Anatomy of the digestive system

Oct 18, 2015

Anatomy of the digestive system

The Oesophagus

The oesophagus is the swallowing pipe. It is a simple muscular tube that connects the mouth to the stomach. When you swallow, the muscles of the oesophagus work to push the food in a coordinated way down into the stomach where it is made ready to be absorbed into the body

FUN FACT: You can eat standing on your head because the muscles work against gravity (but it sure is difficult…)

The Stomach

The stomach is one of the main organs of digestion. It has a volume of approximately 1.5 L although can expand significantly following the consumption of food and drink. The stomach releases chemicals to help digest the food and to protect the body from bacteria and viruses.

  • Protection from bacteria and viruses is provided primarily by hydrochloric acid (HCl). Although HCl is hostile to most foreign invaders, the bacterium Helicobacter pylori is capable of resisting its pungent effects and can cause medical problems such as stomach ulcers
  • Digestive chemicals help breakdown the food into tiny pieces to aid with absorption. If the food were not absorbed, then the body would not be able to extract energy from anything it consumed.

The stomach is normally located just below the nipple line, slightly to the left of the midline of the body. Its shape resembles that of a J although it varies between people.

The stomach can be divided into several parts: the fundus, body and pylorus.

  • The fundus of the stomach rarely contains food and is just full of gas.
  • The primary site of digestion is the body of the stomach. The wall of the body of the stomach is folded in a pattern referred to as rugae, which helps the stomach carry out digestive tasks by increasing the effective surface area for the digestive processes to take place.
  • The pylorus of the stomach acts as a gateway (sphincter) between the stomach and the remainder of the digestive tract and controls the rate at which the stomach empties. Food will normally remain in the stomach for about 4 hours.


The Small Bowel

The small bowel carries food away from the stomach for absorption. The first part of the small bowel is called the duodenum. The next part is the jejunum and the last part is called the ileum.

The small bowel is the place where sugars and other nutrients from the food are absorbed into the body. Nutrients give energy, encourage growth, and satisfy hunger.


The Large Bowel

Once the food has passed through the small bowel, it enters the large bowel where most of the water is absorbed. Without the large bowel, poo would be incredibly watery!

After most of the useful content of the food has been absorbed, the remainder is stored towards the end of the large bowel. This is called the sigmoid colon.


Going to the Toilet

When the body determines it is time to go to the toilet, and you are ready to relieve yourself, the poo will pass from the sigmoid colon, through the rectum and out of the anus. Babies have no control over the last stage and will therefore poo whenever their body tells them too. Fortunately, adults are able to control when they poo to avoid socially awkward situations!




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