Human Digestive System

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. 

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. 

Hepatic caecum is found in grasshopper, which secretes enzymes into the stomach here they assist in the digestive process.
The food in the grasshopper, after entering into oesophagus, enters into the crop. here, the masticated food is temporary stored.
The hemolymph is equivalent to blood of grasshopper
Egestion is the process of discharging undigested or waste material from a cell of organ.
Therefore, the correct answer is option A.

Hydra is a freshwater sessile organism belonging to the phylum Cnidaria and class Hydrozoa. They are found in lakes, pond, and stream. Hydra is ammonotelic i.e they secrete ammonia as chief excretory nitrogenous waste. In hydra specialized excretory organs are absent hence in hydra, wastes of food digestion and nitrogenous wastes are removed from mouth and body wall.

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.

Amoeba takes its food by the method of phagocytosis (i.e ingesting or engulfing the food particles), also by means of pinocytosis (wherein amoeba wraps around its membranes around the food forms vesicles and pinch it inside the membrane and then gradually digests it) and by endocytosis (in which the outermost the membrane of amoeba either stretches inwards or projects outwards to obtain nutrition.

The correct answer is D.

Excessive alcohol causes fatty liver or steatosis. It describes the buildup of fats in the liver. It occurs when the body creates too much fat or cannot metabolize fat fast enough. As a result, the left over is stored in the liver cells where it accumulates to become fatty liver disease.
Therefore, the correct answer is option A.

Abuse of alcohol may cause three types of liver damage, which often develop in the following order: Accumulation of fat (fatty liver, or steatosis): This type is the least serious and can sometimes be reversed. It occurs in more than 90% of people who drink too much alcohol