Watch: [Understanding Your Body] Small Intestine

⭐English subtitles available⭐

 

 

When people feel bloated and uncomfortable, they often say, ‘I’m having indigestion,’

suspecting something may be wrong with their stomach.

 

The small intestine, the longest digestive organ,

spanning 7 out of the total 9 meters from the mouth to the anus

 

But what exactly happens inside this lengthy small intestine?

 

Stretching across the entire abdomen,

the small intestine receives food passed from the stomach,

breaks it down, absorbs it, and moves the waste to the large intestine.

 

The small intestine can be broadly divided into the duodenum, jejunum, and ileum.

 

Among these, the duodenum is connected to the stomach in a C shape

and measures about 25-30 cm in length.

 

The duodenum has an outlet connected to the pancreas,

through which about 3 liters of pancreatic juice are secreted per day.

 

Pancreatic juice is weakly alkaline with a pH of 8.0 or higher

and neutralizes the acidic contents passed through the stomach.

 

Along with bile produced by the liver, it serves to digest the food we consume.

 

Additionally, the duodenum releases various hormones

to regulate the secretion of bile, pancreatic juice, and intestinal fluid.

 

The food we consume moves through the small intestine

by peristaltic movements and segmentation contractions of the muscle layers.

 

Among these, the jejunum is where the most active digestion and absorption of food takes place.

 

The jejunum measures about 2.5m in length, accounting for about 40% of the small intestine.

 

As the food we consume passes through the jejunum,

digestive enzymes and bile break down carbohydrates into monosaccharides,

proteins into amino acids, and fats into glycerol and fatty acids.

 

In particular, the mucosa of the jejunum is densely packed with heavily wrinkled, hair-like villi,

providing a large surface area for absorption.

 

Most nutrients, broken down into their smallest units,

are absorbed through these villi and delivered throughout the body via lymphatic vessels and capillaries.

 

The last part of the small intestine is called the ileum, bumpy on the inside with finger-like projections.

As the longest part of the small intestine, it starts at the end of the jejunum and connects to the cecum.

 

The ileum has fewer folds and thinner wall compared to the jejunum.

 

While absorption occurs minimally in the ileum,

it plays a crucial role in the reabsorption of vitamin B12 and bile salts.

 

The ileocecal valve at the end of the ileum helps move the contents

from the small intestine to the large intestine while preventing backflow.

 

In this manner, it typically takes 3 to 6 hours for food to pass through the duodenum, jejunum, and ileum.

 

Despite the significant risks associated with small intestine disorders,

screening tests or preventive measures are not well-known.

 

Moreover, due to its considerable length and the fact that it is not anchored within the abdominal cavity,

conducting an endoscopic examination of the small intestine can be quite challenging.

 

Recently, however, capsule and balloon-assisted endoscopy

have been developed to aid in the diagnosis and treatment of small intestine disorders.

 

If there are unusual symptoms such as unexplained weight loss

or bloody stool that cannot be identified through an endoscopic examination,

or have a family history of conditions like familial polyposis or Crohn’s disease,

it is essential to confirm the presence of any small intestine disorders.