Breast Chapter 3: Anatomy and Physiology

Breast Anatomy Image

1. Cooper's Ligaments 2. Breast Lobule 3. Extralobular Duct 4. Ductal Ampulla 5. Main Duct 6. Nipple 7. Skin 8. Subcutaneous Fat 9. Mammary Layer 10. Retromammary Layer 11. Lymph Nodes 12. Pectoralis Major 13. Pectoralis Minot 14. Ribs

TDLU Anatomy Image

1. Ductle 2. Lobular Stroma 3. Intralobular Terminal Duct 4. Lobule 5. Extralobular Terminal Duct 6. TDLU

Two main arteries that supple blood to breast tissue

1. Lateral thoracic artery (supply lateral region) 2. Internal mammary artery (supply medial region) Secondary sources: Thoracoacromial artery (superior) and Intercostal artery (inferior).

Most common causes of increase of glandular tissue:

1. Pregnancy/lactation 2. Hormone replacement therapy (HRT) 3. Significant weight loss

Anatomic Layers of the Breast

1. Skin 2. Subcutaneous (pre-mammary) layer 3. Mammary layer 4. Retromammary layer 5. Muscle layers (pectoralis major/minor) 6. Chest wall (ribs and intercostal muscles)

Areola

Circular area of dark pigmentation surrounding the nipple consisting of smooth muscle. - Contain Montgomery glands

*Intercostal Veins

Communicate with vertebral veins - may be route for metastatic disease.

Lobule

Composed of approximately 30 acini, intralobular terminal ducts, and intralobular stroma tissue (loose connective tissue). - Medium size functional unit.

Nipple

Composed of dense connective tissue and erectile muscle - Contain many sensory nerve endings - 15-20 collecting (lactiferous) duct openings maybe be seen (each arising from a breast lobe)

Skin

Composed of epidermis and dermis layers measuring 0.5-2.0 mm (thins with age).

Subcutaneous (pre-mammary) Layer

Lies just beneath the skin extending to the mammary layer (not seen posterior to nipple). *Consits primarily of fat - amount increases with age, pregnancy, and obesity. - Contain Cooper's Ligaments

Tail of Spence

Portion of glandular tissue that extends into the axilla.

Stroma

Supportive tissue - consists of interlobular fat and connective tissue (Cooper's Ligaments, loose and dense connective tissue).

TDLU

Terminal Duct Lobular Unit: made up of lobule, intralobule terminal ducts and extralobule terminal ducts. *Nearly all breast pathology originate in the TDLU. - Largest functional unit. - Usually 2.0 mm or less.

Mammary Layer

*Functional tissue of the organ, composed of two type of tissue: 1. Stroma 2. Epithelium AKA: Parenchymal or Glandular Layer

Estrogen stimulates changes of stromal tissue:

- Elongation of mammary ducts - Growth of connective tissue - Increase in adipose tissue - Increase in vascularity

2 venous systems that drain breast tissue

1. Superficial: allow venous communication between the right and left breast (*may be a route for metastatic disease). 2. Deep: drain into Internal Mammary vein, Lateral Thoracic vein, Axillary vein, Subclavian vein, and Intercostal veins. - Lymphatic vessels closely follow the same route as the superficial and deep venous systems.

TDLU Anatomy Image 2

1. TDLU 2. Extralobular Terminal Duct 3. Lobule 4. Ductules 5. Intralobular Terminal Duct 6. Segmental Duct 7. Collecting Duct 8. Lactiferous Sinus

Breast Arterial Supply Image

1. Thoracoacromial Artery 2. Lateral Thoracic Artery 3. Internal Mammary (Thoracic) Artery 4. Posterior Intercostal Artery 5. Nipple

Amazia

Absence of breast tissue with development of the nipple.

Amastia

Absence of one or both breasts.

Athelia

Absence of the nipple.

Polymastia

Accessory breast or more than 2 breasts

*Polythelia

Accessory nipple. *Most common breast anomaly. - Men > women.

Progesterone stimulates growth in

Glandular tissue - TDLUs

Cooper's Ligaments

Provide architectural "framework" of the breast. - AKA: Suspensory Ligaments. - Run between the superficial and deep layers of the superficial fascia.

Montgomery Glands

Sebaceous glands seen as small bumps in the areola.

Lobe

Several lobules (TDLUs) make up a breast lobe. *Largest functional unit. - 15-20 lobes in each breast. - One lactiferous Duct emerges from each lobe and travels towards the nipple.

Acini

Smallest functional unit of the breast. *Milk producing gland - Hundreds in each breast - Each acini gives rise to a ductle or terminal duct

Retromammary Space

Space between the posterior margin of the mammary layer and the pectoral muscles. - Contains layer of fat that increases with age, pregnancy, and obesity. - Contains deep layer of superficial fascia. - Allows movement of breast over the chest wall.

Prolactin

Stimulates acinar cells to secrete milk.

Epithelium

The functional tissue - consists of acini, lobules, TDLU's, lobes, and lactiferous ducts.

*Ratio of glandular tissue to fatty tissue

Total body fat : Total body weight

Lactiferous Ducts

Transports milk from acini to the nipple. - Begins with he ductule or Terminal Duct which arises from the acinar cells. - The Duct enlarges slightly beneath the areola forming the lactiferous sinus. - Lined with double layer of epithelial cells: epithelium (inner) and myoepithelium (outer). - Myoepithelium propels milk within the Duct towards the nipple.