Question 1

Question 3Name the digestive juice secreted by the stomach and give its function.

Accepted Answer

Digestive juice secreted by the stomach is the Gastric juice. The gastric juice contains water, hydrochloric acid and an enzyme pepsin. Its functions are:Hydrochloric acid kills the germs preventing rotting of food during its long stay in stomach. It activates the enzyme pepsin.Pepsin converts proteins into a simpler compound called peptones.

Question 2

Question 4Answer the following questions:(i) Name the types of teeth present in humans.(ii) How is the small intestine best suited for the digestion and absorption of food?(iii) What do you mean by absorption of food?

Accepted Answer

(i) Four types of teeth present in humans are:IncisorsCaninesPremolarsMolars(ii) Small intestine is a long coiled tube of about 7 metres. The food remains in it for about 3-5 hours for digestion and absorption. Small intestine has Duodenum and Ileum. Duodenum receives bile from liver and pancreatic juice from pancreas that help in the digestion of carbohydrates, proteins and fats. Semi-digested food is completely digested in the Ileum by the intestinal juices secreted by the intestinal glands present in the inner lining of Ileum. Villi are tiny finger-like projections present in the inner lining of the small intestine that greatly increase the inner surface area for absorption of the digested food. They absorb the amino acids and glucose. Vitamins and minerals salts are mostly soluble in water and are directly absorbed through the walls of the intestine.(iii) Absorption of food means passing the digested food into the blood system and lymph vessels to be supplied to the rest of the body. Major portion of the digested food is absorbed by the villi present in the small intestine. It absorbs the amino acids and glucose to pass them into the blood system, whereas the fatty acids pass into the lymph vessels. Vitamins and minerals are soluble in water and are mostly absorbed through the walls of the intestine.

Question 3

Question 5Define the following terms : Egestion, Digestion, Assimilation.

Accepted Answer

Egestion — The process of eliminating the undigested food through the anus is called Egestion.Digestion — The process by which the complex chemical compounds present in the food are broken down into simpler substances that are readily absorbed and utilized by the body is called Digestion.Assimilation — The utilization of the digested food and nutrients by the body cells is called Assimilation.

Question 4

Question 8Define the term "digestion".

Accepted Answer

The process by which the complex chemical compounds present in the food are broken down into simpler substances that are readily absorbed and utilized by the body is called digestion.

Question 5

Question 9State the four ways in which saliva is useful to us.

Accepted Answer

The four ways in which saliva is useful to us are:It moistens and lubricates the mouth cavity and the tongue to make speaking and swallowing easy.It cleans the mouth and destroys germs.The saliva binds the food particles and makes it into a mass called the bolus.Digestion begins in the mouth. Saliva contains an enzyme (amylase) which helps in the breakdown of starch to simple sugars (maltose).

Question 6

Question 10Foods are classified into three groups on the basis of the functions they perform in our body. Name these three groups, and briefly state their functions. Also give two sources of each.

Accepted Answer

The three groups into which the foods are classified are:Energy-giving foods — They are made up of carbohydrates and fats. Carbohydrates provide us with instant energy, while fats are stored as energy resources. Its sources are:RicePotatoFatsBody-Building foods — Proteins are considered to be body building food. Such foods help in the growth and repair of damaged cells and tissues. Its sources are:PulsesMilkProtective foods — They are mainly vitamins and minerals. Minerals are needed for their specific roles in the body. Vitamins are needed for the normal functioning of various body processes. Its sources areFruits and VegetablesDairy products

Question 7

Question 11(i)Distinguish between bolus and chyme on the basis of occurrence in the part of alimentary canal.

Accepted Answer

BolusChymeBolus is the term for chewed food mixed with saliva in the mouth and esophagus.Chyme is the semi-liquid mixture of partially digested food and gastric juices formed in the stomach and small intestine.

Question 8

Question 11(ii)Distinguish between saliva and bile on the basis of source of secretion.

Accepted Answer

SalivaBileThe saliva is secreted by three pairs of salivary glands (one below the tongue, second at the base of the ear, and third on the inner side of the angles of the lower jaws).Bile is secreted by the liver.

Question 9

Question 11(iii)Distinguish between milk teeth and permanent teeth on the basis of number.

Accepted Answer

Milk TeethPermanent TeethMilk teeth are 20 in number.Permanent Teeth are 32 in number.

Question 10

Question 11(iv)Distinguish between lactase and lipase on the basis of substrate on which they act.

Accepted Answer

LactaseLipaseLactase acts on Lactose.Lipase acts on emulsified fats.

Question 11

Question 11(v)Distinguish between small intestine and large intestine on the basis of the absorbed materials.

Accepted Answer

Small intestineLarge intestineThe small intestine absorbs nutrients from digested food like amino acids, glucose, fatty acids, vitamins and minerals.The large intestine mainly absorbs water from undigested food.

Question 12

Question 12Draw a neat diagram of the "vertical section of a grinding tooth" and label all its important parts. Answer the following questions :(i)	Name the substance which covers the visible portion of the tooth.(ii) Which of the above labelled parts of the tooth is hard like a bone ?(iii) Name the substance which covers the embedded part of the tooth.(iv) What are caries ?(v) Define plaque.

Accepted Answer

Diagram of "vertical section of a grinding tooth"(i) Enamel(ii) Dentine(iii) Cement(iv) The acid produced by the bacteria slowly corrodes the enamel of the teeth and forms cavities known as caries(v) Sometimes the sugary or starchy foods that we eat get stuck to the teeth. This along with bacteria on the teeth's surface form a yellow coloured film called plaque.

Question 13

Question 2Identify and name the "four" types of teeth shown below and state their functions.

Accepted Answer

The four types of teeth shown in the figure are listed below along with their functions:A → IncisorsFunction — Incisors are used for biting and cutting.B → CaninesFunction — Canines are used for tearing the food.C → PremolarsFunction — Premolars help in crushing and grinding the food.D → MolarFunction — Molars help in finer crushing and grinding of food.

Question 14

Question 6Given alongside is the diagram of the human alimentary canal.(i) Name the parts 1-11 indicated by guidelines.(ii) State the function of the juice secreted by part 1.(iii) State the function of the three enzymes found in the juice secreted by part 3.

Accepted Answer

(i) The parts areStomachBile ductPancreasLarge intestineSmall intestineRectumAppendixDuodenumGall bladderLiverAnus(ii) The juice secreted by part (1) is the Gastric juice.Gastric juice being acidic in nature kills the germs and activates pepsin.(iii) The function of the three enzymes found in the gastric juice areAmylase enzyme digest starch into maltose.Trypsin enzyme digest proteins into peptides.Lipase enzyme digest emulsified fats into fatty acids anf glycerols.

Question 15

Question 7Define the terms given below :NutrientsNutritionWisdom teethEmulsificationEgestion

Accepted Answer

Nutrients — A nutrient can be defined as "a constituent of food that helps one way or the other in the body's functions".Nutrition — The process by which all organisms obtain or synthesize their food and convert it into simpler substances, so that it can be absorbed and utilized by the cells of the body is called nutrition.Wisdom teeth — The last molar on each side in each jaw is called the Wisdom Tooth. The wisdom tooth appears at the age of 17-20 years. In some people, however, wisdom teeth may not come out of the gums at all.Emulsification — The bile juice breaks down fats into tiny droplets and this process is called emulsification.Egestion — The process of eliminating the undigested food through the anus is called egestion.

Question 16

Question 1Write True or False in the following statements.Molars help in cutting and tearing food.Carbohydrates are digested into glucose.Proteins are digested into fatty acids.Wisdom tooth appears at the age of 5-6 years when the child starts going to school.The temporary set of teeth includes incisors, canines and premolars only.The ducts from the salivary glands open into the duodenum.Saliva changes starch into maltose.

Accepted Answer

FalseReason — Molars help in finer crushing and grinding the food.TrueReason — The end products of carbohydrate digestion are simple sugars (glucose & fructose) which can easily be absorbed in our blood system.FalseReason — Proteins are digested into amino acid.FalseReason — The wisdom tooth appears at the age of 17-20 years. In some people, however, wisdom teeth may not come out of the gums at all.FalseReason — The temporary teeth consist of 20 teeth (8 incisors, 4 canines and 8 molars only).FalseReason — The ducts from the salivary glands open into the mouth.TrueReason — Saliva contains an enzyme called amylase which converts starch into maltose.

Digestive System

Long Answer Questions

Short Answer Questions

True Or False