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