The Breast Flashcards
What is mammogenesis?
Development of the breast to prepare for milk production fully completed during pregnancy and lactation. Structures continue to bud until 35 years old.
Where is the breast located anatomically?
Between the 2nd and 6th costal cartilage. It is anterior to the pectoralis major and serratus anterior muscle. Consists of units called the lactiferous ducts lined with epithelial cells called lactocytes.
What are the 2 main regions of the breast?
1)Circular body: main region of the breast containing lobes for milk production
2) Axillary tail
What is the axillary tail?
Extension of breast tissue from the lateral edge of pectoralis major to the axillary line
What is the areola?
Pigmented area surrounding the nipple which contains Montgomery’s tubercules. These are sebaceous oily glands that lubricate the nipple.
What are the components of the breast?
Lobes which consists of lobules.
Lobules contain many sacs called alveoli that produce milk and drain into the lactiferous duct. They dilate at the lactiferous sinus.
What produces milk in the breast?
Lactocytes line the alveoli of the lobules and store and produce milk into alveolar lumen. Myoepithelial cells lining the lobules are stimulated by oxytocin to contract during pregnancy and post-natal.
What separates the lobes of the breast?
Fibromuscular stroma called Cooper’s ligaments which support breast and connect breast to the skin and to the pectoralis fascia.
What is the pectoral fascia?
Flat sheet of connective tissue on the pectoralis major muscle which is an attachment point for Cooper’s ligament to connect to breast.
What is the retromammary space?
Potential space of loose connective tissue between the breast and pectoralis fascia
What is the arterial blood supply to breast?
Branches of
1) Axillary Artery
2) Subclavian artery
The mammary glands are highly vascularised with a high metabolic rate. Venous drainage is the same.
What are the branches of the axillary artery?
Acrothoracic artery
Lateral thoracic artery
-> Supply lateral part of breast along with lateral posterior intercostal artery
What are the branches of the subclavian artery?
Lateral posterior intercostal artery
-> Supplies lateral aspect of breast
Internal thoracic artery
-> Supplies medial aspect of breast
What is the major arterial supply to breast?
1) 60% by Internal thoracic artery from subclavian artery
2) 30% by lateral thoracic artery from axillary
What is the lymphatic drainage of the breast tissue?
Axillary nodes
Parasternal nodes
Posterior intercostal nodes
What is the lymphatic drainage of the skin of the breast?
Axillary nodes,
Deep cervical nodes
infraclavicular nodes
What is the nerve supply to the breast?
Branches of the 4th to 6th thoracic intercostal nerve. They regulate the tone of blood vessels and smooth muscle
What is the Tubercule of Montgomery?
Sebaceous oil glands which keeps the nipple lubricated.
When does the breast begin to develop in embryological development?
During W4, where ectodermal mammary specific progenitor cells form.
Which germ layer gives rise to mammary gland?
Ectoderm
Which germ layer gives rise to nipples and aereola?
Mesoderm
How does mammogenesis begin in embryological development?
Mammary progenitor cells form 2 thickened lines of ectoderm which migrate down the mamillary line from axillae to thorax. They thicken and regress/atrophy back to thoracic region.
What is the mammary line?
Thickenings of the epidermis along the front surface of the body where the mammary glands will form and proliferate. It also contains the mammary pit.
What is the mammary pit?
Depressed region along the mammary line where the future nipple develops
What happens following regression of mammary buds?
Milk hills stage where mammary line grows inward into the mesenchyme of the chest wall.
Mesenchyme differentiates into smooth muscle of nipple and aerola. Epithelial cells will join the mammary buds to form the lactiferous ducts and alveoli
What happens in the third trimester in embryological development of the mammary gland?
Mammary line becomes depressed to form mammary pit, where the future nipple will form. Lactiferous ducts and alveoli drain into this region and may produce colostrum.
Invagination of ectoderm here stimulates mesoderm proliferation for nipple and areola to develop and become pigmented
Which hormones in the anterior hypophysis stimulate mammogenesis?
Occurs from puberty onwards:
1) LH
-> Promotes the synthesis and secretion of oestrogen and progesterone
2) Prolactin
-> Promotes the growth of mammary alveoli and growth of the nipple produces milk.
What is prolactin?
Synthesised by lactotrophic cells in anterior hypophysis which stimulates gland growth and proliferation.
It is structurally similar to growth hormone and lactogen. It is inhibited by dopamine.
Which hormones directly produced by the placenta stimulate mammogenesis?
1) Human placental lactogen
2) Oestrogen
3) Progesterone
What is human placental lactogen?
Aka Somatomammatrophin
Similar structure to growth hormone. Role is to regulate metabolism and insulin sensitivity for energy supply to the foetus.
What is the role of HPL in mammogenesis?
Produced during pregnancy for ductal and alveolar growth and differentiation. It mimics prolactin and growth hormone for the enlargement of the breast, nipples and areola.
What is the role of progesterone in breast development?
Growth of alveoli and lobules to widen.
What is the role of oestrogen in breast development?
Growth and development of milk ducts to widen.
What are the accessory hormones?
Hormones which work with prolactin and progesterone to promote mammary gland growth.
What are the examples of accessory hormones?
Human growth hormone
Adrenocorticotrophic hormone
What are the features of breast tissue at birth?
Breast tissue is confined to the nipple area
What are the features of breast tissue pre-puberty?
Mammary gland undergoes limited general growth
What are the features of breast tissue during puberty?
A breast bud develops under the nipple. Areola grows in size due to oestrogen and growth hormone and becomes more pigmented. Rise in oestrogen causes fat deposition
What is lactogenesis?
Changes in mammary gland epithelium for secretion of milk and maturation of alveolar cells.
What is the first stage of lactogenesis?
At 16 weeks of gestation, high levels of progesterone induces alveolar cells of the breast produce colostrum.
What is colostrum?
Thick yellowish fluid which is nutrient rich and filled with immunoglobins. Provides low volume milk to help the newborn regulate suckling and a healthy gut microbiome.
What suppresses milk production in pregnancy?
Oestrogen and progesterone.
What is the second stage of lactogenesis?
Copious milk secretion between 32 hours and 96 hours after birth due to low progesterone and elevated prolactin along with swelling of the breast
What is the third stage of lactogenesis?
Maintenance of milk production which is initially dependent on delivery of prolactin. Eventually by regular removal of milk and stimulation of nipple for triggering prolactin release.
What prevents milk production?
Dopamine
Substance in milk called FIL (feedback inhibitor of lactation) which accumulates with milk secretion.
What happens if milk is not removed?
Elevated intramammary pressure and accumulation of FIM which can lead to drop in prolactin and mastitis.
How does growth occur in childhood?
Isometric growth where development is proportional.
How does growth occur for girls in puberty?
Allometric growth: specific changes to the organ tissues due to influence of hormones from the hypothalamus and anterior pituitary.
What happens after birth?
Drop in oestrogen and progesterone levels after birth.
What does interaction with the baby stimulate?
Prolactin and oxytocin levels increase and initiate mothering behaviours.
Which hormones stimulate mothering behaviour?
Prolactin and oxytocin
How is oxytocin involved in mood?
Lowers blood pressure and cortisol, pain sensitivity and boosts immune system. Proximal to amygdala nucleus which improves sleep and associated with positive emotions.
What is the role of oxytocin?
Pulsatile action on muscle cells for myoepithelial contraction for milk delivery. Levels are higher when the baby is near and released upon suckling.
What is the role of prolactin?
Responsive to stimulation and touch via suckling. It is higher at night and frequent feeding means long term production.
What is the prolactin theory?
Prolactin binds to receptors on the lactocyte. The efficiency of binding is controlled by the frequency of suckling and when alveoli are empty
How many times do infants feed?
8-12 times in 24 hours
What is the role of oxytocin?
Increased levels when abby is near. Stimulates pulsatile action of myoepithelial cells for milk delivery.
What does breastmilk contain?
Contains enzymes and anti-inflammatory, Bifidus factor, WBC, hormones, Oligosaccharides, viral fragment, transfer factor, IgA
What are the benefits of breastfeeding?
Higher RBC count in babies, builds stronger immune system and microbiome, easily digested, contains micronutrients, species specific to baby.
What is Bifidus factor?
Molecule in breast milk which enhances growth of lactobacillus bifidus in the intestines for acidic environment in intestines against bacteria.
What is transfer factor?
Small immune messenger molecules and assists the baby in absorbing the nutrients.
What is the role of oligosaccharides?
Carbohydrates which prevents pathogens to attaching to gut wall.
What does formula milk contain?
Vitamins and minerals, proteins, carbohydrates, fats, water.
What are the issues with formula milk?
Highly processed
GI issues
Preparation
Unsterile
What are the common causes of issues in breastfeeding?
Nipple trauma
Breastfeeding management
Poor positioning and attachment
What is mastitis?
Inflammation of the breast tissue. Majority is not associated with infection which affects lactating women, commonly when there is abrupt weaning.
What causes non-infective mastitis?
Poor positioning and attachment means there is inadequate removal of milk leads to milk stasis. This back pressure leaks into the interstitial tissues via paracellular pathways causing inflammation.
What are the features of non-infective mastitis?
Swelling and flu with sudden onset. More painful before feed and relief post-feed.
How is mastitis treated?
Correct positioning and lactating for breastfeeding, milk removal, analgesics, breast massage during feeding.
What is the cause of infective mastitis?
Staphylcoccus/Streptococcal aureus or E.Coli infection
Progression of non-infective mastitis.
What are the features of infective mastitis?
Pyrexia, rigor, discharge of pus or blood from nipple.
How is infective mastitis treated?
Warm compress and warm showers to increase milk flow. Analgesics and increases fluid intake and correct positioning.
