Revision: Human Body >> Digestive System Biology ICSE ICSE Class 6 CISCE

Saprozoic nutrition refers to nutrition in which animals feed on dead or decaying matter.

Vitamins are organic compounds regularly required in minute quantities in the diet for normal metabolism, health, and growth.

The organisms which feed on all kinds of plant and animal food are called omnivores.

Examples - Cockroach and human beings.

These are the organisms which prepare organic food in their body from simple inorganic materials like carbon dioxide, water, etc.

Example - green plants and certain protests.

The organisms that feed on plants only are termed as herbivores.

Examples - sheep, cow, goat, etc.

Peristalsis is the rhythmic contraction and relaxation of the muscles of the alimentary canal that pushes the food along the gut.

Pylorus is the passage at the lower end of the stomach that opens into the duodenum.

Omnivores are organisms that consume both plants and animals.

Absorption of substances which are built into other compounds in the organisms. 

The organisms which feed upon other animals and animal products.

Examples - tiger, lion, cat, etc.

Egestion — The process of removal of the undigested food from the body is defined as egestion.

Digestion — The process of breaking the food into smaller and simpler substances so that they can be easily used by the body is called digestion.

The process by which all organisms obtain or synthesize their food and convert it into simpler substances, so that it can be absorbed and utilized by the cells of the body is called nutrition.

Assimilation — The process of using the digested food by the body is called assimilation.

The process of converting complex food substances into simpler and smaller units so that they can be easily utilised by the body is defined as digestion.
E.g. proteins are converted to amino acids.

The organisms which cannot prepare their own food and depends on ready-made food synthesized by green plants are called heterotrophs.

Examples - animals and human beings.

A kilocalorie is a unit of energy. It is the energy required to raise the temperature of 1 kg of water by 1 Celsius.

It is the breaking down of complex insoluble food components into simple soluble substances.

• According to WHO, nutrition means taking in food in relation to the body’s dietary needs.
• It includes five main processes: ingestion, digestion, absorption, assimilation and egestion, which together describe how the body handles food.

• Digestion is the conversion of complex food into soluble forms that can be absorbed into the blood.
• The digestive system has two main components: the alimentary canal (mouth to anus) and associated digestive glands.
• The alimentary canal is a long muscular tube about 9 m in adults, including mouth, pharynx, oesophagus, stomach, small intestine, large intestine, rectum and anus.
• Salivary glands, liver and pancreas are accessory digestive glands that open into this canal and secrete juices needed for digestion.
• Different organs of the digestive system act in sequence; each stage of digestion occurs in a specific organ that performs a specialised mechanical or chemical role.

• The stomach is a muscular J‑shaped sac in the upper left abdomen, between oesophagus and small intestine.
• It has four regions: cardiac, fundus, body and pyloric, each with specific roles in food storage and mixing.
• The body region mainly stores food, churns it and mixes it with gastric juice to form chyme.
• The pyloric region opens into the duodenum and its pyloric sphincter controls the release of chyme.
• The cardiac (lower oesophageal) and pyloric sphincters prevent backflow and regulate movement of food, so regurgitation is avoided.

• The large intestine has a wider diameter than the small intestine.
• It is the terminal part of the alimentary canal.
• It is divided into three main parts: caecum, colon and rectum.
• The rectum opens to the outside through the anus.
• Only minimal digestion occurs here, but water and electrolytes are absorbed efficiently.

• Absorption of nutrients occurs via passive and active transport across the intestinal mucosa.
• In the mouth/buccal cavity, certain drugs that contact the mucosa (e.g., under the tongue) are absorbed directly into blood capillaries.
• In the stomach, a small amount of water, simple sugars, electrolytes, alcohol and some drugs (like aspirin) are absorbed.
• The small intestine is the main site of absorption; final products of digestion such as glucose, fructose, fatty acids, glycerol and amino acids enter blood and lymph here.
• Lipids and fat‑soluble vitamins (A, D, E, K) are absorbed via micelles, converted to chylomicrons in intestinal mucosa, taken up by lacteals in villi and then released into the bloodstream.
• The large intestine absorbs most of the remaining water, some minerals and certain drugs.

• The large intestine has a wider diameter than the small intestine.
• It is the terminal part of the alimentary canal.
• It is divided into three main parts: caecum, colon and rectum.
• The rectum opens to the outside through the anus.
• Only minimal digestion occurs here, but water and electrolytes are absorbed efficiently.