Human Digestive System

The stomach is a hollow organ, or container, that holds food while it is being mixed with enzymes that continue the process of breaking down food into a usable form. Cells in the lining of the stomach secrete a strong acid and powerful enzymes that are responsible for the breakdown process. When the contents of the stomach are sufficiently processed, they are released into the small intestine.

Large intestine is divided into three parts. The first organ of the large intestine is the cecum. The cecum is attached to the appendix and is also the connecting pouch between the small and the large intestines. The colon comes after the cecum and is responsible for the abrogation of water and salts from the digested foods. The third part of the large intestine is the rectum, which acts as the connection between the intestines and anus.It is an organ of lower gastrointestinal tract .

Salivary amylase (ptyalin) is an enzyme that catalyses the breakdown of starch into sugars. Amylase is present in human saliva, where it begins the chemical process of digestion.

Chyme is the semifluid mass of partly digested food expelled by the stomach into the duodenum. In other words, chyme is partially digested food.

The rectum is the final straight portion of the large intestine in some mammals and the gut in others, terminating in the anus. The human rectum is about 12 cm long.

Lactose intolerance occurs due to an inadequate production of lactase. This enzyme breaks down or digests lactose in the digestive tract. While most babies produce sufficient amount of lactase, the gene for its production often later gets turned off.

Emulsification of fats is done by the bile secreted by the liver. 

Pepsin is secreted  in  inactive form  pepsinogen. it is activated by HCl in the stomach

Trypsinogen is activated to trypsin by bile in the small intestine.

Peristaltic movement occurs in the oesophagus or food pipe. It involves rhythmic contraction of muscles, which pushes the food forward in the oesophagus. 

An enterogastrone is any hormone secreted by the mucosa of the duodenum in the lower gastrointestinal tract, in response to dietary lipids, that inhibits the caudal motion of the contents of chyme.

Bile acids are conjugated with taurine or glycine in the liver, forming bile salts. Primary bile acids are those synthesized by the liver. These help in the digestion of lipids.

Histamine is an amine and is produced as part of a local immune response to cause inflammation.

Digestion of proteins begins in the stomach (in the acidic phase) and continues in the duodenum or small intestine (in the alkaline phase). The digestion is completed here by the pancreatic and intestinal enzymes.

Correct answer is option (3).