Question

describe the human digestive system with diagram?

Answer 1

The human digestive system consists of the gastrointestinal tract plus the accessory organs of digestion (the tongue, salivary glands, pancreas, liver, and gallbladder).[1] In this system, the process of digestion has many stages, the first of which starts in the mouth. Digestion involves the breakdown of food into smaller and smaller components, until they can be absorbed and assimilated into the body.

Chewing, in which food is mixed with salivabegins the process of digestion. This produces a bolus which can be swallowed down the esophagus and into the stomach. Here it is mixed with gastric juice until it passes into the duodenum where it is mixed with a number of enzymes produced by the pancreas. Saliva also contains a catalyticenzyme called amylase which starts to act on food in the mouth. Another digestive enzymecalled lingual lipase is secreted by some of the lingual papillae on the tongue and also from serous glands in the main salivary glands. Digestion is helped by the masticationof food by the teeth and also by the muscular actions of peristalsis and segmentation contractions. Gastric juice in the stomach is essential for the continuation of digestion as is the production of mucus in the stomach.

Peristalsis is the rhythmic contraction of muscles that begins in the esophagus and continues along the wall of the stomach and the rest of the gastrointestinal tract. This initially results in the production of chymewhich when fully broken down in the small intestine is absorbed as chyle into the lymphatic system. Most of the digestion of food takes place in the small intestine. Water and some minerals are reabsorbed back into the blood in the colon of the large intestine. The waste products of digestion (feces) are defecated from the anus via the rectum.

Answer 2

$\textbf{Alimentary Canal }$:

The digestive system from Oesophagus to the anus is called alimentary canal. It is about 9 metre long. It is also called food tube.

It constitutes the organs namely :

Buccal cavity, Oesophagus, Stomach, Small intestine, Large intestine, Rectum, Anus.

$\textbf{Role of mouth }$:

Humans take in food through the mouth. It is the uppermost part of alimentary canal which is bounded by lips and cheeks, and contains tongue and slaivary gland. The food taken in is chewed or groinded by teeth at the same time in the salivary glands, saliva starts to secrete which contains enzymes( $\textbf{Salivary Amylase }$ )that breaks search into sugar.

Now the tongue helps in mixing this saliva with food, it also gives taste of food also it helps in swallowing the food.

$\textbf{Role of oesophagus}$ :

It is tubular part of alimentary canal about 25cm long. It is also the narrowest part of alimentary canal. It is hollow which allows the passage of food from Buccal cavity to the stomach. During which food gets mixed with various digestive juices.

$\textbf{Role of Stomach }$

It is J-shaped bag like structure made of muscle. Here gastric glance are present which secret mucus, HCL and digestive enzymes. The function of mucus is to protect stomach lining from the action of enzymes and acid. HCL kills bacteria present in food, making the food acidic; so that enzymes can act on it. Here food stays for 4-5 hours.

$\textbf{Role of Small intestine }$:

It is located below the stomach and is coiled in appearance. This tube is abour 7.5 m long. It has three main divisons : duodenum, jejunum and ileum. Duodenum is the first part having two different ducts namely bile duct and pancreatic duct. In this tube digested food (partially) is mixed with pancreatic juice, bile juice anf other juices. Jejunum is the middle pary, found only in man. Ileum is the last part of Small intestine.

Total absorbtion takes place in the ileum. This ileum has villi on its surface. This villi increases surface area for absorbtion. The villi have blood vessels, digested food passes villi passes to there and enters the blood stream. Which then transfers to liver and then to the heart.

$\textbf{Role of Large intestine, Rectum and Anus}$:

It is about 1.5 m long organ Food from small intestine moves here. Here the most of water and salt be removed from the water by the absorbtion. This intestine allow the passage of faecal matter through the anus.