Topography and external anatomy
The gland is located on the anterior thoracic wall. It lies on the surface of the pectoralis major muscle and partially overlies the serratus anterior muscle. The vertical boundaries of the organ extend from the III to the VI rib, and the horizontal boundaries extend from the parasternal line to the anterior axillary line.
The external surface of the organ features characteristic structures:
- Nipple (papilla mammaria) — located centrally. The openings of the lactiferous ducts open at its apex.
- Areola (areola mammae) — surrounds the nipple. The skin in this area is heavily pigmented and contains specific sebaceous glands as well as sweat glands (glandulae areolares).
Internal structure
The basis of the organ is the body of the mammary gland (corpus mammae). It has a lobular structure and consists of 15–20 lobes (lobi glandulae mammariae). Strong connective tissue septa lie between the lobes, forming the framework of the organ.
Each individual lobe is divided into smaller structures — lobules (lobuli glandulae mammariae). It is within these that the alveolar-tubular secretory units responsible for milk production are located.
A lactiferous duct (ductus lactifer) extends from each lobe toward the center of the gland. Before entering the nipple and opening onto its surface, each such duct forms a local dilation — the lactiferous sinus (sinus lactifer), which serves as a small reservoir for the secretion.
Fascial sheaths and suspensory apparatus
The glandular tissue itself is surrounded on all sides by masses of adipose and fibrous tissue, which determine the shape and volume of the organ.
Special connective tissue strands — suspensory ligaments of the breast (ligg. suspensoria mammaria) — serve to hold the organ against the anterior thoracic wall. These dense structures securely anchor the gland to the deep layers of the skin and underlying fascia. The posterior surface of the gland is separated from the fascia of the pectoral muscles by a layer of loose connective tissue, which provides the organ with some mobility.
Features of the male mammary gland
In men, the organ is termed the mamma masculina. Normally, it is completely rudimentary and performs no secretory functions. The male gland is represented only by a small amount of connective tissue interspersed with poorly developed, non-functioning ducts.
Blood supply, innervation, and lymphatic drainage
The blood supply to the organ is characterized by a wealth of sources. Arterial blood comes from branches of:
- Internal thoracic artery (a. thoracica interna).
- Lateral thoracic artery (a. thoracica lateralis).
- Intercostal arteries.
Venous drainage is carried out via veins of the same name accompanying the arteries.
Innervation is provided by branches of the intercostal nerves (nn. intercostales) and supraclavicular nerves (nn. supraclaviculares).
The lymphatic system plays a critically important role. The bulk of lymph from the breast tissue drains predominantly into the axillary lymph nodes (nodi lymphatici axillares).
Briefly: answers to topical questions
Where do the lactiferous ducts open at the apex of the nipple?
At the apex of the nipple, the lactiferous ducts open via lactiferous orifices. Distally (toward the apex), the ducts narrow, change their epithelial type to stratified squamous keratinized epithelium, and emerge onto the surface. It is important to note that the number of orifices ranges from 8 to 15, which is fewer than the number of lobes (15–20), as some ducts fuse with one another before exiting.
Which groups of lymph nodes receive lymph from the mammary gland?
Lymph from the mammary gland is received by several groups of lymph nodes that form the main drainage pathways.
- Axillary lymph nodes (nodi lymphatici axillares) — receive about 75% of the lymph (predominantly from the outer quadrants).
- Paramammary lymph nodes (nodi lymphoidei paramammarii) — located along the lateral thoracic artery.
- Interpectoral lymph nodes (nodi lymphoidei interpectorales) — situated between the pectoralis major and minor muscles.
- Parasternal lymph nodes (nodi lymphatici parasternales) — receive lymph from the medial quadrants.
- Supraclavicular lymph nodes — collect lymph from the upper portions of the gland.
- Subclavicular nodes — receive lymph after the axillary nodes.
- Intercostal lymph nodes — receive drainage from the posterior regions.
Which fascia and muscles are in contact with the posterior surface of the mammary gland?
The posterior surface of the mammary gland is separated from the fascia of the pectoral muscles by a layer of loose connective tissue. The gland lies on the surface of the pectoralis major muscle and partially the serratus anterior muscle.
Which glands are located in the skin of the areola?
Sebaceous and sweat glands are located in the skin of the areola.
- Areolar glands (glandulae areolares) — a complex of sebaceous and sweat glands characteristic of this region.
The sebaceous glands in this zone have a specific feature: they are not associated with hair follicles, as hair is absent on the areola. Inflammation of the glands of the areola is referred to in clinical practice as areolitis.
Class and exam questions
What is the origin of the mammary gland in embryogenesis?
From a developmental standpoint, the mammary gland is a modified cutaneous sweat gland.
At the level of which ribs is the organ located?
Normally, the mammary gland is located at the level of the III to VI ribs.
Where does the main lymphatic drainage occur?
Lymph drains predominantly into the axillary lymph nodes (nodi lymphatici axillares).
How many lobes are contained on average in the body of the mammary gland?
The body of the mammary gland consists of 15–20 lobes separated by connective tissue septa.
What else to study on this topic
- Histological structure of alveolar-tubular secretory units
- Topography of the axillary lymph nodes
- Structure and functions of the suspensory ligaments (ligg. suspensoria mammaria)
- Differences in duct structure between the rudimentary and lactating gland
- Relationship of the posterior surface of the gland to the fascia of the pectoralis major muscle
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