The thoracic wall or chest wall is the boundary of the thoracic cavity.

Structure

The bony skeletal part of the thoracic wall is the rib cage, and the rest is made up of

muscle Muscle is a soft tissue, one of the four basic types of animal tissue. There are three types of muscle tissue in vertebrates: skeletal muscle, cardiac muscle, and smooth muscle. Muscle tissue gives skeletal muscles the ability to muscle contra ...

skin Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation. Other animal coverings, such as the arthropod exoskeleton, have different ...

, and fasciae. The chest wall has 10 layers, namely (from superficial to deep)

(

epidermis The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and Subcutaneous tissue, hypodermis. The epidermal layer provides a barrier to infection from environmental pathogens and regulates the ...

and

dermis The dermis or corium is a layer of skin between the epidermis (skin), epidermis (with which it makes up the cutis (anatomy), cutis) and subcutaneous tissues, that primarily consists of dense irregular connective tissue and cushions the body from s ...

), superficial fascia, deep fascia and the invested extrinsic muscles (from the

upper limb The upper Limb (anatomy), limbs or upper extremities are the forelimbs of an upright posture, upright-postured tetrapod vertebrate, extending from the scapulae and clavicles down to and including the digit (anatomy), digits, including all the musc ...

s), intrinsic muscles associated with the ribs (three layers of intercostal muscles), endothoracic fascia and parietal pleura. However, the extrinsic muscular layers vary according to the region of the chest wall. For example, the front and back sides may include attachments of large

muscles like pectoralis major or latissimus dorsi, while the sides only have serratus anterior.The thoracic wall consists of a bony framework that is held together by twelve thoracic vertebrae posteriorly which give rise to ribs that encircle the lateral and anterior thoracic cavity. The first nine ribs curve around the lateral thoracic wall and connect to the manubrium and sternum.

Function

Diving reflex

When not breathing for long and dangerous periods of time in cold water, a person's body undergoes great temporary changes to try to prevent death. It achieves this through the activation of the

mammalian diving reflex The diving reflex, also known as the diving response and mammalian diving reflex, is a set of physiology, physiological responses to immersion that overrides the basic homeostasis, homeostatic reflexes, and is found in all air-breathing verteb ...

, which has three main properties. Other than bradycardia and peripheral vasoconstriction, there is a blood shift which occurs only during very deep dives that affects the thoracic cavity (a chamber of the body protected by the thoracic wall.) When this happens, organ and circulatory walls allow plasma/water to pass freely throughout the thoracic cavity, so its pressure stays constant and the organs are not crushed. In this stage, the lungs' alveoli fill up with blood plasma, which is reabsorbed when the organism leaves the pressurized environment. This stage of the diving reflex has been observed in humans (such as world champion freediver Martin Štěpánek) during extremely deep (over 90 metres or 300 ft) free dives.

Clinical significance

In rare cases, intentional or accidental, trauma may lead to chest wall (thoracic wall) necrosis.

References

External links

* * {{Thoracic cavity Thorax (human anatomy)