Human Digestive System & How it Works | Health Takers

HUMAN DIGESTIVE SYSTEM & HOW ITS WORKS

Human beings are omnivorous in nutrition. Like other multicellular animals,humans have a digestive system for nutrition. Digestive system is a group of organs and associated digestive gland that take part in ingestion of food, it's crusing, digestion, absorption of digested material and egestion of indigestible matter. It contains number of digestive gland of its own.

Three types of external gland s also pour their secretion into alimentary canal.They are salivary gland, liver and pancreas .

Alimentary canal :-

It is tubular passage extending from mouth to anus through which food passes during its digestion and absorption. It is about 9 meters in length. Alimentary canal consists of mouth, buccal cavity, oesophagus, stomach, small intestine, large intestine and anus.

1. Mouth:-

It is a transverse silt like aperture that occurs in between the nose and the chin. Mouth is bounded by two soft, movable sensitive lips, upper and lower. Lips help in holding the food. They also aid in phonation.

2. Buccal or Oral Cavity

It is anterior part of alimentary canal that extends From mouth to pharynx and lies between two jaws,upper and lower. 

(I) Tongue

Tongue Bears taste buds for tasting the quality of food--sweet anteriorly, salt anterio-laterally, sour postero-laterally.It moves food in the buccal cavity for crushing under teeth, mixing with saliva and pushing the food.

(ii) Teeth

They are hard structures which are used for cutting, chewing and crushing the food.

(iii) Salivary Glands

Three pairs of salivary glands open into buccal cavity.Saliva consists of mucus, water, lysozyme and enzyme s ptylin.

(a) Lysozyme

It is antimicrobial enzyme which kill's bacteria by cleaving their walls.

(b) Ptyalin

This digestive enzymes acts on starch and glycogen of cooked food and changes the same into sweet sugar called maltose.

(iv) Pharynx

It is a funnel-shaped common passage of respiratory and digestive tract s which is also connected with middle ear. The act of pushing food into oesophagus is called swallowing.

3. Oesophagus (Food pipe)

It is narrow muscular distensible tube that connects pharynx with stomach. It does not contain digestive glands. However,its wall secretes mucus for lubrication of passing food.Action of Salivary amylase over starch continues in oesophagus.

4. Stomach

It is large J-shaped, widest, thick walled but distensible and muscular organ of the alimentary canal. Stomach lies in the left upper part of abdomen below diaphragm.

Gastric Juice

The secretion of gastric glands is called Gastric Juice.It contains HCL, Mucus, Pepsin, Gastric Lipase and Rennin .

Pepsin And Rennin are secreted in their inactive states of Pepsinogen and prorennin .

HCL (hydrochloric acid)

It has five Functions

(I) It softens the food.

(ii) HCL makes the food acidic for proper functioning of Pepsin

(iii) HCL stops action of Salivary amylase.

(iv) It kill's the germs and bacteria so as to disinfect food.

Small Intestine

Made up of three segments, the duodenum, jejunum, and ileum, the small intestine is a long tube loosely coiled in the abdomen (spread out, it would be more than 20 feet long). The small intestine continues the process of breaking down food by using enzymes released by the pancreasand bile from the liver. Bile is a compound that aids in the digestion of fat and eliminates waste products from the blood. Peristalsis (contractions) is also at work in this organ, moving food through and mixing it up with digestive secretions. The duodenum is largely responsible for continuing the process of breaking down food, with the jejunum and ileum being mainly responsible for the absorption of nutrients into the bloodstream.

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Three organs play a pivotal role in helping the stomach and small intestine digest food:

Pancreas

Among other functions, the oblong pancreas secretes enzymes into the small intestine. These enzymes break down protein, fat, and carbohydrates from the food we eat.

Liver

The liver has many functions, but two of its main functions within the digestive system are to make and secrete bile, and to cleanse and purify the blood coming from the small intestine containing the nutrients just absorbed.

Gallbladder

The gallbladder is a pear-shaped reservoir that sits just under the liver and stores bile. Bile is made in the liver then if it needs to be stored travels to the gallbladder through a channel called the cystic duct. During a meal, the gallbladder contracts, sending bile to the small intestine.

Once the nutrients have been absorbed and the leftover liquid has passed through the small intestine, what is left of the food you ate is handed over to the large intestine, or colon.

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Colon (Large Intestine)

The colon is a 5- to 6-foot-long muscular tube that connects the cecum (the first part of the large intestine to the rectum (the last part of the large intestine). It is made up of the cecum, the ascending (right) colon, the transverse (across) colon, the descending (left) colon, and the sigmoid colon (so-called for its "S" shape; the Greek letter for S is called the sigma), which connects to the rectum.

Stool, or waste left over from the digestive process, is passed through the colon by means of peristalsis (contractions), first in a liquid state and ultimately in solid form as the water is removed from the stool. A stool is stored in the sigmoid colon until a "mass movement" empties it into the rectum once or twice a day. It normally takes about 36 hours for stool to get through the colon. The stool itself is mostly food debris and bacteria. These bacteria perform several useful functions, such as synthesizing various vitamins, processing waste products and food particles, and protecting against harmful bacteria. When the descending colon becomes full of stool, or feces, it empties its contents into the rectum to begin the process of elimination.

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Rectum

The rectum (Latin for "straight") is an 8-inch chamber that connects the colon to the anus. It is the rectum's job to receive stool from the colon, to let you know there is stool to be evacuated, and to hold the stool until evacuation happens. When anything (gas or stool) comes into the rectum, sensors send a message to the brain. The brain then decides if the rectal contents can be released or not. If they can, the sphincters (muscles) relax and the rectum contracts, expelling its contents. If the contents cannot be expelled, the sphincters contract and the rectum accommodates, so that the sensation temporarily goes away.

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Anus

The anus is the last part of the digestive tract. It consists of the pelvic floor muscles and the two anal sphincters (internal and external muscles). The lining of the upper anus is specialized to detect rectal contents. It lets us know whether the contents are liquid, gas, or solid. The pelvic floor muscle creates an angle between the rectum and the anus that stops stool from coming out when it is not supposed to. The anal sphincters provide fine control of stool. The internal sphincter keeps us from going to the bathroom when we are asleep, or otherwise unaware of the presence of stool. When we get an urge to go to the bathroom, we rely on our external sphincter to keep the stool in until we can get to the toilet.