Human_abdomen

[[Image:Rectus abdominis.png|thumb|right|200px|The human [[rectus abdominis]] muscle, part of the human abdomen]]
The '''human abdomen''' (from the [[Latin]] word meaning "belly") is the part of the body between the [[pelvis]] and the [[chest|thorax]]. Anatomically, the abdomen stretches from the thorax at the [[thoracic diaphragm]] to the pelvis at the [[pelvic brim]]. The '''pelvic brim''' stretches from the lumbosacral angle (the [[intervertebral disk]] between L5 and S1) to the [[pubic symphysis]] and is the edge of the [[pelvic inlet]]. The space above this inlet and under the thoracic diaphragm is termed the [[abdominal cavity]]. The boundary of the abdominal cavity is the abdominal wall in the front and the peritoneal surface at the rear.

Functionally, the human abdomen is where most of the [[alimentary tract]] is placed and so most of the absorption and digestion of food occurs here. The alimentary tract in the abdomen consists of the lower [[esophagus]], the [[stomach]], the [[duodenum]], the [[jejunum]], [[ileum]], the [[cecum]] and the [[Vermiform appendix|appendix]], the [[ascending colon|ascending]], [[transverse colon|transverse]] and [[descending colon]]s, the [[sigmoid colon]] and the [[rectum]]. Other vital organs inside the abdomen include the [[liver]], the [[kidneys]], the [[pancreas]] and the [[spleen]].

The [[abdominal wall]] is split into the posterior (back), lateral (sides) and anterior (front) walls.

==Muscles of the abdominal wall==
[[Image:Grays Anatomy image392.png|thumb|RIGHT|200px|''Henry Gray (1825–1861). Anatomy of the Human Body.'']]

{| class="wikitable"
| '''Muscle''' || '''Origin and insertion'''
|-
| The obliquus externus ([[external oblique muscle|external oblique]]) [[muscle]] is the outermost muscle covering the side of the abdomen. It is broad, flat, and irregularly quadrilateral. || It originates on the lower eight [[rib]]s, and then curves down and forward towards its insertion on the outer anterior crest of the [[Ilium (bone)|ilium]] and (via the sheath of the [[rectus abdominis]] muscle) the midline [[linea alba]].
|-
| The obliquus internus ([[internal oblique muscle|internal oblique]]) muscle is triangularly shaped and is smaller and thinner than the external oblique muscle that overlies it. || It originates from [[Poupart's ligament]]/[[inguinal ligament]] and the inner anterior crest of the ilium. The lower two-thirds of it insert, in common with fibers of the external oblique and the underlying transversus abdominis, into the [[linea alba]]. The upper third inserts into the lower six ribs.
|-
| The [[transversus abdominis]] muscle is flat and triangular, with its fibers running horizontally. It lies between the internal oblique and the underlying transversalis fascia. || It originates from Poupart's ligament, the inner lip of the ilium, the lumbar fascia and the inner surface of the [[cartilage]]s of the six lower ribs. It inserts into the linea alba behind the [[rectus abdominis]].
|-
| The [[rectus abdominis muscle]]s are long and flat. The muscle is crossed by three [[tendon|tendinous]] intersections called the [[linae transversae]]. The rectus abdominis is enclosed in a thick sheath formed, as described above, by fibers from each of the three muscles of the lateral abdominal wall. || They originate at the [[pubic bone]], run up the abdomen on either side of the linea alba, and insert into the cartilages of the fifth, sixth, and seventh ribs.
|-
| The [[pyramidalis muscle]] is small and triangular. It is located in the lower abdomen in front of the rectus abdominis. || It originates at the pubic bone and is inserted into the linea alba half way up to the [[umbilicus]].

|}

== Abdominal organs ==
[[Image:Gray1120.png|thumb|RIGHT|200px|The relations of the viscera and large vessels of the abdomen, seen from behind.]]
The abdomen contains most of the tubelike organs of the digestive tract, as well as several solid organs. Hollow abdominal organs include the [[stomach]], the [[small intestine]], and the [[colon (anatomy)|colon]] with its attached [[Vermiform appendix|appendix]]. Organs such as the [[liver]], its attached [[gallbladder]], and the [[pancreas]] function in close association with the digestive tract and communicate with it via ducts. The [[spleen]], [[kidney]]s, and [[adrenal gland]]s also lie within the abdomen, along with many blood vessels including the [[aorta]] and [[venae cavae|inferior vena cava]]. Anatomists may consider the [[urinary bladder]], [[uterus]], [[fallopian tube]]s, and [[ovary|ovaries]] as either abdominal organs or as pelvic organs. Finally, the abdomen contains an extensive membrane called the [[peritoneum]]. A fold of peritoneum may completely cover certain organs, whereas it may cover only one side of organs that usually lie closer to the abdominal wall. Anatomists call the latter type of organs ''retroperitoneal.''

== Surface landmarks of the anterior abdomen ==
[[Image:Nbodybuilder.jpg|thumb|Human with defined abdominal muscles]]

In the mid-line a slight furrow extends from the ensiform cartilage/[[xiphoid process]] above to the [[symphysis pubis]] below, representing the [[linea alba]] in the abdominal wall. At about its midpoint sits the umbilicus or navel. On each side of it the broad recti muscles stand out in muscular people. The outline of these muscles is interrupted by three or more transverse depressions indicating the [[lineae transversae]]. There is usually one about the [[ensiform cartilage]], one at the [[umbilicus]], and one between. It is the combination of the linea alba and the linea transversae which form the abdominal "six-pack" sought after by many people. A body fat of around 10% or below is required to see them.{{Fact|date=August 2007}}

The upper lateral limit of the abdomen is the subcostal margin formed by the cartilages of the false ribs (8, 9, 10) joining one another. The lower lateral limit is the anterior
crest of the [[ilium (bone)|ilium]] and [[Poupart's ligament]], which runs from the anterior superior spine of the ilium to the spine of the [[pubis (bone)|pubis]]. These lower limits are marked by visible grooves. Just above the pubic spines on either side are the external abdominal rings, which are openings in the muscular wall of the abdomen through which the [[spermatic cord]] emerges in the male, and through which an [[inguinal hernia]] may rupture.

One method by which the location of the abdominal contents can be appreciated is to draw three horizontal and two vertical lines.

===Horizontal lines===
[[Image:Gray1225.png|thumb|Front of abdomen, showing surface markings for duodenum, pancreas, and kidneys.]]
* The highest of the former is the [[transpyloric line]] of C. Addison, which is situated half-way between the [[suprasternal notch]] and the top of the symphysis pubis, and often cuts the pyloric opening of the stomach an inch to the right of the mid-line. The [[hilum]] of each [[kidney]] is a little below it, while its left end approximately touches the lower limit of the [[spleen]]. It corresponds to the first lumbar vertebra behind.

* The second line is the ''[[subcostal line]]'', drawn from the lowest point of the [[subcostal arch]] ([[tenth rib]]). It corresponds to the upper part of the third lumbar vertebra, and it is an inch or so above the umbilicus. It indicates roughly the [[transverse colon]], the lower ends of the kidneys, and the upper limit of the transverse (3rd) part of the [[duodenum]].

* The third line is called the ''[[intertubercular line]]'', and runs across between the two rough [[Tubercle (anatomy)|tubercles]], which can be felt on the outer lip of the crest of the ilium about two and a half inches (60 mm) from the anterior superior spine. This line corresponds to the body of the fifth lumbar vertebra, and passes through or just above the [[ileo-caecal valve]], where the [[small intestine]] joins the [[large intestine|large]].

===Vertical lines===
The two vertical or mid-Poupart lines are drawn from the point midway between the anterior superior spine and the pubic symphysis on each side, vertically upward to the costal margin.

* The right one is the most valuable, as the [[ileo-caecal valve]] is situated where it cuts the intertubercular line. The orifice of the [[vermiform appendix]] lies an inch lower, at [[McBurney's point]]. In its upper part, the vertical line meets the transpyloric line at the lower margin of the ribs, usually the ninth, and here the [[gallbladder]] is situated.

* The left mid-Poupart line corresponds in its upper three-quarters to the inner edge of the [[descending colon]].

The right subcostal margin corresponds to the lower limit of the [[liver]], while the right nipple is about half an inch above the upper limit of this [[viscus]].

==Regions of the abdomen==
[[Image:Gray1220.png|thumb|Surface lines of the front of the thorax and abdomen.]]
These three horizontal and two vertical lines divide the abdomen into nine "regions." (Note that "hypo" means "below" and "epi" means "above", while "chond" means "cartilage" (in this case, the cartilage of the rib) and "gast" means stomach. The reversal of "left" and "right" is intentional, because the anatomical designations reflect the position on the patient. )
{| class="wikitable"
| right hypochondriac/[[hypochondrium]] || epigastric/[[epigastrium]] || left hypochondriac/hypochondrium
|-
| right [[lumbar]]/[[flank]]/[[Latus (anatomy)|latus]]/lateral || [[Umbilical region|umbilical]] || left lumbar/flank/lateral
|-
| right [[inguinal]]/[[iliac]] || [[Hypogastrium|hypogastric]]/[[pubic]] || left inguinal/iliac
|}

Another way of dividing the abdomen is by using quadrants:
{| class="wikitable"
| upper right quadrant ([[RUQ]]) || upper left quadrant
|-
| lower right quadrant|| lower left quadrant
|}

==See also==
* [[Waist]]
* [[List of muscles of the human body]]
* [[Alimentary canal]]
* [[Abdominal pain]]
* [[Abdominal hair]]

==References==
*Tortora, Gerard J., Anagnostakos, Nicholas P. (1984) ''Principles of Anatomy and Physiology'', Harper & Row Publishers, New York ISBN 0-06-046656-1
*Gray, Henry, (1977) ''Anatomy, Descriptive and Surgical (Gray's Anatomy)'' Bounty Books
*Taber, Clarence Wilber, (1981) ''Taber's Cyclopedic medical dictionary 14 Edition'', F.A Davis Company, Philadelphia ISBN 0-8036-8307-3
*[http://www.kmle.com/search.php?Search=abdomen KMLE Medical Dictionary definition of abdomen] retrieved from [http://www.kmle.com KMLE Medical Dictionary] on 2007-03-25

{{Human anatomical features}}
{{Torso general}}
[[Category:Abdomen]]
[[Category:Human anatomy]]

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