The Human Body
How is the human body organized? The levels of structural organization in the human body start with atoms, as all matter on Earth is made of these. There are several elements in particular that makeup living things:
These types of atoms make up most of the molecules in our body. Those molecules form the basic units of life, cells. Cells come together in different levels of organization in the human body to form an entire organism or living thing.
Levels of Organization in the Human Body
All matter in the universe is made of atoms, which are made of sub-atomic particles, like neutrons, protons, and electrons. Atoms are organized into molecules, and molecules are organized into cells, the basic units of life, which make up the organization of the human body. The levels of organization in anatomy and levels of organization examples include the following:
|Organ systems||Cardiovascular system|
The highest level of organization in the body is the organism level. This is the entirety of a living thing, such as the entire human body.
Organ System Level of Organization
An organ system is a collection of organs in the body that works together to perform a function. There are eleven examples of organ systems in the human body including:
- Cardiovascular system
- Nervous system
- Respiratory system
- Endocrine system
- Reproductive system
- Digestive system
- Immune system
- Integumentary system
- Muscular system
- Skeletal system
- Excretory system
For example, the job of the cardiovascular system is to pump blood around the body to distribute oxygen and nutrients and remove metabolic waste, such as carbon dioxide. The main organs of the cardiovascular system are the heart, blood, and blood vessels, like arteries, veins, and capillaries. The cardiovascular system is essential for distributing oxygen and nutrients to cells all over the body. Cells require oxygen to make energy. Thus, without the cardiovascular system, there won't be enough oxygen, and thus not enough energy for the cells and they will die. This is what happens during a heart attack. The heart stops working and the body doesn't get oxygen or nutrients and can die.
Another example of an organ system is the nervous system. The nervous system is responsible for electrochemical communication in the body. The main organs in the nervous system are the brain, spinal cord, and nerves. The nervous system is important for the organism to be able to detect changes in the surroundings and within the body itself. It also is responsible for our thoughts, feelings, and actions. For example, when we feel something too hot or too cold, the nervous system registers this and processes the information in the brain. The brain then sends signals that allow the body to shiver or sweat and take conscious action to change our temperature.
Organ Level of Organization
An organ is a biological unit made up of tissue and independently performs a specific function for the body. Some examples of organs in the body include:
For example, the heart is the main organ of the cardiovascular system. It is made mostly of muscle tissue and acts as a pump. Sending blood to the lungs to get oxygenated and out to the body to deliver that oxygen and important nutrients. The brain is the main organ of the nervous system. It is made of neurons and other connective tissue and is the main processing center for information in the body.
Tissue Level of Organization
Tissue is a biological unit made up of several cells acting in conjunction with each other. What are the four levels of organization in an organism? There are four main types of tissue level of organization in the body:
Epithelial tissue forms the covering of the body and organs. Its main function is to offer protection and separation from the environment. Connective tissue binds, connects, and cushions the body. Muscle tissue is for contraction and movement. Nervous tissue is for communication. The table below details the different functions of the four tissues in the body and examples.
|Epithelial||Cover and protect||Skin|
|Connective||Connect and cushion||Fat|
|Muscle||Movement and contraction||Cardiac muscle|
Cellular Level of Organization
Cells are the basic structural units of living matter. Most cells in the human body contain one or more nuclei, which hold the genetic instructions for the cell's structure and function. There are several main functions of cells in the body including absorbing nutrients and converting food into energy through the process of cellular respiration. There are over 200 cell types in the human body. Some examples of cells at the cellular level of organization include:
Cells are considered the basic units of life because they are self-sustaining. All cells are capable of making more of themselves through cell division. The information needed for cellular structure and function is coded for in the DNA. In eukaryotic cells, like human cells, DNA is enclosed in an organelle called the nucleus. Cells also have other organelles as well, such as ribosomes for making protein, mitochondria for making energy, the Golgi apparatus for sorting proteins and more. Different cells have different compositions of organelles depending on their job inside the body. For example, cardiomyocytes or heart cells, have lot of mitochondria because they need to make energy to contract and keep the heart beating. Hepatocytes, or liver cells, have lots of smooth endoplasmic reticulum to help the liver detoxify the body.
Sub-Atomic, Atomic, and Molecular Level
Beneath cells are molecules, which are made of atoms, which are made of sub-atomic particles. Cells are made of many types of molecules, but there are four macromolecules that make up most of the cellular structure:
- Nucleic acids
These molecules are made of different types of atoms. grouped together by chemical reactions. For example, hydrogen and water can be combined to make water.
Atoms are composed of subatomic particles. Each atom has a nucleus made of positively charged protons and neutral sub-atomic particles called neutrons. Electrons are smaller, negatively charged subatomic particles that orbit the nucleus.
The levels of organization from the most complex to least complex in the human body are summarized in the table below:
|Atoms||Made of subatomic particles||Carbon|
|Molecules||Made of atoms||Water|
|Cells||The basic units of life, made of molecules||Cardiomyocyte|
|Tissues||Units of one type of cell that do a job. There are four tissue types in the body.||Epithelial, Connective, Muscular, Nervous|
|Organs||Units made of multiple tissues that perform an independent function||Heart|
|Organ system||Groups of organs that work together to perform a function||Cardiovascular system|
|Organism||A single living thing made of multiple organ systems, organs, tissues and cells||Human|
Cells are the basic units of life and make up all living things. The human body has many types of cells that are arranged into four distinct tissues. These tissues form organs, which perform a specific job in the body. Organs work together in organ systems, which form an organism.
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What are the six levels of organization in the body from simplest to most complex?
The six levels of organization in the body from simplest to most complex are:
- Organ system
What are the 12 levels of biological organization?
The twelve levels of biological organization are:
- Organ systems
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