The Breast Flashcards
(36 cards)
What hormones are required for complete mammary growth and differentiation
- LH and prolactin from the anterior pituitary. Influence growth of the nipple
- human placental lactogen = responsible for ducal development and differentiation
- oestrogen and progesterone = from the ovaries and placenta. The sex hormones are responsible for lobe and lobule development. Widening of ducts to allow secretory function
- adrenocorticotrophic hormone and human growth hormone from anterior pituitary. Combined with prolactin and progesterone promotes mammary growth
The timeline of breast development
Occurs from embryonic/fetal life all the way through to pregnancy and lactation. Breast structures will continue to bud until the age of 35 years
Differentiation between males and females occurs at puberty when differences in hormonal signalling will give rise to the biological differences between the two sexes
Mammogenesis at 4 gestational weeks
Two milk lines/streaks from axils to groin (thickening of epithelial cells - line of glandular tissue)
Mammogenesis at 7-8 weeks
Milk hills stage = thickening and inward growth into the chest wall of the developing embryo
Mammogenesis at 12-16 gestational weeks
Differentiation into smooth muscle cells of nipple and areola
Epithelial cells develop mammary buds which branch in a tree-like pattern - create alveoli of the glands
Mammogenesis at 28 - 32 weeks
Canalisation of branched epithelial tissue
Primary milk ducts by 32 weeks of gestation
Mammogenesis at 32- 40 weeks
Lobular alveolar structures constraining colostrum will begin to develop = witches milk produced by baby
Ducts open into area which becomes the nipple
The nipple and areola develop and become pigmented
What type of growth is experienced by females in childhood vs puberty
Childhood = isometric growth = develop in same proportions as size of child
Allometric growth = specific changes due to influence of hormones from hypothalamus and anterior pituitary
By 10-12 yrs a girls breast has formed primary and secondary ducts which continue to grow and from club shaped termini
Why do females experience breast discomfort in each reproductive cycle
Due to proliferation and active growth of mammary glands.
Size of the breasts/glandular tissue grow from puberty onwards under influence of oestrogen and human growth hormone
The shaped of breast is controlled by deposition of fat which is controlled by the release of oestrogens in the system
What is the structural anatomy of the breast
Located between the 2nd rib and 6th intercostal space
Comprised of parenchyma and stroma
The nipple openings are continuous with lactiferous ducts which carry out the milk outwards from inside the glandular tissue
Glandular tissues can extend towards the axillary tail of Spence.
What determines the functional capacity of the breast
The quality of the glandular tissue instead of the size of the breast is more important
Those with smaller breasts will produce the same amount of milk to feed child but will feed more regularly
What is the basic secretory unit of the breast
Several alveoli make up a lobule which is connected via a lacterious duct
Each alveolus is made of many lactocytes and on the external border is a layer of myoepithelial cells (smooth muscle) = important in expulsion of milk
The alveoli are in close intact with capillaries - provides nutrients such vitamins and minerals from mothers digestive system
What is the blood supply to the breast to meet its high metabolic demand in pregnancy and lactation
60% is from the internal thoracic/mammary artery
30% is from the lateral thoracic artery
What is the nerve supply to the breast tissue
Branches from the 2nd to the 6th intercostal nerve
What is a tubercle of Montgomery
The areola has openings to it and each one is connected to a tubercle of Montgomery
Within the tubercle there is a true mammary lobule structure and sebaceous glands (babies attach to breast more quickly (olfactory stimulation?)
What occurs in the first stage of lactogenesis
In the first and second trimester: breast development allows for secretion of colostrum/first milk for premature delivery/lactation in miscarriage can be traumatic
What occurs in the second stage of lactogenesis
1-5 days post birth
The baby will receive copious milk secretion regardless of whether mother wants to breastfeed or not
What occurs in the 3rd stage of lactogenesis
Up to 6 months (maintenance of long term milk production)
Initially breast milk production is dependent on the release of prolactin to the mammary glands but later is dependent on concentrations of feedback inhibitor of lactation FIL. When the mother feeds this exits in the milk and therefore concentrations of this reduces
How much should young infants be fed in a 24 hour period
8-12 times
What happens of the levels of major hormones after birth
Oestrogen and progesterone drops
Oxytocin and prolactin levels rise in response to touch, smell and sight of the baby
What constitutes the prolactin receptor theory and how does this explain how milk is produced
Sensory stimulation such as suckling relays information to the hypothalamus which sends prolactin releasing hormones to the anterior pituitary such as
- vasoactive intestinal polypeptide
- oxytocin
Prolactin arrives at breast and binds to its receptor on the lactocyte
More suckling = greater affinity for binding to receptor
Prolactin receptors bind prolactin more effectively when alveoli are empty and as alveoli fill with milk the receptors undergo conformational change which reduces binding affinity
The hypothalamus Down regulates which hormones which inhibit prolactin secretion
Dopamine
Actions/roles of prolactin
Responsible for milk production
Responsive to touch and stimulation
Levels are higher at night
Frequent contact/feeds sets up long term production
Actions/roles of oxytocin
Responsible for milk delivery
Acts on muscle cells in pulsatile action
Levels are higher when the baby is near
Stress can temporarily delay the let down reflex
