Our digestive has the following parts:
Small Intestine
Colon (Large Intestine)

The mouth is the beginning of the digestive tract. In fact, digestion starts here as soon as you take the first bite of a meal. Chewing breaks the food into pieces that are more easily digested, while saliva mixes with food to begin the process of breaking it down into a form your body can absorb and use.Also called the pharynx, the throat is the next destination for food you've eaten. From here, food travels to the esophagus or swallowing tube.The esophagus is a muscular tube extending from the pharynx to the stomach. By means of a series of contractions, called peristalsis, the esophagus delivers food to the stomach. Just before the connection to the stomach there is a "zone of high pressure," called the lower esophageal sphincter; this is a "valve" meant to keep food from passing backwards into the esophagus.The stomach is a sac-like organ with strong muscular walls. In addition to holding the food, it's also a mixer and grinder. The stomach secretes acid and powerful enzymes that continue the process of breaking down the food. When it leaves the stomach, food is the consistency of a liquid or paste. From there the food moves to the 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 pancreas and 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.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.
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.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.

The mouth or the buccal cavity bounded by the upper and lower lips is the intiation of the digestive system in the human body. Internally, the  buccal cavity is provided with three pairs of salivary glands, namely the parotid, sublingual and submaxillary that produces saliva.
The floor of the buccal cavity is provided with the muscular tongue  with tastebuds  that helps in tasting and mastication of the food.Man is heterodont and has inscisiors(2), canine(1), premolar(2)  and molar teeth (3 ,last molar als called wisdom teeth) in each half of the jaw. 
In the mouth , the food is ingested ,and masticated, mixed with saliva and converted into bolas for swallowing by the pharynx. Pharynx  is the region where both the digestive tract and the respiratory tracts join together.The opening of the trachea is provided with an opening called glottiswhich gets closed by the membranous epiglottis during swallowing.It prevents entry of  food particles in the trachea .If  it enters accidentally,cough reflex is initiated
The oesophags  is the tubular pathway leading from the mouth to the stomach and is involved ib transport of the bolas by means of involuntary peristalsis .It  is an alternate contraction and relaxation of the circular and longitudinal  muscles that forces the food  downwards.The oesophagus moves thorugh the diaphragm via oesophageal biatus and enters the stomach at the cardiac end through the cardiac sphincter.
The stomach is a larger sac like organ with a J shaped structure.underr the diaphragm.the stomach  ids divided into four regions -Cardia, surrounding the lower esophqageal sphincter, fundus- rounded portion aboveand to the left of the cardia; body- large central portion below the  fundus and the narrow inferior region called pylorus.
The Concave medial border  of the stomach is called the lesser curvature and the convex border is called the greater curvature. te pyloric region joins with the duodenum through the pyloric sphincter.

 ti is the largest digestive gland (i.4kg) occupying  most of the right  half of the abdomen below  the diaphragm and is almost completely covered by peritoneum.It is divided into two major lobes, larger right and smaller left lobe separated by falciform ligament.
The ligamentum teres (round ligament) extends from the free borde of the falciform ligament to the umbilicus (derived from the foetal umbilical cord.)The right lobe is considered to be of an inferior quadrate lobe and a posterior caudate lobe, but basing on onternal structures they belong more tothe left lobe.
The bile canaliculi merge to form the the right and left hepatic ducts that unites to form the common hepatic duct. It joins the cystic ductforming the gall bladder and the two together form the common bile duct, which enters the duodenum by ampulla of Vater or hepatopancreatic ampulla.
Hepatic lobes are made of lobules of   hepatocytes in irregular , branching interconnected plates around central vein and produce bile
Between the plates are paved with endothelial lining called sinusoids having stellate cells--  Kupffer'scells. The hepatic portal artery, he[patic portal vein and bile duct arecollectively called protal triad
It is a  pear shaped sac  about  7 to 10 cms long and located in ther fossaa of the visceral surface of the liver.It is a store for bile and when intestine is empty,the sphincter of hepatopancreatic ampulla or sphincter of Oddi closes .

The pancreas  is an oblong ,tuboacinar gland (12.5 cmsX 2.5 cms)located posterior to the greater curvature of the stomach and is usually connected to the duodenum by two ducts.It has a head, body and tail.The head is expanded and near the  C shaped curve of the duodenum.
the larger  of the two ducts is called the pancreatic duct (duct of Wirsung) , while the smaller one is called the accessory duct or duct of Santorini, leading form the pancreas into the duodnum.
Histology: The pancreas consists of two types of cells -the pancreatic acini and the pancreatic islets or Islets of langerhans.The Islets of langerhans possess  the α,  β, and δ  cells  that secretes glucagon, Insulin ans somatostatin respectively. The acini produce the   pancreatic  juice.Pancreas is also an important structure of the digestive system in the human body.Hence it is also called  mixed gland.

                                                              SMALL INTESTINE

 It initiates from the pyloric end of the stomach and consists of anterior (duodenum), middle (jejunum ) and terminal (ileum).this region is specialized by the presence of numerous finger like projections called  villi with efferent and afferent blood vessels that serves in absorption of food  as a part of the digestive system in the human body.

 The large intestine or the colon initiates from the ileum of the small  intestine and consists of ascending ,descending and transverse colon.the opening of the ileum and the  colon is guarded by the ileocecal ends in at the rectum and the anus.   

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