Learning Objectives
- Identify the terminal duct lobular unit (TDLU) as the functional unit of the breast.
- Distinguish between the fibrous stroma and adipose tissue in the breast parenchyma.
- Understand the hormonal influences (Estrogen vs. Progesterone) on breast microanatomy.
- Recognize the histological appearance of the inactive breast at low power.
Histology of the Normal Breast
The normal female breast is composed of a complex arrangement of glandular elements, supportive connective tissue, and fat.
- Glandular Elements: Consist of ducts and lobules. The lobules are clusters of small glands (acini) where milk is produced, while the ducts transport it toward the nipple.
- Stroma: The glandular elements are embedded in a fibrous stroma (connective tissue) that provides structural support.
- Adipose Tissue: Significant amounts of fat are present between the fibrous elements. In the non-lactating state, adipose tissue forms the bulk of the breast volume and is the primary determinant of breast size.
Hormonal and Physiological Changes
The breast is a dynamic organ that undergoes significant structural changes based on the hormonal environment:
| Phase/Hormone | Histological Response |
|---|---|
| Estrogen | Stimulates the proliferation and lengthening of ducts. |
| Progesterone | Causes lobular hypertrophy and alveolar development (prominent during pregnancy). |
| Pregnancy | Marked increase in the number and size of lobules, displacing stroma and fat. |
Activity
