The human digestive system starts with mouth and ends with anus. Intake of food into to mouth is called Ingestion.Mouth encloses a cavity within called Buccal cavity or Oral cavity. Three pairs of salivary glands pour their secretions called saliva in to this cavity. The muscular tongue pushes the food under grinding teeth as it mixes with saliva, this process is called "Mastication". Mastication makes the food into ball of paste. Salivary amylase" an enzyme in saliva starts the digestion of starch right away from mouth. As soft ball of food enters Oesophagus, the wavy movements (Peristaltic movements) drive the bolus into stomach. Oxyntic cells present in inner lining of stomach secrete Hcl acid which has killing action on Microbes and partially denatures the proteins in food.Slimy mucous secreted my mucous glands of stomach protect inner lining from self destruction due to acid. Gastric juices of stomach starts digestion of Proteins, lipids but not carbohydrates.
Human digestive system mainly have three parts to be drawn in proportion they are the Stomach, Liver and Intestines.Students feel difficult while drawing the duodenum, bile duct, Gall bladder and Pancreas in a narrow space. Even the coiled small intestines look complicated.Now, lets start drawing in easy steps.
Draw two parallel lines horizontally and two vertically as shown.
The middle box is for Stomach.
Draw Stomach as shown, ensure left side of stomach touches the left line. Accommodate Liver too as shown.
Draw bile duct opening into duodenum, represent overlapped part of liver on stomach with dotted lines
Draw pancreas below stomach as shown.
Draw large intestine along the guide lines as shown.
Now draw small intestine along the guide curve.
Now draw Oesophagus and salivary glands.
Complete the man's face and now label the parts neatly.
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