Breast Structure & Function)

Read from Dr. JPJ’s notes!

Location

• Vertically
• 2-6 ribs
• in mid-clavicular line
• Horizontally
• lateral border of the sternum to the mid axillary line

Mammary bed:

• Pectoralis major
• Serratus anterior
• Rectus abdominis

Retromammary space

• Loose connective tissue
• between base of gland and the fascia covering the muscles
• Gives mobility

Axillary tail (of Spence)

• Tail like projection
• from the upper & outer quadrant of the gland entering the axilla

Nipple

• cylindrical/conical projection
• 4th intercostal space
• in nulliparous females
• pierces by 15-20 lactiferous ducts
• contains
• circular muscle fibres
• erection
• longitudinal muscle fibres
• retraction
• Rich nerve supply
• sensory receptors for sucking

Areola

• pigmented
• pink in nullipara
• irreversible darkening after 1st pregnancy
• outer margin contains
• modified sebaceous glands
• Montgomery’s tubercles
• enlargement of sebaceous glands
• Devoid of hair & subcutaneous fats

Breast

MALE

• have duct system, but do not have alveoli
• some fibro-fatty tissues
• breast tissue does not extend beyond margin of areola
• richly drained by lymphatics
• Gynecomastia common
• Klinefelters (47XXY)
• Endocrine disorders
• decreased liver function
• Carcinoma rare
• but worse prognosis!

FEMALE

• 3 major components:
• Glandular tissue
• tubulo-alveolar glands arranged in lobes
• 15-20 pyramidal love
• drained by single lactiferous duct
• arranged radially
• converge towards areola
• each duct drains a segmental system of smaller ducts & lobules
• each duct dilates towards the end to form the lactiferous sinus
• reservoir for milk
• have myoepithelial cells
• smooth muscle
• for secreting milk
• Fibrous tissue
• support the lobes
• by suspensory ligaments of Cooper
• form septa which anchor the parenchyma to the overlying skin & the underlying pectoral fascia
• Fatty tissue
• fills space
• give rounded contour
• beneath nipple & areola

Functions of breast

• lactation
• synthesis, secretion, ejection of milk
• myoepithelial cells
• resting & lactating (look for photo)
• anatomy
• histology

Embryology

• develop from
• ectoderm (all glands)
• epithelial lining of ducts & alveoli
• mesoderm (fibrous tissue, fats)
• stroma
• develop along milk line/ridges
• Amastia: absense of breast
• Polythelia
• supernumerary nipples found irregularly over the breast and not along the milk ridges
• thelia: nipple, poly: many
• Polymastia
• accessory breasts along the milk line

Changes of structure of breast with age

• Up to prepuberty
• have lactiferous ducts
• no alveoli
• Puberty
• ducts undergo branching
• form solid masses of cells: precursors of alveoli
• Pregnancy
• Alveoli secrete milk & enlarge
• Colustrum: 1st mik (rich in Ig & cholesterol)
• Lactation
• Myoepethelial cells help in milk ejection
• After lactation
• shrinking of alveoli
• return to resting condition

Arterial supply

• Lateral mammary branches
• from lateral thoracic artery of axillary artery
• Superior thoracic artery
• from axillary artery
• Medial mammary branches
• from perforating branches of the internal thoracic artery (2,3,4 spaces)
• Lateral branches
• of 2,3, 4 intercostal arteries

Venous drainage

• Circular venosus
• plexus below areola
• drains into axillary, internal thoracic & intercostal veins
• Communication with internal vertebral venous plexus (of Batson)
• through intercostal & azygos veins
• metastasis by retrograde venous flow to sagittal & transverse sinuses, clavicle, humerus & cervical vertebrae
• no valves, can move in any way

Nerve supply

• Anterior & lateral cutaneous branches
• of 4th & 6th intercostal nerves
• carry motor (skin) & sympathetic nerves (vasomotor)

Lymph node & drainage

• Parenchyma (including nipple & areola)
• drain into
• axillary nodes (70%)
• parasternal nodes
• posterior intercostal nodes
• deep lymphatics
• Skin (excluding nipple & areola)
• outer
• axillary nodes
• upper
• supraclavicular nodes
• inner
• parasternal nodes
• can spread to subdiaphragmatic nodes?
• abdomen
• can spread to ovary
• Krukenberg’s tumour

Clinical anatomy

• Witch’s milk
• baby express milk
• esposed to maternal hormone
• not really milk
• Breast abscess
• improper hygiene during breastfeeding
• Incision of lactiferous ducts
• radial incision
• Carcinoma
• usually arises from epithelium of larger ducts
• Benign fibrodenomas
• usually arise from distal smaller ducts
• Tumour
• retraction of skin & fixation
• retraction of nipple
• Peau d’orange
• pull Cooper’s ligament
• skin pulled back
• lymph duct blocked
• lymph oedema
• Diagnosis of breast cancer:
• mammography
• radical mastectomy
• Breast self examination