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Introduction to Abdomen

The abdomen is also called the belly, tummy, midriff, or stomach. It is the part of the body between the thorax and pelvis in every human and in other vertebrates. The abdomen is the front part of the abdominal segment of the trunk. The abdominal cavity is the area that is occupied by the abdomen. In the arthropods, the abdomen is the posterior tagma of the body and it follows the thorax or the cephalothorax.

In human beings, the abdomen is between the thorax at the thoracic diaphragm and the pelvis at the pelvic brim. The space above the pelvis inlet and under the thoracic diaphragm is termed the abdominal cavity. The boundary of the abdominal cavity is nothing but the abdominal wall which is in the front and the peritoneal surface at the rear. 

In all the vertebrates, the abdomen is a large body cavity that is enclosed by the abdominal muscles at the front and to the sides and by the part of the vertebral column at the back. The ventral and the lateral walls are also enclosed by the lower ribs. The abdominal cavity is very continuous with and above the pelvic cavity. The abdominal cavity is attached to the thoracic cavity by the diaphragm. Through the diaphragm, many structures such as the aorta, inferior vena cava, and the esophagus pass through. A serous membrane line known as the parietal peritoneum lines both the abdominal and pelvic cavities. This membrane is known to be continuous with the visceral peritoneum which lines the organs. The abdomen is known to have many organs such as the digestive system, urinary system, and muscular system. 

In this article, we are going to give information about the abdomen, its layers of muscles, functions, various diseases related to the abdomen, and also a few frequently asked questions will also be answered. 

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About Abdomen 

The abdomen which is commonly known as the belly is the body space found between the thorax and the pelvis. The upper surface of the abdomen is formed by the diaphragm. At the level of the pelvis bones, the abdomen is found to end and the pelvis initially begins. 

The abdomen is found to contain all the important organs such as the stomach, small intestines, and the large intestine, the liver, the pancreas, and the gallbladder. All these organs are held together loosely by the connecting tissues which allow them to expand and slide against each other. The kidneys and spleen are also found to be contained within the abdomen. The uterus, urinary bladder, fallopian tubes, and ovaries may be seen as either the pelvic organs or the abdominal organs. The abdomen also contains an extensive membrane known as the peritoneum. An initial fold of the peritoneum is found to completely cover certain organs, whereas it may also cover only one side of the organs that usually lie closer to the abdominal wall, this is called the retroperitoneum. The ureters and the kidneys are known as the retroperitoneal organs.

Muscles of the Abdomen

  • The abdominal wall is made up of three layers of muscles. External oblique, internal oblique, and transverse abdominal are the three types, from outside to within. Around the vertebral spine, the lower ribs, the iliac crest, and the pubis of the hip are the first three layers. Their fibres both converge at the midline and form a sheath around the rectus abdominis before entering on the opposite side at the linea alba. 

  • The external oblique, which runs downward and forward, the internal oblique, which runs upward and forward, and the transverse abdominal, which runs horizontally forward, provide power.

  • The fibres of the transverse abdominal muscle run horizontally and are smooth and triangular. It's located between the internal oblique and the transverse fascia underneath it. Poupart's ligament, the inner lip of the ilium, the lumbar fascia, and the inner surface of the six lower rib cartilages are all sources. It goes behind the rectus abdominis and into the linea alba.

  • The muscles of the rectus abdominis are long and smooth. The tendinous intersections are three fibrous bands that cross the muscle. The rectus abdominis is encased in a dense sheath made up of fibres from each of the three lateral abdominal wall muscles. They start at the pubis bone, run up the abdomen on both sides of the linea alba, and insert into the fifth, sixth, and seventh rib cartilages. 

  • The inguinal canal which is located in the groin region is a passageway between the layers. The testes will fall through the wall here, and the fibrous cord from the female uterus passes through it. This is also where inguinal hernias can develop due to weakness. The pyramidalis muscle is very small and triangular in shape. It is located in the lower abdomen which is in front of the rectus abdominis. The pyramidalis muscle originates at the pubic bone and is inserted into the linea alba halfway up to the navel

Abdomen Functions 

The primary functions of the abdomen consist of breathing, digestion, posture, and balance as well as movement. All the major organs that are located in the abdomen are associated with digestion. The abdomen is very important for breathing via the accessory muscles of respiration. These muscles are also involved in postural support, balance, movement, coughing, urination, vomiting, singing, defecation, and childbirth. A detailed explanation of the function with which the abdomen is associated is given below. 


Under steady-state conditions, the diaphragm is known to control respiration, the accessory muscles of respiration help in respiration when a greater effort is required for breathing. The scalene and the sternocleidomastoid muscles are the muscles that serve to raise the ribcage. Whenever these muscles are engaged, it is a sign of respiratory distress, such as the one that is observed during an asthma attack. 

Movement and Posture 

To maintain the posture, the balance of the body, and the movement, the abdominal muscles are required. The internal obliques and the abdominis muscle greatly affects the posture by providing spinal support during rotation and lateral flexion and also stabilize the spine when a person is in a standing position. Both of these muscles are situated deep in the abdomen. The external oblique muscles are also known to support the lateral flexion and stabilize the spine when standing. The rectus abdominis main function is to help the spine bend in the forward position.


Abdomen Conditions 

Here are a few of the abdominal conditions that everyone should be aware of:

  • Peritonitis: It is the inflammation of the covering of the abdominal structures. This causes the abdominal wall to get rigid and also causes immense pain. This condition is usually caused by ruptured or infected abdominal organs.

  • Appendicitis: It is caused due to the inflammation of the appendix in the lower right colon. The only treatment of this condition is to remove the inflamed colon with the help of surgery. 

  • Cholecystitis: It is the inflammation of the gallbladder and it causes immense pain in the right side of the abdomen. Many cases have been found to suggest that a gallstone blocking the duct exiting the gallbladder could be the main reason behind this condition. 

  • Dyspepsia: It is the feeling of an upset stomach or indigestion and it is believed that Dyspepsia could be caused by benign or any other series of conditions. 

  • Constipation: A person who has less than three bowel movements per week might be suffering from this condition. It could be caused due to an inappropriate diet or not doing enough exercise.

  • Gastritis: In this condition, there is an inflammation of the stomach which often causes nausea and pain. Gastritis can also be caused due to the consumption of alcohol, NSAIDs, H. pylori infection, or other factors.

  • Peptic Ulcer Disease: It is a condition where there are ulcers in the stomach and the duodenum. It is usually caused due to an infection with H. pylori or by taking any anti-inflammatory medications like ibuprofen.

  • Intestinal obstruction may occur in a particular region of the small or large intestine, or the whole intestine may quit functioning. Symptoms include nausea and stomach distension.

  • Gastroparesis is a disorder in which the stomach empties painfully as a result of nerve damage caused by diabetes or other disorders. Symptoms include nausea and vomiting.

  • Pancreatitis is a condition in which the pancreas is inflamed. The two frequent causes of pancreatitis are alcohol and gallstones. Other factors include medications and trauma; about 10% to 15% of cases are caused by unexplained factors.

  • Hepatitis is an inflammation of the liver caused by a virus. Hepatitis can also be caused by drugs, alcohol, or immune system issues.

  • An abdominal hernia occurs when the abdominal fascia weakens or a void opens, allowing a portion of the intestine to protrude.

  • Abdominal distension is the swelling of the belly caused by an excess of intestinal gas.

  • An aortic aneurysm is a balloon-like extension of the vessel caused by a fracturing of the aorta's wall that expands with time. Aortic aneurysms in the abdomen can burst if they develop large enough.

  • Cirrhosis is a condition in which the liver scars as a result of chronic inflammation. The most prevalent causes are over alcohol or untreated hepatitis.

  • Cirrhosis is a common cause of ascites, which is an accumulation of fluid in the abdomen. Ascites can make the abdomen protrude noticeably.

Abdomen Treatments 

There are many treatments that will help in treating the various conditions related to the abdomen, a few of them are listed below. 

  • Abdominal surgery is done when there are a series of abdominal conditions like cholecystitis, appendicitis, colon or stomach cancer, or an aneurysm. 

  • Histamine(H2) Blockers: Histamine in our body is known to increase stomach acid secretion which causes many complications in our body. Blocking the histamine will evidently reduce the acid production and the GERD symptoms. 

  • Proton Pump Inhibitors: These are the medicines that will directly inhibit the acid pumps in the stomach. They are prescribed in such a way that they should be consumed every day. 

  • Motility Agents: These are the medicines or the drugs that will increase the contractions in the stomach and the intestines. These drugs are used in the management of intestinal motility disorders which include cholinergic agonists, prokinetic agents, opioid antagonists, and antibiotics. These are used to improve the symptoms of constipation.

  • Antibiotics: Antibiotics can help in curing many infections of the stomach. These antibiotics can be taken with other medicines to help heal the stomach.

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FAQs on Abdomen

Q1: Why Does Someone Feel Pain in Abdomen?

Ans: The pain in abdomen is a pain that a person feels anywhere between the chest and the groin. This is mostly referred to as the stomach region or the belly region. There are many different conditions that are known to cause abdominal pain. Few of the less serious causes of abdominal pain include constipation, irritable bowel syndrome, food allergy or intolerance, food poisoning, and stomach flu. Other major causes of pain in abdomen include Appendicitis, bowel blockage or obstruction, cancer of the stomach, colon (large bowel), and other organs, decreased blood supply to the intestines (ischemic bowel), and kidney stones.

Q2: Why is the Lower Abdominal Pain and the Upper Abdominal Pain Caused?

Ans: Abdominal pain can be caused by many conditions, but the main causes are infections, abnormal pain, inflammation, and intestinal disorders. Abdominal pain can be caused due to infections in the throat, intestines, and blood which is usually caused by the bacteria which enters the digestive tract. 

  • The upper abdominal pain or pain in lower right abdomen can be caused by gallstones, heart attack, pneumonia, and hepatitis or liver inflammation. 

  • The lower abdominal pain or the left side abdominal pain can be caused due to various reasons such as cancer, kidney infection, ovarian cysts, appendicitis, and Crohn’s disease.

Q3: What are the Causes of the Left Side Stomach Pain and the Pain in Right Side of Stomach?

Ans: In many cases, many people feel left side stomach pain or lower abdominal pain and it is found to be caused by diverticulitis. Diverticula are small pouches that are created from pressure on the weak spots in the colon. Diverticula are found to be very common, and when the pouch tears, swells or gets infected, it causes diverticulitis. Symptoms such as fever, nausea, vomiting, abdominal tenderness, and constipation are other symptoms associated with diverticulitis. In case of mild diverticulitis, many people are suggested to take rest, change the diet such as adding fibre in it, and antibiotics.

The upper part of the abdomen has many important and necessary organs such as the stomach, spleen, pancreas, kidneys, adrenal glands, part of the colon, gallbladder, and liver. The pain in the right side of stomach may be caused due to the deposition of the gallstones, hepatitis, Gastroesophageal reflux disease (GERD), Gastritis, Hiatal hernia, and Gastroparesis.

Q4: What Does the Pain in Lower Left Side of Abdomen Female or an Aching Stomach Mean?

Ans: The pain in lower left side of abdomen of female or aching stomach may be caused by gas, indigestion, diarrhoea, or cancer, or it may be caused by menstrual cramps, endometriosis, or pelvic inflammatory disorder. Kidney stones can cause severe pain that comes in waves. Trauma to the body wall, hernias, and shingles will also induce discomfort in the left lower quadrant.

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