Human Digestive System

The sense of smell and sight of food are governed by olfactory and optic responses which work together to initiate the neural response during the cephalic phase of digestion. Sight, smell and sense of food initiate the neural response in which central nervous system prepares the stomach to receive food. The responses include salivation and secretion of gastric juices. The ingestion of food stimulates the hormonal responses to food which includes endocrine system to ensure releases of various digestive hormones at appropriate time. Thus, tye correct answer is option B.

The stomach and intestines receive dual innervation from both the sympathetic and parasympathetic nervous systems to regulate motility and secretion.

Soluble fiber attaches to cholesterol and takes them out of the body from our system that helps in reducing blood cholesterol and also reducing the risk of heart disease. These are found in the food like oats, apples, nuts etc.

Stomach - Foveolar cells are mucus-producing cells, which cover the inside of the stomach, protecting it from the corrosive nature of gastric acid. The mucus produced by these cells is extremely important, as it prevents the stomach from digesting itself.
Duodenum - Brunner's glands (or duodenal glands) are compound tubular submucosal glands present in the duodenum. The main function of these glands is to produce a mucus-rich alkaline secretion (containing bicarbonate) in order to: protect the duodenum from the acidic content of chyme (which is introduced into the duodenum from the stomach); provide an alkaline condition for the intestinal enzymes to be active, thus enabling absorption to take place and lubricate the intestinal walls.
Large intestine - Goblet cells reside throughout the length of the small and large intestine and are responsible for the production and maintenance of the protective mucus blanket by synthesizing and secreting high-molecular-weight glycoproteins, known as mucins. 

The oesophagus leads into the stomach. The stomach is a muscular sac. The stomach is the most important site of protein digestion. Stomach wall has peptic cells, chief cells secrete pepsinogen and oxyntic and parietal cells secrete hydrochloric acid. The pepsinogen is activated to pepsin on exposure to hydrochloric acid. The pepsin is a chief proteolytic enzyme of the alimentary canal. Another important enzyme of the stomach is lysozyme which is antibacterial. Thus, the correct answer is option C.

The pylorus is a narrow cone shaped constriction present at the end of the stomach and the beginning of the small intestine. It contains two region antrum which connects the parts of the stomach and pyloric canal which connects the stomach and small intestine.  Thus, the correct answer is option B.

The gastric mucosa is present is in the inner wall of the stomach which secretes 1.2 to 1.5 litres of gastric juice per day. Gastric juice is a mixture of HCl, mucous and digestive enzymes which makes food particles soluble, initiates protein digestion and converts the gastric contents to a semiliquid mass called chyme, thus preparing it for further digestion in the small intestine. This juice is highly acidic because of its hydrochloric acid content, and it is rich in enzymes. 

Indigestion is inability to properly digest food resulting in abdominal distension due to gas or flatus. It is caused by overeating, spicy food, anxiety and disturbed secretions of digestive tract.

Pharynx  connects the nasal cavity and mouth to the larynx and esophagus. It is the common pathway for food and air. There are three regions nasopharynx, oropharynx, and laryngopharynx. Nasopharynx  an air passage; uvula prevents food from entering it during swallowing. Oropharynx posterior to the mouth, passageway for food and air. Laryngopharynx passageway for food and air. Directly posterior to the epiglottis and extends to the larynx, then becomes continuous with esophagus. 

Small intestine is made up of three parts- duodenum, jejunum and ileum. The intestinal wall bears microscopic finger like projections called villi. The Mucosa layer forms crypts in between the bases of villi in the intestine (crypts of Lieberkuhn). The crypts produce digestive juice.

Liver along with muscles stores excess glucose as glycogen, which can be used in times of starvation to maintain blood glucose levels. Excess carbohydrates are also stored as fat in adipose tissue around visceral organs and underneath the skin. During starvation the fat in the adipose tissue can be metabolised to derive energy.

The excretory organs of earthworm are coiled tubular structures, known as nephridia. A nephridium consists of a ciliated nephridial canal, that opens into the coelom by nephrostome and to the exterior or in the gut by nephridiopore. The walls of nephridia are glandular and richly supplied with blood vessels, they extract solutes and water from the blood by ultra filtration, and discharge the filtrate into the nephridial canal. 

Chemical digestion involves enzymes. In the mouth, chemical digestion is initiated when the food comes in contact with saliva, which is secreted by salivary glands. It contains salivary amylase which begins the digestive process by breaking down starch and converting it into maltose. Chemical digestion then further continues in stomach and then finally in the small intestine.

Chemical digestion food starts in the mouth as saliva is secrets from salivary gland which consists salivary amylase enzyme which acts on starch and converts it into the simpler form the churned food particles with saliva is called as the bolus then transferred to the stomach through the esophagus.

Pancreas helps in digestion by secreting pancreatic juice in small intestine. However pancreas is a gland and is not a part of alimentary canal. Alimentary canal is a muscular tube which extends from mouth to anus and includes the mouth, pharynx, oesophagus, stomach and the intestines.