视频：Body regions

Learning a new language may initially seem like a daunting task. As beginners, we need to start by learning a few simple rules and basic words which form the foundations of a new language. Only when this base is strong and without cracks, we can slowly build our knowledge. Much like learning a language, learning anatomy also requires strong foundations. Advancing in anatomy is impossible without first conquering the anatomical alphabet. Today, we're learning about one of the building blocks in the language of anatomy. Welcome to this short and sweet tutorial on the regions of the body.

Before we start, let's take a quick look at what we'll cover in this video. We'll start with answering the question – what is a region of the body – and the relevance of a regional anatomy approach. Then we're going to look at the two main anatomical divisions of the body starting with the axial region followed by the appendicular region. As we go through, we will also take a look at the major divisions of each of these regions. And finally, we'll talk about the relevance of these topics in clinical practice.

But first things first, what is a region of the body or an anatomical region? It's an area of the body defined by landmarks provided by evident structures that are easily palpable or visible. To put it simply, it is a part of the body that, because of its shape and form, easily stands out as distinct from the other regions. These shapes are created by various structures found underneath the skin such as bones, muscles, or ligaments.

Just like a map, a region of the body refers to a certain distinct area. You can think of the body as a country and the regions of the body as districts. This approach to the study of the human body is called regional anatomy. You might be wondering why do we need to split up the body into anatomical regions. This is essentially a way of compartmentalizing the body so it is easier to learn the overwhelming amount of information available regarding its anatomy. These concepts are also fundamental to communicate effectively in day-to-day clinical practice.

In this tutorial, we will use images of both male and female individuals to demonstrate the regions in question. However, it is important to note that for the most part, the regions are exactly the same and are not sex-specific. Broadly speaking, the body can be divided into two primary areas – the axial and the appendicular regions. The axial region consists of the head, neck, and trunk, and the appendicular region is composed of the upper and lower limbs or extremities. Both the axial and appendicular regions encompass an anterior and a posterior surface.

Now that we understand the definition of region and the necessity to divide the body into regions, let's begin with the axial region.

Axial comes from the word axis so basically axial refers to parts of the body that are at the center and around which something is arranged – in this case, the limbs. And as I mentioned before, the axial region includes the head, neck, and trunk.

Going from top to bottom, we'll start with the head. The head is the most superior part of the body and is attached to the trunk by the neck. The anterior and posterior surfaces of the head combined are often referred to as the cephalic region, which comes from the Greek word for “head.” The head is a complex anatomical structure weighing up to five kilograms. It houses the brain and special sensory organs so there is no arguing that it's a special, important, and vital part of us.

If we move inferiorly just a little bit, we have the neck attaching the head to the trunk. It is also a part of the axial region and encompasses an anterior and a posterior surface. This region may also be called the cervical region, and similar to the head, the neck also contains many vital structures such as airways and major blood vessels compressed into a relatively small area. It is sturdy enough to support a five-kilogram weight 24/7 yet sufficiently mobile to move it in several directions.

The neck is in continuity with the trunk which is also known as the torso. The trunk of a human body is not unlike the trunk of a tree. The trunk of a tree is the main woody stem to which the branches and roots are attached. Similarly, the human trunk is the central bulky part of the body to which the neck with the head and the limbs are connected.

The trunk can be further divided into four sub-regions or parts. On the anterior aspect, we have the thorax, abdomen, and pelvis. On the posterior aspect, we have the back. Let's start with the first region of the anterior aspect of the trunk.

The thorax, also known as the thoracic region or the chest, is a region located between the neck and the abdomen. The word thorax has its origins in the ancient Greek and Latin meaning “breastplate.” It includes the thoracic wall composed mainly of bones and muscles and the thoracic cavity. The thoracic cavity contains vital organs of the respiratory and cardiovascular systems such as the heart and lungs as well as various other internal structures. That explains why a penetrating wound to the thoracic region is potentially life-threatening.

The abdomen, or abdominal region, is the body region located between the thorax and the pelvis. Similarly to the thorax, the abdomen also comprises a wall and a cavity. The costal margin and the xiphoid process are readily palpable and form the border between the abdominal wall and the thoracic wall.

Pelvis, or the pelvic region, is the lower part of the trunk. It extends between the abdomen and the lower limbs bounded by the bones of the pelvic girdle. It contains the pelvic cavity which is continuous superiorly with the abdominal cavity. So, as you can see, despite being described separately, the abdomen and pelvis are actually continuous with each other, making up the inferior part of the trunk. In fact, in some resources, the whole area is referred to as the abdominopelvic region.

The thorax, abdomen, and pelvis are all regions of the anterior surface of the trunk. The posterior surface of the trunk only comprises one region, and that is the back, which is an area located between the neck and the buttocks. The back includes the vertebral column, or spine, which protects the spinal cord and several back muscles. The scapulae and its muscles forming the scapular region are located at the posterior aspect of the trunk but are actually classified as part of the upper limb. However, due to its location, we cover it in detail on our regions of the back video.

Now that wraps up the axial region, so let's move on to the appendicular region.

Appendicular means something relating to an appendage or limb so it is no surprise that the appendicular region includes the upper and lower limbs. They are often referred to as the arms and legs, but as you'll learn today, that is not exactly accurate.

First, we're going to take a look at the upper limb. The upper limb is fundamental for our daily functioning. It is a multi-jointed lever that is freely movable on the trunk at the shoulder. Its primary function is to maneuver the hand into positions where it can manipulate objects. Thanks to the upper limb, we are able to grip, write, lift, and throw, among many other movements.

The upper limb is organized into several smaller regions – shoulder, arm, elbow, forearm, wrist, and hand. Each compartment has its own muscles as well as neurovascular supply. Let's take a quick look at them one by one.

Going from proximal to distal, the first region is the shoulder, which is the part that connects the upper limb to the trunk. It houses the shoulder joint which is the most mobile joint in the body enabling to position the upper limb in a wide range of positions.

The next region is the arm. In a colloquial sense, the term arm refers to the whole upper limb, but in an anatomical sense, it's only the portion located between the shoulder and the elbow. It is the longest segment of the upper limb and extends around the humerus. The elbow is the small region of the upper limb that connects the arm to the forearm. You probably already know where it is. Most of us have hit our funny bone once or twice – guilty. This region contains the elbow joint which allows for the movements of the forearm.

The forearm is the second longest segment of the upper limb. It extends between the elbow and wrist and overlies the radius and ulna. The forearm helps the shoulder, arm, and elbow in force application and precise placement of the hand in space. The wrist is the region that connects the forearm to the hand. This is also a small, yet complex region where we find the wrist joint and the small carpal bones.

The hand is the most distal part of the upper limb. It is a highly evolved structure with a unique ability to grasp items. Much of the importance of the hand centers around the pincer-like opposable action of the thumb, which enables the tip of the thumb to contact tips of other digits. That's actually what allows you to grab that much needed cup of coffee, okay? The hand contains many smaller subdivisions which you can learn all about in our video on the regions of the upper limb.

Now that we've explored the different regions of the upper limb, it's time to move on a bit further down to the lower limb. While the upper limb has been shaped by evolution into a highly mobile part of the human body, in contrast, the lower limb has been developed for stability and locomotion. The lower limb also has several regions with their own boundaries and contents. These regions are the hip, gluteal region, thigh, knee, leg, ankle, and foot.

Let's start looking into the subdivisions with the most proximal and lateral region known as the hip region. It is the area overlying the proximal part of the femur, and most importantly, the hip joint. The gluteal region, also known as the buttocks, belongs to the posterior surface of the lower limb and is located inferior to the lower back. It lies behind the pelvis and extends from the iliac crest of the bony pelvis to the gluteal fold. This is a highly muscular region and a great place to give intramuscular injections.

Moving down the lower limb, the next region is the thigh, also known as the femoral region, because it contains most of the femur or thigh bone. The thigh is the most superior part of the free lower limb and lies between the gluteal and pelvic regions proximally and the knee region distally. The transition from the trunk to the free lower limb occurs abruptly in the inguinal region or groin. Posteriorly, the gluteal fold separates the gluteal and femoral regions.

The knee region is located between the thigh and the leg and contains the knee joint. This joint is the largest, and arguably, the most biomechanically stressed joint in the body. Similar to the arm in the upper limb, the term leg is also used in common day language to refer to the whole lower limb; however, anatomically-speaking, the leg strictly means the portion of the lower limb located between the knee and the ankle.

The leg includes most of the tibia, or shin bone, and fibula, or calf bone. The ankle is the region connecting the leg to the foot. It accommodates the ankle joint which allows for movement of the foot and acts as a shock absorber in gait. The foot is the most distal part of the lower limb and the last region we will cover today. It is a resilient structure that supports your body weight while standing, walking, running, or jumping.

And that wraps up all the regions we wanted to cover in this video. The body is complex and many of these regions are further divided into smaller areas. If you feel ready to go a little deeper and dig into the specifics of this language of anatomy, check out our detailed videos on specific regions of the body.

Now it's time to talk about practical applications of the regional anatomy approach. While there isn't a specific clinical condition for this topic, it's worth mentioning that the concepts discussed here are fundamental for clinical practice. It's important that healthcare professionals know the descriptive terms used for the regions of the body in order to precisely localize and diagnose different injuries and diseases. On the other hand, having a common language is also essential for clear and accurate communication between healthcare professionals. I'm sure you wouldn't want to be admitted for knee surgery and instead leave the hospital without your appendix, right?

All right, guys, that's everything we wanted to teach you today. Before we finish up, let's recap what we learned.

The entire body is divided into regions. Broadly speaking, there are two primary regions – the axial and the appendicular. The axial region includes the head, neck, and trunk, which in turn comprises the thorax, abdomen, and pelvis on the anterior surface and the back on the posterior surface. The appendicular region refers to the upper and lower limbs, or extremities, which are also divided into smaller parts. The upper limb is made up of the shoulder, arm, elbow, forearm, wrist, and hand. The lower limb is formed of the hip, gluteal region, thigh, knee, leg, ankle, and foot.

Having a good grasp of these concepts is fundamental not only to facilitate anatomy learning but also for efficient communication between healthcare professionals.

That's all folks. This is how we split up the body – well, not literally. We hope you enjoyed this tutorial and see you next time.