Editing Breast reduction (section)

==Anatomy of the breast==

===The procedure===
A '''reduction mammoplasty''' to re-size enlarged breasts and to correct [[Ptosis (breasts)|breast ptosis]] resects (cuts and removes) excess tissues ([[Mammary gland|glandular]], [[adipose]], [[skin]]), overstretched [[Cooper's ligaments|suspensory ligaments]], and transposes the NAC higher upon the breast hemisphere. During [[puberty]], the breast grows in consequence to the influences of the [[hormone]]s [[estrogen]] and [[progesterone]]; as a [[mammary gland]], the breast is composed of lobules of glandular tissue, each of which is drained by a [[lactiferous duct]] that empties to the nipple. Most of the volume (ca. 90%) and rounded contour of the breasts are conferred by the adipose fat interspersed amongst the lobules, except during [[pregnancy]] and [[lactation]], when [[Human breast milk|breast milk]] constitutes most of the breast volume.<ref name="Grippaudo" />

===Composition===
Surgically, the breast is an [[Apocrine|apocrine gland]] overlaying the chest – attached at the nipple and suspended with ligaments from the chest – which is integral to the skin, the [[Integumentary system|body integument]] of the individual. The dimensions and weight of the breasts vary with age and habitus (body build and physical constitution); hence, small-to-medium-sized breasts weigh approximately 500 gm, or less, and large breasts weigh approximately 750–1,000 gm.<ref>{{cite journal |last1=Pamplona |first1=Djenane Cordeiro |last2=de Abreu Alvim |first2=Cristina |title=Breast Reconstruction with Expanders and Implants: A Numerical Analysis |journal=Artificial Organs |volume=28 |issue=4 |pages=353–6 |year=2004 |pmid=15084195 |doi=10.1111/j.1525-1594.2004.47354.x }}</ref><ref>{{cite journal |last1=Grassley |first1=Jane S. |title=Breast Reduction Surgery |journal=AWHONN Lifelines |volume=6 |issue=3 |pages=244–9 |year=2002 |pmid=12078570 |doi=10.1111/j.1552-6356.2002.tb00088.x }}</ref><ref>{{cite journal|last1=Azar|first1=Fred S.|last2=Metaxas|first2=Dimitris N.|last3=Schnall|first3=Mitchell D.|title=A Deformable Finite Element Model of the Breast for Predicting Mechanical Deformations under External Perturbations|journal=Academic Radiology|date=October 2001|volume=8|issue=10|pages=965–975|doi=10.1016/S1076-6332(03)80640-2|pmid=11699849|citeseerx=10.1.1.458.3818}}<!--|access-date=13 October 2015--></ref> Anatomically, the [[Superficial anatomy|breast topography]] and the hemispheric locale of the NAC are particular to each individual; thus, the desirable, average measurements are a 21–23&nbsp;cm sternal distance (nipple to sternum-bone notch), and a 5–7&nbsp;cm inferior-limb distance (NAC to IMF).

===Blood supply and innervation===
The [[arterial blood]] supply of the breast has medial and lateral vascular components; it is supplied with blood by the [[Internal thoracic artery|internal mammary artery]] (from the medial aspect), the lateral thoracic artery (from the lateral aspect), and the 3rd, 4th, 5th, 6th, and 7th [[Intercostal arteries|intercostal perforating arteries]]. Drainage of [[venous blood]] from the breast is by the superficial vein system under the [[dermis]], and by the deep vein system parallel to the artery system. The primary [[Lymphatic system|lymph]] drainage system is the retromammary lymph plexus in the [[pectoral fascia]]. Sensation in the breast is established by the [[Peripheral nervous system|peripheral nervous system innervation]] of the anterior and lateral cutaneous branches of the 4th, 5th, and 6th intercostal [[nerve]]s, and [[thoracic spinal nerve 4]] ('''T4 nerve''') innervates and supplies sensation to the NAC.<ref name="Tortora, Gerard J.">{{cite book |title=Introduction to the Human Body |edition=5th |publisher=John Wiley & Sons |location=New York |year=2001 |page=560}}</ref><ref name="Ramsay">{{cite journal |last1=Ramsay |first1=D. T. |last2=Kent |first2=J. C. |last3=Hartmann |first3=R. A. |last4=Hartmann |first4=P. E. |title=Anatomy of the lactating human breast redefined with ultrasound imaging |journal=Journal of Anatomy |volume=206 |issue=6 |pages=525–34 |year=2005 |pmid=15960763 |pmc=1571528 |doi=10.1111/j.1469-7580.2005.00417.x }}</ref>

[[File:Breast anatomy normal scheme.png|thumb|Surgical anatomy of the [[mammary gland]] for reduction mammoplasty correction: {{ordered list |[[Chest wall]]  |[[Pectoralis muscle]]s |[[Lobules]] |[[Nipple]] |[[Areola]] |[[Lactiferous duct|Milk duct]] |[[Adipose tissue|Fatty tissue]] |[[Human skin|Skin envelope]]}}]]

===Mechanical structures of the breast===
In realizing the breast-reduction corrections, the plastic surgeon takes [[Human anatomy|anatomic]] and [[Histology|histologic]] account of the [[Biomechanics|biomechanical]], load-bearing properties of the glandular, adipose, and skin tissues that compose and support the breast; among the properties of the soft tissues of the breast is near-incompressibility ('''Poisson's ratio of ~0.5''').

# '''Rib cage.''' The 2nd, 3rd, 4th, 5th, and 6th ribs of the thoracic cage are the structural supports for the mammary glands.
# '''Chest muscles.''' The breasts overlay the [[pectoralis major muscle]], the [[pectoralis minor muscle]], and the intercostal muscles (between the ribs), and can extend to and cover a portion of the (front) [[serratus magnus|anterior serratus muscle]] (attached to the ribs, the rib muscles, and the shoulder blade), and to the [[Rectus abdominis|rectus abdominis muscle]] (a long, flat muscle extending up the torso, from pubic bone to rib cage). The body posture of the patient exerts physical stresses upon the pectoralis major muscles and the pectoralis minor muscles, which cause the weight of the breasts to induce static and dynamic [[shear force]]s (when standing and when walking), compression forces (when lying supine), and tension forces (when kneeling on four limbs).
# '''Pectoralis fascia.''' The pectoralis major muscle is covered with a thin superficial membrane, the [[pectoral fascia]], which has many prolongations intercalated among its fasciculi (fascicles); at the midline, it is attached to the front of the [[sternum]], above it is attached to the [[clavicle]] (collar bone), while laterally and below, it is continuous with the fascia.
# '''Suspensory ligaments.''' The subcutaneous layer of [[adipose tissue]] in the breast is traversed with thin suspensory ligaments ([[Cooper's ligaments]]) that extend obliquely to the skin surface, and from the skin to the deep [[pectoral fascia]]. The structural stability provided by the Cooper's ligaments derives from its closely packed bundles of [[collagen]] fibers oriented in parallel; the principal, ligament-component cell is the [[fibroblast]], interspersed throughout the parallel collagen-fiber bundles of the shoulder, [[axilla]], and [[thorax]] ligaments.
# '''Glandular tissue.''' As a mammary gland, the breast comprises lobules (milk glands at each lobe-tip) and the [[lactiferous duct]]s (milk passages), which widen to form an ampulla (sac) at the nipple.
# '''Adipose tissue.''' The fat tissue of the breast is composed of [[Lipid|lipidic fluid]] (60–85% weight) that is 90–99 per cent [[triglycerides]], free [[fatty acids]], [[diglycerides]], cholesterol [[phospholipids]], and minute quantities of [[cholesterol]] [[ester]]s, and [[monoglycerides]]; the other components are water (5–30% weight) and protein (2–3% weight).
# '''Fatty tissue.''' In biology, adipose tissue (/ˈædəˌpoʊs/), or body fat, fat depot, or just fat, is loose connective tissue composed of adipocytes. It is technically composed of roughly only 80% fat; fat in its solitary state exists in the liver and muscles. Adipose tissue is derived from lipoblasts. Its main role is to store energy in the form of lipids, although it also cushions and insulates the body. Far from hormonally inert, adipose tissue has in recent years been recognized as a major endocrine organ[1], as it produces hormones such as leptin, resistin, and the cytokine TNFα. Moreover, adipose tissue can affect other organ systems of the body and may lead to disease. Obesity or being overweight in humans and most animals does not depend on body weight but on the amount of body fat – to be specific, adipose tissue.{{citation needed|date=June 2012}} Two types of adipose tissue exist: white adipose tissue (WAT) and brown adipose tissue (BAT). The formation of adipose tissue appears to be controlled in part by the adipose gene. Adipose tissue was first identified by the Swiss naturalist Conrad Gessner in 1551.
# '''The skin envelope.''' The breast skin is in three layers: (i) the [[epidermis (skin)|epidermis]], (ii) the [[dermis]], and (iii) the [[hypodermis]]. The epidermis is 50–100&nbsp;μm thick, and is composed of a [[stratum corneum]] of flat [[keratin]] cells, that is 10–20&nbsp;μm thick; it protects the underlying viable epidermis, which is composed of keratinizing [[Epithelium|epithelial cells]]. The dermis is mostly [[collagen]] and [[elastin]] fibers embedded to a viscous water and [[glycoprotein]] medium. The fibers of the upper dermis ("papillary dermis") are thinner than the fibers of the deep dermis, thus the skin envelope is 1–3&nbsp;mm thick. The thickness of the hypodermis (adipocyte cells) varies between individuals, and between body parts.<ref>{{cite journal |last1=Gefen |first1=Amit |last2=Dilmoney |first2=Benny |title=Mechanics of the normal woman's breast |journal=Technology and Health Care |volume=15 |issue=4 |pages=259–71 |year=2018 |pmid=17673835 |url=https://www.breastsurgeryclinic.ae/blog/mechanics-of-the-normal-womans-breast/ |doi=10.3233/THC-2007-15404 |url-access=subscription }}</ref> The skin of the nipple and areola is further composed of a modified and specialized myoepithelium that is responsible for contraction in response to stimuli.