The thoracic wall or chest wall is the boundary of the

thoracic cavity The thoracic cavity (or chest cavity) is the chamber of the body of vertebrates that is protected by the thoracic wall (rib cage and associated skin, muscle, and fascia). The central compartment of the thoracic cavity is the mediastinum. There ...

Structure

The bony skeletal part of the thoracic wall is the

rib cage The rib cage, as an enclosure that comprises the ribs, vertebral column and sternum in the thorax of most vertebrates, protects vital organs such as the heart, lungs and great vessels. The sternum, together known as the thoracic cage, is a semi- ...

, and the rest is made up of

muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscl ...

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 cuticle, animal coverings, such as the arthropod exoskeleton, have diffe ...

, 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 hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the amount of water rele ...

and dermis), superficial fascia,

deep fascia Deep fascia (or investing fascia) is a fascia, a layer of dense connective tissue that can surround individual muscles and groups of muscles to separate into fascial compartments. This fibrous connective tissue interpenetrates and surrounds the ...

and the invested extrinsic muscles (from the

upper limb The upper limbs or upper extremities are the forelimbs of an upright-postured tetrapod vertebrate, extending from the scapulae and clavicles down to and including the digits, including all the musculatures and ligaments involved with the shou ...

s), intrinsic muscles associated with the ribs (three layers of

intercostal muscles Intercostal muscles are many different groups of muscles that run between the ribs, and help form and move the chest wall. The intercostal muscles are mainly involved in the mechanical aspect of breathing by helping expand and shrink the size of ...

endothoracic fascia The endothoracic fascia is the layer of loose connective tissue deep to the intercostal spaces and ribs, separating these structures from the underlying pleura. This fascial layer is the outermost membrane of the thoracic cavity. The endothor ...

and

parietal pleura The pulmonary pleurae (''sing.'' pleura) are the two opposing layers of serous membrane overlying the lungs and the inside of the surrounding chest walls. The inner pleura, called the visceral pleura, covers the surface of each lung and dips be ...

. 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 serratus anterior is a muscle that originates on the surface of the 1st to 8th ribs at the side of the chest and inserts along the entire anterior length of the medial border of the scapula. The serratus anterior acts to pull the scapula fo ...

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 physiological responses to immersion that overrides the basic homeostatic reflexes, and is found in all air-breathing vertebrates studied to date. It o ...

, which has 3 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)