There's a Gut Feeling About This Quiz

The mouth, or oral cavity, is where food enters the body and digestion begins. The teeth begin the process of mechanical digestion by chewing and breaking food down into smaller pieces and, at the same time, mixing food with saliva, which begins the process of chemical digestion. Saliva contains the enzyme amylase which breaks down starch. Saliva also helps lubricate food for ease of swallowing.

After swallowing, food enters the oesophagus.

The oesophagus (or esophagus for American spellers) is a simple straight tube, about 28-30 cm (11-12 inches) in length, with muscular walls. Food moves down the oesophagus by waves of muscular contractions called peristalsis. Food only takes about 3 to 6 seconds to travel its length to reach the stomach.

The stomach is a large muscular J-shaped sac containing digestive fluids such as hydrochloric acid and the enzyme pepsin which continue the process of chemical digestion. The main function of the stomach is to reduce the food to a semi-liquid state called chyme before the food progresses to the intestines.

The duodenum is the first of the three segments that make up the small intestine. The name is derived from the Latin word "duodeni", meaning twelve, because the duodenum is approximately 12 finger-widths (an ancient unit of measurement), which means it is about 10-12 inches or 26-30 cm in length.

The duodenum secretes mucus to protect itself from the acidity of the liquid chyme. This section of the small intestine is the main site of chemical digestion in the gut. Digestive juices continue to break down the chyme coming from the stomach.

They come from the liver (bile) and the pancreas (pancreatic juice). Bile breaks down fats. Pancreatic juice breaks down sugars, fats, and starches.

The next segment of the small intestine is the jejunum. Its main function is to absorb sugars, amino acids, and fatty acids. The jejunum is about 2.5 metres or 8 feet long. Its name is derived from the Latin "ieiunum" meaning empty. It makes sense when you know that the i's in the word ieiunum were eventually replaced by j's in English for ease of pronunciation.

The Latin alphabet does not have the letter J. In Latin, ieiunum would be pronounced yuh-yoonum. It was so-named because it was noticed that this section of the intestine was always empty at dissection, because it tends to drain when a body is placed on its back.

The third or last part of the small intestine is the ileum, named for its location - Latin "ilia" meaning groin or flank. Its function is to absorb nutrients not absorbed previously in the jejunum, the major ones being vitamin B12 and bile acids. The ileum is the longest section of the small intestine at 3 metres or 10 feet.

Fun fact: on average, the female small intestine is slightly longer than a male small intestine - 7.1 metres (23.3 feet) compared to 6.9 meters (22.6 feet) respectively.

After passing through the small intestine, food enters the large intestine or colon. At this junction, we find a small pouch called the caecum. At the lower end of the caecum is the appendix. Its name comes from the Latin "caecus" meaning blind or hidden.

It is believed that in our ancestors it played a role in digesting cellulose but in modern humans its function is to absorb water and salts or electrolytes.

The ascending colon, as the name implies, extends upward for about 20 cm (8 inches) from the junction where the ileum, caeceum, and ascending colon meet on the right-hand side of the body in most humans. (Note: there can be exceptions to this - some people have a rare medical condition in which their internal organs are reversed).

It absorbs water and nutrients from the food which has not been digested and absorbed in the small intestine, thus beginning the process by which stools are formed.

Like the other segments of the large intestine, the function of the transverse colon is to absorb water and nutrients from undigested food and to form stools. "Trans" means across and "verse" means to turn, which describes the way the transverse colon goes across the body, normally from right to left, twisting approximately 90 degrees to the point where the descending colon begins.

It is the longest segment of the large intestine at about 45-60 cm (18-24 inches).

The descending colon, as the name implies, extends downward on the left-hand side of the body for about 22 cm (9 inches). It stores stools or faeces, ready for evacuation.

The sigmoid colon is so-named because it is the shape of the letter S (sigma in the Greek alphabet). Its function is to contract and push the faeces along to the next segment, the rectum. The sigmoid colon is about 45 cm (18 inches) long.

After the sigmoid colon is the rectum, the last section of the intestine, so-called because this is where the alimentary canal straightens out and descends vertically. In Latin, "rectum" means straight. The rectum holds faeces prior to expulsion from the alimentary canal. It is about 15 cm (6 inches) in length.

The word anus is Latin for ring. The anus is the opening at the lower end of the alimentary canal through which undigested food waste is eliminated from the body; that process is called defaecation. It consists of two circular sphincter muscles which are normally closed but open to allow defaecation.

Fun fact: the process of digestion is not significantly affected by standing on your head because food moves along the alimentary canal by muscular contraction; gravity does not play a role. However, as it is difficult to eat upside down and potentially dangerous, it is not recommended so don't try this at home!