Video: Cardinal body planes and axes

Have you ever used a compass or GPS to figure out where you’re going? North, south, east, west—these are the cardinal directions. They’re the big, essential ones that help us get oriented in the world.

Well, just like we need directions to navigate the planet, we also need a set of directions to navigate the human body. Something like the body’s personal GPS system—fundamental reference points that help us describe where things are and how they move. In other words, the cardinal axes and planes!

Before we move on to talk in more detail about the axes and planes, we have to ask the question: what exactly do we mean by "cardinal" in anatomy?

Like a cardinal (no, not that one!), the word “cardinal” means something of primary importance—fundamental, or essential—the way a cardinal is important to the head of the Roman Catholic church. So, when we say cardinal planes or cardinal axes, we’re talking about the main reference lines and planes that help us understand human anatomy, especially when describing positions or movements.

Before we can describe where anything is, we need a standard map—what we call the anatomical position. No matter if someone’s lying down, standing on their head, or mid-cartwheel, anatomists use this standard position as the reference point.

In the anatomical position, the person is standing upright, looking forward, with their arms relaxed at the sides, palms facing forward and thumbs pointing away from the body. At the same time, the feet are placed slightly apart and parallel, with the toes pointing forward.

With this position as our baseline, let’s now talk about planes and axes, starting with the cardinal planes!

Planes are like invisible sheets of glass slicing through the body in specific directions. These are imaginary flat surfaces that help us divide the body into different sections.

There are three main cardinal planes you need to know:

The first plane is the coronal plane. This is a vertical plane that divides the body into front, or anterior, and back, or posterior parts. It runs parallel to the coronal suture of the skull—hence the name.

When it cuts exactly in the middle, it’s called the mid-coronal plane, splitting the body into equal front and back halves.

The second plane to know is the sagittal plane. This is another vertical plane, but this one divides the body into unequal left and right parts.

This plane is named because it runs parallel to the sagittal sutureof the skull.

If the plane cuts exactly through the middle, it’s known as the median, or mid-sagittal plane, splitting the body into equal left and right halves.

The final cardinal plane is the transverse plane. This is a horizontal plane that divides the body into upper, or superior, and lower, or inferior, parts. It’s like slicing the body into top and bottom sections—think of it as a cross-section, which you’ll often see in medical imaging like CT or MRI scans.

Next up are the cardinal axes—these are straight imaginary lines that run through the body in different directions. We use them to describe how joints move, like when you flex your elbow or rotate your neck.

The first axis is the horizontal axis, or the x-axis. This axis runs left to right, or along the medial to lateral line, from one side of the body to the other. It lies at the intersection of the coronal and transverse planes. Movements like flexion and extension, such as bending and straightening the elbow, happen along this axis.

The next axis is the vertical axis, or the Y-Axis. This is a line that runs from superior to inferior, top to bottom, running straight down the body. It sits at the intersection of the coronal and sagittal planes. Movements like rotation happen around this axis—think of shaking your head when saying "no!."

The final axis is the sagittal axis, or the Z-Axis. This axis runs from front to back, passing through the body in an anteroposterior direction. It lies at the intersection of the sagittal and transverse planes. Movements like abduction and adduction, such as lifting your arm away from the body or bringing it back in, happen around this axis. For example, the thumb’s carpometacarpal joint moves this way.

That’s it for our tour of the cardinal planes and axes! Now you have a solid map of the human body to help chart your learning.

And if you need more guides on the human body, don’t forget to check out our study units and quizzes at Kenhub!