Anatomy and Histology of the Breast Flashcards
How are breasts different in non-lactating mothers?
They lack the glandular components and instead have fibrous components.
What do suspensory ligaments do?
They keep the breasts close to the body and prevent sagging.
What are the external components of the breast?
The body
The axillary extension/process that extends to the armpit.
What is the function of areolar glands?
They have sebaceous glands that produce sebum to prevent chaffing of the breasts.
What structures make up the breast internally?
The lobes (consist of lobules containing ductoalveolar components)
4 - 18 lactifrous ducts which meet at the lactiferous sinus.
What are the structures contained in the nipple that can be seen on a cross-section?
Stratified squamous epithelium (keratinized)
Sebaceous glands (Not associated with hair follicles because sebum is secreted directly onto epidermal surface)
Dense CT with smooth muscle bundles. Smooth Muscles contract in response to cold, touch, and sexual arousal.
What does cross section of inactive human breast show on histology?
Mainly duct elements and connective tissue
Cyclical changes in non-pregnant women (Some duct growth, limited lobular alveolar development, fluid accumulation in CT)
What determines breast size?
The amount of fat in the breast.
What changes cyclically in breast?
The lumen of the ducts in the breast fill with fluid if under the stimulation of oestrogen.
What does cross section of active human breast show on histology?
Less CT
Lobulo-alveolar development
Lobules separated by septa of dense CT
Myoepithelial cells are located around alveolar cells to produce milk
What do myoepithelial cells do? What hormone do they respond to?
They are located around alveolar cells and are important for milk production and secretion. (myoepithelial cells contract around the alveolar cells to release milk)
They respond to prolactin
What arteries supply the breasts?
Laterally: Branches from the axillary artery
Medially: Branches from the internal thoracic artery
What veins drain the breasts?
Veins parallel the arteries
What lymph nodes drain the breasts?
Superior and lateral: Axillary nodes receive 75% of drainage.
Medial: Parasternal nodes
Inferior may be some drainage into the abdomen.
What nerves innervate the breast?
2nd to 6th intercostal nerves give anterior and lateral cutaneous branches.
Nipple is innervated by the 4th intercostal nerve.
What embryological tissue are breasts derived from?
Embryologically derived from ectoderm; visible ~4 weeks.
Paired epidermal thickenings extending from mid-axilla to inguinal region -> milk line.
What is witches milk?
Secretory activity of newborn breasts due to exposure to mother’s hormones. This is normal
How does breast size change during puberty?
Due to increase in amount of fat and the proliferation of the ducts.
Rudimentary lobules of alveoli develop in response to progesterone.
What are the stages of growth of breasts during puberty?
1) Preadolscent
2) Breast bud stage - breast and papilla elevated; increase in areolar area
3) Increase in amount of breast tissue; increased pigmentation of areola
4) Areola and papilla form secondary mound above the level of the breast
5) Mature stage; erect papilla projecting above areolar, classification is independent of breast size.
What stimulates fat increase in the breasts?
Oestrogen
What stimulates lactiferous duct growth in the breasts?
Oestrogen
GH
Adrenal steroids
What stimulates rudimentary lobules of alveoli?
Progesterone
What are the stages of breast development during pregnancy to make it ready for lactation?
Proliferation (continues during gestation, breast milk is produced early during gestation to account for premature babies)
Lactogenesis (Secretory activation which occurs 40 - 48 hours after birth)
Lactation (Maintained by milk removal i,e infant demand) [prolactin controls milk production and oxytocin milk ejection]
Involution (Induced by accumulation of milk, loss of epithelial cells, gradual replacement of ducts and alveoli with stromal and fat tissue, involution process takes ~3 months due to lack of milk being consumed by the baby)
How is lactogenesis initiated?
Drop in progesterone and oestrogen at parturition releases the inhibition on secretory alveolar cells. (in other animals prolactin is produced way earlier)
*Increase in milk volume by 50ml/day on day 2 to 500 ml/ on day 4 post-partum
