Breast Physiology and Benign Diseases 1

Question 1

Describe breast development up to week 12.

Answer 1

• —5th week of fetal development
  
  • —Bilateral ectodermal ridges originating from the axilla to the inguinal region develop into 15-20 buds
• —7th week
  
  • —Buds undergo apoptosis except for a single pair at the 4th-5th intercostal space called the primary mammary buds
  • —Breast development begins as these buds penetrate into underlying mesoderm
• —12th week
  
  • —Primary buds develop into secondary buds which will eventually form into mammary lobules

Question 2

Describe breast development from weeks 12 to birth.

Answer 2

• —20th week
  
  • —Mammary ridge penetrates the mesoderm and sending radial ingrowths into the breast
  • —Areola begins to develop
• —2nd and 3rd trimester
  
  • —Sweat, sebaceous, and apocrine glands develop into Montgomery glands
  • —Lumina develop within the mammary buds developing into the lactiferous ducts, a mammary pit, and eventually a nipple in infancy
• —After birth
  
  • —Protrusion of the nipple and development of terminal ducts

Question 3

Describe breast development from birth to 2 years.

Answer 3

• —At birth
  
  • —15-20 radial mammary lobes
  • colostrum within the lactiferous ducts due to placental hormones results in normal milky discharge post partum days 4-7
• —From birth-2years
  
  • —Further branching and terminal lobule development occurs
• —From 2 years-thelarche
  
  • —No further development

Question 4

What is the breast development during puberty?

Answer 4

• —Puberty begins between ages 8-12 years
  
  • —Hypothalamus releases increased GnRH
  • —Increased secretion of FSH and LH from the pituitary
  • —Leads to maturation of the ovarian follicles resulting in production of estrogen and progestins
  • —Mammary ductal epithelium and stroma proliferate under ovarian estrogen
  • —Terminal duct lobules, collecting ducts and breast buds proliferate
  • —Vascular and connective tissue proliferate increasing breast size—

Question 5

What are the important factors of complete breast development?

Answer 5

• —Complete breast development requires:
  
  • insulin, cortisol, thyroxine, prolactin and GH
  • adequate body fat: 16-24% to maintain normal cycles
  • adequate sleep: gonadotropins released during sleep cycles required for nl menstrual cycles
  • exposure to sunlight: optimizes pituitary secretion of gonadotropins
• —Breast development stops 2 years after onset of menarche

Question 6

Describe the Tanner staging of breast development.

Answer 6

• —Stage I (Preadolescent):
  
  • —Papilla elevation above the level of the chest wall.
• —Stage II (Breast budding):
  
  • —Breast and papilla elevation, along with increased areola diameter.
• —Stage III:
  
  • —Ongoing enlargement of the breasts and areola.
• —Stage IV:
  
  • —Elevation of the areola and papilla above the breast mound.
• —Stage V (Mature breast):
  
  • —Elevation of the papilla with regression of the areola.

Question 7

Describe surface breast anatomy.

Answer 7

• Spans from 2nd intercostal space to 6th or 7th intracostal fold at the level of the inframammary fold
• Laterally - begins at sternum and extends to mid-axillary line
  
  • axillary tail of SPence extends to theh axilla
• Breast divided into four quadrants:
  
  • upper outer
  • upper inner
  • lower outer
  • lower inner
• Upper quadrant is most fibroglandular and most frequent area for tumors of the breast
• Nipple is at the 4th intercostal space with multiple sensory nerve endings
  
  • includes Ruffini corpuscles and Krause end bulbs
  • areola has sebaceous and apocrine sweat glands as well as Montogmery glands along periphery
  • radial smooth muscle extends toward the dermis of the nipple and lead to the nipple erection with stimulation

Question 8

Describe cross sectional breast anatomy.

Answer 8

• Thinnk skin with hair follicles and sebaceous and eccrine glands
• Underneath skin is subcutaneous fat
  
  • superficial fascia within is fibroglandular breast tissue
• Deep fascia below fibroglandular layer and is anterior to pectoralis major
  
  • Cooper’s ligaments attach to superficial and deep fascias to provide support
• Fibroglandular tissue (breast parenchyma) is composed of 15-20 lobes, each with 15-20 lobules and consistin gof 10-100 alveoli
  
  • each lob with minor interlobular ducts that drain into major lactiferous ducts
  • about 10 major collecting milk ducts open into the nipple

Question 9

Describe the blood supply of the breast.

Answer 9

• —Arterial blood supply:
  
  • —Internal mammary artery 60%
  • —Lateral thoracic artery 30%
  • —Minor contributions from thoracoacromial, intercostals, subcapsular, and thoracodorsal arteries
• —Venous drainage:
  
  • —Courses towards the axilla along the same path as the arteries
  • —Circulus venosus: an anastamotic circle of veins underlying the nipple-areolar complex

Question 10

What is the sensory inntervation of the breast?

Answer 10

• —3rd-6th intercostal nerves, lateral and ant cutaneous branches
  
  • —majority of breast
• —Supraclavicular nerve, ant cutaneous branches
  
  • —skin of the upper portion of the breast
• —Intercostobrachial nerve is the lateral cutaneous branch of the 2nd intercostal nerve
  
  • —medial aspect of the upper arm

Question 11

Describe the lymphatics of the breast.

Answer 11

• —Axillary lymph nodes (75%)
  
  • —Level I: Lateral to the pec minor
    
    • axillary vein, external mammary, scapular
  • —Level II: Superficial and deep to the pec minor
    
    • central, Intra pectoral (Rotter’s nodes)
  • —Level III: Medial to the pec minor
    
    • —subclavicular
• —Internal mammary lymph nodes
  
  • medial aspect of the breast—