The tube emerging from the right side of the stomach and extending to the anus is called the intestine. Its main function is to absorb water, electrolytes, and nutrients from the food to provide to the body. It is divided into two types; the small intestine and the large intestine.
The small intestine and large intestine differ from each other in both structure and function. The small intestine is known as a small bowel, which is 20 feet in length, whereas the large intestine is also called colon or large bowel, which is 1.5 meters in length. Although the small intestine is longer than the large intestine, it is called the small intestine because of its small diameter, which is 3.4 to 4.5 cm. The large intestine has a diameter of 4 to 6 cm.
The main role of the small intestine is the absorption of the nutrients from the digested food, whereas the large intestine absorbs water and salt and involve in the production of vitamins.
|Basis for Comparison||Small intestine||Large intestine|
|Definition||The small intestine is the part of the digestive system that runs between the stomach and large intestine||The large intestine is the ending part of the intestine which is shorter and wider than the small intestine|
|Length||4.5 to 7 meters||1.5 meters|
|Diameter||3.5 to 4.5 cm||4 to 6 cm|
|Others name||Small bowl||Colon or large bowl|
|Circular folds||Have circular folds called “palicae circulares”||Absent|
|Nature of walls||Smooth||Sacculated|
|Motility||Shows small movements||Shows very few movements|
|Hormones secreted||Numerous hormones are secreted||No hormones are secreted|
|Functions||Absorbs nutrients from the absorbed food||Takes part in the absorption of water and electrolytes and in the production of vitamins|
What is Small Intestine?
The small intestine is located between the stomach and the large intestine. It is coiled in the abdomen. This tube-like structure has the narrowest diameter of all the parts of the alimentary canal, but its length is 4.5 to 7 meters, which is the longest one. Internally, the small intestine has two growths, villi (microscopic finger-like projections) and circular folds (palicae circulares).
Villi help in enhancing the surface area for absorbing the maximum nutrients available. Circular fold slows down the movement of the food in the small intestine. So, the food remains for a longer time in this intestine for digestion and absorption.
The small intestine possesses three parts; duodenum, jejunum, and ileum. Duodenum is the smallest part of these three parts. It starts at the end of the stomach. It is located adjacent to the stomach. Duodenum has a small opening through the biliary system (liver), gallbladder, and pancreas, which helps it in the breaking of carbohydrates, fats, and proteins. This small opening also allows the digestive secretion to flow into it.
The second and middle part of the small intestine is the jejunum. It is the central section of the abdomen. It is deep red because of the extensive blood supply. The peristaltic movements of this part are very rapid and vigorous. The mesentery ducts that support this region have little fat. The finger-like projections (villi) are also found in jejunum, which helps in the absorption of the digested products.
The third part and the last part, ileum, end in the large intestine. It is located in the lower abdomen and helps in the absorption of the remaining vitamins, nutrients, and bile salts. Its walls are thinner and narrower than the duodenum and jejunum. Blood supply to this part is very limited, and peristaltic movements are very slow. The mesentery ducts that support this region have more fatty areas.
What is Large Intestine?
The large intestine also has other names as the colon or the large bowel. It has a wider diameter and short length than the small intestine. It is the hindermost part of the alimentary canal and opens outside through the anus. It starts from the point where the small intestine ends. It has smooth muscles that contract and relax to work until the blood gets out through the anus.
The large intestine has four regions; rectum, colon, caecum, and the anal canal. Colon has into four parts; ascending colon, transverse colon, descending colon, and sigmoid colon. The material passes through these portions of the colon and reaches finally into the rectum. The large intestine absorbs water and salts from the digested products and stores remaining as feces. As this intestine does not contain villi, it does not have the ability of absorption. Caecum has an accessory to a vestigial organ known as Appendix.
Microflora of the large intestine helps in the production of vitamins (vitamin B1, B2, vitamin K, vitamin B12). It has longitudinal muscles called taeniae Coli which starts from the appendix base and ends up to the rectum. Along with the taeniae Coli, tags of the peritoneum filled with fats are found, which are called epiploic appendages or appendices epiploicae. The large intestine has sac-like structures called hastura, which are the contraction of the taeniae Coli.
Key Differences between Small Intestine and Large Intestine
- The small intestine has a longer length than the large intestine, whereas the large intestine is shorter than the small intestine.
- The small intestine is small in diameter than the large intestine, whereas the large intestine is wider than the small intestine.
- The small intestine aids in the absorption of nutrients from the digested food, whereas the large intestine helps in the absorption of water and electrolytes.
- The small intestine possesses circular folds called “palicae circulares” in the inner surface, whereas these folds are absent in the large intestine.
- The small intestine possesses hair-like structures “villi” that help in digestion, whereas the large intestine does not have these structures.
- The small intestine has “Peyer’s Patches,” which are the aggregations of the lymphoid tissue located on the mucous membrane, whereas these are absent in the large intestine.
- The small intestine lacks the Taenia Coli (which is strap-like structure) and Hastura (which is sac-like structure), whereas the large intestine possesses these two structures.
- The small intestine shows small movements in the abdomen, whereas the large intestine is fixed and shows very little abdominal changes.
- Digestion is the main function of the small intestine, whereas absorption is the main function of the large intestine.
- The small intestine secretes numerous hormones, whereas the large intestine secretes no hormones.
- The small intestine forms the layer of the continuous bands of muscles around it, whereas the large intestine has three types of muscle bands called “taeniae coli”.
- Fatty tags called “Epiploic appendages” are absent in the small intestine, whereas these are present in the large intestine.
Key Similarities between Small Intestine and Large Intestine
- Both small and large intestines are parts of the same system, intestine, which is the constant tube that starts from the stomach and ends to the anus.
- Both play a role in the absorption of substances from the food.
- Both are convoluted in structure inside the abdominal cavity.
- Both possess longitudinal muscles.
- Both have goblet cells.
In conclusion, both small and large intestines are parts of the alimentary canal and play a role in the process of digestion. The small intestine is involved in the digestion and absorption of food whereas the large intestine is involved in the absorption of water and the production of vitamins.