Breast Reduction - Surgical Anatomy of The Breast

Surgical Anatomy of The Breast

The procedure

A reduction mammoplasty to re-size enlarged breasts and to correct breast ptosis resects (cuts and removes) excess tissues (glandular, adipose, skin), overstretched suspensory ligaments, and transposes the nipple-areola complex (NAC) higher upon the breast hemisphere. At puberty, the breast grows in consequence to the influences of the hormones 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 breast milk constitutes most of the breast volume.

Composition

Surgically, the breast is an apocrine gland overlaying the chest — attached at the nipple and suspended with ligaments from the chest — which is integral to the skin, the body integument of the woman. The dimensions and weight of the breasts vary with her 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. Anatomically, the breast topography and the hemispheric locale of the nipple-areola complex (NAC) are particular to each woman; thus, the desirable, average measurements are a 21–23 cm sternal distance (nipple to sternum-bone notch), and a 5–7 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 mammary artery (from the medial aspect), the lateral thoracic artery (from the lateral aspect), and the 3rd, 4th, 5th, 6th, and 7th 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 lymph drainage system is the retromammary lymph plexus in the pectoral fascia. Sensation in the breast is established by the peripheral nervous system innervation of the anterior and lateral cutaneous branches of the 4th, 5th, and 6th intercostal nerves, and thoracic spinal nerve 4 (T4 nerve) innervates and supplies sensation to the nipple-areola complex.

Mechanical structures of the breast

In realizing the breast-reduction corrections, the plastic surgeon takes anatomic and histologic account of the 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).

1. Rib cage. The 2nd, 3rd, 4th, 5th, and 6th ribs of the thoracic cage are the structural supports for the mammary glands.
2. 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) anterior serratus muscle (attached to the ribs, the rib muscles, and the shoulder blade), and to the rectus abdominis muscle (a long, flat muscle extending up the torso, from pubic bone to rib cage). The body posture of the woman 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 forces (when standing and when walking), compression forces (when lying supine), and tension forces (when kneeling on four limbs).
3. 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.
4. 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.
5. Glandular tissue. As a mammary gland, the breast comprises lobules (milk glands at each lobe-tip) and the lactiferous ducts (milk passages), which widen to form an ampulla (sac) at the nipple.
6. Adipose tissue. The fat tissue of the breast is composed of lipidic fluid (60–85% weight) that is 90–99 per cent triglycerides, free fatty acids, diglycerides, cholesterol phospholipids, and minute quantities of cholesterol esters, and monoglycerides; the other components are water (5–30% weight) and protein (2–3% weight).
7. Fatty Tissue. In Biology, adipose tissue (/ˈædəˌpoʊs/) or body fat or 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, 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. 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.
8. The skin envelope. The breast skin is in three (3) layers: (i) the epidermis, (ii) the dermis, and (iii) the hypodermis. The epidermis is 50–100 µm thick, and is composed of a stratum corneum of flat keratin cells, that is 10–20 µm thick; it protects the underlying viable epidermis, which is composed of keratinizing 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 mm thick. The thickness of the hypodermis (adipocyte cells) varies from woman to woman, and body part. The skin of the nipple and areola is further composed of a modified and specialized myoepthelium that is responsible for contraction in response to stimuli.