Generality
The armpit is the anatomical area of the human body located below the shoulder joint, where the lateral edge of the chest meets the proximal portion of the arm.
Comparable to a cavity, the axilla contains several tens of lymph nodes and has a rich content of hair follicles and sweat glandular; moreover, it is a transit site for important blood vessels and nerves.
The axilla has a crucial role in odor release containing much of the pheromones involved in mating.
What is Ascella?
The armpit is the area of the human body located below the joint that connects the arm to the trunk, or the glenohumeral joint (or shoulder joint ).
According to another definition, as appropriate as the previous one, the axilla is the anatomical space between the upper portion of the side of the thorax and the upper end of the arm.
Anatomy
The axilla is actually a cavity, which results from the particular arrangement of: chest wall, bones and muscles of the shoulder, and proximal portion of the humerus .
Representing one of the hottest anatomical areas of the human body, the axilla is the site of transit of numerous blood and lymphatic vessels as well as very important nerves; moreover, it hosts between 20 and 40 lymph nodes (not perceptible to the touch in normal conditions) and has a high concentration of hair follicles and sweat glands.
Chest wall, bones and muscles of the shoulder, and proximal portion of the humerus
To fully understand the anatomy of the armpit, it is necessary to review the following concepts: chest wall, bones and muscles of the shoulder, and proximal portion of the humerus.
- Chest wall: it is the edge of the thoracic cavity; it includes the thoracic cage (therefore the rib complex - sternum - thoracic vertebrae), the respiratory muscles (diaphragm and intercostal muscles), a series of connective tissues and, finally, the skin that covers the thoracic cage.
- Shoulder bones: the bones that contribute to the formation of the anatomical region of the shoulder are the clavicle, the scapula and the humerus.
- Shoulder muscles: the shoulder muscles are numerous and are divided into intrinsic and extrinsic; among the intrinsic muscles, there are: the deltoid, the supraspinatus, the sundown, the small round, the subscapularis, the large round; the extrinsic muscles, on the other hand, include: the anterior dentate, the subclavian, the large pectoralis, the small pectoralis, the large dorsal, the sternocleidomastoid, the scapula elevation, the large rhomboid, the small rhomboid, the trapezium, the coracobrachial, the brachial biceps and the brachial triceps.
- Proximal portion of the humerus: the proximal portion of the humerus, or proximal epiphysis of the humerus, is the upper extremity of the humerus, that which borders the trunk and which participates in the aforementioned glenohumeral joint.
Curiosity
Given the importance of the glenohumeral joint in the description of the axilla, it is worth clarifying what it consists of: it is the joint element that connects the so-called humeral head to the so-called glenoid cavity of the scapula .
Armpit borders
Armpit borders:
- Above, with the outer edge of the first rib, the upper edge of the scapula and the posterior edge of the scapula;
- Medially (ie towards the inside of the human body), with the dentate muscle and the rib cage;
- Anteriorly, with the pectoralis major muscle, the pectoralis minor muscle and the subclavian muscle;
- Later, with the subscapular muscle, the large round muscle and the large dorsal muscle. It should be pointed out that the subscapularis resides above the axilla, while the large round and the large dorsal localize under the armpit;
- Laterally (that is to the outside of the human body), with the so-called intertubercular groove of the proximal end of the humerus, the coracobrachial muscle and the short head of the biceps brachialis muscle.
Anterior axillary fold and posterior axillary fold
In anatomy, the front edge of the axilla is called the anterior axillary fold, while the posterior border of the axilla is called the posterior axillary fold .
The anterior axillary fold is a rounded region, formed mainly by the inferior margin of the pectoralis major muscle; the posterior axillary fold, on the other hand, is a flat area, consisting for the most part of the large dorsal and large round muscles.
Curiosity
The anterior axillary fold and the posterior axillary fold are the two regions of the axilla which, on the occasion of a considerable weight loss starting from a condition of obesity, denote this loss of fat by modifying their appearance (generally they take on a drooping aspect ).
Blood vessels passing through the armpit
Among the arterial blood vessels that pass through the axilla, include the axillary artery and its branches (upper thoracic artery, thoraco-acromial artery, lateral thoracic artery, subscapular artery, anterior circumflex artery of the humerus and posterior circumflex artery of the Homer).
As for the venous blood vessels that pass through the axilla, these include the axillary vein and its so-called tributary vessels (brachial veins, cephalic vein and basilic vein).
Nerves passing through the armpit
At the armpit level, the terminal part of the brachial plexus and the initial portion of the terminal branches of the brachial plexus reside; in addition, the long thoracic nerve and the intercostobrachial nerves pass.
- Brachial plexus: is the reticular formation of the cervical spinal nerves C5, C6, C7 and C8, and of the thoracic spinal nerve T1, which provides, through its innumerable branches both sensitive and motor, to the innervation of the shoulder, part of the thorax, arm, forearm and hand;
- Brachial plexus terminal branches: these are the most important branches of the brachial plexus; with principle right at the height of the armpit, there are 5 in all and are called: axillary nerve, musculocutaneous nerve, radial nerve, ulnar nerve and median nerve;
- Long thoracic nerve: it is a collateral branch of the brachial plexus;
- Intercostobrachial nerves: they are branches of the intercostal nerves and have a sensory function.
Axillary lymph nodes
Axillary lymph nodes, also known as axillary lymph nodes, can be divided into 6 groups: the anterior group (or pectoral group), the posterior group (or subscapular group), the lateral group, the central group, the deltopectoral group (or group infraclavicular) and the apical group.
The lymph nodes of the axilla drain the lymphatic vessels of the lateral quadrants of the ipsilateral breast, the superficial lymphatic vessels of the thoracic wall, the superficial lymphatic vessels of the part of the abdomen above the navel and, finally, the lymphatic vessels of the ipsilateral upper limb.
Short clarification
According to some anatomical visions, the lymph nodes of the deltopectoral group do not belong to the category of axillary lymph nodes, as they reside outside the axillary region.
Armpit muscles
The armpit has relationships with different muscles, but only for two of them is it a place of transit. The muscles in question are the biceps brachialis muscle and the coracobrachialis muscle, which cross the axillary region with the tendons having insertion at the level of the coracoid process of the scapula.
Armpit fatty tissue
The axilla region includes a certain amount of adipose tissue ; particularly visible in overweight or obese people, this adipose tissue is distributed around the blood vessels, nerve structures and lymph nodes described in the previous sections.
Function
Scientific studies have shown that the axillary region (ie where the axilla resides) produces and emits most of the characteristic odor of a human being; a smell that among other things, according to the same scientific studies, seems to contain a large number of pheromones related to mating .
Curiosity
According to the experts, the smell emanating from the armpit would be more important, as regards the presence in it of pheromones related to the coupling, of the smell emanating from the genital area.
diseases
In the pathological field, the axilla region is important in numerous clinical circumstances, since it is a site of pain (see pain in the armpit) and other symptoms useful for diagnosis; Among the aforementioned clinical circumstances, it is worth mentioning: thoracic outlet syndrome, breast cancer, intertrigo, reverse psoriasis, hyperhidrosis, hidradenitis suppurativa, herpes zoster, irritative contact dermatitis resulting from from excessive use of skin cleansers, all those infections that cause enlargement of the axilla lymph nodes, axillary folliculitis and axillary pimples.
