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FAT ANATOMY Embryology During 3rd month of gestation perivascular stem cells—adipoblasts give rise to adipocyte precursors which then differentiate into mature fat cells Some adipocytes differentiate into postadipocytes—capable of cellular replication After adolescence, no new adipocytes are formed. Fat cell replication by postadipocytes Ultimate number of fat cells is genetically determined and only slightly influenced by environment and nutrition. Histology lipid droplets in adipose tissue can be unilocular and/or multilocular. Unilocular cells contain a single large lipid droplet which pushes the cell nucleus against the plasma membrane, giving the cell a signet-ring shape. Unilocular cells, characteristic of white adipose tissue, range in size from 25 to 200 microns. Mitochondria are found predominately in the thicker portion of the cytoplasmic rim near the nucleus. The large lipid droplet does not appear to contain any intracellular organelles. Multilocular cells, typically seen in brown adipose tissue, contain many smaller lipid droplets. A cell in brown adipose tissue may reach a diameter of 60 microns and the lipid droplet within the cell may reach 25 microns in diameter.The brown color of this tissue is derived from the cells' rich vascularization and densely packed mitochondria. These mitochondria vary in size and may be round, oval, or filamentous in shape. Physiology Brown adipose tissue is found in minor amounts near the thymus and in the dorsal midline region of the thorax and abdomenplays a role inregulating body temperature via non-shivering thermogenesis - mechanism of heat generation is related to the metabolism of the mitochondria which have a specific carrier called uncoupling protein that transfers protons from outside to inside without subsequent production of ATP. White adipose tissue serves three functions 1. heat insulation 2. mechanical cushion, 3. source of energy (more energy can be derived per gram of fat (9 kcal/gm) than per gram of carbohydrate (4 kcal/gm) or protein (4 kcal/gm).) Adipocytes have 2 different receptors for catecholamines -1—lipolytic and secrete lipase -2—block lipolysis In areas of fat deposition eg steatomas and trochanteric lipodystrophy, high concentratrion of -2 receptors In weight gain o fat is deposited throughout the subcutaneous and visceral areas fairly evenly. o Fat is initially accumulated in existing adipocytes (hypertrophic growth) o When >30% above ideal body weight or BMI>35 then new fat cells are produced (hyperplastic obesity). This is more resistant to dieting and exercise. In weight loss whether by diet or exercise – preferential fat loss in visceral areas o visceral fat is more sensitive than subcutaneous fat to lipolytic stimulation o reduction in visceral fat is associated with improvements in insulin resistance o bariatric surgery reduces both visceral and subcutaneous fat, leading to improved metabolic profiles o liposuction and abdominal plasty is effective in removing subcutaneous fat but does not, in itself lead to improved metabolic profiles. The largest amount of this visceral fat occurs at the level of the umbilicus, and the greatest amount of subcutaneous fat occurs in the region of the buttock There are racial and sexual differences in fat distribution – not all environmental o Women have higher percentage of body fat(30%) than men(20%) Women (gynoid pattern) - in lower trunk, hips, upper thighs and buttocks – gives a hourglass silhouette appearance which is desirable. Weight gain becomes male pattern after menopause Men (android pattern) – evenly around trunk and nape o Blacks have increased fat accumulation in the buttocks With increasing age: o Proportion of intraabdominal and truncal fat increases o Extremities lose fat from subcutaneous tissue—shifts to intra and inter muscular Classification Limitation of BMI : does not provide a description regarding distribution of adipose tissue. BMI is less useful in 1. Children 2. muscular patients 3. amputees 4. Elderly Subcutaneous vs visceral fat mass. 1) Central obesity: 2) 3) 4) 5) Subcutaneous: Visceral fat ratio <1.5 in woman and 0.75 in men The fat tissue is mainly located in the abdomen, whereas limbs and face are often normal. Fat tissue is markedly distributed in the viscera. Central obesity is most frequently associated with metabolic disorders (diabetes, dyslipidemia) and with severe cardiovascular pathologies (hypertension, atherosclerosis and cardiopathies). This type of obesity requires dietological, exercise, and possibly psychological therapy. The latter are frequently unsuccessful in the long-term, and the intervention of a bariatric surgeon is necessary to reduce the intake or absorption of food (endogastric balloon, gastric banding, vertical gastroplasty, gastric bypass, or biliopancreatic diversion with or without duodenal switch, depending on the degree of obesity and co-morbidities and on the surgeon’s experience. The plastic surgeon later intervenes for body sculpturing and repair of recti abdominis muscles diastasis Peripheral Obesity Subcutaneous: Visceral fat ratio >2 fat tissue is in the limbs and particularly in the regions situated below the navel. Peripheral obesity is infrequently associated with metabolic disorders, and a few researchers have stated a beneficial role of larger thigh and hip circumferences on glucose tolerance. Often resistant to dietologic treatment, this type of obesity may require intervention of a plastic surgeon in those parts where adipose tissues proves to be resistant to hypocaloric diets. Diffuse obesity This is the most common form of obesity, and consists of a homogenous increase of adipose tissue in the whole body. The ideal therapy should be a synergic approach by the dietologist, the bariatric surgeon and the plastic surgeon. Localised obesity i. Lipodystrophies ii. Lipomas iii. Lipomatoses Resistant to dieting, may be associated with metabolic problems Benefits can be achieved through plastic sculpturing (liposuction, localized dermo-lipectomy). Formerly obese The patient after successfully achieving weight loss, presents a redundant cutaneous mantle (hanging rubbing skin, intertrigos) from which fat has been depleted The plastic surgeon’s duty is to re-establish the morphofunctional balance by reducing the excess skin in the various body districts. Anatomy Superficial fascia of the abdomen o Above the umbilicus, it contains fat and connective tissue fibers as a single layer of tissue. o Below the umbilicus, the fatty layer is divided by Scarpa's fascia (membranous layer of superficial fascia). o Scarpa's fascia is continuous over penis and scrotum as superficial perineal fascia (Colles fascia) o attaches to the fascia lata below the inguinal ligament, and to the pubic tubercle more medially o blends with the deep fascia of the external oblique muscle at the level of the anterior axillary line Fatty layers of the abdomen (separated by Scarpa’s) o Superficial layer (Camper’s fascia)—compact, dense pockets of fat within well organised fibrous septa o Deep layer—looser more areolar fat bound by haphazard network of septa. o With liposuction, the deep and intermediate layers are always safe to treat, while the superficial layer of densely compacted fat should be suctioned with extreme caution because of the greater risk of deformities and skin irregularities afterwards o Male, female differences: There are zones of adherence where the superficial fascia is adherent to the muscle (PRS May 2001, Rohrich) o These zones exist where there is a minimal or no deep fat layer and the superficial layer and its overlying dermis are thin. o These zones are therefore more susceptible to contour deformities during liposuction and should be avoided o they include 1. gluteal crease 2. lateral gluteal depression 3. middle medial thigh 4. inferolateral iliotibial tract 5. distal posterior thigh 3 vascular zones (Huger 1979) 1. I—mid abdomen (down to ~ arcuate line bounded laterally by rectus sheath a. Supplied by deep epigastric vessels 2. II—lower abdomen (below arcuate line) a. Supplied by DCIA, SCIA, SIEA – these vessels are interrupted after wedge excision 3. III—lateral areas (lat to rectus) a. Supplied by subcostal, intercostal and lumbar arteries During abdominoplasty, zones I and most of zone II are sacrificed. Abdominal flap is perfused via vessels from Zone III and SCIA from zone II With combined abdominoplasty and liposuction, Matarasso has defined safe areas of liposuction. Liposuction to lateral areas and to the deep fat layer is safest The nerve supply to the abdominal wall is via intercostal nerves VIII-XII. These nerves pass between the internal oblique and transversus abdominis muscles. The motor branches pass behind the rectus muscles and enter the muscles at the junction of the lateral one third and medial two thirds (Moon, 1988). The skin of the infraumbilical and suprapubic areas of the abdomen is supplied by the iliohypogastric(L1), ilioinguinal(L1), and genitofemoral(L1,2) nerves 7 aesthetic units of female abdomen(males have six – minus the dorsal back rolls) Surface contour of ideal mid torso. Umbilicus is 2.5 cm below waist and 18– 21 cm above anterior vulvar commissure. Distance from top of pubic hair line to anterior vulvar commissure is 5–7 cm. Umbilicus measures 1.5 to 2 cm in diameter and lies anatomically within the midline at the level of the superior iliac crests, midway between xiphoid and pubis. umbilicus is formed as a result of contraction of four fibrous cords. These consist of the obliterated left umbilical vein, which runs superiorly in the round ligament of the liver; the obliterated urachus centrally, which runs inferiorly to the bladdder; and the two obliterated umbilical arteries, which run laterally to their corresponding internal iliac artery. The resultant vector of these four cord contractures is usually directed inward and upward, resulting in a characteristic skin overhang superiorly with a shelving of the lower margin A youthful and thin individual has a small and vertically oriented umbilicus The older or more obese individual has a rounder, transversely oriented, and hooded umbilicus superiorly Arterial supply: 1. subdermal plexus 2. right and left deep inferior epigastric arteries that each give off several small branches, and a large ascending branch, which courses between the muscle and the posterior rectus sheath passing directly to the umbilicus (dominant supply) 3. ligamentum teres hepaticum (obliterated umbilical vein) 4. median umbilical ligament (urachus) A large perforator to the umbilicus is shown (double arrow), as are numerous small perforators (single arrows). The small perforators approach the umbilicus (circle) from premuscular, intramuscular, and postmuscular routes. large perforators to the umbilicus are seen to pierce the rectus sheath just posterior to the fusion of the anterior and posterior sheaths (linea alba) in most cases. In unilateral TRAM, umbilicus mainly survives on contralateral DIEA perforators In bilateral TRAM, depends on supply from ligamentum teres and median umbilical ligament. Gluteal crease separates thigh from buttock typically ends about two-thirds of the way to the lateral-most portion of the thigh. viewed from the side, the youthful gluteal mass meets the upper thigh at an obtuse angle, and the upper buttock projects as a rounded, subtle fullness. Excessive fullness of the lower buttock, ptosis of the buttocks, and lateral extension of the gluteal crease are signs of age or obesity. Cellulite Cellulite – dimpling of skin in thigh and buttocks most often seen in women o Theories i. sexually dimorphic skin architecture o Males may have fat storage chambers that are arranged in smaller, diagonal units which store smaller quantities of fat . This allows fat hypertrophy in rostral / caudal direction abd thusno dimpling o In female—adipose projects into dermis with dimpling ii. altered connective tissue septae iii. vascular changes iv. inflammatory factors. o According to Lockwood, there are 2 types 1. Primary – fat hypertrophy within superficial fibrous septa bulges out 2. Secondary – due to skin laxity. With age and sun damage, the entire skin–superficial fat–SFS [superficial fascial system] relaxes and stretches, resulting in ptotic soft tissues, pseudo-fat deposit deformity, and cellulite. Treatment modalities can be divided into four main categories: 1. attenuation of aggravating factors 2. physical and mechanical methods infrared heating - heat and metabolise the affected fatty layer mechanical rollers and vacuum suction aid circulation to the area and smooth by massage. 3. pharmacological agents cellulite creams (fat dissolving) mesotherapy - Phosphatidylcholine/deoxycholate injections 4. laser There are no truly effective treatments for cellulite. Body Shapes (William Sheldon (1898-1977) -American psychologist) 1) Ectomorph – tall, skinny, hunched 2) Endomorph – short, fat, round 3) Mesomorph – square, muscular, blocky Nerves at risk Branches of the lumbar plexus 1. Iliohypogastric L1 a. lateral branch - pierces the IO and EO immediately above the iliac crest b. anterior branch - pierces EO aponeurosis about 2.5 cm. above the superficial inguinal ring - distributed to the skin of the hypogastric region. 2. Ilioinguinal L1 a. size of this nerve is in inverse proportion to that of the iliohypogastric b. accompanies the spermatic cord through the superficial inguinal ring, is distributed to the skin of the upper and medial part of the thigh, to the skin over the root of the penis and upper part of the scrotum in the male (mons pubis and labium majus in the female) 3. Genitofemoral L1,2. a. external spermatic nerve(genital branch of genitofemoral) - descends behind the spermatic cord to the scrotum, supplies the Cremaster, and gives a few filaments to the skin of the scrotum. b. lumboinguinal nerve(femoral branch of genitofemoral)- passes beneath the inguinal ligament, enters the sheath of the femoral vessels, lying superficial and lateral to the femoral artery. Supplies skin on anterior part of proximal thigh 4. Lateral femoral cutaneous L2,3 (posterior division) 5. Femoral L2, 3, 4 (posterior division) 6. Obturator L2,3,4 (anterior division) Lateral cutaneous nerve of thigh (L2,3) At risk from body contouring operations Emerges from lateral body of psoas. Surface marking anterior superior iliac spine and the midpoint of the upper margin of the patella. divides into two branches, and anterior and a posterior o anterior branch becomes superficial about 10 cm. below the inguinal ligament, and divides into branches which are distributed to the skin of the anterior and lateral parts of the thigh, as far as the knee o osterior branch pierces the fascia lata, and subdivides into filaments which pass backward across the lateral and posterior surfaces of the thigh, supplying the skin from the level of the greater trochanter to the middle of the thigh. Variations : Dellon PRS 1997 Variations in the course and location of the LFCN as it exits the abdomen. The nerve may course across the iliac crest 2-3cm posterior to the ASIS (type A) (4%); may be ensheathed in the inguinal ligament just medial to the ASIS superficial to sartorius(type B) (27%); may be ensheathed in the tendinous origin of the sartorius muscle medial to the ASIS (type C) 23%); may be found in an interval in between the sartorius muscle and the iliopsoas muscle deep to the inguinal ligament (type D) (26%); or may be found in the most medial position on top of the iliopsoas muscle, contributing the femoral branch to the genitofemoral nerve (type E) (20%).