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.