CBSE Class 10 Answered

1. Why is small intestine in herbivores longer than in carnivores?

2. What will happen if mucus is not secreted by the gastric glands?

3. What is the significance of emulsification of fats?

4. What causes movement of food inside the alimentary canal?

5. Why does absorption of digested food occur mainly in the small intestine?

6. Describe the alimentary canal of man.

7.How do carbohydrates, proteins and fats get digested in human beings?

Asked by niyati | 30 May, 2015, 10:12: AM

Expert Answer

1. Herbivores have longer intestines than carnivores to digest grass. These intestines have many small bacteria that processes and breaks down cellulose into glucose, a source of energy that the host herbivore can use. Without these long intestines, animals such as cows could still eat grass, but would not be able to use the glucose stored in the grass structure.

2. The alkaline mucous layer protects epithelial cells of stomach wall against the acids and enzymes in the gastric lumen. If mucus is not secreted by the gastric glands, then the hydrochloric acid secreted by the glands will digest or corrode the walls of the stomach.

3. Emulsification helps the large globules of fat to be broken down into smaller globules and made water soluble. This provides lipase i.e. the fat digesting enzyme with an enormously increased surface to work on.

4. Peristalsis mainly causes movment of food inside the alimentary canal. In addition other movements of the stomach and intestines like segmenting movements and sphincter relaxation also help in propelling food through the alimentary tract.

5. The length of small intestine is longer and it has more number of villi as it will absorb food faster due to increased surface area. Large intestine will absorb water and minerals from the remaining food.

6. The human alimentary canal, also called the gastrointestinal (GI) tract, consists of all the structures from the mouth to the anus, through which food is consumed and digested, and waste is excreted. Structures of the alimentary canal include the mouth, pharynx, esophagus, stomach, intestines, and anus. The GI tract of a mature male human measures approximately 20 feet (6.5 meters).

(a)The mouth, also called the buccal cavity or oral cavity, contains a number of structures that help in the initial digestion of food, namely, the salivary glands, tongue, and teeth. The pharynx, the portion of the throat directly behind the mouth, serves to direct food into the oesophagus and prevent it from entering the trachea or windpipe.

(b)The oesophagus helps move ingested food towards the stomach through peristalsis, a type of wave-like muscular contraction. The second stage of digestion takes place in the stomach. As digested food passes out of the stomach, it enters the duodenum, where digestive juices from the liver and pancreas are combined.

(c)The lower GI tract consists of most of the intestines and the anus. The intestines are divided into the small and large intestine, both of which have three subparts. Two of the sections of the small intestine consists of jejunum and the ilium.The jejunum is the midsection of the small intestine. It moves food from the duodenum to the ilium through peristalsis, and aids in the absorption of nutrients The majority of nutrient absorption takes place in the ilium, which is lined with villi, microscopic finger-like projections that increase surface area for greater absorption. All soluble molecules are absorbed into the blood in the ilium.

(d)The large intestine is comprised of the cecum, the colon, and the rectum. The caecum connects the small and large intestines, while the colon absorbs water and salt from the digested material before it is excreted as waste. The colon itself has four different parts: the ascending colon, the transverse colon, the descending colon, and the sigmoid colon. The rectum is a temporary storage area for feces or solid waste before it is excreted. The last portion of the lower GI tract, the anus, is the exit point of feces, the waste product of the alimentary canal, from the body.

7. Carbohydrates are digested by salivary amylase and pancreatic amylase, fats are digested by pancreatic lipase and proteins are digested by pepsin and trypsin

Answered by Sivanand Patnaik | 31 May, 2015, 03:34: PM