The depression with the magical name Fossa axillaris can be compared to a modern road junction in an advanced metropolis. Bundles of large vessels, the most important nerves, lymph nodes, and muscle ligaments are intertwined here.
This axillary fossa is one of the busiest crossroads in the human body. Fossa axillaris is a magnificent example of the architecture of the human body with its complex communications and functional diversity.
Pole, depression, cavity: what's the difference?
First you need to understand the terms. Fossa and depression (the same Fossa axillaris) are one and the same. This is a superficial 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 when the arm is raised.
There is another 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 intocavity.
The word "armpit" needs special clarification. This name is not very trusted and is often considered to be folk slang. Quite 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 prepositions: “in the armpit”, “under the armpit”, etc.
It should be noted that the above terms are described in different ways in medical sources. This review provides general basic information about the axillary region, so there is no fundamental difference between the terms "fossa", "depression" and "cavity" here.
Communication node of the highest category
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, the axillary vein and seven branches of the powerful nerve plexus from the shoulder node, is stretched through this fossa. Accompanying paths in the closest neighborhood lie numerous lymphatic ducts. Lymph nodes in the armpit are presented in bulk in large quantities - they are located in fatty tissue. Their number is due to the most important function - the protection of the 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 infections.
The contents of the armpit can be divided into the following components:
- Arteries - the main axillary artery with its branches.
- Veins - 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 suggests a high degree of safety in this area. The armpit is superbly protected. This is perhaps the most protected external area in the human body.
All four walls of the armpit are formed by groups of shoulder and pectoral muscles and their muscle fascia:
- The front 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 muscle, subscapularis, infraspinatus and supraspinatus, as well as round muscles: small and large.
- The medial wall is formed by the serratus anterior, attached to the lateral chest wall up to the 5th rib.
- The lateral wall is formed by the coracobrachialis muscle attached from the inside of the shoulder.
Muscularpyramid
When the arm is raised, the armpit has the shape of a quadrangular pyramid with four walls as described above. The pyramid has a top and a bottom:
- The apex is located between the clavicle 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 adjacent muscles. It is formed by the common fascia, which, in turn, is formed from the fascia of the adjacent muscles of the back: pectoralis major and latissimus dorsi.
Thus, the muscles of the axilla create a distinct "geography" for it and provide excellent external protection.
Arteries
The axillary artery (Arteria axillaris) is one of the most important main 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 runs 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 depart from the axillary artery: the thoracoacromial artery, which carries blood to the shoulder joint and the deltoid muscles, and the upper pectoral, which supplies two pectoral muscles: small and large.
Lateral artery of the chest (A. Thoracica lateralis) - another branch that begins in the middle segment 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 departpowerful branches: subscapular and dorsal arteries of the chest, circumflex artery of the scapula. All of them take part in anastomoses and collateral circulation of the 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 clavicle, 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 nerve trunks of the armpit are divided into short (eg, axillary nerve) and long branches (eg, median nerve). Functionally, short branches innervate the muscles and bones of the shoulder girdle, while long ones are responsible for the upper limb. The nerve bundle of the axillary fossa is formed at the level of the middle part 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 - radial andaxillary nerves.
The subscapularis nerves can vary in number 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 dorsi.
Lymphatic network
The lymph nodes in the armpit are often ranked as the most "restless" glands in the human body. And indeed, they carry 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 (“a logistical node” consisting of many components) and problems in the mammary glands, chest and upper limbs - areas of the body that are innervated and supplied with blood from nearby vessels and nerves.
Lymph nodes are scattered 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.
