MAMMO 2 - Internal Breast Anatomy

• Mammary glands

• lobes

• lobules

• ductal systems

• connective tissues

Main components of internal breast anatomy

Internal breast

Has crucial role in milk production and nourishment during lactation

• Camper’s

• Scarpa’s

Layers of Superficial fascia

• Superficial fascia

  • Deep layer

  • Superficial layer

Fascial Layer of the Breast

Superficial fascia

Fascial Layer

• thin connective tissue encircling breast

Deep layer

Superficial Fascia Layer

• sits atop pectoralis muscle

Superficial layer

Superficial Fascia Layer

• sits just under skin

Retromammary Space

• aka Subglandular Space

• Potential space between breast tissue & pectoralis fascia

• Allows breast movement

• Lies between fatty matrix & glandular tissue

• Fibrous tissue

• Glandular tissue

• Adipose tissue

Tissues of the Breast

Fibrous tissue

Tissues of the Breast

• holds breast tissue in place

Glandular tissue

Tissues of the Breast

• makes milk (lobes)

Ducts

tubes carrying milk to nipple

Ducts

Component of the TDLU responsible for transporting milk.

Fibroglandular tissue

Tissues of the Breast

• fibrous + glandular

Adipose tissue

Tissues of the Breast

• fills spaces; gives breast size & shape

Lobes

Feel like round, movable lumps (sometimes tender)

15–20 lobes

How many lobes per breast?

20–40 lobules

How many lobules for each lobes?

Lobules

attached to small milk ducts

Lobules

Component of the TDLU responsible for milk production.

Lobules

Smaller units within lobes that contain milk-producing glands.

Lobes

composed of glandular structures called lobules which empty via ductules into lactiferous ducts

Lumen

The hollow space inside ducts or acini where milk flows.

Acinus

Cluster of cells that produce milk.

Stromal ECM

Supports the lobular stroma and helps maintain tissue architecture and signaling.

Stromal ECM

A network of proteins and molecules that surround cells, helping with tissue structure, signaling, and cell behavior.

Extracellular Matrix

the non-cellular component that provides structural and biochemical support

• Lobe

• Lobule

• Terminal Ductal Lobular Unit

• Extralobular Duct

• Lactiferous Duct

Structural Units involved in milk production and transport

Extralobular Duct

Ducts outside the lobules that carry milk toward the nipple.

Intralobular Duct

Ducts within the lobule that carry milk from alveoli to the extralobular ducts.

Lactiferous Duct

• draining each lobe of the breast pass thru the nipple and open onto its tip as 15-20 orifices

• contains ampulla near its end

• Lobules

• Ductules

• Lactiferous duct

• Lactiferous sinus

• Nipple

Order of milk transport

Lobular Stroma

Connective tissue surrounding the lobules, providing structural support and housing blood vessels and immune cells.

Ductules

Small ducts that carry milk from lobules to larger ducts.

Ampulla

reservoir of milk or abnormal discharge

Lactiferous Duct

channels milk from each lobe to the nipple.

Lactiferous Sinus

• aka Ampulla

• A widened part of the duct near the nipple that acts as a reservoir for milk or discharge.

Nipple

The external opening where milk exits the body.

Secretory Cell

Produces milk within the alveolus.

Lactiferous Duct

Final ducts that deliver milk to the nipple.

Terminal Ductal Lobular Unit

The most common site for breast cancer development; includes lobules and ducts.

Terminal Ductal Lobular Unit

• Includes terminal ducts, ductules, lobules, stroma

• Site of hormonal changes

• Origin of most breast cancers

• Ducts: transport milk

• Lobules: produce milk

Stroma

• Connective tissue supporting organs

• Connects with parenchyma cells (blood vessels, nerves)

Cooper’s Ligaments

• Found under breast skin, through & around breast tissue

• Connect to tissue around chest muscles

• Function: maintain breast shape & structure, prevent sagging

Epithelial Cell

Line the ducts and lobules; involved in secretion and absorption.

Myoepithelial cells

Contracts to push milk out of the alveolus into the ducts.

Contractile Unit

Functional unit involving myoepithelial cells and alveoli for milk ejection.

Alveolus

• aka Acinus

• The milk-producing unit within the lobule.

Myoepithelial cells

Contract to help push milk through ducts.

Adipocyte

Store fat and contribute to the breast’s shape and energy storage.

Fibroblast

Produce extracellular matrix and collagen, supporting tissue structure.

Dendritic Cell

Present antigens to T cells, initiating immune responses.

Macrophage

Immune cells that engulf pathogens and debris.

CD8+ T Cell

Immune cells that help fight infections and may play a role in cancer surveillance.

Myoepithelial cells

form protective sheet between epithelium & stroma; contractile function

Basement membrane

Thin layer that separates epithelial cells from underlying tissue; important for structural integrity and signaling.

Basement membrane

between epithelium & mesenchymal tissue; barrier against tumor infiltration

Ducts

• Thin tubes carrying milk from lobules to nipple

• ~10 ____ systems per breast

• Each has its own nipple opening

Lymphatic System

• “Sewerage system” of the body

• Maintains tissue fluid levels by draining leaked fluids

• Supports immune responses

• In breast: regulates fluid balance, filters harmful substances

• Clinical significance: cancer spreads through lymphatic route

• Metastatic dissemination: mainly via lymphatics

• Includes Berg’s Levels

• Axillary (85%)

• Internal Mammmary/Parasternal (10%)

• Others (5%)

Lymph Node Stations

• Anterior (Pectoral)

• Posterior (Subscapular)

• Central

• Lateral (Humeral)

• Apical

• Interpectoral (Rotter’s nodes)

Axillary Nodes

• Supraclavicular

• Cephalic / Deltopectoral

• Posterior Intercostal

• Subdiaphragmatic

• Subperitoneal

Other Nodes

Berg’s level of axillary lymph nodes

• these are defined according to the surgeon’s approach to the axillary nodes during dissection.

• pectoralis major

• 3 levels

Level 1

• Location: Lateral to the lateral border of the pectoralis minor.

• Includes: Anterior (pectoral), posterior (subscapular), and lateral (humeral) lymph nodes.

• Function: Primary drainage from the breast and upper limb.

Level 2

• Location: Directly under the pectoralis minor.

• Includes: Central axillary nodes.

• Function: Receives lymph from Level I nodes.

Level 3

• Location: Medial to the pectoralis minor, near the apex of the axilla.

• Includes: Apical and infraclavicular nodes.

• Function: Final filtering station before lymph enters the subclavian vein.

• Axillary artery

• Internal thoracic

  • 2nd to 4th anterior intercostal arteries

Blood Supply

• Superior thoracic

• Thoracoacromial artery

• Lateral thoracic artery

• Subscapular artery

Axillary artery

Internal thoracic

perforating branches to the anteromedial breast

Anterior intercostal arteries

second perforating artery is usually the largest; supplies the upper region of the breast, the nipple, areola, and the adjacent breast

Venous drainage

• carries deoxygenated blood back to heart for reoxygenation

• Essential for circulation

Venous drainage

• veins follow the arteries

• first converge around the nipple to form an anastomotic venous circle & then form 2 sets of veins.

  • superficial

  • deep

• intercostal veins communicate with the vertebral veins. this route is responsible for metastasis of CA breast to vertebral bodies, sacrum and pelvic bones

Superficial veins

drain into internal thoracic vein & superficial veins of the lower part of the nect

Deep veins

drain into internal thoracic, axillary & posterior intercostal veins

• Internal Jugular vein

• Subclavian vein

• Celiac vein

• Axillary vein

• Lateral thoracic vein

• Internal thoracic vein

Venous drainage

Nerve Supply

• Provides sensation: touch, pressure, temperature, pain

• Sensitivity varies (hormonal changes, surgeries, medical conditions)

Nerve Supply

• 4th - 6th intercostal nerves by their anterior & lateral cutaneous branches

• the nipple is supplied from the anterior branch of the lateral cutaneous branch of t4

  • forms an extensive plexus within the nipple; its sensory fibers terminate close to the epithelium as free endings, Meissner corpuscles and Merkel disc endings. These are essential in signaling suckling to the CNS.

• secretory activities of the gland are largely controlled by ovarian and hypophyseal hormones rather than by efferent motor fibers

• the areola has few sensory endings

Pectoral Muscles

• Not part of breast tissue, but support structure & appearance

• Functions:

  • Support breasts & maintain position

  • Contribute to chest contour/firmness

  • Aid posture (balance shoulders/upper body)

  • Respond to exercise (push-ups, presses) → improved tone & aesthetics

  • In surgery (augmentation, reconstruction): implants may be placed under pecs

Support and Structure

Provide foundational support to the breasts and help maintain their position on the chest wall.

Aesthetics

Well-developed pectoral muscles improve firmness and contour in the chest, indirectly affecting breast appearance.

Posture

Assist in balancing shoulders and upper body, helping maintain good posture that affects how breasts are carried.

Exercise and Fitness

Exercises such as chest presses and push-ups strengthen and tone these muscles, enhancing chest appearance.

Recovery

In breast augmentation or reconstruction, implants may be placed beneath these muscles (submuscular placement).