Transcript of the breast

Module Three
Anatomy and Physiology
Holdorf PhD, MPA, RDMS (Ob/Gyn, Ab, BR), RVT, LRT(AS,) CCP
Module Three: Anatomy and
Physiology
Anatomic Layers
 From Anterior to Posterior
 Skin
 Subcutaneous (premammary) layer
 Mammary Layer
 Retromammary Space
 Muscle Layers (pectoralis Major m. and Pectoralis minor
m.)
 Chest wall (ribs and intercostal muscles)
Skin
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The skin is composed of the epidermis and dermis layers
The thickness is 0.5 to 2 mm
It is slightly thicker in young females and thins with age.
NIPPLE
 Consists of dense connective tissue and erectile muscle.
 It contains many sensory nerve endings.
 15 to 20 collecting (lactiferous) duct openings may be seen
(each of which arise from a breast lobe)
 AREOLA
 Circular area of dark pigmentation seen around the nipple.
 Consists of smooth muscle.
 Slightly thicker than surrounding skin.
 Contains Montgomery glands- sebaceous glands seen as small
bumps in the areola.
 1. Subcutaneous (Premammary Layer)
 2. Superficial layer
 3. Deep layer
 4. Superficial fascia
 5. Mammary Layer
Layers of the breast
Subcutaneous (Premammary )
Layer
 Lies just beneath the skin extending to the mammary
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layer
Consists primarily of fat
It is not seen posterior to the nipple
Amount of fat increases with age, pregnancy, and
obesity
Cooper’s ligaments appear as prominent structures
within the subcutaneous layer.
Superficial Fascia
 The breast tissue is completely contained between the
layers of the superficial fascia.
 At the breast, the superficial fascia divides into the
superficial and deep layers
 The superficial layer of the superficial fascia is simply
known as the superficial fascia.
 The superficial fascia is contained within the
subcutaneous layer anterior to the mammary layer.
Mammary Layer
 The mammary layer is also known as the parenchymal
or Glandular layer.
 A portion of glandular tissue extends into the axilla.
This is known as the axillary Tail of Spence.
 The mammary layer is composed of two types of
tissue:
 Stroma- is the supportive tissue of the breast
 Consists of interlobular fat and connective tissue (Cooper’s
ligaments, loose and dense connective tissue)
 Epithelium – is the functional tissue
 Consist of acini, lobules, TDLU’s, lobes and lactiferous ducts.
Mammary layer- continued
 Cooper’s Ligaments (Suspensory Ligaments) Part of the stoma and supportive tissue of he Mammary layer
 Provide the architectural “framework” of the breast
 Run between the superficial and deep layers of the superficial
fascia.
 Acini
 Also called Acinus or Acinar cell
 Smallest functional unit of the breast
 Milk-producing gland
 Hundreds of acini in each breast
 Each acini gives rise to a ductule or terminal duct
 Lobule
 Is composed of approximately 30 acini, intralobular terminal
ducts, and intralobular stromal tissue (loose connective
tissue).
 TDLU
 Terminal Duct Lobular Unit
 TLDU is made up of: Lobule, intralobular terminal ducts,
extralobular terminal duct
 Usually measures 2.0 mm or less
 Nearly all breast pathology originates in the TDLU.
 Lobe
 Several lobules (TDLUs) make up a breast lobe
 15 to 20 lobes in each breast
 One lactiferous duct emerges from each lobe and travels
toward the nipple.
Mammary Layer (continued)
 Lactiferous Ducts Transport milk from the acini to the nipple
 Begin with the Ductule of Terminal Duct which arises
from the acinar cell
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Intralobular terminal Duct-within the lobule
Extralobular Terminal Duct- outside the lobule
 Interlobular ducts travel between the lobes
 The duct enlarges slightly beneath the areola forming
the Lactiferous Sinus.
 Collecting Duct empties milk from the nipple.
Layers of the breast
Cross section of Breast Duct lumen
 Lactiferous ducts are lined with a double layer of epithelial
cells
 Epithelium (inner layer)
 Myoepithelium
 The epithelial cells are supported by a basement membrane
(adventitia) which is the outer fibrous portion of the duct
 The function of the my0epithelium is to produce milk
within the ducts toward the nipple.
 Deep Fascia
 The deep layer of the superficial fascia is often referred to as
the deep fascia.
 Located within the retromammary space posterior to the
mammary layer.
 Maintaining integrity of the deep fascia is important in
deterring the spread of cancer to the chest wall.
Retromammary Space
 Space between the posterior margin of the mammary
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layer and the pectoral muscles
Contains thin layer of fat
Amount of fat increases with age, pregnancy, and
obesity.
Also contains the deep layer of the superficial fascia.
This layer allows movement of the breast over the
chest wall.
Muscles
 Pectoralis Major arises from the clavicle and costal cartilage
of the sternum, attaching to the proximal humerus.
 Pectoralis Minor arises from the 3rd, 4th, and 5th ribs
attaching to the scapula.
 The pectoral (muscular) fascia encloses the chest muscles
and may appear deep to the retromammary layer.
 Pectoralis Major muscle is located anterior to pectoralis
minor muscle. Both are found immediately posterior to the
breast tissue.
Chest Wall
 Ribs are located posterior to the pectoral muscles.
 In small breasted females, it is important not to
confuse a rib with an intra-mammary tumor on a
physical or sonographic examination.
 Intercostal muscles are located between the ribs.
 Deep to the chest wall layer is the lung.
Deltoid, Pectoralis Major M.
Standard Anatomic Reference
 Quadrant Method
 Each breast can be divided into quadrants (4):
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UO – Upper Outer
UI – Upper Inner
LO- Lower Outer
LI – Lower Inner
Glandular tissue is usually thicker in the Upper-Outer
quadrant of both breasts
Therefore, a larger percentage of cancers are found there.
Clock method
 Regions of the breast are correlated with positions of a
clock. This method allows a more precise location to
be documented.
 Correlating clock locations from right to left side is
important in evaluating the breast for symmetry. For
example, the 10:00 position in the right breast
correlates with the 2:00 position on the left.
Embryologic Development
 The Early mammary gland begins development during
the 4th week of embryologic life. The glandular tissue
of the breast begins to evolve into epithelial buds that
eventually form approximately 20 epithelial cords
(lobes). At 15 weeks gestation, testosterone in the male
fetus prohibits further breast development and
estrogen in the female fetus continues to stimulate
early development. Once the fetus is born, the breast
tissues are dormant until puberty.
 Breast enlargement in the male or female newborn
may be seen due to placental and maternal hormone
stimulation.
 The breasts develop along a line extending from the
axilla to the inguinal region known as the MILK LINE.
Occasionally, accessory or supernumerary breasts are
found along this line.
The milk line
Development Anomalies
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Amastia- absence of one or both breasts
Polymastia – accessory breast or more than two breasts.
Athelia- absence of the nipple.
Polythelia – accessory nipple (most common breast
anomaly).
 Amazia- absence of the breast tissue with development of
the nipple.
 Nipple flattening or Nipple inversion.
 Unilateral early ripening – asymmetric growth of the
breasts.
 Polythelia is more common in men than in women.
Arterial Supply
 Two main arteries supply blood to the breast tissues. These
include the
 Lateral thoracic artery
 Internal mammary artery
 The lateral thoracic artery arises from the axillary artery
and courses inferior and lateral along the pectoralis major
muscle. It gives rise to small perforating branches to supply
the lateral regions of the breast.
 The internal mammary artery (also known as the internal
thoracic artery) arises from the subclavian artery. It courses
lateral to the sternum and inferiorly behind the upper ribs.
Small perforating branches supply the medial region of the
breast.
Arteries of the Breast
 The internal mammary artery is often used in coronary
artery bypass graft (CABG) procedures.
 Two secondary sources of blood supply to the breast tissues
include the
 Thoracoacrominal artery (supplying a superior region)
 Intercostal artery (supplying the inferior region)
 The arteries of the breast
 1. Internal mammary artery (IMA)
 2. perforating branches of the IMA
 3. Intercostal artery
 4. perforating branch of intercostal artery
 5. Lateral Thoracic Artery
 6. Axillary artery
 7. Thoracoacromial artery
Venous Return
 There are two venous systems that drain the breast
tissue:
 Superficial
 Deep
 The superficial veins of the breast are located just deep
to the superficial fascia.
 The superficial veins allow venous communication
between the right and left breasts. This may be a route
for cancer metastasizing to the opposite breast.
 The Deep veins of the breast include small branches
that drain into the internal mammary vein, lateral
thoracic vein, axillary vein, subclavian vein, and the
intercostal veins.
 The intercostal veins also communicate with the vertebral veins.
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This may be a route for bone metastasis from breast cancer.
The superficial and deep venous systems communicate within
the breast parenchyma.
It is also important to note the lymphatic vessels of the breast
tissues closely follow the same route as the superficial and deep
venous systems.
Breast cancer most frequently spreads by the hematogeneous
route.
Veins of the breast
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1. Internal mammary vein
2. perforating branches of IMV
3. intercostal vein
4. perforating branch of intercostal vein
5. lateral thoracic vein
6. axillary vein
7. subclavian vein.
The venous return from the breast
The Lymphatic System
 The Lymphatic System transports a watery clear fluid
called lymph. The lymphatic system aids the immune
system in destroying pathogens and filtering waste so
that the lymph can be safely returned to the
circulatory system. The lymphatic system contains
immune cells called lymphocytes, which protect the
body against antigens such as harmful bacteria and
viruses that invade the body.
Lymphatic System
 Lymph flow begins deep within the breast tissues through
lymphatic vessels that originate in the stroma and
lactiferous ducts (deep system). Intramammary Lymph
Nodes are seen throughout the breast parenchyma as part
of the deep system.
 Flow direction from the deep system is toward the areola
into the periareolar plexus and continues into the
subdermal lymphatic vessels (superficial system). From the
subdermal vessels, lymph flows outward to the outer
lymphatic chains that drain the breast. The outer lymphatic
chains are located in multiple areas surrounding the breast.
Intra-mammary Lymph Node
 Approximately 75% of lymphatic drainage is to the axilla.
Therefore, the axillary lymph node chain becomes
extremely important in predicting the spread of breast
cancer.
The axillary lymph node chain consists of 6 groups of nodes:
 1. External mammary group-located along the lateral
thoracic vessels.
 2. Scapular group-run with the subscapular vessels.
 3. Axillary group- run with the axillary vessels.
 4. Central group – run with the axillary vessels
 5. Subclavicular group – run with the subclavian vessels.
 6.Interpectoral (Rotter’s) nodes – found between pectoralis
major and minor muscles.
Lymph nodes of the axillary region
 The remaining 25% of lymphatic drainage include:
 1. Internal mammary lymph nodes – lie along the
internal mammary vessels.
 2. Intercostal Lymph nodes
 3. Flow to the opposite breast
 4. Subclavicular Lymph nodes – Within the
subclavicular fossa
 5. Diaphragmatic Lymph Nodes – allow drainage to the
abdomen.
 The lymph node is reniform (kidney – like) in shape. It
has an outer cortex and medial hilum where the small
artery, vein, and lymph vessel enter and exit the node.
Outer afferent lymphatic vessels carry lymph into the
node where it is filtered and released through the hilar
vessel.
Nerves
 A complicated network of nerves serve the breast,
chest muscles, an surrounding tissues.
 These include:
 1. Long thoracic nerve
 2. thoraco-doral verve
 3. Thoracic intercostal nerves
 4. 3rd and 4th Branch of the cervical plexus
 5. Circumflex nerve (Axillary Nerve)
 6. Subcapular nerves
 7. Anterior thoracic nerves
Circumflex (Axillary) nerve
The nerves of the axilla region
Physiology and Hormonal
Influences
 Puberty
 At puberty, breast development occurs due to hormonal
stimulation by the ovaries (the larche).
 The amount of growth of breast size and volume will
vary with each individual.
 Estrogen stimulates changes of stromal tissues:
elongation of the mammary ducts, growth of connective
tissue, increase in adipose tissue and increased
vascularity.
 Progesterone stimulates growth of the glandular tissue:
TDLUs.
Mature female breast
 The mature female breast is sensitive to the menstrual
cycle and responds to fluctuating hormone levels
every month. Early in the proliferative phase of the
menstrual cycle, changes in the epithelium occur.
Later in the secretory phase, the ducts and veins
increase in size, the stroma becomes edematous, and
the epithelium produces secretions. These changes
may account for premenstrual breast discomfort. At
the onset of menses, the breast tissues decrease in size.
Pregnancy
 During pregnancy, there is considerable change in the
breast tissue. The TDLUs increase in size as the
epithelium begins to swell. The acinar cells enlarge in
response to a variety of hormones including estrogen
and progesterone, and lactogen, prolactin, and
chorionic gonadrotrophin from the placenta. Late in
the pregnancy, the lactiferous ducts increase in size.
Lactation
 Shortly after birth, the estrogen and progesterone
levels diminish rapidly and Prolactin dominates. This
hormone causes the acinar cells to secrete milk.
 After the termination of breast-feeding, the ducts and
lobules return to their normal size in approximately 3
months.
Menopause
 In the prei-menopausal female, the lobules of the breast
involute (roll inward, invert). Also, the connective and
stromal tissues are largely replaced by fat. Involuation is
thought to begin long before menopause as a gradual
decrease in glandular tissue with fatty replacement.
 There are only a few situations, however, when breast
parenchyma or glandular tissue increase with age.
 The most common causes of increased glandular tissue
development are:
 pregnancy/lactation
 Hormone replacement therapy (HRT)
 Significant weight loss
 The ratio of glandular to fatty tissue in the breasts is
determined by
 Total body fat : Total body weight
End modules one, two, three
 Next week
 Test on modules one, two, and three.