of human physiology are performed in cells or are initiated by cells
- A human cell typically consists of flexible membranes that enclose cytoplasm, a water-based cellular fluid, together with a variety of tiny functioning units called organelles.
- A tissue is a group of many similar cells (though sometimes composed of a few related types) that work together to perform a specific function.
- An organ is an anatomically distinct structure of the body composed of two or more tissue types. Each organ performs one or more specific physiological functions.
An organ system is a group of organs that work together to perform major functions or meet the physiological needs of the body.
Did You Know?
- Organs are very collaborative and work with multiple body systems.
- For example, the heart (cardiovascular system) and lungs (respiratory system) work together to deliver oxygen throughout the body and remove carbon dioxide from the body.
Consider the bre