Digestive System Of Human
Digestive system

The whole human digestive system is around 9 meters long. In a healthy human adult this process can take between 24 and 72 hours.

In humans, digestion begins in the Mouth, where food is chewed. Saliva is secreted in large amounts from 1 to 1.5 litres/day by three pairs of exocrine salivary glands and is mixed with the chewed food by the tongue. Saliva moistens the food, and contains digestive enzymes such as salivary amylase, which aids in the chemical breakdown of starch into maltose. It also contains mucus that helps soften the food and form it into a bolus (A bolus is a mass of food that has been chewed at the point of swallowing) .

Then the food is swallowed, swallowing transports the chewed food into the esophagus.The reflex is initiated by touch receptors in the pharynx as the bolus of food is pushed to the back of the mouth.
The bolus travels throught esophagus to stomach. The esophagus is a narrow muscular tube about 20-30 centimeters long, which starts at the pharynx at the back of the mouth, passes through the thoracic diaphragm, and ends at the cardiac orifice of the stomach.  It takes only about seven seconds for food to pass through the esophagus and now digestion takes place.

Food reduced to very small particles in the stomach are more likely to be fully digested in the small intestine, and stomach churning has the effect of assisting the physical disassembly begun in the mouth.Other small molecules such as alcohol are absorbed in the stomach, passing through the membrane of the stomach and entering the circulatory system directly. Food in the stomach is in semi-liquid form, which upon completion is known as chyme.

digestive system
After being processed in the stomach, food is passed to the small intestine . The majority of digestion and absorption occurs here after the milky chyme enters the duodenum. Here it is further mixed with three different liquids bile, pancreatic juice and intestinal juice.

After the food has been passed through the small intestine, the food enters the large intestine.The large intestine absorbs water from the chyme and stores feces until it can be egested. The feces (also known as excrement) is stored in the rectum for a certain period and then the stored feces is eliminated from the body due to the contraction and relaxation through the anus. The exit of this waste material is regulated by the anal sphincter.
Essential components of the human digestive system

In humans, digestion begins in the Mouth, otherwise known as the "Buccal Cavity", where food is chewed and is the first portion of the alimentary canal that receives food and saliva.

Saliva is secreted in large amounts (1-1.5 litres/day) by three pairs of exocrine salivary glands: parotid, submandibular, and sublingual, and is mixed with the chewed food by the tongue.
Saliva cleans the oral cavity, moistens the food, and contains digestive enzymes which aids in the chemical breakdown of starch into maltose. It also contains mucus, a glycoprotein that helps soften the food and form it into a bolus.

Then the food is swallowed, swallowing transports the chewed food into the esophagus.The reflex is initiated by touch receptors in the pharynx as the bolus of food is pushed to the back of the mouth. The reflex is initiated by touch receptors in the pharynx as the bolus of food is pushed to the back of the mouth.

The esophagus commonly known as the gullet is a narrow muscular tube about 20-30 centimeters long which consists of a muscular tube through which food passes from the pharynx to the stomach. During swallowing, food passes from the mouth through the pharynx into the esophagus and travels via peristalsis to the stomach.

The wall of the esophagus is made up of two layers of smooth muscles, which form a continuous layer from the esophagus to the colon and contract slowly, over long periods of time.

The stomach is located between the esophagus and the small intestine. The stomach is a muscular, hollow, dilated part of the digestion system which functions as an important organ of the digestive tract. It secretes protein-digesting enzymes called protease and strong acids to aid in food digestion,through smooth muscular contortions called segmentation before sending partially digested food called chyme to the small intestines.

The stomach process the food as mentioned below:

  • Bolus the masticated food enters the stomach through the esophagus via the esophageal sphincter.
  • The stomach releases proteases the protein-digesting enzymes such as pepsin and hydrochloric acid, which kills or inhibits bacteria and provides the acidic pH of two for the proteases to work.
  • Food is churned by the stomach through muscular contractions of the wall called peristalsis – reducing the volume of the fundus
  • .The boluses are converted into chyme the partially digested food.
  • Chyme slowly passes through the pyloric sphincter and into the duodenum of the small intestine, where the extraction of nutrients begins.
In adult humans, the stomach has a relaxed, near empty volume of about 45 to 75 ml. Because it is a distensible organ, it normally expands to hold about one litre of food, but can hold as much as two to three litres. The stomach of a newborn human baby will only be able to retain about 30 ml.

The stomach is divided into four sections, each of which has different cells and functions. The sections are:

  • Cardia : Where the contents of the esophagus empty into the stomach.
  • Fundus : Formed by the upper curvature of the organ. As the rounded part of the upper stomach, it allows for an accumulation of stomach gases produced by chemical digestion.
  • Body or Corpus :The main, central region of stomach.
  • Pylorus: The lower section of the organ that facilitates emptying the contents into the small intestine.
The liver is a vital organ. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion.

Liver plays a major role in metabolism and has a number of functions in the body, including
- Glycogen storage,
- Decomposition of red blood cells
- Plasma protein synthesis
- Hormone production and
- Detoxification

The liver is a reddish brown organ with four lobes of unequal size and shape. A human liver normally weighs 1.44–1.66 kg and is a soft, pinkish-brown, triangular organ.

It is both the largest internal organ and the largest gland in the human body.

It is connected to two large blood vessels, one called the hepatic artery and one called the portal vein. The hepatic artery carries blood from the aorta, whereas the portal vein carries blood containing digested nutrients from the entire gastrointestinal tract and also from the spleen and pancreas.

The liver is thought to be responsible for up to 500 separate functions, usually in combination with other systems and organs.

The liver produces and excretes bile a yellowish liquid required for emulsifying fats and help the absorption of vitamin K from the diet.

The gallbladder is a small organ that aids mainly in fat digestion and concentrates bile produced by the liver.

The gallbladder is a hollow system that sits just beneath the liver. In adults, the gallbladder measures approximately 8 centimetres in length and 4 centimetres in diameter.It is divided into three sections: fundus, body, and neck.

When food containing fat enters the digestive tract, it stimulates the secretion of cholecystokinin (CCK).
In response to CCK, the adult human gallbladder, which stores about 50 millilitres of bile, releases its contents into the duodenum. The bile, originally produced in the liver, emulsifies fats in partly digested food.

In humans, the loss of the gallbladder is, in most cases, easily tolerated. The surgical removal of the gallbladder is called a cholecystectomy.
The pancreas is a gland about 6 inches long that is shaped like a flattened pear and lies next to the stomach.

The pancreas is both an endocrine gland producing several important hormones, including insulin, glucagon, somatostatin, and pancreatic polypeptide, and a digestive organ, secreting pancreatic juice containing digestive enzymes that assist the absorption of nutrients and the digestion in the small intestine. These enzymes help to further break down the carbohydrates, proteins, and lipids in the chyme.
The intestine is the segment of the alimentary canal extending from the pyloric sphincter of the stomach to the anus and, in humans and other mammals, consists of two segments, the small intestine and the large intestine.

The small intestine is subdivided into
- The duodenum,
- The jejunum and
- The ileum

The large intestine is subdivided into
- The cecum and
- The colon

The small intestine is where most chemical digestion takes place.

Most of the digestive enzymes that act in the small intestine are secreted by the pancreas and enter the small intestine via the pancreatic duct. The three major classes of nutrients that undergo digestion are proteins, lipids (fats) and carbohydrates.

Digested food is now able to pass into the blood vessels in the wall of the intestine through the process of diffusion. The small intestine is the site where most of the nutrients from ingested food are absorbed.

The large intestine (or bowel, colon) is the last part of the digestive system . Its function is to absorb water from the remaining indigestible food matter, and then to pass useless waste material from the body.The large intestine consists of the cecum, rectum and anal canal. The large intestine is about 1.5 m long, which is about one-fifth of the whole length of the intestinal canal.

Change in state of water
Water and it's states
Spheres of the earth
Nutrients & Deficiency Of Nutrients & It's Effect
Interesting Facts About Human Organs
Circulatory system
Digestive system
Endocannabinoids system
Endocrine system
Excretory system
Integumentary system
Immune system
Lymphatic system
Nervous system
Respiratory system
Musculoskeletal system
Vestibular system

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