Describe the alimentary canal of man.
[Review question: Pg. No: 245]
[Review question: Pg. No: 245]
Alimentary canal is a muscular coiled, tubular structure. It consists of mouth, buccal cavity, pharynx, oesophagus, stomach, small intestine (consisting of duodenum, jejunum and ileum), large intestine (consisting of caecum, colon and rectum) and anus.
Mouth:
Leads into the buccal cavity. It is bound 2 soft movable upper and lower lips. The buccal cavity is a large space-bound above by the palate (which separates the windpipe and food tube), below by the throat and on the sides by the jaws. The jaws bear teeth.
Teeth: Hard structures meant for holding, cutting, grinding and crushing the food.
Salivary glands: There are 3 pairs
- Parotid glands Largest salivary glands, which lie in the cheeks in front of the ears.
- Sublingual glands Smallest lands and lie beneath the tongue.
- Submaxillary or Submandibular-glands-lie at the angles of the lower jaw.
Tongue:
Muscular, sensory organ – Helps in mixing the food with the saliva.
Pharynx:
It is a membrane-lined cavity behind the nose and mouth, connecting them to the oesophagus. Serves as” a pathway for the movement of food from mouth to oesophagus.
Oesophagus:
Muscular-membranous canal about 22 cm in length. It conducts food ‘ from pharynx to the stomach by peristalsis (wave-like movement) produced by the rhythmic contraction and relaxation of the muscular walls of alimentary canal.
Stomach:
The stomach is a wide J-shaped muscular organ located between oesophagus and the small intestine.
Small intestine: The small intestine is the longest part of the alimentary canal, which is a long coiled tube measuring about 5 – 7 m. It comprises three parts- duodenum, jejunum, and ileum.
- Duodenum – C-shaped and receives the bile duct (from the liver) and pancreatic duct (from Pancreas). ’
- Jejunum Middle part of the small intestine. A short region of the small intestine.
- Ileum – Forms the lower part of the small intestine and opens into the large intestine.
Liver:
Largest digestive gland of the body, reddish-brown in colour. Bile salts help in the digestion of fats by emulsification (conversion of large fat droplets into small ones).
Pancreas:
Lobed, a leaf-shaped gland situated between the stomach and duodenum.
Pancreas acts both as an exocrine gland and as an endocrine gland.
Large intestine:
The unabsorbed and undigested food is passed into the large intestine.
It extends from the ileum to the anus. About 1.5 meters in length. Has 3 parts colon and rectum.
Caecum:
Small blind pouch-like structure at the junction of the small and large intestine. From its blind end, a finger-like structure called a vermiform appendix arises. It is a vestigeal (functionless) organ in human beings.
Colon:
Much broader than ileum. Passes up the abdomen on the right ascending colon, crosses to the left just below the stomach (transverse colon) and down on the left side – (descending colon).
Rectum:
Last part which opens into the anus muscles called anal sphincter opens when passing stools.
Mouth:
Leads into the buccal cavity. It is bound 2 soft movable upper and lower lips. The buccal cavity is a large space-bound above by the palate (which separates the windpipe and food tube), below by the throat and on the sides by the jaws. The jaws bear teeth.
Teeth: Hard structures meant for holding, cutting, grinding and crushing the food.
Salivary glands: There are 3 pairs
- Parotid glands Largest salivary glands, which lie in the cheeks in front of the ears.
- Sublingual glands Smallest lands and lie beneath the tongue.
- Submaxillary or Submandibular-glands-lie at the angles of the lower jaw.
Tongue:
Muscular, sensory organ – Helps in mixing the food with the saliva.
Pharynx:
It is a membrane-lined cavity behind the nose and mouth, connecting them to the oesophagus. Serves as” a pathway for the movement of food from mouth to oesophagus.
Oesophagus:
Muscular-membranous canal about 22 cm in length. It conducts food ‘ from pharynx to the stomach by peristalsis (wave-like movement) produced by the rhythmic contraction and relaxation of the muscular walls of alimentary canal.
Stomach:
The stomach is a wide J-shaped muscular organ located between oesophagus and the small intestine.
Small intestine: The small intestine is the longest part of the alimentary canal, which is a long coiled tube measuring about 5 – 7 m. It comprises three parts- duodenum, jejunum, and ileum.
- Duodenum – C-shaped and receives the bile duct (from the liver) and pancreatic duct (from Pancreas). ’
- Jejunum Middle part of the small intestine. A short region of the small intestine.
- Ileum – Forms the lower part of the small intestine and opens into the large intestine.
Liver:
Largest digestive gland of the body, reddish-brown in colour. Bile salts help in the digestion of fats by emulsification (conversion of large fat droplets into small ones).
Pancreas:
Lobed, a leaf-shaped gland situated between the stomach and duodenum.
Pancreas acts both as an exocrine gland and as an endocrine gland.
Large intestine:
The unabsorbed and undigested food is passed into the large intestine.
It extends from the ileum to the anus. About 1.5 meters in length. Has 3 parts colon and rectum.
Caecum:
Small blind pouch-like structure at the junction of the small and large intestine. From its blind end, a finger-like structure called a vermiform appendix arises. It is a vestigeal (functionless) organ in human beings.
Colon:
Much broader than ileum. Passes up the abdomen on the right ascending colon, crosses to the left just below the stomach (transverse colon) and down on the left side – (descending colon).
Rectum:
Last part which opens into the anus muscles called anal sphincter opens when passing stools.
