CLASS 6TH | DIGESTIVE SYSTEM | REVISION NOTES

The Human Digestive System

Nutrition – It is a process which involves the utilization of food by an organism
to give out energy for growth and development.

Stages of Nutrition in Humans –

1. Ingestion – process of taking food into the body
2. Digestion – breakdown of large insoluble food molecules into small
   water soluble molecules.
3. Absorption – the digested food is absorbed and passed through the
   intestinal wall into the bloodstream.
4. Assimilation – process of utilization of absorbed food
5. Egestion – elimination of undigested food.
   Human Digestive System – The digestive system is made up of two parts.
6. Alimentary canal – It is a muscular and tubular structure which starts
   from the mouth and ends at the anus. The important parts of alimentary
   canal are
   i. Mouth – the ingestion and digestion of food starts here.
   ii. Pharynx – it receives food from the mouth and air from the nose
   to throat. It is meant only for food to pass through.
   iii. Oesophagus – also known as food pipe. It connects pharynx to the
   stomach.
   iv. Stomach – it a muscular, J shaped, bag like structure. The food is
   churned and gets mixed well with the digestive juices.
   v. Small intestine – Most of the digestion and absorption of nutrients
   and minerals from the food takes place here.
   vi. Large intestine – It is mainly involved in absorption of water from
   the undigested food.
   vii. Rectum
   viii. Anus
7. Digestive glands – These are associated with alimentary canal. They
   secret enzymes that speed up the biochemical reaction and aid in
   digestion of food. In digestive system, there are –
   

1. i. salivary glands
2. a. submandibular
3. b. sublingual and
4. c. parotid
5. ii. Pancreas – It secrets pancreatic juices which are poured into small
6. intestine along with bile.
7. iii. Liver – It is the largest gland of the body. It secretes bile juice.
8. Process of Digestion – It involves the breakdown of complex food
9. molecules into simpler food particles. There are seven different stages of
10. process of digestion. These are –

• In mouth – breakdown of carbohydrates
• In the pharynx and oesophagus
• In the stomach
• Food in small intestine
• Absorption of digested food in the small intestine
• In the large intestine
• Assimilation
  Enzymes and their functions – they are proteins which act as biological
  catalysts.
  Properties of enzymes –
• They are more active at optimum temperature.
• They are not destroyed during catalysis and can be reused.
• They are sensitive to pH.
• They are specific in their actions.
• They are needed in small amount.
  Indigestion – it is a common condition which is related to upset
  stomach. It is also called dyspepsia.
  Symptoms –
• Pain or discomfort in belly.
• Bloating (Swelling of stomach)
• Sense of uncomfortably full after eating.
• Heartburn – it is caused due to the release of acid by stomach.
  

Healthy eating habits –

1. Eat healthy food like green leafy vegetables
2. Eat food slowly helps in detecting hunger.
3. Eat oats and other fibre rich grain.
4. Have a regular family meal.
5. Always turn the TV off while having meal.
   Unhealthy eating habits –
6. We should never skip breakfast as doing so drains out energy from
   our body.
7. Energy large amount of food in one sitting is also an unhealthy eating
   habit that should be avoided.
8. Eating food while watching TV, working, reading, even cooking food
   is also unhealthy eating behaviour.
9. Eating junk and oily food also sets you up for even gain.
10. Consuming sugar in large amount is also an unhealthy eating habit.
    Ways to keep oneself healthy –
11. Eating many small meals instead of two or three meals.
12. Avoiding snacks at last time.
13. Avoiding spicy food and coffee.
14. Avoiding smoking and chewing tobacco.
15. Avoiding laying down immediately just after eating food