Describe alimentary canal.
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Answer:
ALIMENTARY CANAL
It is the passage which starts from mouth and ends to anus. It includes Mouth, Pharynx, Oesophagus, Stomach, Small intestine, large intestine, rectum and anus.
It is a passage where ingestion, digestion, absorption, assimilation and elimination of food particles take place.
1. MOUTH - It is also known as Buccal Cavity or Oral Cavity. It contains 32 teeth and a tongue. 16 teeth are fixed to upper jaw and 16 teeth are fixed to lower jaw. Teeth help in cutting and chewing of food particles. Tongue is a muscular leaf like structure attached to the floor of buccal cavity posteriorly and free to move interiorly. Tongue helps in hold and mixing of food with saliva. It contains several taste buds which helps in recognition of different tastes like sweet, sour, bitter and salty.
2. PHARYNX - Buccal cavity opens into pharynx. Pharynx is a narrow 10-14 cm long tubular passage through which food enters into Oesophagus.
3. OESOPHAGUS - Food enters into Oesophagus from pharynx through an opening called as Gullet. Oesophagus is also a 25 cm long tubular structure which moves in the middle of thorax and crosses the diaphragm. It opens in stomach.
4. STOMACH -. It is a bag like structure situated in upper abdominal cavity slightly at left side. It contains HCl which helps to break food particles into simple absorbable parts. HCl also helps to kill germs which enters into Stomach with food particles. Wall of stomach contains mucus glands whose secretion prevents stomach wall from high acidity of HCl. There are some Gastric Glands also reported in the wall of stomach which secrets Gastric Juice. Food converts into Chyme in stomach.
5. SMALL INTESTINE - It is the longest part of alimentary canal. It's length is about 4-6 meters. Complete digestion of food particles occurs here. It is also known as the site of digestion and absorption. It is differentiated into three parts. Upper one is Duodenum, middle part is Jejunum and last and longest part is Ileum. Ilum opens in Large Intestine at Caecum. It's opening is known as ileo-caecal opening.
6. LARGE INTESTINE - It is also a tubular structure where mainly absorption of water from undigested food occurs. At it's caecum a finger like vestigeal part is present known as Appendix. It's posterior part forms Rectum.
7. RECTUM - It's a site where temperorry storage of undigested food particles occurs.
8. ANUS - It's an opening through which undigested food eliminated from the body. These undigested food called Faeces or Faecal matter.
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This is all about Alimentry Canal.
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Digestive System includes Alimentry Canal along with their Digestive glands.
Digestive Glands -
1. Salivary Glands - Releases saliva in mouth.
2. Liver - Releases bile juice.
3. Pancreas - Releases pancreatic juice.
4. Gastric Gland - found in wall of stomach, releases gastric juice.
5. Crypt of liberkun - Found in Intestine, releases Succus Entericus.
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