Physicians and anatomists divide the human abdomen into four different regions or quadrants. The quadrants are: the left lower quadrant, the right lower quadrant, the left upper quadrant, and the right upper quadrant.
The reason for dividing the abdomen into four different quadrants is that it assists physicians and anatomists in diagnosing, studying, and giving therapy to problems associated with the different regions of the abdomen.
How Is The Abdomen Defined?
Physicians and anatomists use two different planes, or regions that divide the body, to define the quadrants. The median plane, also dubbed the midsagittal plane, divides the body into left and right sides by using the navel as a mid-point and extending upwards/downwards from there. A parasagittal plane is any dividing plane that runs parallel to the sagittal or medial planes. Meanwhile, the umbilical plane or umbilical region is a transverse plane that runs through the umbilicus, the navel region. It divides the body into approximately two halves, an upper half (torso, arms, head, etc.) and bottom half (legs, pelvis).
The four quadrants of the human abdomen: The right upper quadrant runs from the median plane (center dividing line) of the patient and runs to the right, also extending from the umbilical plane to the right portion of the ribcage. The left upper quadrant starts at the median plane of the body and extends up, and it also extends out over the left rib cage from the umbilical region. The right lower quadrant runs to the right from the median plane, extending over the right inguinal ligament from the umbilical plane. The left lower quadrant runs left from the median plane, and over the iliac fossa down from the umbilical region.
Let’s take a closer look at the structures contained within each of one of the four different quadrants.
Left Lower Quadrant:
The left lower quadrant is home to the sigmoid colon, the descending colon, the left ureter, the left ovary, and the left fallopian tube.
The descending colon belongs to the large intestine, and it runs from the splenic flexure down to the sigmoid colon. The primary function of the descending colon is to store what remains of digested food and these remains will eventually flow into the rectum for discharge from the body. Similarly, the sigmoid colon is the portion of the large intestine nearest the rectum, and it connects the descending colon to the rectum.
The ureters are collections of muscle fiber that function to move urine from the kidneys down to the bladder, where the urine is stored until excretion. Both sides of the body have a ureter. The ovary is part of the female reproductive system, responsible for producing ovum, or eggs. When the eggs are released, they will travel to the uterus via the fallopian tube. Both sides of the body possess an ovary and a fallopian tube.
Left Upper Quadrant:
The left upper quadrant is home to the following structures: the stomach, the left kidney and adrenal gland, the body of the pancreas, the left half of the liver, the spleen, the splenic flexures of the colon, and parts of the transverse/descending colon.
The stomach is a large hollow organ that holds digestive enzymes and gastric acid, which breaks down food following the chewing and swallowing of food. The kidneys are small organs, roughly bean-shaped, that work to break down toxic products and clean the blood, passing the waste products as urine to the bladder. The adrenal glands are responsible for producing hormones like adrenaline, cortisol, and aldosterone. The adrenal glands function to burn fat and protein, react to stress signals and control the body’s blood sugar. The pancreas is an organ within the digestive system that produces important hormones like pancreatic polypeptides, insulin, and glucagon. In addition to producing hormones, it secretes digestive enzymes that help the small intestine absorb nutrients.
The primary function of the spleen is to filter the blood and remove toxic compounds. It plays a critical role in the immune system, recycles iron, and removes old red blood cells. The colic flexures are part of the transverse colon, which runs across the abdomen and connects the ascending colon to the descending colon on the other side. There are two colic flexures, one on each side of the body that join the transverse colon to the other areas of the colon.
Right Upper Quadrant:
The right upper quadrant is home to these structures: The liver, the gallbladder, and biliary tree, the duodenum, the head of the pancreas, the hepatic flexure of the colon, and the right kidney and adrenal gland.
The gallbladder is a hollow organ that functions to concentrate and store bile. This bile is later released into the large intestine to aid in the digestion of fats/lipids. The gallbladder, liver and bile ducts all make up the biliary tract. The duodenum is the first portion of the small intestine, and it receives partially digested food from the stomach, preparing it to be absorbed in the small intestine.
Right Lower Quadrant:
The right lower quadrant is where the following structures can be found: The cecum, the appendix, the right ureter, the right ovary, and fallopian tube, and the ascending colon.
The cecum is a large pouch that is usually considered the beginning of the large intestine, receiving partially digested food from the final portion of the small intestine and pushing the food into the longer large intestine. The appendix is a small tail/tube that is connected to the cecum. The exact function of the appendix is unknown, and many scientists believe it to be a vestigial organ that is of little consequence to the body as a whole.
A Note On Animal Quadrants:
It should be noted that the field of comparative anatomy doesn’t usually use the quadrant system, as most other animals don’t stand erect like humans do. The equivalent to the right upper quadrant in animals is the right anterior quadrant, while the equivalent to the left upper quadrant is the left anterior quadrant. The animal equivalent to the right lower quadrant is the right posterior quadrant, and the animal equivalent of the left lower quadrant is the left posterior quadrant.