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
GALL BLADDER :
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.
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 sphincter.it ends in at the rectum and the anus.