World Library  
Flag as Inappropriate
Email this Article

Abdomen

Article Id: WHEBN0003191861
Reproduction Date:

Title: Abdomen  
Author: World Heritage Encyclopedia
Language: English
Subject: Surface anatomy, Insect wing, Crab, Water retention (medicine), Aorta
Collection: Abdomen, Animal Anatomy, Human Anatomy
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Abdomen

Abdomen
The human abdomen and organs which can be found beneath the surface
Details
Latin Abdomen
Insertion Rib cage
Vertebral column
Actions Movement and support for the torso
Assistance with breathing
Protection for the inner organs
Postural support
Anatomical terminology

The abdomen (less formally called the belly, stomach, tummy or midriff) constitutes the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The region enclosed by the abdomen is termed the abdominal cavity. In arthropods it is the posterior tagma of the body; it follows the thorax or cephalothorax.[1][2] The abdomen stretches from the thorax at the thoracic diaphragm to the pelvis at the pelvic brim. The pelvic brim stretches from the lumbosacral joint (the intervertebral disc 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.

Contents

  • Structure 1
    • Contents 1.1
    • Muscles 1.2
  • Function 2
    • Movement, breathing and other functions 2.1
    • Posture 2.2
  • Society and culture 3
    • Exercise 3.1
  • Clinical significance 4
    • Disease 4.1
    • Examination 4.2
      • Surface landmarks 4.2.1
        • Horizontal lines 4.2.1.1
        • Vertical lines 4.2.1.2
      • Regions 4.2.2
        • 9-region scheme 4.2.2.1
        • 4-region scheme 4.2.2.2
  • Other animals 5
  • See also 6
  • References 7
  • External links 8

Structure

Contents

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 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.

Abdominal organs can be highly specialized in some animals. For example, the stomach of digestive tract and urinary system.

Muscles

(left) Henry Gray (1825–1861). Anatomy of the Human Body.
(Right) A modern example of a human male abdomen above

There are three layers of the abdominal wall. They are, from the outside to the inside: external oblique, internal oblique, and transverse abdominal.[5] The first three layers extend between the vertebral column, the lower ribs, the iliac crest and pubis of the hip. All of their fibers merge towards the midline and surround the rectus abdominis in a sheath before joining up on the opposite side at the linea alba. Strength is gained by the criss-crossing of fibers, such that the external oblique are downward and forward, the internal oblique upward and forward, and the transverse abdominal horizontally forward.[5]

The transverse abdominal muscle is flat and triangular, with its fibers running horizontally. It lies between the internal oblique and the underlying transverse fascia. It originates from Poupart's ligament, the inner lip of the ilium, the lumbar fascia and the inner surface of the cartilages of the six lower ribs. It inserts into the linea alba behind the rectus abdominis.

The rectus abdominis muscles are long and flat. The muscle is crossed by three fibrous bands called the tendinous intersections. 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 pubis bone, run up the abdomen on either side of the linea alba, and insert into the cartilages of the fifth, sixth, and seventh ribs. In the region of the groin, the inguinal canal, a passage through the layers. This gap is where the testes can drop through the wall and where the fibrous cord from the uterus in the female runs. This is also where weakness can form, and cause inguinal hernias.[5]

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 halfway up to the navel.

Function

Functionally, the human abdomen is where most of the liver, the kidneys, the pancreas and the spleen.

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

Movement, breathing and other functions

The abdominal muscles have different important functions. They assist in the breathing process as glottis is closed and the thorax and pelvis are fixed, they are integral in the cough, urination, defecation, childbirth, vomit, and singing functions.[5] When the pelvis is fixed, they can initiate the movement of the trunk in a forward motion. They also prevent hyperextension. When the thorax is fixed, they can pull up the pelvis and finally, they can bend the vertebral column sideways and assist in the trunk's rotation.[5]

Posture

The transverse abdominus muscle is the deepest muscle, therefore, it cannot be touched from the outside. It can greatly affect the body posture. The internal obliques are also deep and also affect body posture. Both of them are involved in rotation and lateral flexion of the spine and are used to bend and support the spine from the front. The external obliques are more superficial and they are also involved in rotation and lateral flexion of the spine. Also they stabilize the spine when upright. The rectus abdominus muscle is not the most superficial abdominal muscle. The tendonous sheath extending from the external obliques cover the rectus abdominus. The Rectus abdominus is the muscle that very fit people develop into the 6-pack ab look. Although, it should really be a 10 pack as there are 5 vertical sections on each side. The 2 bottom sections are just above the pubic bone and usually not visible, hence, the 6 pack abs. The rectus abdominals' function is to bend one's back forward (flexion). The main work of the abdominal muscles is to bend the spine forward when contracting coencentrically.[6]

Society and culture

Exercise

Being a key element to support the spine and contribute to a good posture, it is important to properly exercise the abdominal muscles together with the back muscles as when weak or overly tight they can suffer painful spasms as well as injuries. When properly exercised, these muscles contribute to improve posture and balance, reduce the likelihood of back pain episodes, reduce the severity of back pain, protect against injury by responding efficiently to stresses, help avoid some back surgeries, and help healing from a back problem or after spine surgery. Also, when strengthened, the abdominal muscles provide flexibility as well.

The abdominal muscles can be worked out by practicing disciplines of general body strength such as Pilates, yoga, T'ai chi, and jogging among others. There are also specific routines to target each of these muscles.

Clinical significance

heart disease, asthma and type 2 diabetes.

severe blood loss and infection.[7] Injury to the lower chest can cause injuries to the spleen and liver.[8]

A scaphoid abdomen is when the abdomen is sucked inwards.[9] In a newborn, it may represent a diaphragmatic hernia.[10] In general, it is indicative of malnutrition.[11]

Disease

Many stomach disease, liver disease, pancreatic disease, gallbladder and bile duct disease; intestinal diseases include enteritis coeliac disease diverticulitis and IBS.

Examination

Different endoscopy, colonoscopy, sigmoidoscopy, enteroscopy, oesophagogastroduodenoscopy and virtual colonoscopy. There are also a number of medical imaging techniques that can be used. Surface landmarks are important in the examination of the abdomen.

Surface landmarks

Surface projections of the organs of the vertebra levels, ribs and the ilium.

In the mid-line a slight furrow extends from the xiphoid process above to the pubic symphysis below, representing the linea alba in the abdominal wall. At about its midpoint sits the umbilicus or navel. The rectus abdominis on each side of the linea alba stands out in muscular people. The outline of these muscles is interrupted by three or more transverse depressions indicating the tendinous intersections. There is usually one about the xiphoid process, one at the navel, and one in between. It is the combination of the linea alba and the tendinous intersections which form the abdominal "six-pack" sought after by many people.

The upper lateral limit of the abdomen is the subcostal margin (at or near the subcostal plane) 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 and Poupart's ligament, which runs from the anterior superior spine of the ilium to the spine of the 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
Front of abdomen, showing markings for duodenum, pancreas, and kidneys.
  • The highest of the former is the transpyloric line of C. Addison, which is situated halfway between the suprasternal notch and the top of the pubic symphysis, 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 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.
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 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 its upper limit.

Regions

9-region scheme
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.)

right hypochondriac/hypochondrium epigastric/epigastrium left hypochondriac/hypochondrium
right lumbar/flank/latus/lateral umbilical left lumbar/flank/latus/lateral
right inguinal/iliac hypogastric/suprapubic left inguinal/iliac
4-region scheme
Quadrants of the abdomen.

Another way of dividing the abdomen is by using 4 quadrants:

right upper quadrant (RUQ)

left upper quadrant (LUQ)

right lower quadrant (RLQ)

left lower quadrant (LLQ)

Other animals

The analogous gross morphologies of a human and an ant
In the worker ant, the abdomen consists of the propodeum fused to the thorax and the metasoma, itself divided into the narrow petiole and bulbous gaster.

The invertebrate abdomen is built up of a series of upper plates known as tergites and lower plates known as sternites, the whole being held together by a tough yet stretchable membrane.

The abdomen contains the insect's digestive tract and reproductive organs, it consists of eleven segments in most orders of insects though the eleventh segment is absent in the adult of most higher orders. The number of these segments does vary from species to species with the number of segments visible reduced to only seven in the common honeybee. In the Collembola (Springtails) the abdomen has only six segments.

The abdomen is sometimes highly modified. In Apocrita (bees, ants and wasps), the first segment of the abdomen is fused to the thorax and is called the propodeum. In ants the second segment forms the narrow petiole. Some ants have an additional postpetiole segment, and the remaining segments form the bulbous gaster.[12] The petiole and gaster (abdominal segments 2 and onward) are collectively called the metasoma.

Unlike other arthropods, insects possess no legs on the abdomen in adult form, though the Protura do have rudimentary leg-like appendages on the first three abdominal segments, and Archaeognatha possess small, articulated "styli" which are sometimes considered to be rudimentary appendages. Many larval insects including the Lepidoptera and the Symphyta (Sawflies) have fleshy appendages called prolegs on their abdominal segments (as well as their more familiar thoracic legs), which allow them to grip onto the edges of plant leaves as they walk around.

In arachnids (spiders, scorpions and relatives), the term "abdomen" is used interchangeably with "opisthosoma" ("hind body"), which is the body section posterior to that bearing the legs and head (the prosoma or cephalothorax).

See also

References

  1. ^ Abdomen. (n.d.). Dictionary.com Unabridged (v 1.1). Accessed: 22 Oct 2007
  2. ^ Abdomen. Dictionary.com. The American Heritage Dictionary of the English Language, 4th Edition. Accessed: 22 October 2007
  3. ^ "Ruminant." The Veterinary Dictionary. Elsevier, 2007. Accessed: 22 Oct 2007
  4. ^ Peritoneum. The Veterinary Dictionary. Elsevier, 2007. Accessed: 22 Oct 2007
  5. ^ a b c d e "Abdominal cavity". Encyclopædia Britannica. I: A-Ak - Bayes (15th ed.). Chicago, IL: Encyclopædia Britannica, Inc. 2010. pp. 19–20.  
  6. ^ "The Abdominal Muscle Group". Retrieved 2010-07-13. 
  7. ^ Jansen JO, Yule SR, Loudon MA (April 2008). "Investigation of blunt abdominal trauma". BMJ 336 (7650): 938–42.  
  8. ^ Wyatt, Jonathon; Illingworth, RN. Graham, CA. Clancy, MJ. Robertson, CE (2006). Oxford Handbook of Emergency Medicine. Oxford University Press. p. 346.  
  9. ^ al.], consultants Daniel Albert ... [et (2012). Dorland's illustrated medical dictionary. (32nd ed.). Philadelphia, PA: Saunders/Elsevier. p. 2.  
  10. ^ Durward, Heather; Baston, Helen (2001). Examination of the newborn: a practical guide. New York: Routledge. p. 134.  
  11. ^ Ferguson, Charles (1990). "Chapter 93: Inspection, Auscultation, Palpation, and Percussion of the Abdomen". In Walker, HK; Hall, WD; JW, Hurst. Clinical Methods: The History, Physical, and Laboratory Examinations (3rd ed.). Boston: Butterworths. Retrieved 2013-11-27. 
  12. ^ "Glossary of Descriptive Terminology". Desertants.org. Retrieved 2013-07-08. 

External links

  •  
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 



Copyright © World Library Foundation. All rights reserved. eBooks from Hawaii eBook Library are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.