The thorax is a structure found in humans, but it is not unique to humans; it exists in all mammals and arthropods. In this lesson, you'll learn what the thorax is and where it's located in the human body.
Anatomical terms may not sound like particularly important things, but think about how difficult it would be for a nurse to explain to a doctor where a patient was injured or what it might be like to discuss a surgical procedure without having a unified and universal set of terms. Yikes! A victim would much rather have the doctor know that it was, say, their 'upper limb' or their 'arm' rather than 'that long bendy thing off the top of my body.' Anatomical terms not only provide us with a universally accepted vocabulary, but they also enable us to convey more specific, detailed, and succinct information much faster.
That said, there are many different levels of regional classifications for the body. They can be general and refer to large regions of the body, such as the thorax, or they can be very specific and refer to a particular subregion, such as the oropharynx (the region of your throat between your soft palate and your epiglottis (the tissue flap that closes off your airway when you swallow food). See how much easier it was to name the oropharynx than it was to describe it? Thanks anatomical terminology! Here we are going to focus on the broad region of the body called the thorax.
Major Body Regions
What determines the boundaries of a region varies with each particular region. Some regions identify structures off of the main trunk of the body, such as the upper limb region, lower limb region, cephalic region (head), or cervical region (neck). Others refer to subsections of the trunk and are delineated by either the walls of a body cavity or by the bone structures housed within those regions, such as the thoracic region (thorax), abdominal region, pubic region, and the pelvic region.
The thorax is a body region found in all mammals and refers to the upper area of the trunk, between the base of the neck and the diaphragm. The diaphragm is the fibrous membrane that separates your lungs from your abdomen and helps you breathe.
Internally, the thoracic region houses your heart and lungs and is encased by your ribs. The long bony structure of your sternum (also known as the breast bone) supports your ribs at the front of your thorax, while specialized vertebrae of your spine, called thoracic vertebrae, support your ribs in the back.
The thorax isn't just all bones and organs though - it also includes a lot of accessory muscles (such as those in between your ribs) and nerve bundles, such as your thoracic nerves. These nerves exit your spinal cord in your thorax and are responsible for sending and receiving signals from all over your body. They do everything from control the movement of the muscles in your chest and arm muscles to all of the major organs of your body.
Arthropods are organisms with an exoskeleton like insects, crustaceans, and spiders. They all have a body plan based on three regions: a head, abdomen, and, that's right, a thorax. In arthropods, the thorax is the middle segment of the body, where the legs and wings are attached.
These three regions are not always clearly distinct like they are in, say, a spider or a honey bee. Some creatures have a fused head and thorax, like crabs for example, called a cephalothorax, which literally means 'head thorax.'
The thorax is a region of the mammalian body that refers to the upper trunk, between the base of the neck and the diaphragm. It houses the heart and the lungs and is encased by the ribs. The thorax also includes a lot of accessory muscles and nerve bundles such as your thoracic nerves. Arthropods also have a thorax, which refers to the middle segment of their body where the appendages (legs and wings) attach.