Mamma - description and structure, blood supply and innervation, lymphatics

Description and structure

The breasts are paired structures that are located on the anterior thoracic wall, in the pectoral region, present in both male and female.

In females, the breasts contain the mammary glands, which are accessory glands of the female reproductive system.

They are exocrine, modified apocrine glands

They are structurally dynamic, which means they change with the womans age, menstrual cycle and reproductive statues. They have 15-20 secretory lobes which are separated via fibrous bands known as suspensory ligaments of the breast. The lobes contain locules comprised of tubuloalveolar glands. The glands drain to the ducts of these lobes , known as the lactiferous ducts , which open into the nipple.

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Vasculature

The arterial supply of the breast is rich and varied, drawing from multiple sources to ensure adequate blood flow.

Branches of the Axillary Artery:

• Superior Thoracic Artery: Supplies the upper part of the breast.
• Thoracoacromial Artery: Provides branches to the pectoral region and the breast.
• Lateral Thoracic Artery: Particularly important for the lateral aspect of the breast.
• Subscapular Artery: Contributes to the blood supply of the breast and surrounding regions.

Branches from the Internal Thoracic (Mammary) Artery: These branches run along the sides of the sternum and provide medial mammary branches to the breast.

Perforating Branches of the 2nd, 3rd, and 4th Intercostal Arteries: These arteries pierce through the intercostal spaces and supply the deeper tissues of the breast.

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Innervation:

The breast is innervated primarily by the intercostal nerves, providing sensory and autonomic innervation.

• Intercostal Nerves 2-6:
  • Anterior Cutaneous Branches: These branches supply the skin over the medial aspect of the breast.
  • Lateral Cutaneous Branches: These branches innervate the skin over the lateral aspect of the breast.
• Nipple Innervation:
  • 4th Intercostal Nerve: Specifically, the nipple and areola receive sensory innervation from the anterior and lateral cutaneous branches of the 4th intercostal nerve.

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Lymphatics:

The lymphatic system plays a crucial role in the drainage of the breast, and its understanding is needed, especially in the case of breast cancer.

• Subareolar Lymphatic Plexus:
  • Collection Point: Lymph from the breast and nipples first collects into the subareolar lymphatic plexus.
• Primary Drainage Pathway:
  • 75% of Lymph: The majority of lymph (approximately 75%) drains from the subareolar plexus into the pectoral lymph nodes.
  • Pectoral to Axillary Lymph Nodes: From the pectoral lymph nodes, lymph travels to the axillary lymph nodes.
  • Axillary to Subclavian Lymphatic Trunk: Finally, lymph from the axillary lymph nodes drains into the subclavian lymphatic trunk.
• Secondary Drainage Pathway:
  • 25% of Lymph: The remaining 25% of lymph drains into the parasternal lymph nodes.
  • Parasternal to Bronchomediastinal Lymphatic Trunk: The parasternal lymph nodes subsequently drain into the bronchomediastinal lymphatic trunk.

Clinical Significance:

Breast Cancer Staging: During the staging and treatment of breast cancer, axillary lymph nodes are often the first to be examined and potentially removed to check for metastasis, as they are a primary drainage site and can indicate the spread of cancer.

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Structures associated with the mammary gland

Areola

A circular, pigmented area surrounding the nipple. It serves as a visually distinct region that becomes darker during pregnancy and lactation to help infants locate the nipple.

Nipple

The central raised structure within the areola containing the openings of the lactiferous ducts, which are channels through which milk is secreted during lactation.

Areolar Tubercles

Small elevations on the areola produced by the areolar glands, also known as Montgomery glands. These glands secrete an oily substance that lubricates and protects the nipple and areola during breastfeeding.

Suspensory Ligaments of the Breast (Cooper's Ligaments):

A fibrous network that inserts into the pectoral fascia and dermis over the skin of the breast. These ligaments provide structural support to the breast, maintaining its shape and anchoring it to the chest wall.

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reference

Salvador notes