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Describe the alimentary canal of man. Give a labelled diagram

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Alimentary Canal: 

  • The alimentary canal is a simple tube between the mouth & the anus which exhibits many modifications to perform different functions. 
  • The alimentary canal originates from embryonic ectoderm & endoderm.

1. Mouth and Buccal Cavity:

  • It is a transverse slit-like structure. 
  • The mouth is guarded by a pair of lips viz. upper lip and lower lip. The lips of the mammals are muscular and movable. 
  • The mouth opens into a buccal cavity. 
  • It is a cavity in the head region. Its dorsal side is made up of palate, the ventral side is made up of throat while both the lateral sides are made up of cheeks. 
  • The ventral side of the buccal cavity is occupied by a flat and muscular tongue. 
  • The tongue bears taste buds which are sensory to sour, salty, sweet and bitter tastes. 
  • Human tongue bears three types of taste buds. viz., 

1. Circumuallate 

2. Fungiform 

3. Filiform 

4. Foliate taste buds are absent in human beings. 

Functions of the tongue 

1. It functions as gusto-receptor. 

2. It helps in the mastication of the food. 

3. It helps in the swallowing of the bolus. 

4. It acts as a brush to clean the teeth. 

5. In human beings, it helps in speech.

  • The buccal cavity has upper & lower jaws which are beset with teeth.
  • The arrangement of the teeth on the jaws is called dentition. 

1.1. Salient Features of Teeth: 

  • The mammalian teeth are thecodont. 
  • The mammalian teeth are diphyodont i.e. there are two sets of the teeth in the life viz., 1. Milk or Deciduous teeth – the There number is 20. 

2.Permanent or Non-deciduous teeth – the There number is 32.

  • The mammalian teeth are heterodont i.e. 
  • 4 types of teeth are found viz., 

1. Incisors 

2. Canines 

3.Premolars 

4. Molars

  • Last four molars are called wisdom teeth. 

Dental formula: 

1.The dental formula denotes position, number & type of teeth in the jaws. 

2. The dental formula denotes teeth in half of the jaws. 

3. The total number of teeth can be obtained by doubling the dental formula. 

4. The dental formula of Man 

  • Infant ⇒ 12/2, C 1/1, Pm 0/0, M2/2 

⇒ 10 × 2

⇒ 20

1.2. Pharynx:

  • The buccal cavity opens into pharynx which is comparatively less distinct in mammals. 
  • The dorsal part of the pharynx is called as nasopharynx whereas its ventral part is termed as the oropharynx. 
  • The pharynx is lined by stratified squamous epithelium. 
  • Posteriorly, the pharynx has 2 openings viz., gullet and glottis. 
  • The oropharynx opens into the oesophagus through the gullet.

1.3. Oesophagus: 

  • The oesophagus passes through the neck & thorax. It pierces through the diaphragm and finally opens into the stomach. 
  • Its length depends upon the length of the neck. In man, it’s length is about 25 cm. 
  • Internally, it has many longitudinal folds. 
  • The anterior part of the oesophagus is made up of striated (Voluntary) muscles.
  • Rest part is made up of smooth muscles. 
  • The wall of Oesophagus consists of follower layers: 

1.Serosa: Outermost layer 

2. Musculature: It includes an outer layer of longitudinal muscles and an inner layer of circular muscles. 

3.Submucosa: It is made up of connective tissues. It has blood vessels, nerves and lymph ducts. 

4. Mucosa: It is the innermost layer which is made up of stratified squamous epithelium

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