In Depth: Bones and Organs
The liver, the body’s largest solid organ, functions as a filtration system. It rids the body of toxins and produces bile, which aids in the digestion and absorption of fats and vitamins that dissolve in fat, such as A, D, E, and K.
The gallbladder is a small sac underneath the liver that holds extra bile made by the liver until it is pumped into the small intestine.
The stomach stores food and prepares it for digestion. In the stomach, food mixes with digestive juices. The stomach muscles churn this mix, breaking it down further before it passes into the small intestine. Digestive juices in the stomach include hydrochloric acid, electrolytes, and enzymes, like pepsin.
The pancreas is a gland that produces enzymes to help your body digest proteins, carbohydrates, and fats. It also makes the hormones insulin and glucagon, which help regulate the distribution of nutrients, including sugar.
In the average adult, the small intestine is a 21-foot long tube. The small intestine breaks down fats, carbohydrates, and proteins into fatty acids, which can then be absorbed. The food you consume takes three to five hours to work its way through the small intestine.
Despite its misleading name, the large intestine is shorter than the small intestine — it’s about five feet long — but it is wider in girth. It is the last part of the digestive tract and made up of the cecum, colon, and rectum.
Behind the intestines are the kidneys, important organs that contain an estimated 1 million filtering units called nephrons. The kidneys play a vital role in processing the blood the heart pumps before it goes into general circulation. Every minute, about 1,200 milliliters of blood flows through the kidneys, about one-fifth of all the blood pumped from the heart. Blood is pumped from the heart into the kidneys through the renal artery, which branches directly from the abdominal aorta, a section of the body’s main artery.
Directly on top of the kidneys are the suprarenal (adrenal) glands. Part of the endocrine system, these glands are divided into two portions, the adrenal cortex and the adrenal medulla, and each synthesizes and secretes a different set of hormones. The various hormones help the kidneys to conserve sodium, thus conserving water. They also play a role in supporting the body’s sexual functions, among other things.
The ureters are two tubes that carry urine from the kidneys to the urinary bladder. The ends of each tube act as valves by closing when the bladder is full and preventing backflow of urine.
The main bones in the abdominal region are the ribs. The rib cage protects vital internal organs. There are 12 pairs of ribs and they attach to the spine. There are seven upper ribs, known as “true” ribs, which attach to the sternum (breastbone) in the front of body. The eighth, ninth, and tenth pairs are known as “false” ribs because they are not attached to the sternum but, instead, to the seventh rib. The eleventh and twelfth pairs of ribs are called floating ribs because they attach only to the spine, leaving their opposite ends unattached.
The seven pairs of true ribs are connected to the sternum by costal cartilage, which is flexible and allows the rib cage to expand and retract during breathing.