Breast Anatomy/Embryology - Board Review Flashcards
Smallest functional unit of the breast?
Acini cell
When do the mammary ridges develop in an embryo?
5-6 weeks
What is the path of the mammary ridge along the ventral aspect of an embryo?
Base of the forelimb (future axilla) to the base of the hindlimb (inguinal area)
What is the result of incomplete involution of the mammary ridge?
accessory breast tissue and super numerary nipples
What is the difference between accessory and ectopic breast tissue?
Accessory breast tissue is along the mammary ridge and ectopic is elsewhere
What is polymastia?
Accessory breast tissue, usually found in axilla
What is polythelia?
Accessory nipples (along the milk line)
What is amazia?
Nipple development without breast development
What is athelia?
Breast development without nipple development
Is amastia more common unilateral or bilateral?
Unilateral
What is the cause of unilateral amastia?
Arrested mammary ridge development during the sixth week of fetal development
Where is the most common site of aberrant breast tissue?
axilla
Which is more concerning, unilateral or bilateral inverted nipples?
Unilateral may be associated with cancer; bilateral is usually associated with benign congenital conditions.
What is the most common site for supernumerary nipples?
Inframammary area
The breast overlies which ribs?
2-6
Each cluster of alveoli leads to a milk duct that empties into a lactiferous sinus. Each lactiferous sinus drains into one lobe of the breast.
How many lobes are in the breast?
15-25 lobes
What is the difference between a breast lobule and a breast lobe?
Lobes consist of multiple lobules and their respective interlobular ducts. Lobules are composed of glandular tissue containing acini cells that produce milk.
Which quadrant of the breast contains the most glandular tissue?
Upper outer
What is the most common bacteria cultured from breast tissue?
Staph epidermidis
Which vessel provides the dominant blood supply to the breast?
Internal mammary
The internal mammary artery is a branch of which vessel?
Subclavian artery (left) and brachiocephalic (right)
Usually, what vessel is the largest artery entering the pectoralis major muscle and the overlying breast parenchyma?
The second intercostal mammary perforator
Name three branches of the axillary artery (from medial to lateral) that serve as blood supply to the breast
Thoracoacromial, lateral thoracic, and thoracodorsal
During dissection of the axilla, if you cut the intercostobrachial nerve, where will you lose sensation?
upper medial aspect of the arm and axilla
The intercostobrachial nerve is a branch of which nerve?
Lateral branch of the second intercostal nerve
Axillary nodes are noted as level I, level II and level III. What anatomic structure determines their level?
Pectoralis minor muscle
Where are Level I axillary nodes located?
Lateral/below pectoralis minor muscle
Where are Level II axillary nodes located?
Behind pectoralis minor muscle
Where are Level III axillary nodes located?
Medial/Above border of pectoralis minor muscle
Where is a Rotter’s node?
Interpectoral
What is the primary innervation of the NAC?
Lateral branch of the fourth intercostal nerve
What is the course of the lateral branch of the fourth intercostal nerve?
It pierces the deep fascia in the mid axillary line and takes an inferomedial course within the pectoral fascia. On reaching the mid clavicular line, it turns 90° and continues through the glandular tissue toward the posterior surface of the nipple.
What is the normal diameter of the NAC?
35-45mm
What is the dominant blood supply to the NAC?
perforators from the internal mammary artery
What is the function of the Montgomery glands?
They are sebaceous glands that produce a waxy substance to assist with lubrication and protection of the NAC
What ligaments provide support to the breast tissue and what do they connect?
Cooper’s ligaments; between deep pectoralis fascia and the skin (dermis)
What are the borders of the breast?
Latissiumus dorsi (lateral), clavicle(superior), lateral sternum(medial), IMF (inferior) pectoralis major (deep)
What is the major component of the anterior axillary fold?
Pectoralis major muscle
What is the origin of the pectoralis major muscle?
Medial sternal half of the clavicle and lateral aspect of the sternum/costochondral region, from sternal notch down to the 6-7 costal cartilage
The insertion of the pectoralis major muscle lies between which muscles?
coracobrachialis (posterior) and deltoid (anterior)
Which nerve provides motor innervation to the lateral and inferior pectoralis major muscles?
Medial pectoral nerve
Serratus anterior origin and insertion, innervation
Origin: the costal attachments of the anterolateral aspects of the first through 8th ribs.
Insertion: Deep medial surface of the scapula
Innervation: Long thoracic nerve
What is the clinical manifestation of injury to the long thoracic nerve?
Winged scapula
Where is the long thoracic nerve located?
Positioned laterally, superficial to the external surface of the serratus anterior muscle in the mid axillary line
Which nerves supply innervation to the medial breast?
The 2nd-6th intercostal nerves
What is Poland Syndrome ?
Associated with congenital absence of the pectoralis major muscle, usually sternal component, and breast/areolar hypoplasia, costal cartilage and rib defects, hypoplasia of the subcutaneous tissues of the chest wall, brachysyndactyly
Following efferent lymphatic drainage pathway of the breast, what are the nodal basins in order?
Deep pectoral, subscapular, central axillary, apical axillary, supraclavicular nodes
If lymphatic drainage takes a medial pathway (vs draining into the axilla), what is the primary nodal basin?
Internal mammary/parasternal nodes
T/F: Axillary nodes drain the lateral breast and medial nodes drain medial breast?
FALSE. Both nodal basins receive drainage from the whole breast
Which hormone is principally responsible for ductal development and maintenance of the glandular elements during reproductive years?
Estrogen
Which hormone is principally responsible for lobular development and differentiation of the epithelial cells?
progesterone
Which hormone stimulates the differentiation of milk-producing components?
Prolactin
Which hormone, produced by the pituitary gland, causes ductal contraction with lactation?
Oxytocin
What tanner stage is the adult breast?
Tanner 5
What is the etiology of a congenital inverted nipple? What is its incidence?
Failure of the mammary pits to elevate above the skin during infancy; 2-4%
What are the normal measurements for a non-ptotic breast?
Location of NAC
SN to Nipple
Nipple to IMF
Above IMF
17-21cm
7-8cm
What is the average diameter and projection of the nipple?
5-8mm
5mm
What is the anatomic abnormality with tuberous breast deformity?
NAC hypertrophy, constricted breast/lower pole, herniation of the breast tissue into the NAC, high IMF
