Human Digestive System

Human Digestive System

• The human digestive system consists of a complete digestive tract (gastrointestinal tract or G.I.T.) and accessory glands.
• The digestive tract is a tube-like gut with two openings: mouth and anus.
• The system consists of mouth, oral cavity, pharynx, esophagus, stomach, small intestine, large intestine, and anus.
• Associated accessory glands include salivary glands, liver, and pancreas.

Mouth

• The mouth is the anterior opening of the alimentary canal bounded by two fleshy lips (upper and lower).
• It is meant for ingestion of food.

Oral Cavity

• The mouth opens into the oral cavity, a wide space formed by the upper and lower jaws.
• The oral cavity has a muscular tongue on its floor.
• The roof is formed by a dome-shaped hard palate (anteriorly) and a soft palate (posteriorly).
• The oral cavity has a muscular uvula hanging down from the soft palate.
• Laterally, it has cheeks, and posteriorly, it is connected to the pharynx.

Teeth

• Teeth are embedded in sockets along the length of the lower and upper jaws (thecodont).
• Humans have two sets of teeth during their lifetime (diphydont).
• Initially, there are 20 deciduous or milk teeth, which are later replaced by 32 permanent teeth.
• Teeth are different in shape and size (heterodont), correlated with different functions and diet.
• The 32 permanent teeth include 8 incisors, 4 canines, 8 premolars, and 12 molars.
• Incisors are for cutting and biting, canines are for tearing and pulling flesh, and premolars and molars are for grinding and crushing food.

Tongue

• The tongue is a muscular organ attached to the floor of the oral cavity through the hyoid bone.
• Its upper surface has numerous projections (papillae) containing nerve endings for the sense of taste.
• The under surface of the tongue has a fold of mucous membrane called the frenulum.
• The tongue helps in mastication, swallowing, taste, and speech.