Small intestine :
A thin membrane known as the mesentery extends from the posterior body wall of the abdominal cavity to surround the small intestine and anchor it in place. Blood vessels, nerves, and lymphatic vessels pass through the mesentery to support the tissues of the small intestine and transport nutrients from food in the intestines to the rest of the body.
The small intestine can be divided into 3 major regions:
  1. The duodenum is the first section of intestine that connects to the pyloric sphincter of the stomach. It is the shortest region of the small intestine, measuring only about 10 inches in length. Partially digested food, or chyme, from the stomach is mixed with bile from the liver and pancreatic juice from the pancreas to complete its digestion in the duodenum.
  2. The jejunum is the middle section of the small intestine that serves as the primary site of nutrient absorption. It measures around 3 feet in length.
  3. The ileum is the final section of the small intestine that empties into the large intestine via the ileocecal sphincter. The ileum is about 6 feet long and completes the absorption of nutrients that were missed in the jejunum.
structure of small intestine :

Like the rest of the gastrointestinal tract, the small intestine is made up of four layers of tissue. The mucosa forms the inner layer of epithelial tissue and is specialized for the absorption of nutrients from chyme. Deep to the mucosa is the submucosa layer that provides blood vessels, lymphatic vessels, and nerves to support the mucosa on the surface. Several layers of smooth muscle tissue form the muscularis layer that contracts and moves the small intestines. Finally, the serosa forms the outermost layer of epithelial tissue that is continuous with the mesentery and surrounds the intestines.
The interior walls of the small intestine are tightly wrinkled into projections called circular folds that greatly increase their surface area. Microscopic examination of the mucosa reveals that the mucosal cells are organized into finger-like projections known as villi, which further increase the surface area. Each square inch of mucosa contains around 20,000 villi. The cells on the surface of the mucosa also contain finger-like projections of their cell membranes known as microvilli, which further increase the surface area of the small intestine. It is estimated that there are around 130 billion microvilli per square inch in the mucosa of the small intestine. All of these wrinkles and projections help to greatly increase the amount of contact between the cells of the mucosa and chyme to maximize the absorption of vital nutrients.
The small intestine processes around 2 gallons of food, liquids, and digestive secretions every day. To ensure that the body receives enough nutrients from its food, the small intestine mixes the chyme using smooth muscle contractions called segmentations. Segmentation involves the mixing of chyme about 7 to 12 times per minute within a short segment of the small intestine so that chyme in the middle of the intestine is moved outward to the intestinal wall and contacts the mucosa. In the duodenum, segmentations help to mix chyme with bile and pancreatic juice to complete the chemical digestion of the chyme into its component nutrients. Villi and microvilli throughout the intestines sway back and forth during the segmentations to increase their contact with chyme and efficiently absorb nutrients.
Once nutrients have been absorbed by the mucosa, they are passed on into tiny blood vessels and lymphatic vessels in the middle of the villi to exit through the mesentery. Fatty acids enter small lymphatic vessels called lacteals that carry them back to the blood supply. All other nutrients are carried through veins to the liver, where many nutrients are stored and converted into useful energy sources.
Chyme is slowly passed through the small intestine by waves of smooth muscle contraction known as peristalsis. Peristalsis waves begin at the stomach and pass through the duodenum, jejunum, and finally the ileum. Each wave moves the chyme a short distance, so it takes many waves of peristalsis over several hours to move chyme to the end of the ileum.

gall bladder artery or vein :
Hollow, muscular and pear-shaped, the gallbladder is a small organ – only about 3 inches in length and 1.5 inches in width at its widest point. The larger end of the gallbladder extends inferiorly and to the right while the tapered end points superiorly and medially. The tapered end of the gallbladder narrows into a small bile duct known as the cystic duct. The cystic duct connects to the common hepatic duct that carries bile from the liver. These ducts merge to form the common bile duct that extends to the wall of the duodenum.
Microscopic Anatomy
The mucosa, which forms the innermost layer of the gallbladder, lines the gallbladder with simple columnar epithelial tissue. The columnar epithelial tissue contains microvilli on its surface, increasing the surface area and allowing the lining to absorb water and concentrate the dilute bile.
Beneath the columnar tissue is a thin lamina propria layer made of connective tissue and capillaries that support and anchor the epithelial layer.
Deep to the lamina propria is the muscularis layer that contains smooth muscle tissue. Contraction of the muscularis pushes bile out of the gallbladder and into the cystic duct.
Surrounding the muscularis is a thin layer of fibrous connective tissue that helps to reinforce and strengthen the wall of the gallbladder.
Finally, the serosa forms the outermost layer of the gallbladder. The serosa is an epithelial layer that forms part of the peritoneum, or lining of the abdominal cavity. The serosa gives the gallbladder a smooth, slick surface to prevent friction between moving organs.
Pancreas :
Pancreas is located deep in the abdomen. Part of the pancreas is sandwiched between the stomach and the spine. The other part is nestled in the curve of the duodenum (first part of the small intestine). To visualize the position of the pancreas, try this: touch your right thumb and right "pinkie" fingers together, keeping the other three fingers together and straight. Then, place your hand in the center of your belly just below your lower ribs with your fingers pointing to your left. Your hand will be the approximate shape and at the approximate level of your pancreas.
Because of the deep location of the pancreas, tumors of the pancreas are rarely palpable (able to be felt by pressing on the abdomen). This explains why most symptoms of pancreatic cancer do not appear until the tumor has grown large enough to interfere with the function of the pancreas or other nearby organs such as the stomach, duodenum, liver, or gallbladder.
Diagram showing pancreas location

  • The pancreas is located in the abdomen and is a gland organ.
  • It is an important part of the digestive system, producing enzymes and hormones that help break down foods.
  • The pancreas is a 6 to 10 inch organ and is located behind the stomach.
  • It is fish shaped and extends horizontally across the abdomen.
  • A healthy pancreas produces the correct chemicals to effectively digest the food we eat.
  • The endocrine portion of the pancreas is made up of several cells that secrete hormones straight into the bloodstream.
  • Insulin is a hormone secreted by pancreatic beta cells in response to a rise in blood sugar.
  • Acute or chronic inflammation of the pancreas could signify a presence of pancreatitis.
  • It is possible for cancer to develop in the pancreas.





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