Anatomy of the mammary gland

In this note, we will consider the anatomy of the mammary gland.

The mammary gland (mamma). It is a paired gland of the female reproductive system

As a gland of external secretion, it produces milk during lactation. And as an organ of internal secretion, it produces mammary hormones.

As a gland of external secretion, it produces milk during lactation. And as an organ of internal secretion, it produces mammary hormones.

It adheres to the anterior surface of the pectoralis major muscle, enclosed in a fascial sheath (capsule) formed by pectoral fascia.

There are the following parts in the mammary gland.

The body of the mammary gland (corpus mammae), which has the shape of a disk with a smooth posterior surface and a rough convex surface.

Body of the mammary gland (corpus mammae)

In the middle of the convex surface of the gland, there is a nipple (papilla mammaria).

At the top of the nipple, 10-15 excretory lactiferous ducts (ductus lactiferi) open.

The areola (areola mammae), which is an area of skin around the nipple up to 1.5 cm wide.

The areola is pink in young girls, and dark brown in women. On the skin of the areola, there are 15-20 small eminences, up to 1 mm in size, on the surface of which the ducts of the mammary glands of areola (glandulae areolares) open.

Mammary glands of areola (glandulae areolares)

In the skin of the nipple and the areola, there are bundles of smooth muscle cells oriented circularly and longitudinally, which form the muscle of the nipple. When contracting, it strains the nipple.

Between the capsule of the gland and the superficial layer of the pectoral fascia, covering the pectoralis major muscle, there is a loose connective tissue that provides a slight displacement of the gland along the anterior surface of the chest.

Behind the gland in the retromammary space (spatium retromammarium), loose connective tissue is located.

By its internal structure, the mammary gland is a parenchymal organ.

The body of the gland consists of 15-20 radially arranged lobes (lobi glandulae mammariae), which are complex tubuloalveolar glands.

The lobes are separated by connective tissue septa and adipose tissue.
The tubuloalveolar glands spread radially from the nipple and are divided into lobules.
The lobules consist of the lactiferous alveoli (alveolae lactiferi), which are the structural and functional unit of the mammary gland.
The lactiferous alveoli are surrounded by plexuses of capillaries and a smooth muscle capsule. The contraction of the smooth muscle capsule ensures the release of milk during breastfeeding
Alveolar ducts (ducti alveolares) drain into the collecting duct (ductus lactiferi colligens), arise from the alveoli.
Each lobe has its proper collecting duct.
The collecting duct in the nipple area forms an extension called the lactiferous sinus (sinus lactiferi).

A short lactiferous duct comes out of the lactiferous sinus. Only 10-15 foramina open on the nipple, so there are fewer lactiferous ducts than lobes.
Connective tissue septa separating the lobes are called the suspensory ligaments of the mammary gland (ligg. suspensoria mammariae).

Suspensory ligaments of the mammary gland (ligg. suspensoria mammariae)

They are derivatives of the superficial pectoral fascia (fascia pectoralis superficialis).

Blood supply

Branches of the mammary gland (rr. mammarii) from the posterior intercostal artery (a. intercostales posteriores).
Medial branches of the mammary gland (rr. mammarii mediales) from the perforating branches (rr. perforantes).
Pectoral branches (rr. pectorales) from the thoraco-acromial artery (a. thoracoacromialis).

Venosus drainage

Venous blood drains through the eponymous veins to:

The azygos vein (v. azygos);
The hemi-azygos vein (v. hemiazygos);
The brachiocephalic vein (v. brachiocephalica);
The axillary vein (v. axillaris).

Innervation

Afferent and sympathetic innervation are provided by fibers of the intercostal nerve (n. intercostalis) and the supraclavicular nerve (n. supraclavicularis) from the cervical plexus (plexus cervicalis).

Lumph drainage

Lymph drains mainly into:

Axillary lymph nodes (nodi lymphatici axillares)
Parasternal lymph nodes (nodi lymphatici parasternales);
Internal thoracic lymph nodes (nodi lymphatici thoracici interni);
Deep cervical lymph nodes (nodi lymphatici cervicales profundae);
Supraclavicular lymph nodes (nodi lymphatici supraclaviculares).

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