Download Anatomy of Fat

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
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-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
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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:
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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
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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
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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
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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
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With combined abdominoplasty and liposuction, Matarasso has defined safe areas
of liposuction. Liposuction to lateral areas and to the deep fat layer is safest
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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
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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.
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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
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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.
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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%).