Physiology is the study of normal function within living creatures. It is a sub-section of biology, covering a range of topics that include organs, anatomy, cells, biological compounds, and how they all interact to make life possible.

From ancient theories to molecular laboratory techniques, physiological research has shaped our understanding of the components of our body, how they communicate, and how they keep us alive.

Merrian-Webster defines physiology as:

[A] branch of biology that deals with the functions and activities of life or of living matter (such as organs, tissues, or cells) and of the physical and chemical phenomena involved.

Here are some key points about physiology. More detail and supporting information is in the main article.

The study of physiology is, in a sense, the study of life. It asks questions about the internal workings of organisms and how they interact with the world around them.

Physiology tests how organs and systems within the body work, how they communicate, and how they combine their efforts to make conditions favorable for survival.

Human physiology, specifically, is often separated into subcategories; these topics cover a vast amount of information.

Researchers in the field can focus on anything from microscopic organelles in cell physiology up to more wide-ranging topics, such as ecophysiology, which looks at whole organisms and how they adapt to environments.

The most relevant arm of physiological research to Medical News Today is applied human physiology; this field investigates biological systems at the level of the cell, organ, system, anatomy, organism, and everywhere in between.

In this article, we will visit some of the subsections of physiology, developing a brief overview of this huge subject. Firstly, we will run through a short history of physiology.

The study of physiology traces its roots back to ancient India and Egypt.

As a medical discipline, it goes back at least as far as the time of Hippocrates, the famous father of medicine around 420 BC.

Hippocrates coined the theory of the four humors, stating that the body contains four distinct bodily fluids: black bile, phlegm, blood, and yellow bile. Any disturbance in their ratios, as the theory goes, causes ill health.

Claudius Galenus (c.130-200 AD), also known as Galen, modified Hippocrates theory and was the first to use experimentation to derive information about the systems of the body. He is widely referred to as the founder of experimental physiology.

It was Jean Fernel (1497-1558), a French physician, who first introduced the term physiology, from Ancient Greek, meaning study of nature, origins.

Fernel was also the first to describe the spinal canal (the space in the spine where the spinal cord passes through). He has a crater on the moon named after him for his efforts it is called Fernelius.

Another leap forward in physiological knowledge came with the publication of William Harveys book titled An Anatomical Dissertation Upon the Movement of the Heart and Blood in Animals in 1628.

Harvey was the first to describe systemic circulation and bloods journey through the brain and body, propelled by the heart.

Perhaps surprisingly, much medical practice was based on the four humors until well into the 1800s (bloodletting, for instance). In 1838, a shift in thought occurred when the cell theory of Matthias Schleiden and Theodor Schwann arrived on the scene, theorizing that the body was made up of tiny individual cells.

From here on in, the field of physiology opened up, and progress was made quickly:

The major systems covered in the study of human physiology are as follows:

There are a great number of disciplines that use the word physiology in their title. Below are some examples:

The topics mentioned above are just a small selection of the available physiologies. The field of physiology is as essential as it is vast.

Anatomy is closely related to physiology. Anatomy refers to the study of the structure of body parts, but physiology focuses on how these parts work and relate to each other.

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Introduction to physiology: History, biological systems, and ...