Abdomen internal organs

The Abdomen (Human Anatomy) - Picture, Function, Parts, Definition, and More

Human Anatomy

Written by Matthew Hoffman, MD

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The abdomen (commonly called the belly) is the body space between the thorax (chest) and pelvis. The diaphragm forms the upper surface of the abdomen. At the level of the pelvic bones, the abdomen ends and the pelvis begins.

The abdomen contains all the digestive organs, including the stomach, small and large intestines, pancreas, liver, and gallbladder. These organs are held together loosely by connecting tissues (mesentery) that allow them to expand and to slide against each other. The abdomen also contains the kidneys and spleen.

Many important blood vessels travel through the abdomen, including the aorta, inferior vena cava, and dozens of their smaller branches. In the front, the abdomen is protected by a thin, tough layer of tissue called fascia. In front of the fascia are the abdominal muscles and skin. In the rear of the abdomen are the back muscles and spine.

Abdomen Conditions

• Peritonitis: Inflammation of the covering of the abdominal structures, causing abdominal wall rigidity and severe pain. Usually, this is due to a ruptured or infected abdominal organ.
• Acute abdomen: A medical phrase doctors use to suggest that peritonitis or some other emergency is present and surgery is likely needed.
• Appendicitis: Inflammation of the appendix, in the lower right colon. Usually, an inflamed appendix must be removed by surgery.
• Cholecystitis: Inflammation of the gallbladder, causing severe right-sided abdominal pain. A gallstone blocking the duct exiting the gallbladder is usually responsible.
• Dyspepsia: The feeling of an upset stomach or indigestion. Dyspepsia can result from benign or more serious conditions.
• Constipation: Having fewer than three bowel movements per week. Diet and exercise may help but many people will need to see their health care providers.
• Gastritis: Inflammation of the stomach, often causing nausea and/or pain. Gastritis can be caused by alcohol, NSAIDs, H. pylori infection, or other factors.
• Peptic ulcer disease: Ulcers are erosions and peptic refers to acid. Peptic ulcers are ulcers in the stomach and duodenum (the first part of the small intestine). The usual cause is either an infection with H. pylori or taking anti-inflammatory medications like ibuprofen.
• Intestinal obstruction: A single area of the small or large intestine can become blocked or the entire intestine may stop working. Vomiting and abdominal distension are symptoms.
• Gastroparesis: The stomach empties slowly due to nerve damage from diabetes or other conditions. Nausea and vomiting are symptoms.
• Pancreatitis: Inflammation of the pancreas. Alcohol and gallstones are the most common causes of pancreatitis. Other causes include drugs and trauma; about 10% to 15% of cases are from unknown causes.
• Hepatitis: Inflammation of the liver, usually due to viral infection. Drugs, alcohol, or immune system problems can also cause hepatitis.
• Cirrhosis: Scarring of the liver caused by chronic inflammation. Heavy drinking or chronic hepatitis are the most common causes.
• Ascites: Abdominal fluid buildup often caused by cirrhosis. Ascites may cause the abdomen to protrude impressively.
• Abdominal hernia: A weakening or gap in the abdominal fascia allows a section of the intestine to protrude.
• Abdominal distension: Swelling of the abdomen, usually due to an increased amount of intestinal gas.
• Abdominal aortic aneurysm: A weakening of the aorta's wall creates a balloon-like expansion of the vessel that grows over years. If abdominal aortic aneurysms grow large enough, they may burst.

Abdomen Tests

• Physical examination: By listening with a stethoscope, pressing, and tapping on the abdomen, a doctor gathers information that helps diagnose abdominal problems.
• Upper endoscopy (esophagogastroduodenoscopy or EGD): A flexible tube with a camera on its end (endoscope) is inserted through the mouth. The endoscope allows examination of the stomach and duodenum (small intestine).
• Lower endoscopy (colonoscopy): An endoscope is advanced through the anus into the rectum and colon. Colonoscopy can help identify problems in these areas, such as cancer or bleeding.
• Abdominal X-ray: A plain X-ray of the abdomen can help see the organs and conditions in the belly including intestinal obstruction or perforation.
• Computed tomography (CT scan): A CT scanner uses X-rays and a computer to create images of the abdomen. CT scanning can help identify some abdominal conditions, such as appendicitis and cancer.
• Magnetic resonance imaging (MRI scan): Using radio waves in a magnetic field, a scanner creates highly detailed images of the abdomen. In the abdomen, MRI is usually used to check the liver, pancreas, and gallbladder, but a CT scan may also be used.
• Abdominal ultrasound: A probe on the abdomen reflects high-frequency sound waves off the abdominal organs, creating images on a screen. Ultrasound can detect problems in most abdominal organs, such as the gallbladder, liver, and kidneys.
• Endoscopic retrograde cholangiopancreatography (ERCP): Using an endoscope advanced to the intestine, a tube is placed into the duct from the pancreas and a fluid that blocks X-rays is squirted into the tubes that serve the gall bladder, liver, and pancreas. Then an X-ray picture is taken to find problems with those organs. 
• pH testing: Using a tube through the nose or a capsule in the esophagus, acid levels in the esophagus can be monitored. This can help diagnose GERD or evaluate a treatment's effectiveness.
• Upper GI series (with small bowel follow-through): After swallowing a barium solution, X-ray films of the esophagus and stomach are taken. This can sometimes diagnose ulcers or other problems. In some cases they continue taking pictures as the barium courses through the small intestine.
• Gastric emptying study: A test of how rapidly food passes through the stomach. The food is labeled with a radioactive substance and its movement viewed on a scanner.
• Biopsy: A small piece of tissue is taken to help diagnose cancer, liver or other problems.

Abdomen Treatments

• Abdominal surgery: Surgery is often necessary for serious abdominal conditions like cholecystitis, appendicitis, colon or stomach cancer, or an aneurysm. Surgery may be laparoscopic (several small incisions and using a camera and small tools) or open (one large incision, what most people think of as a typical surgery).
• Histamine (h3) blockers: Histamine increases stomach acid secretion; blocking histamine can reduce acid production and GERD symptoms.
• Proton pump inhibitors: These medicines directly inhibit the acid pumps in the stomach. They must be taken daily to be effective. There is, though, some concern about taking them for more than a few months.
• Endoscopy: During upper or lower endoscopy, tools on the endoscope can sometimes treat problems (like bleeding or cancer) that are discovered.
• Motility agents: Medicines can increase contraction of the stomach and intestines, improving symptoms of gastroparesis or constipation.
• Antibiotics: H. pylori infection can be cured with antibiotics, which are taken with other medicines to help heal the stomach.
• Laxatives: Various over-the-counter and prescription medicines can help relieve constipation.

Anatomy, Abdomen and Pelvis, Abdomen - StatPearls

Introduction

The definition of the human abdomen is the anterior region of the trunk between the thoracic diaphragm superiorly and the pelvic brim inferiorly. 

Understanding the anatomy of the abdomen will ultimately serve as one's cornerstone to understanding, diagnosing, and treating the pathology within.[1]

Structure and Function

The abdomen ultimately serves as a cavity to house vital organs of the digestive, urinary, endocrine, exocrine, circulatory, and parts of the reproductive system.

The anterior wall of the abdomen has nine layers. From outermost to innermost, they are skin, subcutaneous tissue, superficial fascia, external obliques, internal obliques, transversus abdominis, transversalis fascia, preperitoneal adipose and areolar tissue, and the peritoneum. The peritoneum is one continuous membrane; however, it is classified as either visceral (lining the organs) or parietal (lining the cavity wall). A peritoneal cavity is therefore formed and filled with extracellular fluid used to lubricate the surfaces to reduce friction. The peritoneum is comprised of a layer of simple squamous epithelial cells. 

The subcutaneous tissue of the anterior abdominal wall below the umbilicus also separates into two distinct layers: the superficial fatty layer known as Camper's fascia, and the deeper membranous layer known as Scarpa's fascia. This membranous layer is continuous with Colles fascia within the perineal region inferiorly. 

The true abdominal cavity consists of the stomach, duodenum (first part), jejunum, ileum, liver, gallbladder, the tail of the pancreas, spleen, and the transverse colon.   

The posterior wall of the abdominal cavity is known as the retroperitoneum.[2] The retroperitoneal structures include the suprarenal glands, aorta and inferior vena cava, duodenum (parts 2 to 4), pancreas (head and body), ureters, colon (descending and ascending), kidneys, esophagus (thoracic), and rectum.[3] One can use the mnemonic SAD PUCKER. 

Embryology

The abdomen derives from three primary germ layers as an embryo. These are the ectoderm, which forms the epidermis, the somatic and splanchnic mesoderm, which forms the skeletal muscle of the abdominal wall and smooth muscle of the bowel, respectively, and the endoderm which forms the majority of the alimentary canal. 

Embryologically, the gastrointestinal system develops as the foregut, midgut, and hindgut.

• Foregut: esophagus to the proximal duodenum where the bile duct enters

• Midgut: distal duodenum to proximal two-thirds of the transverse colon

• Hindgut: the distal third of the transverse colon to anal canal above the pectinate line

Blood Supply and Lymphatics

The central abdominal wall is perfused by the superior epigastric artery (branch of the internal thoracic artery) above the umbilicus, and the inferior epigastric artery (branch of the external iliac artery) below the umbilicus. Venous drainage is accomplished via the internal and lateral thoracic veins superiorly, and the superficial epigastric (branch of the femoral vein) and inferior epigastric (branch of external iliac) veins inferiorly. Lymphatic drainage above the umbilicus is accomplished mainly via the axillary lymph nodes but does drain small amounts to the parasternal lymph nodes. Below the umbilicus, lymph drains to the superficial inguinal lymph nodes.

Internally, the abdomen contains two major blood vessels - the aorta and the inferior vena cava. The aorta has three main branches that serve to supply the organs of the gastrointestinal tract, which includes the celiac, superior mesenteric, and inferior mesenteric arteries. These arteries branch off of the aorta anteriorly, while arteries that supply non-GI tract structures branch either laterally or posteriorly. Examples of such include the renal or gonadal arteries. 

• The blood supply of the gastrointestinal tract follows the embryonic gut regions:

• The celiac artery supplies the foregut.

• The superior mesenteric artery supplies the midgut.

• The inferior mesenteric artery supplies the hindgut.

Note: The splenic flexure is known as a "watershed" area due to dual blood supply from distal artery branches, which can result in colonic ischemia.

Venous drainage from the organs of digestion occurs through the portal system, whereas non-digestion venous drainage occurs through the inferior vena cava and its tributaries. 

The portal venous system consists of the superior mesenteric vein, inferior mesenteric vein (along with the superior rectal vein), and splenic vein and its tributaries, which all join to form the portal vein. The ligamentum teres, which contains the remnant of the umbilical vein, is of clinical significance due to its connection of the portal system to the abdominal wall. In the setting of portal hypertension, patients may experience dilation of the periumbilical veins, termed caput-medusae. Additionally, gastrointestinal cancers may metastasize to the anterior abdominal wall through the lymphatics that parallel the venous drainage, termed the Sister Mary Joseph sign/nodule.

Nerves

Important dermatomes include the xiphoid process at T6, the umbilicus at T10, and the umbilical fold at L1. 

The skin and muscles of the abdominal wall receive their innervation by the anterior and lateral cutaneous branches of the thoracoabdominal nerves (T7-T11), the subcostal nerve (T12), the iliohypogastric nerve (L1, sensation to the suprapubic region), and the ilioinguinal nerve (L1, sensation to the ipsilateral medial thigh and scrotum). 

Viscerally, the vagus nerve serves to parasympathetically innervate the vast majority of the gastrointestinal tract to include the foregut and midgut. The hindgut receives parasympathetic input from the sacral roots S2, S3, and S4. 

• The foregut receives sympathetic innervation from the greater thoracic splanchnic nerve.

• The midgut receives sympathetic innervation from the lesser thoracic splanchnic nerve.

• The hindgut receives sympathetic innervation from the lumbar splanchnic nerves.

It is important to note that the visceral peritoneum and the underlying organs are insensitive to touch, temperature, or laceration, but rather perceive pain through stretch and chemical receptors. Due to the innervation of the organs, pain is poorly localized and refers to the dermatomes of the spinal ganglia that provide the sensory fibers. Consequently, foregut pain is usually referred to the epigastrium, midgut to the umbilicus, and hindgut to the pubic region. 

Muscles

The abdominal muscles assist in the process of respiration, protect the inner organs, provide postural support, and serve to flex, extend, and rotate the trunk of the body.[4]

The four main abdominal muscle groups, from innermost to outermost, can be remembered by the mnemonic TIRE: Transversus abdominis, internal oblique, rectus abdominis, and external oblique.[5] The external and internal obliques run diagonally and perpendicular to each other. An easy way to remember which way the fibers run is to think of putting your hands in your pockets. The hand position represents the direction of the external obliques, and the internal obliques run perpendicular to this. 

A midline raphe, the linea alba, is formed from the interweaving of the aponeuroses of the external oblique, internal oblique, and transversus abdominis. 

The aponeurosis of the internal oblique muscle splits to encapsulate the rectus abdominis muscles above the arcuate line, however, below the arcuate line, both the aponeurosis of the internal oblique and the transversus abdominis are anterior to the rectus abdominis.

Physiologic Variants

Various birth defects of the abdominal anatomy can occur. Examples include but are not limited to gastroschisis, omphalocele, congenital umbilical hernia, intestinal atresia, hypertrophic pyloric stenosis, annular pancreas, Hirschsprung disease, malrotation, agenesis, etc. 

Surgical Considerations

Clinically, the abdomen is roughly divided into nine regions by two sagittal planes from the midclavicular lines to the mid inguinal lines, and two transverse planes, one at the subcostal line and one at the iliac tubercles. The umbilicus serves at the center of the nine regions. Each region and its associated organs are detailed below:

• Right hypochondrium: liver, gallbladder

• Epigastrium: stomach, liver, pancreas, duodenum, adrenal glands

• Left hypochondrium: spleen, colon, pancreas

• Right lumber region: ascending colon, right kidney

• Umbilical region: navel, small intestine

• Left lumbar legion: descending colon, left kidney

• Right iliac fossa: appendix, cecum

• Hypogastric: Urinary bladder, sigmoid colon, female reproductive

• Left iliac fossa: descending colon, sigmoid colon

Surgically, the portal triad within the hepatoduodenal ligament is of considerable significance and includes the proper hepatic artery, common bile duct, and portal vein. The Pringle maneuver is when pressure is applied to this ligament to control hemorrhage.[6]

Clinical Significance

Abdominal signs and symptoms can be from a wide variety of disease processes to include vascular, infectious, trauma, autoimmune, musculoskeletal, idiopathic, neoplastic, congenital, etc. The details below are not meant to serve as an exhaustive list; however, it should serve as a guide for commonly encountered pathology within their respective quadrants and can help guide clinical decision making, especially with regards to imaging and surgery.[7][8][9][10]

Right upper quadrant (RUQ) pain

Commonly due to gastric reflux, gallbladder disease, hepatitis, peptic ulcer disease, pancreatitis, pyelonephritis, kidney stone, retrocecal appendicitis, or bowel obstructions

Right lower quadrant (RLQ) pain

Commonly due to appendicitis, Crohn disease, cecal diverticulitis, ectopic pregnancy, endometriosis, inguinal hernia, ischemic colitis, ovarian cyst, ovarian torsion, pelvic inflammatory disease, psoas abscess, testicular torsion, or kidney stones 

Left upper quadrant (LUQ) pain

Commonly due to gastric reflux, peptic ulcer disease, pancreatitis, splenic infarction or rupture, pyelonephritis, bowel obstruction, or aortic dissection

Left lower quadrant (LLQ) pain

Commonly due to diverticulitis, kidney stones, pyelonephritis, ectopic pregnancy, inflammatory bowel disease, inguinal hernia, ovarian cysts, ovarian torsion, pelvic inflammatory disease, psoas abscess, testicular torsion, abdominal aortic aneurysm, irritable bowel syndrome, or small bowel obstructions

Pectinate Line

The pectinate (dentate) line also serves as clinical significance. Above the pectinate line, one can expect internal hemorrhoids and adenocarcinoma. The internal hemorrhoids are not painful due to their visceral innervation. Below the pectinate line, one can expect external hemorrhoids, anal fissures, and squamous cell carcinoma. The external hemorrhoids are painful due to their somatic innervation.

Inguinal Hernias

A hernia, which is a protrusion of abdominal contents through an opening, can cause extreme pain, incarceration, and potential strangulation. Two types of inguinal hernias exist - direct and indirect. One can remember the anatomical difference through the mnemonic "MDs don't LIe." If the hernia is Medial to the epigastric blood vessels, then it is a Direct inguinal hernia. However, if the hernia is Lateral to the epigastric blood vessels, then it is an Indirect inguinal hernia. 

Direct inguinal hernias, usually in older men, are only covered by external spermatic fascia and go through only the external inguinal ring.  

Indirect inguinal hernias protrude through the internal and external inguinal rings and into the scrotum. They are covered by all three spermatic fascial layers: internal, cremasteric, and external. 

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Figure

Front of abdomen, showing surface markings for liver, stomach, and great intestine. Contributed by Gray's Anatomy Plates

References

1.

Brogi E, Kazan R, Cyr S, Giunta F, Hemmerling TM. Transversus abdominal plane block for postoperative analgesia: a systematic review and meta-analysis of randomized-controlled trials. Can J Anaesth. 2016 Oct;63(10):1184-1196. [PubMed: 27307177]

2.

Lambert G, Samra NS. StatPearls [Internet]. StatPearls Publishing; Treasure Island (FL): Jul 26, 2021. Anatomy, Abdomen and Pelvis, Retroperitoneum. [PubMed: 31751047]

3.

Selçuk İ, Ersak B, Tatar İ, Güngör T, Huri E. Basic clinical retroperitoneal anatomy for pelvic surgeons. Turk J Obstet Gynecol. 2018 Dec;15(4):259-269. [PMC free article: PMC6334244] [PubMed: 30693143]

4.

Tesh KM, Dunn JS, Evans JH. The abdominal muscles and vertebral stability. Spine (Phila Pa 1976). 1987 Jun;12(5):501-8. [PubMed: 2957802]

5.

Tsai HC, Yoshida T, Chuang TY, Yang SF, Chang CC, Yao HY, Tai YT, Lin JA, Chen KY. Transversus Abdominis Plane Block: An Updated Review of Anatomy and Techniques. Biomed Res Int. 2017;2017:8284363. [PMC free article: PMC5684553] [PubMed: 29226150]

6.

Thomas JM, Van Fossen K. StatPearls [Internet]. StatPearls Publishing; Treasure Island (FL): Sep 26, 2022. Anatomy, Abdomen and Pelvis, Foramen of Winslow (Omental, Epiploic) [PubMed: 29489171]

7.

Heiken JP, Katz DS, Menu Y. Emergency Radiology of the Abdomen and Pelvis: Imaging of the Non-traumatic and Traumatic Acute Abdomen. In: Hodler J, Kubik-Huch RA, von Schulthess GK, editors. Diseases of the Abdomen and Pelvis 2018-2021: Diagnostic Imaging - IDKD Book [Internet]. Springer; Cham (CH): Mar 21, 2018. pp. 123–143. [PubMed: 31314362]

8.

Patterson JW, Kashyap S, Dominique E. StatPearls [Internet]. StatPearls Publishing; Treasure Island (FL): Jul 11, 2022. Acute Abdomen. [PubMed: 29083722]

9.

Li PH, Tee YS, Fu CY, Liao CH, Wang SY, Hsu YP, Yeh CN, Wu EH. The Role of Noncontrast CT in the Evaluation of Surgical Abdomen Patients. Am Surg. 2018 Jun 01;84(6):1015-1021. [PubMed: 29981641]

10.

Puylaert JB. Ultrasound of acute GI tract conditions. Eur Radiol. 2001;11(10):1867-77. [PubMed: 11702119]

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