Abdominals anatomy includes everything between the chest and the pelvis. The organs in this region sit below the diaphragm — a thin muscle at the base of the chest that is vital to breathing — in an area called the abdominal cavity. The abdominal muscles wrap around the front and sides protect these organs.
An essential part of abdominals anatomy is the abdominal wall. It consists of skin and muscle, and fascia made of collagen and other connective tissue. The function of the abdominal wall is to protect the abdominal organs from injury and keep them in the proper position. Abdominal wall muscles also help with expiration, pushing the abdominal organs toward the diaphragm to push air out of the lungs, and increase abdominal pressure to assist coughing and vomiting.
One of the essential organs of the abdominals is the stomach. It receives food and drinks from the esophagus and filters them into the duodenum, the first part of the small intestine. It sits in the center of the abdomen and slightly to the left side. The main job of the stomach is to store and break down food before sending it further along in the digestive system. The lower part of the stomach secretes acids to chemically digest the food before sending it through the pyloric sphincter into the duodenum. On average, it takes two to four hours for the stomach to empty its contents into the small intestine.
The stomach empties into the small intestine. In all, the small intestine is about 10 to 15 feet long and made up of muscles, nerves, and blood vessels that break down and absorb nutrients. It has three parts.
The duodenum collects food from the stomach. It is the shortest part of the small intestine, and it collects pancreatic enzymes and bile to further digest food. The middle part of the small intestine is the jejunum, which absorbs sugars, fatty acids, and amino acids. From there, food passes into the third part, the ileum, which absorbs nutrients, specifically vitamin B12 and bile.
From the ileum, food travels into the large intestine, which processes everything that is left after the small intestine absorbs the necessary nutrients. The large intestine has four parts: the cecum, the ascending colon, the transverse colon, and the sigmoid colon.
The cecum absorbs salts and fluids and lubricates the digested food with mucus before passing it into the ascending colon, which absorbs more water and nutrients. The descending colon stores feces and the sigmoid colon moves the stool to the rectum.
The liver plays an essential role in digestion. It sits on the upper right-hand side of the abdomen, on top of the stomach. The liver holds about a pint of blood. It has two lobes and produces the bile that is sent to the gall bladder and duodenum. All of the blood from the stomach and intestines travels through the liver, which acts as a filter, breaking it down, metabolizing drugs, and removing bacteria and toxins. The liver has many other essential functions, including converting glucose to glycogen for storage, regulating amino acids, processing hemoglobin, and clearing bilirubin from the blood.
The kidneys are located on either side of the spine, below the ribs. They filter blood, removing extra water and waste and sending urine through two thin tubes called the ureters to the bladder. The kidneys play a role in removing acid produced in the body to maintain a balance of water, sodium, phosphorus, calcium, and potassium in the blood. Kidneys also produce hormones that support bone health, make red blood cells, and regulate blood pressure. Each kidney has millions of filtering cells called nephrons.
The adrenal glands sit on top of the kidneys. They have two parts, the outer part called the adrenal cortex and the inner part called the adrenal medulla. Each produces different hormones. The adrenal cortex produces cortisol, an important hormone that controls how the body uses proteins, fats, and carbohydrates, regulates blood pressure, prevents inflammation, and increases blood sugar. It also makes aldosterone, which signals the kidneys to regulate electrolytes in the blood.
The adrenal medulla secretes adrenaline, signaling the fight or flight response, increasing heart rate, and maintaining blood pressure to increase blood flow to the brain and muscles.
The gallbladder is in the right upper quadrant of the abdominals. It is a small organ that sits underneath the liver, and its main purpose is to store bile collected from the liver. The gallbladder releases bile into the intestines for digestion, particularly after a large, fatty meal.
The spleen sits inside the left rib cage and is part of the lymphatic system. It has two parts, white pulp and red pulp. The white pulp acts as part of the immune system, producing white blood cells and making antibodies. The red pulp behaves as a filter, destroying viruses and bacteria, getting rid of waste, and removing damaged blood cells from circulation.
The pancreas sits between the duodenum and spleen at the back of the abdomen. The majority of the pancreas is exocrine cells that synthesize enzymes that enter the duodenum. These cells produce enzymes, including insulin and glucagon, that enter the blood.
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