Grade 4 | Science | Digestive system, Human Body and Health, Olympiad, CBSE, ICSE, SOF, ITO
Digestive system begins at the mouth where food is mixed with saliva to make it soft and it is cut and ground into small pieces.
Buccal cavity, commonly known as the mouth, acts as an entrance to the digestive system. It consists of lips, cheeks, teeth and gums.
Food then goes into the stomach via Esophagus. The esophagus is also known as food pipe.
The stomach secretes HCL and pepsin. These juices mix with food and break it down further.
Partially digested food (also known as chyme) then moves into the duodenum. The duodenum is the first and shortest segment of the small intestine. Digestive juices from pancreas, liver and gall-bladder mix with chyme here to break it down further.
Food particles then move into lower segments (jejunum and ileum) of the small intestine. The ileum is the longest section of small intestine. Tiny finger like structures are present on the lining of the small intestine. These structures are called villi of the small intestine. Villi absorb nutrients from digested food into the blood. Digestion of food ends at the small intestine.
Undigested food enters large intestine and large intestine absorbs water and salt from it. and The remaining waste material is stored as feces before being removed by defecation.
The whole passage along which food passes through the body from the mouth and expelled as solid waste from the anus is known as alimentary canal. This also known as the digestive tract or GI tract (Gastro-Intestinal tract). It takes 2-3 hours for food to move through GI tract thus digestion of food takes place in 2 to 3 hours.
Saliva is secreted by salivary glands.
Hydrochloric acid (HCL) and pepsin are secreted by the stomach. Pepsin helps in digestion of proteins.
The liver is the largest gland in the human body. The liver secretes bile juice. Bile is useful is digestion and absorption of fats in the small intestine.
Gall-bladder stores bile juice. It squeezes bile in the duodenum when fatty food enters the small intestine.
Pancreas secretes pancreatic juice that helps body to break down carbohydrates, proteins and fats.