Anatomy of The Abdomen, Its Fat Layers and Underlying Muscles

Although you most certainly don't need to know what the Obliquus externus abdominis and fascia of Scarpa are to have an abdominoplasty, but I just thought I'd offer a description in simple terms so that you will know what muscles are responsible for what if you so choose.

Let's start with the skin. It is the most visible of course and many times the most depressing aspect after it has lost its ability to spring back from being all stretched out. We aren't going to talk too much about exfoliation, skincare and that business - we are going tot talk about what is affected by the laxity of the tissues due to pregnancy, weight gain or age...

The Skin

Your skin is constantly replenishing itself. When you are younger your skin's turnover rate is about every 15-18 days. When you start approaching your mid-thirties the process slows down to as much as every 28 days. The upper most layer, the epidermis, is where we shed our skin cells and reveal the newer cells that are produced in the basal layer (the bottom)

Any product that is bought in the stores and make up counters at those expensive boutiques affect this layer only. So if you think that those miracle skin-firming creams are going to work - they're not. If skin is stretched out, and it hasn't bounced back yet, it's not going to. This is the exception of course if you have a significant fat layer and you haven't lost it or had it removed yet. Many times, only liposuction is needed for these cases. Another exception is for patients who really don't have redundant skin or excess fat pocket issues but rectus abominus diastases. This is when there is separation of the muscles and fascia in the middle area of the abdomen. You may THINK you have excess skin - but it may just be your muscles. If you have lost the fat that you want to lose, maintained a good weight for your body frame and your muscles are relatively tight but still have excess skin - simple skin excision may be your best bet. But I get ahead of myself...

The next level down is the dermis. This level contains oil glands, nerves, capillaries, your body's melanin (the cells that are responsible for your coloring and a tan) plus sweat glands that moderate your body's temperature. The dermis also contains your natural collagen and elastin in addition to your fat and water storage. Your collagen and elastin are responsible for that springiness that gives your skin its youthful vitality. Without this, your skin would feel like crepe paper and would almost split down the middle when you were pregnant or had excess weight. We tend to lose a lot of our elastin and collagen as we age, hence the skin-thinning and laxity that we hate so much..

Fat Fat Fat!

Many of us hate it, I know I do. BUT we need it. It is essential to health and you would look harsh without it. However, many of us have more than we'd like so here we go...

Many female bodies (including mine) hold excess fat in our thighs, buttocks, hips and stomach. Men seem to hold it in their abdomen and general waist area. Some of us even have excess visceral fat which may give the appearance of a large pot-belly even after superficial liposuction or tummy tuck. Men seem to also have *better* connective tissue as opposed to ours which betray us and fail to keep our superficial fat IN or unrestricted, creating cellulite. Then to top that off, as I am sure you have noticed, as we age our metabolism slows. Resulting in stubborn pockets of fat in areas that we don't want it and fat loss in areas we'd like to keep it. What's up with that??!!

We work out like crazy, diet until we are skinny everywhere else BUT that target area we are trying to lose. We buy girdles, fat-creams, sessions of Endermologie, spend our lunch hour on stairclimbers and still, it is stuck to us like glue. Well, thank goodness for liposuction and manual fat removal, huh? Fat removal is usually a very routine addition to tummy tuck surgery no matter your level of laxity - so hooray for cannulas!

Well What Is Fat?

Called adipose tissue, singularly a fat cell being an adipocyte, this layer is very important. You may hate it and despise its effects on your thighs and abs but you need it! There are primarily two types of fat... White Fat [: normal fat tissue that replaces brown fat in infants during the first year of life] and brown fat [: a mammalian heat-producing tissue occurring esp. in human newborn infants -- called also brown adipose fat]. But you only have to worry about the white fat because if you're reading this - you probably don't have a brown fat "issue". Without a fat layer you would freeze to death, have no energy stores and have to eat constantly, your body would not function properly, you'd burn muscle tissue more often, and worse. But, we all have a little more than we'd like or need - so if you can't work it off, get it sucked out.

There are two layers of fat, actually THREE if you count the deepest, visceral fat, or omentum. There is the normal, extra-abdominal fat layer which is commonly removed in liposuction, there is a more dense, superficial fatty tissue which is less commonly removed although patients with loose skin may benefit from superficial liposuction, and lastly the visceral layer which in my unprofessional opinion, shouldn't be touched. The visceral layer is the deepest area of fat (sometimes called intra-abdominal fat) which surrounds and covers the intestines and other lower body organs in the torso. It can be quite prominent in those who are obese, have typical apple-shaped body types due to diabetes and those who have HIV and are on Protease. This protuberance which can be very pronounced is often referred to The Protease Paunch" It is thought that in male patients who have marked abdominal fat, the majority of this fat is omental. Proper diet and exercise is essential in regulating the amount of omental fat. However, hormonal disorders or fluctuations can have an effect as can some medications (such as Protease).

The greater omentum is a thin and transparent membranous sac (also called the peritoneum) which houses enlarged adipocytes within its membranous pockets. The smaller omentum lies between the stomach and liver and also contains adipose tissue. There are also other, smaller membranous sacs of adipose tissue throughout the viscera. Omental fat can become very distended, however it is still very dangerous to attempt liposuction of this area due to risk of puncturing or otherwise upsetting the lower digestive organs. The Omenta is very important and is not only an energy storage unit, it also protects, insulates and lubricates the organs to shield the delicate tissues from friction injury. Most liposuction procedures target the extra-abdominal layer of fat and not the omentum.

The omental fat can be excessive in persons with diabetes, severe obesity and in HIV patients who use protease inhibitors. Protease Inhibitors (Viracept®, Crixivan®, Norvir® and Invirase®) tend to disrupt fat distribution thought to cause the omenta to become more fatty (called sometimes The Protease Paunch or Crix-belly from use of Crixivan®) as well as the nape (back) of the neck (sometimes horribly called a Buffalo Hump). However, some physicians believe this is not fat but dense scar tissue formation instead which causes the distended abdomen or Buffalo Hump. Oddly, when the protease inhibitors or cocktails of medications were ceased (or regimens altered), the weight gain and fatty deposits resolved. Cases which were analyzed showed that it was a dense form of fatty tissue, described as a cluster if benign lipomas rather than scar tissue or normal adipose tissue. Incidentally "Buffalo Hump" syndrome removal through liposuction or surgical excision is an option. Whereas intra-abdominal (mesenteric) fat removal is very risky and very rarely performed. Some protease inhibitor-induces abnormal fat distribution is extra-abdominal (subcutaneous) and is easily removed with normal liposuction.

The Superficial Fat Layer is more dense and is tightly packed with nerves, and blood vessels. Considerable damage to any of the functional components of the skin can result in visible irregularities and discolorations, permanent irregularities I might add. The superficial fat layer is also something that can cause cellulite to be more visible especially when contracting, tight bands of connective tissue squeeze portions of the fat cells and push them to the surfaces or contract parts of the fatty tissue away from it.

Fat percentage and placement depends upon hormones such as insulin, testosterone and estrogen. The one thing about fat is that once puberty is over - what fat you have is what fat you get forever. Your fat cells only multiply if you reach 200% of your body weight. Which is a rare occurrence indeed. However, fat cells can expand enormously. Insulin is a huge culprit in fat storage. This means anything that can cause your insulin to spike. Candy and sugar aren't the only bad guys, bread, potatoes, carrots, corn anything which has a high glycemic index can increases fat storage. Excess of these items can cause excess fat. And America LIVES off of boxed and processed foods and lots of carbohydrates. Sugar Sugar everywhere, equals a lotta fat, ya think?? Not only does it increase your waistline is disrupts your hormones as well. Sorry, I've gone off on a tangent. Anyway...

Fascia

Fascia is what covers all of our muscles and most organs. It helps keep it's shape, protects it and pretty much keeps us in compact form as opposed to the shapeless jellyfish we would resemble. Okay not THAT bad, but fascia is very important!

Superficial Fascia of the Abdomen[: the thin layer of loose fatty connective tissue underlying the skin and binding it to the parts beneath]The fascia holds everything together and keeps everything compact and tight. When this becomes stretched out, it can create a permanent distended look even if your own muscles are toned.
Deep Fascia [: a firm fascia that ensheathes and binds together muscles and other internal structures]The deep fascia also gets stretched out although it is more sturdy and is responsible for keeping your organs in. The muscles, superficial fascia and skin is what is normally tightened in abdominoplasty.

muscles and fascia of the abdomen

The Muscles of the Abdomen

There are certainly more muscles to the torso than the Obliquus externus, Obliquus internus, transversus and the Rectus abdominus - but to you TT people, they are the ones which matter most. They are responsible for the shape of the abdomen and are the chief muscles which become stretched. However, it is the rectus abdominus muscle/fascia which suffers from diastasis (separation) after they are distended. Rectus muscle/fascia plication[1 : the tightening of stretched or weakened bodily tissues or channels by folding the excess in tucks and suturing; 2 : the folding of one part on and the fastening of it to another]along the linea alba[: a median vertical tendinous line on the abdomen formed of fibers from the aponeuroses of the two rectus abdominis muscles and extending from the xiphoid process to the pubic symphysis]is the main internal event in a full abdominoplasty and will restore a slimmer and flat stomach should you need repair.

exposed core of the Rectus abdominis

The Rectus abdominis is a long, flat muscle which runs along the anterior (front) center of the abdomen. There are actually two parts (sides), held within a sheath of sorts of fascia and are separated by the linea alba. The rectus muscle attaches to the cartilages of the fifth, sixth, and seventh ribs which branch out from the bottom section of the sternum. This muscle and its sheath takes the brunt of the stretching that accompanies pregnancy and weight gain. The linea alba is the line down the center which you can see in a well-toned abdomen. It is also the area which can separate more due to the stretching. We will discuss the plication of this area soon.

Cross-section of the sheath of the Rectus abdominus, linea alba, transversus and Obliquus abdominus (imagine yourself looking down at a cross-section of your tummy (without the organs, of course)

The Rectus is covered, or rather enclosed, in a sheath of connective tissue formed by the aponeuroses[: any of the broad flat sheets of dense fibrous collagenous connective tissue that cover, invest, and form the terminations and attachments of various muscles] of the Obliqui [: one that forms the outer layer of the lateral abdominal wall --called also external oblique, obliquus externus abdominis]and Transversus [: a flat muscle with transverse fibers that forms the innermost layer of the anterolateral wall of the abdomen and that acts to constrict the abdominal viscera and assist in expulsion of the contents of various abdominal organs (as in urination, defecation, vomiting, and parturition)].

Rectus abdominus, linea alba diastasis

The abdominal muscles and skin become lax after this area is distended due to pregnancy and weight gain. Remember even if you have never been pregnancy or overweight, this area becomes lax with age. With the addition of lax muscles and skin sometimes we are plaque by thin white lines and deep purplish fissures in the skin called stretch marks! I have several and it started with weight gain from birth control. Not to mention an increase in the size of the breasts PRE-implants didn't help out.

Well that's about it, at least that's all we truly need to know to understand what the surgeon is going to do. If you'd like more info, ask your surgeon what he is specifically going to do in your own case..

References

The Muscles and Fasciæ of the Abdomen; Henry Gray (1821-1865). Anatomy of the Human Body. 1918
Merriam_Webster Medical Dictionary