Embryo and neonate weeks 3-4
✓- A primitive milk streak running bilaterally from axilla to groin
Embryo and neonate
Weeks 4-5
✓- Milk streak becomes mammary milk ridge or milk line . Paired breasts develop from
this line of glandular tissue
Embryo and neonate weeks 7/8
✓- Thickening and inward growth into chest wall continue
Embryo and neonate weeks 12-16
✓- Specialized cells differentiate into smooth muscle of nipple and areola
- epithelial cells develop into mammary buds
- epithelial branches form to eventually become alveoli
Embryo and neonate weeks 15-25
✓- Epithelial strips are formed which represent future secretory alveoli
- lactiferous ducts and their branches form and open into a shallow epithelial depression
known as the mammary pit
- the mammary pit becomes elevated forming the nipple and the areola
- an inverted nipple results when the pit fails to elevate
Embryo and neonate
After 32 weeks
✓- A lumen ( canal ) forms in each part of the branching system
Embryo and neonate
Near term
✓- 15-25 mammary ducts form the fetal mammary gland
Neonate
✓- - galactorrhea ( witch's milk ) : secretion of colostral like fluid neonate mammary
tissue resulting from influence of maternal hormones
- recommended not to express neonatal colostrum because this might lead to mastitis in
the newborn
Puberty
✓- 1. Breasts keep pace with general physical growth
2. Growth of the breast parenchyma produces ducts , lobes, alveoli, and surrounding fat
pad
3. Onset of menses at 10-12 continues development of the breast
- primary and secondary ducts grow and divide .
,- terminal end buds form , which later become alveoli (small sacs where milk is secreted
) in the mature breast
- proliferation and active growth of duct tissue takes place during each period and
continues to about 35 years of age
Pregnancy breast
Development
✓- 1. Complete development of mammary function occurs only in pregnancy
2. Breast size increases , skin appears thinner , and veins become more prominent
3. Areola diameter increases - Montgomery glands enlarge , and nipple pigment
darkens
Anomalies in breast
Development
✓- 1. Illnesses, chemo, therapeutic radiation to the chest , chest surgery , or injuries to
the chest might affect development
2. Programmed apoptosis ( cell death ) has been suggested as one reason for lower
breast cancer rates in bf women
Exterior breast
✓- Located in the superficial fascia ( fibrous tissue beneath skin) between 2nd rib and
6th intercostal space
Tail of spence
✓- Mammary glandular tissue that projects into the axillary region
- distinguished from the supernumerary tissue because it connects to the duct system
- potential are of milk pooling and mastitis
Skin surface of
Breast contains
✓- Nipple, areola, and Montgomery glands
Size
✓- Not related to functional capacity
Gives breast it's
Shape and size
✓- Fat composition
Size may indicate
✓- Milk storage potential
Nipple
✓- Conical elevation located slightly below center of areola
Average diameter of
,Nipple ✓- 1.6cm
Average length of
Nipple ✓- 0.7 cm
Hoe many milk
Duct openings
In nipple ✓- 5-10
Smooth muscle fibers
Function as a ✓- Closure mechanism to keep milk from continuously leaking from the
nipple
The nipple is
Densely innervated
With ✓- Sensory nerve endings
What makes the nipple erect when contracted ✓- Longitudinal inner muscles and outer
circular and radial muscles
Venostasis ✓- Slows blood flow and decreases surface area
Areola ✓- Dark pigmented area that surrounds the nipple - elastic like nipple
Average diameter
Of areola ✓- 6.4 cm
Areola is constructed
Of ✓- Smooth muscle and collagenous , elastic , connective tissue fibers in radial and
circular arrangement
How does the nipple
Aid infant in latching ✓- Becomes smaller , firmer, and more prominent
What happens to
Areola in pregnancy ✓- Darkens and enlarges
Where are montgomerys tubercules located ✓- Around the areola
The Montgomery tubercules contain ✓- Ductal openings of the sebaceous and
lactiferous glands and sweat glands
What happens to Montgomery glands in pregnancy ✓- They enlarge and resemble
small , raised pimples
, The Montgomery glands secrete ? ✓- A substance that lubricates and protects the
nipple
Some secrete a small amount of milk
Secretions of the Montgomery gland may produce ? ✓- A scent to help the infant locate
the nipple
Parenchyma are ✓- Functional parts of the breast
Alveoli are ? ✓- ( acini) are the basic components of the mature mammary gland .
Secretory cells in which the milk is produced
Lactocytes ( specialized epithelial cells ) that line the interior of the alveolus do ? ✓-
Absorb nutrients , immunoglobulin, and hormones from the mothers bloodstream to
compose milk
Prolactin receptor sites in the lactocytes Allow? ✓- Prolactin to be absorbed from the
blood and enter into the alveoli to stimulate milk production
Myoepithelial cells do what ? ✓- Encase the alveoli and contact in response to oxytocin
to eject milk into ductules
How many lobes does the breast contain ✓- 15-25 that carry the milk through the
ductules from the alveoli to the nipple
Each lobe contains how many alveoli ✓- 10-100 in an intricate system of ductules that
branch out from the lobes to converge into lactiferous ducts behind the nipple
Ultrasound of lobes shows? ✓- Connections between lobes
What do ducts do in response to milk ejection ✓- Temporarily widen
What do ducts do in response to duct drainage ✓- Narrow
What happens to milk that is not removed ✓- It flows backward up the collecting ducts
Lactiferous ducts lead to ✓- 5-10 openings in the nipple
Stroma ✓- Supporting tissues of the breast
Stroma include ✓- Connective tissue , fat tissue, blood vessels , nerves, and lymphatics
Coopers ligaments are ✓- Suspensory ligaments running vertically through the breast
What do coopers ligaments do ✓- Attach the deep layer of subcutaneous tissue to the
dermis layer of the skin