The hollow with the magic name Fossa axillaris can be compared to a modern automotive interchange in an advanced metropolis. Here bundles of large vessels, major nerves, lymph nodes, muscle ligaments intertwine.
This axillary fossa is one of the busiest intersections in the human body. Fossa axillaris is an excellent example of the architecture of the human body with its complex communications and functional diversity.
Pit, cavity, cavity: what is the difference?
First you need to deal with the terms. The pit and the hollow (the same Fossa axillaris) are one and the same. This is the surface hollow visible to the naked eye between the inner surface of the shoulder and the lateral surface of the chest. She has another name - axillary cavity. The axillary fossa is clearly visible with a raised arm.
There is one more term. This is the axillary cavity (axilla, or armpit), which is located deeper, under the fossa: if you cut the skin in the fossa, you can get into the cavity.
The word “armpit” needs special clarification. This name is not very trusted and is often considered its national slang. It’s completely in vain, because the armpit is the official name for the same axillary cavity. This is a single fused word from the Russian dictionary, it can be used with confidence with the pretexts “in the armpit”, “under the armpit”, etc.
It should be noted that in medical sources the above terms are described in different ways. This review provides general basic information about the axillary region, so there is no fundamental difference between the terms “fossa”, “cavity” and “cavity”.
Highest category communication node
A communication node is a concept from modern logistics that perfectly describes the functional purpose of Fossa axillaries. A multicomponent neurovascular bundle, composed of large main vessels — the axillary artery, axillary vein, and seven branches of the powerful nerve plexus from the brachial node — is stretched through this fossa. Accompanying paths in the closest neighborhood are numerous lymphatic ducts. Lymph nodes in the armpit are represented in large quantities in bulk - they are located in fatty tissue. Their number is due to the most important function - the protection of lymphatic fluid circulating in the upper third of the chest, and this is nothing but the upper respiratory tract - one of the most vulnerable organs for various kinds of infections.
The contents of the armpit can be divided into the following components:
- Arteries - The main axillary artery with its branches.
- Veins are the main axillary vein with its tributaries.
- Nerves in the form of the brachial plexus, consisting of three bundles: posterior, lateral, median.
- Lymphatic vessels and five groups of lymph nodes.
- Fiber, consisting mainly of adipose tissue.
Protection and safety
Localization of such a significant neurovascular bundle implies a high degree of safety of this site. The armpit is perfectly protected. Perhaps this is the most protected external area in the human body.
All four walls of the axillary fossa are formed by groups of shoulder and pectoral muscles and their muscle fascia:
- The anterior wall is represented by the clavicular-thoracic fascia and two pectoral muscles - large and small, which are attached to the upper edge of the shoulder and the front side of the upper chest. Thus, both pectoral muscles perfectly protect the axillary vessels and nerves.
- The back wall is formed from the latissimus dorsi, subscapularis, infraspinatus and supraspinatus, as well as round muscles: small and large.
- The medial wall is formed by the anterior dentate muscle attached to the lateral wall of the chest to the 5th rib.
- The lateral wall is formed by the coracorachis muscle attached to the side of the inner surface of the shoulder.
Muscle pyramid
When raising a hand, the armpit has the shape of a quadrangular pyramid with four walls, described above. The pyramid has a top and a bottom:
- The top is located between the collarbone and the first rib. It is through it that the vessels and nerves in the form of a bundle enter the axillary cavity.
- The bottom or base of the pyramid is represented by neighboring muscles. It is formed by a common fascia, which, in turn, is formed from fascia of the adjacent muscles of the back: pectoralis major and latissimus.
Thus, the muscles of the axillary fossa create a distinct “geography” for it and provide excellent external protection.
Arteries
The axillary artery (Arteria axillaris) is one of the most important major vessels in the arterial network into which the subclavian artery passes. Then it passes, in turn, into the brachial artery. The upper segment of the axillary artery passes from the clavicle between the second and third ribs. Here it is perfectly protected by the subclavian muscle (Musculus subclavius). In the same segment, two branches extend from the axillary artery: the thoracromial artery, which carries blood to the shoulder joint and deltoid muscle, and the upper pectoral, supplying two pectoral muscles: small and large.
The lateral artery of the chest (A. Thoracica lateralis) is another branch that begins in the middle section of the axillary artery. Its function is the blood supply to the axillary fossa itself, its lymph nodes and the surface layers of the mammary glands.
In the third, lower, segment from the artery, powerful branches depart: the subscapular and dorsal arteries of the chest, the envelope artery of the scapula. All of them take part in anastomoses and collateral circulation of blood vessels of the neck and upper limbs.
Veins
The axillary vein is formed by the fusion of two brachial veins. In turn, it turns into a subclavian vein. In its upper part, the axillary vein runs in close proximity to the axillary artery in the common vascular canal. Below - in the middle and lower sections - it is separated from the artery by the nerves of the forearm.
Under the collarbone, a powerful inflow flows into the vein - the lateral saphenous vein of the arm, above - the medial saphenous vein of the arm. Most people are familiar with the location of this vein, even those who are not related to medicine: intravenous injections or blood sampling from a vein are most often performed in Vena basilica - in the area of the elbow joint from the inside.
Nerves
All the axillary nerve trunks are divided into short (for example, axillary nerve) and long branches (for example, median nerve). Functionally short branches innervate the muscles and bones of the shoulder girdle, while the long ones are responsible for the upper limb. The nerve bundle of the axillary fossa is formed at the level of the middle section of the axillary artery.
The brachial plexus in the form of three nerve bundles is the beginning of the powerful nerves of the upper limb. Two nerves emerge from the lateral bundle: median (medial) and musculocutaneous. From the median bundle - the ulnar nerve and part of the median nerve. From the back - the radial and axillary nerves.
The subscapular nerves can vary in amount from three to seven, they originate from the cervical vertebrae and lie on the subscapularis muscle, innervating it, as well as the round and latissimus muscles.
Lymphatic network
Lymph nodes in the armpit are often rated as the most “restless” glands in the human body. Indeed, they bring a lot of problems: of all the nodes, they are most often inflamed. The reason for this is the structural features of the axillary fossa (the “logistic node”, which consists of many components) and problems in the mammary glands, chest and upper limbs - parts of the body that are innervated and supplied with blood from nearby vessels and nerves.
Lymph nodes are located in placers and, depending on their location, are divided into five groups: lateral, central, thoracic, subscapular, apical. The size of the axillary lymph nodes also depends on the location, on average they are no more than 1.0 mm.