The Anatomy of Breast

1. 1
© Garaka Rabel – 2009
The Breast

a. Situation and deep relations
b. Structure
c. Blood supply
d. Nerve supply
e. Lymphatic drainage
f. Development
g. Human milk


1. Situation and deep relations
a. Lies in superficial fascia of the pectoral region (except for tail)
b. Axillary tail of Spence pierces the deep fascia & lies in the deep fascia
c. Extent
i. Vertically; 2
nd
to 6
th
ribs
ii. Horizontally; lateral border of sternum to the mid-axillary line
d. Deep relations
i. Pectoral fascia: the deep fascia which the breast lies on
ii. Muscles which lies deeper to the breast
1. Pectoralis major
2. Serratus anterior
3. External oblique
iii. Retro mammary space: loose areolar tissue which separates the breast from the
pectoral fascia

2. 2
© Garaka Rabel – 2009
2. Structure

a. The skin
i. Nipple
1. Conical projection
2. Just below the centre of the breast
3. At the level of 4
th
intercostals space
4. Pierced by 15 to 20 lactiferous ducts
5. Contains circular smooth muscles : make the nipple stiff
6. Contains longitudinal smooth muscles : make the nipple flatten
7. Has few modified sweat & sebaceous glands
8. Rich in nerve supply
9. Has many sensory end organs at the termination of nerve fibres
10. Devoid of hair

3. 3
© Garaka Rabel – 2009
ii. Areola
1. Skin surrounding the base of the nipple
2. Pigmented circular area
3. Rich in modified sebaceous glands (particularly at its outer margin)
a. Become large during pregnancy & lactation (raised tubercles of
Montgomery)
b. Produce oily secretions
i. Lubricate nipple & areola
ii. Prevent them from being cracking during lactation
4. Contain some sweat glands & accessory mammary glands
5. Devoid of hair


b. The parenchyma
i. glandular tissue
ii. 15 to 20 lobes
iii. each lobe is a cluster of alveoli
iv. drained by a lactiferous duct
v. lactiferous ducts converge towards the nipple & open on it
vi. each duct has a dilation called a lactiferous sinus near its termination
vii. Histology of parenchyma
1. Alveolar epithelium
a. In resting phase : simple cuboidal epithelium
b. During lactation :
i. Simple columnar epithelium
ii. Distended alveoli may appear cuboidal due to stretching
(but much larger than those in the resting phase)

2. Smaller ducts : simple columnar epithelium
3. Larger ducts : stratified columnar epithelium (2 or more layers)
4. Terminal parts of lactiferous ducts : stratified squamous keratinized
epithelium
5. Myoepitheliocytes
a. Found around alveoli & ducts
b. Lies between the epithelium & BM
c. Facilitates the passage of milk from alveoli, into & along the ducts

4. 4
© Garaka Rabel – 2009


c. The stroma
i. Fibrous stroma
1. Supporting framework of the gland
2. Forms septa known as the suspensory ligaments of Cooper
3. Anchor the skin to the pectoral fascia
ii. Fatty stroma
1. Main bulk of the gland
2. Distributed all over the breast;
3. except beneath the areola & nipple


3. Blood supply
a. Arterial supply : arteries converge on the breast & are distributed from the anterior
surface; the posterior surface is relatively avascular
i. Internal thoracic artery : through its perforating branches
ii. Some branches of axillary artery;
1. Lateral thoracicartery
2. Superior thoracicartery
3. Acromiothoracic artery (thoracoacromial artery)
iii. Lateral branches of the posterior intercostal arteries

b. Venous drainage : veins follow arteries; first converge towards the base of the nipple
& form an anastomotic venous circle, from where veins run in superficial & deep sets
i. The superficial veins drain into;
1. Internal thoracic vein
2. Superficial veins of the lower part of the neck
ii. The deep veins drain into;
1. Internal thoracic vein
2. Axillaryvein
3. posterior intercostalveins


4. Nerve supply
a. Anterior & lateral cutaneous branches of the 4
th
to 6
th
intercostal nerves
b. Convey sensory fibres to the skin
c. Convey autonomic fibres to smooth muscle & to blood vessels
d. Nerves do not control the secretion of milk (controlled by prolactin hormone)

5. 5
© Garaka Rabel – 2009
5. Lymphatic drainage



a. Lymph nodes
i. Axillary lymph nodes – 75%
1. Anterior(pectoral) group – chiefly
2. Posteriorgroup
3. Lateralgroup
4. Centralgroup
5. Apicalgroup
ii. Internal mammary (parasternal)nodes – 20%
iii. Posterior intercostal nodes – 5%
iv. Some lymph also reaches;
1. Supraclavicularnodes
2. Cephalic(deltopectoral) node
3. Subdiaphragmatic lymph plexus
4. Subperitoneal lymph plexus
directly or indirectly

6. 6
© Garaka Rabel – 2009

b. Lymphatic vessels
i. Superficial lymphatics
1. Drain skin, except for the nipple & areola
2. Pass radially to surrounding lymph nodes;
a. Axillary lymph nodes
b. Internal mammary (parasternal)lymph nodes
c. Supraclavicularlymph nodes
d. Cephalic(deltopectoral)lymph node
ii. Deep lymphatics
1. Drain parenchyma, nipple & areola
iii. Important lymphatic structures:
1.









2. Internal mammarynodes drain lymph from both inner & outer halves of
the breast
3. Subareolar lymph plexus of Sappy (a lymphatic plexus deep to areola)
drain into anterior group of axillary lymph nodes
4. Lymphatic from deep surface pass through pectoralis major &
clavipectoral fascia to reach;
a. Apicalnodes &,
b. Internal mammarynodes
5. Lymphatics from lower-inner quadrants may communicate with
subdiaphragmatic & subperitoneal lymph plexuses, after crossing costal
margin; then pierce anterior abdominal wall through upper part of linea
alba
Breast
Anterior Posterior
Central Lateral
Apical
Supraclavicular
Posterior
intercostal
Parasternal
Axillary
75%
20%
5%

7. 7
© Garaka Rabel – 2009

6. Development

a. Mammary ridge (milk line or line of Schultz)
i. Extends from axilla to groin
ii. Appears during 4
th
week of intrauterine life
iii. In human beings it disappears, persisting only in pectoral region
iv. Breast develops from ectodermal thickening of persisting part of this ridge
v. Gland is ectodermal & stroma is mesodermal in origin

8. 8
© Garaka Rabel – 2009
b. Formation of mammary gland
i. Persisting part of the mammary ridge is first converted into a mammary pit
ii. Secondary buds(15-20) grow down from floor of the pit
iii. These buds divide & subdivide to form lobes
iv. Entire solid system is canalized later
v. At birth, nipple is everted at the original pit
c. Growth ofmammary gland, atpuberty caused by;
i. Oestrogen
ii. Progesterone – stimulates development of secretary alveoli
d. Developmental anomalies
i. Amastia – absence of breast
ii. Athelia – absence of nipple
iii. Polymastia – supernumerary breasts
iv. Polythelia – supernumerary nipples
v. Gynaecomastia – development of breasts in a male (occurs in Klinefelter’s
syndrome)

7. Human milk
a. Contents
i. Water – 88%
ii. Lactose – 7%
iii. Fat – 4%
iv. Proteins – 1% (caseins, lactalbumin)
v. Ions (Ca
2+
, PO
4
3-
, Na
+
, K
+
, Cl
-
)
vi. Vitamins
vii. Antibodies (of IgA variety)
b. Colostrum
i. Milk secreted in later part of pregnancy & few days after parturition
ii. Contain many immunoglobulins
iii. Rich in fat & poor in nutrients
iv. Fat contains in colostral corpuscles
c. “Witch’s milk”
i. Milk secreted by infant’s breast
ii. During first 1 or 2 weeks after birth
iii. Under the influence of maternal oestrogen
d. Lactation
i. Active in mothers, for about 5-6 months after parturition
ii. Thereafter, diminishes progressively
iii. Thus, the infant has to be weaned by about 9 months of age